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[vsnet-grb-info 37240] IceCube-250203A: No transient candidates from the Zwicky Transient Facility
by GCN Circulars 08 Feb '25

08 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39230 SUBJECT: IceCube-250203A: No transient candidates from the Zwicky Transient Facility DATE: 25/02/08 08:28:20 GMT FROM: akshay.eranhalodi(a)desy.de Akshay Eranhalodi (DESY), Robert Stein (JSI), Sven Weimann (Ruhr University Bochum), Jannis Necker (DESY) and Anna Franckowiak (Ruhr University Bochum) report: On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: As part of the ZTF neutrino follow up program (Stein et al. 2023), we observed the localization region of the neutrino event IceCube-250203A (Zegarelli et. al, GCN 39132) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started observations in the g- and r-band beginning at 2025-02-04 12:30 UTC, approximately 32.5 hours after event time. We covered 96.0% (0.9 sq deg) of the reported localization region. This estimate accounts for chip gaps. Each exposure was 300s with a typical depth of 21.0 mag. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019, Stein et al. 2021) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019) . No candidate counterparts were detected. Observations of this localisation will continue over the coming days as part of our standard monitoring cadence for neutrino alerts (Stein et al. 2023). Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-2034437 and a collaboration including Caltech, IPAC, the Oskar Klein Center at Stockholm University, the University of Maryland, University of California, Berkeley , the University of Wisconsin at Milwaukee, University of Warwick, Ruhr University Bochum, Cornell University, Northwestern University and Drexel University. Operations are conducted by COO, IPAC, and UW. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019). Alert filtering is performed with the nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ). View this GCN Circular online at https://gcn.nasa.gov/circulars/39230. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37239] LIGO/Virgo/KAGRA S250206dm: Spectroscopic Classification of AT2025bay and AT2025baz with Keck I/LRIS
by GCN Circulars 08 Feb '25

08 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39229 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Spectroscopic Classification of AT2025bay and AT2025baz with Keck I/LRIS DATE: 25/02/08 07:55:32 GMT FROM: Viraj Karambelkar at Indian Inst of Tech,Bombay <karambelkarvraj21197(a)gmail.com> Viraj Karambelkar (Caltech), Tomás Ahumada (Caltech), Mansi Kasliwal (Caltech) report on behalf of the ZTF and GROWTH collaborations: We report optical spectroscopy of two counterpart candidates reported by the Zwicky Transient Facility, AT 2025bay, AT 2025baz (GCN #39228) in the localization region of LIGO/Virgo S200206dm (LVC, GCN #39175,39184). We used the Low Resolution Imaging Spectrometer (Oke et al. 1995) on the Keck I telescope, reduced data using the idl package lpipe (Perley 2019) and find: ZTF25aaffyzc / AT2025bay shows broad features matching a Type Ia supernova before maximum at z = 0.19 ZTF25aaffzpx / AT2025baz matches a Cataclysmic Variable in the Milky Way and shows Balmer emission lines at z = 0.0 Thus, AT2025bay and AT2025baz are not related to the gravitational wave event. We are grateful to the Keck Observatory staff, Sherry Yeh and Matthew Wahl, as well as observers, Andrew Howard and Howard Isaacson, for swiftly co-operating with these Target-of-Opportunity observations for rapidly setting targets. View this GCN Circular online at https://gcn.nasa.gov/circulars/39229. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37238] LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
by GCN Circulars 08 Feb '25

08 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39228 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility DATE: 25/02/08 07:48:41 GMT FROM: Tomas Ahumada Mena at Caltech <tahumada(a)caltech.edu> Tomás Ahumada (Caltech), Viraj Karambelkar (CIT), Eric Bellm (UW), Mansi Kasliwal (CIT), Shreya Anand (Stanford), Robert Stein (JSI/UMD), Theophile du Laz (CIT), Avery Wold (IPAC), Igor Andreoni (UMD), Varun Bhalerao (IITB), Brad Cenko (NASA GSFC/UMD), Michael Coughlin (UMN), David Kaplan (UWM), Leo Singer (NASA GSFC), Jesper Sollerman (OKC) report on behalf of the ZTF and GROWTH collaborations: We observed the localization region of the LVK trigger S250206dm (GCN 39175) with the Palomar 48-inch telescope equipped with the 47 square-degree Zwicky Transient Facility (ZTF) camera (Graham et al., 2019; Bellm et al., 2019). We obtained images in the g- and r-bands of the Bilby map (GCN 39184). We started observations in the g- and r- beginning at 2024-02-08 02:21 UTC, approximately 29 hours after event time (delay due to wet weather at Palomar on the first night). We targeted 52% (1081 sq deg) of the reported localization region with 300s exposures. We queried the ZTF alert stream using Kowalski (Duev et al. 2019) through Fritz (Coughlin et al. 2023) and emgwcave (Karambelkar et al. in prep). We required at least 2 detections separated by at least 15 minutes to select against moving objects. Furthermore, we cross-match our candidates with the Minor Planet Center to flag known asteroids, reject stellar sources (Tachibana and Miller 2018 and using the GAIA catalog), reject AGNs based on WISE colors, and apply machine learning algorithms for classification (Mahabal et al. 2019). We require that no spatially coincident ZTF alerts were issued before the detection time of the LVK trigger. We also ran forced photometry on ZTF images (Masci et al. 2019) and required no detections before the LVK trigger. Two sources were found within the 95% localization region and reported to TNS: id | AT name |ra |dec | mjd| mag |filter| comment ZTF25aaffzpx | AT 2025baz | 02:19:26.60 | +47:32:49.80 | 60714.15932870 | 20.4 | r | hostless ZTF25aaffyzc | AT 2025bay | 00:30:01.17 | +37:10:06.06 | 60714.13770830 | 20.5 | r | no redshift available Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Award #2407588 and a partnership including Caltech, USA; Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; University of Wisconsin at Milwaukee, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan; Operations are conducted by Caltech's Optical Observatory (COO) and Caltech/IPAC. GROWTH acknowledges the generous support of the NSF under PIRE Grant No 1545949. Alert database searches are done by AMPEL (Nordin et al. 2019) and Kowalski (Duev et al. 2019). The GROWTH India Telescope (GIT, Kumar et al., 2022) is set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. Its operations are partially supported by funding from the IIT Bombay alumni batch of 1994. The Fritz and SkyPortal projects acknowledge the generous support of The Gordon and Betty Moore Foundation. View this GCN Circular online at https://gcn.nasa.gov/circulars/39228. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37237] LIGO/Virgo/KAGRA S250206dm: ePESSTO+ classification of AT2025bar
by GCN Circulars 08 Feb '25

08 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39227 SUBJECT: LIGO/Virgo/KAGRA S250206dm: ePESSTO+ classification of AT2025bar DATE: 25/02/08 07:16:28 GMT FROM: James Gillanders at University of Oxford <jhgillanders.astro(a)gmail.com> J. Gillanders (Oxford), D. Magill, M. Fulton (QUB), S. Srivastav (Oxford), T. de Lourenco Pessi (ESO), P. Pessi (Stockholm), D. O’Neill (Warwick), T.-W. Chen (NCU), J. Anderson (ESO), M. Gromadzki (Warsaw), C. Inserra (Cardiff), E. Kankare (Turku), T. Müller Bravo (Trinity), A. Horowicz, O. Yaron, E. Zimmerman (Weizmann), D. Young (QUB). ePESSTO+, the advanced Public ESO Spectroscopic Survey for Transient Objects (Smartt et al., 2015, 2015A&A...579A..40S) observed AT2025bar, the candidate optical counterpart reported by Steeghs et al., (GCN 39215) for the LIGO/Virgo/KAGRA GW event S250206dm (LVK Collaboration, GCN 39175). Our observation was carried out with ESO’s New Technology Telescope (NTT) at La Silla, employing EFOSC2 and Grism #13 (3985-9315A, 18A resolution). Our observation commenced at 2025-02-08 06:06 UTC, corresponding to 1.36 days (or 32.7 hours) after the GW merger event, and consisted of a single 2100s exposure employing a 1.5 arcsec slit. The reduced spectrum closely resembles a type Ia supernova ~a few days pre-maximum light, with a redshift of ~0.17 (determined from template matching with SNID; Blondin & Tonry, 2007, 2007ApJ...666.1024B). Thus, we conclude that AT2025bar is not related to the GW event S250206dm. This classification spectrum (and additional details) will be publicly available within 24 hours from http://www.pessto.org (via WISeREP) and the IAU Transient Name Server, as part of standard ePESSTO+ science operations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39227. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37236] EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations
by GCN Circulars 08 Feb '25

08 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39214 SUBJECT: EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations DATE: 25/02/07 19:58:43 GMT FROM: Malte Busmann at Ludwig-Maximilians-Universität München <m.busmann(a)physik.lmu.de> Malte Busmann (LMU), Daniel Gruen (LMU), Brendan O’Connor (Carnegie Mellon U.) and Antonella Palmese (Carnegie Mellon U.), Julius Gassert (LMU), Lena Schnappinger (LMU), Julian Sommer (LMU), Lei Hu (Carnegie Mellon U.), Franziska Krause (LMU), Elia Enlghard (LMU) and Yajie Zhang (LMU) report: We observed the 90% localization of EP-WXT trigger 01709131361, which lies inside of the 70% localization of S250206dm (LIGO Scientific Collaboration, GCN 39184) with the Three Channel Imager (3KK) at the Fraunhofer-Telescope Wendelstein (FTW) in the r, i and J band simultaneously for 17 x 180 s under suboptimal sky conditions. The observations started at 2025-02-07T17:52:05 UT (2.0 h after the EP-WXT trigger and 20.4 h after the NSBH/BNS merger). We performed difference imaging in the r band with templates from the DESI Legacy Surveys and do not identify any variable optical sources to a 3-sigma depth of r>20.9 AB mag calibrated to the PS1 catalog. Further observations are encouraged. We thank Christoph Ries from the Wendelstein Observatory for obtaining these observations. UPDATE: We do see the flaring star mentioned by Levan et al. (GCN 39218) but initially rejected it. For details see O'Connor et al. (GCN 39219). View this GCN Circular online at https://gcn.nasa.gov/circulars/39214. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37235] LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
by GCN Circulars 08 Feb '25

08 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39226 SUBJECT: LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates DATE: 25/02/08 06:55:31 GMT FROM: F. Fortin at IRAP <ffortin.sci.edu(a)gmail.com> Francis Fortin (IRAP), Alan M. Watson (UNAM), Sarah Antier (OCA), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Jean-Luc Atteia (IRAP), Rosa L. Becerra (Università degli Studi di Roma Tor Vergata), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Noémie Globus (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), and Benjamin Schneider (LAM) report: We imaged the fields of the two candidates reported by the DDOTI team (Becerra et al., GCN Circ. 39208) as a possible optical counterpart of the GW transient S250206dm (LVK Collaboration, GCN Circ. 39175, GCN Circ. 39184) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We observed source 1 from 2025-02-08 04:48 to 05:20, obtaining 480 seconds of exposure in each of the g and r filters. At the position of the source reported by Becerra et al., we do not detect a source to 3-sigma limiting magnitudes of: g > 22.0 r > 22.1 We observed source 2 from 2025-02-08 05:39 to 06:09, again obtaining 480 seconds of exposure in each of the g and r filters. At the position of the source reported by Becerra et al., we do not detect a source to 3-sigma limiting magnitudes of: g > 22.5 r > 22.6 The data were reduced and stacked using custom software and then calibrated against the PS1 catalog and analysed using STDPipe (Karpov 2021). Our magnitude limits are not corrected for Galactic extinction. Our limits at about 32 hours after the GW event are significantly fainter than the detections reported by the DDOTI team. We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/39226. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37234] GRB 250208A: Fermi GBM Final Real-time Localization
by GCN Circulars 08 Feb '25

08 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39225 SUBJECT: GRB 250208A: Fermi GBM Final Real-time Localization DATE: 25/02/08 05:14:47 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 05:03:59 UT on 8 Feb 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250208A (trigger 760683844.557836 / 250208211). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 191.4, Dec = -11.8 (J2000 degrees, equivalent to J2000 12h 45m, -11d 48'), with a statistical uncertainty of 6.8 degrees. The angle from the Fermi LAT boresight is 39.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250208211/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250208211/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250208211/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39225. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37233] EP250207a: EP-WXT detection and XRT follow-up observation
by GCN Circulars 08 Feb '25

08 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39224 SUBJECT: EP250207a: EP-WXT detection and XRT follow-up observation DATE: 25/02/08 05:14:40 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> D. Y. Li, M. J. Liu, J. An, S.Y. Fu, S. Q. Jiang, X. Liu, D. Xu, Z. P. Zhu, M. H. Zhang (NAOC, CAS), Q. C. Shui (IHEP, CAS), W. D. Zhang (NAOC, CAS) report on behalf of the Einstein Probe team: We report on the detection of an X-ray transient by EP-WXT, designated EP250207a, which triggered the on-board processing unit at 2025-02-07T15:51:17 (trigger ID: 01709131361). The WXT position of the source is R.A. = 356.902 deg, DEC = 27.027 deg (J2000) with an uncertainty of 2.2 arcmin in radius (90% C.L. statistical and systematic). The average 0.5-4 keV spectrum can be fitted with an apec model with a temperature of 3.1 (-1.2, +5.9) keV. No significant absorption is required during the spectral fitting. The derived average 0.5-4 keV flux is 2.9 (-0.7, +0.9) x10^-10 erg/s/cm2. The uncertainties are at the 90% confidence level for the above parameters. We performed a target of opportunity observation with Swift. The Swift XRT observation began at 2025-02-07T17:59:50 (UTC) with an exposure time of 1716 seconds in the Photon Counting mode, about 2 hours after the burst detected by EP-WXT. A bright X-ray source, which is spatially consistent with the low-mass star 2MASS J23473680+2702068 (distance ~ 21.3 pc), was detected within the WXT error circle. The X-ray spectrum can be fitted with two apec components, with temperature of 0.75 (-0.3, +0.2) keV, and 2.6 (-0.6, +1.3) keV, respevtively. No significant absorption is required during the spectral fitting. The derived 0.3-10 keV flux is 9.2 (-1.0, +1.1)x10^-12 erg/s/cm2, corresponding to a luminosity of around 5x10^29 erg/s. We suggest this transient is a stellar flare from this low-mass star. We thank the Neil Gehrels Swift team for making the quick follow-up observation possible. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/39224. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37232] LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
by GCN Circulars 08 Feb '25

08 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39223 SUBJECT: LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate DATE: 25/02/08 04:34:56 GMT FROM: chl20171(a)outlook.com The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S250208ad during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2025-02-08 03:51:06.789 UTC (GPS time: 1423021884.789). The candidate was found by the CWB [1], CWB BBH [2], GstLAL [3], MBTA [4], PyCBC Live [5], and SPIIR [6] analysis pipelines. S250208ad is an event of interest because its false alarm rate, as estimated by the online analysis, is 3.7e-10 Hz, or about one in 84 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250208ad After parameter estimation by RapidPE-RIFT [7], the classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), NSBH (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [8] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [8] Both HasNS and HasRemnant consider the support of several neutron star equations of state. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [8], distributed via GCN notice about 31 seconds after the candidate event time. * bayestar.multiorder.fits,2, an initial localization generated by BAYESTAR [8], distributed via GCN notice about 5 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,2. For the bayestar.multiorder.fits,2 sky map, the 90% credible region is 1750 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 3453 +/- 1025 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Klimenko et al. PRD 93, 042004 (2016) doi:10.1103/PhysRevD.93.042004 [2] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018 [3] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. (2023) arXiv:2305.05625 [4] Aubin et al. CQG 38, 095004 (2021) doi:10.1088/1361-6382/abe913 [5] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [6] Chu et al. PRD 105, 024023 (2022) doi:10.1103/PhysRevD.105.024023 [7] Rose et al. (2022) arXiv:2201.05263 and Pankow et al. PRD 92, 023002 (2015) doi:10.1103/PhysRevD.92.023002 [8] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [9] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/39223. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37231] LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
by GCN Circulars 08 Feb '25

08 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39222 SUBJECT: LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations DATE: 25/02/08 01:45:30 GMT FROM: Harsh Kumar at Center for Astrophysics | Harvard & Smithsonian <harshkosli13(a)gmail.com> H. Kumar, E. Berger, A. Villar, D. Hiramatsu, P. K. Blanchard, K. D. Soto, S. K. Yadavalli, M. Hussaini, A. Gagliano, S. Gomez and C. Ransome (Harvard) report: We obtained imaging with Binospec on the 6.5m MMT to search for an optical counterpart to the gravitational wave event S250206dm (GCN #39175, #39184). A series of 120-second r-band images were obtained starting about 5 hours after the GW trigger, targeting Glade+ galaxies (G. Dálya et al. 2021) coincident with the 3D localization (bayestar.fits.gz,1) of the event. We do not detect any new transients near targeted galaxies within the localization volume compared to PS1/3pi images down to ~21.7 mag. A list of observed galaxies is listed below: -------------------------------------- GLADE ID | RA (J2000) | Dec (J2000)| -------------------------------------- 03WFD | 34.07875 | 51.68233 | 01JP0 | 41.07416 | 53.40766 | 01HGY | 37.20916 | 52.92669 | 0650c | 36.18916 | 52.67455 | 048BX | 34.57416 | 51.97930 | 06IPX | 34.02416 | 51.86102 | 001TW | 41.78666 | 53.72905 | 1XD7Y | 15.89166 | 44.00536 | 065O8 | 36.20291 | 52.59722 | 065O6 | 36.29791 | 52.25575 | 0I29U | 41.80708 | 53.73738 | 00BDI | 42.80416 | 54.14144 | 01JNX | 36.19875 | 51.99944 | 00PCL | 43.07583 | 53.98008 | -------------------------------------- We thank Ryan Howie, Ben Weiner, and MMT staff for the rapid execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39222. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37230] GRB 250207A: Swift-XRT refined Analysis
by GCN Circulars 08 Feb '25

08 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39221 SUBJECT: GRB 250207A: Swift-XRT refined Analysis DATE: 25/02/08 01:34:17 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), D.N. Burrows (PSU), M. A. Williams (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), P. D'Avanzo (INAF-OAB) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 6.0 ks of XRT data for GRB 250207A, from 100 s to 73.6 ks after the BAT trigger. The data comprise 370 s in Windowed Timing (WT) mode (the first 4 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The late-time light curve (from T0+4.2 ks) can be modelled with a power-law decay with a decay index of alpha=1.22 (+0.13, -0.10). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.14 (+/-0.06). The best-fitting absorption column is 6.7 (+/-1.2) x 10^20 cm^-2, in excess of the Galactic value of 2.4 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.02 (+0.16, -0.15) and a best-fitting absorption column of 5.5 (+3.5, -3.1) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.3 x 10^-11 (3.8 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 5.5 (+3.5, -3.1) x 10^20 cm^-2 Galactic foreground: 2.4 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 2.02 (+0.16, -0.15) If the light curve continues to decay with a power-law decay index of 1.22, the count rate at T+24 hours will be 0.010 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.4 x 10^-13 (3.9 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01287821. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39221. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37229] LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect.
by GCN Circulars 08 Feb '25

08 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39220 SUBJECT: LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect. DATE: 25/02/08 00:32:54 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V. Lipunov, I. Panchenko, G. Lipunova (Lomonosow Moscow State University) In connection with the close in time (less than 1 minute) discovery of the source FRB 20250206A (GCN 39216) following the registration of the gravitational-wave signal LIGO/Virgo/KAGRA S250206dm (GCN 39175; likely either BH-NS or NS-NS) we note that this could be the first observation of the "Time Machine" effect (Lipunova, Lipunov & Panchenko, New Astronomy, Volume 2, Issue 6, 1997, 555-558;) of the FRB radio precursor phenomenon predicted earlier (Lipunov & Panchenko, 1996, A&A, 312,937L). As the authors of CHIME (GCN 39216) note, the probability of a random coincidence of the two events is quite high. However, we are confident that such an effect will inevitably be detected by means of radio and gravitational wave astronomy. We also note that the absence of a host galaxy is quite possible due to the kick velocity effect of the two supernova explosions in this binary system. View this GCN Circular online at https://gcn.nasa.gov/circulars/39220. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37228] EP-WXT trigger 01709131361: correction to GCN 39214
by GCN Circulars 08 Feb '25

08 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39219 SUBJECT: EP-WXT trigger 01709131361: correction to GCN 39214 DATE: 25/02/08 00:05:18 GMT FROM: Brendan O'Connor at Carnegie Mellon University <boconno2(a)andrew.cmu.edu> Brendan O’Connor (Carnegie Mellon U.), Malte Busmann (LMU), Daniel Gruen (LMU), Antonella Palmese (Carnegie Mellon U.), Julius Gassert (LMU), Lena Schnappinger (LMU), Julian Sommer (LMU), Lei Hu (Carnegie Mellon U.), Franziska Krause (LMU), Elia Enlghard (LMU) and Yajie Zhang (LMU) report: In Busmann et al. (GCN 39214), we reported observations of EP-WXT trigger 01709131361 with the Fraunhofer-Telescope Wendelstein (FTW). The flare star reported by Levan et al. (GCN 39218) is present in our observations, but was mistakenly rejected as an optical transient in our difference imaging due to the high proper motion and, therefore, unreliable template from the Legacy Survey. The EP trigger is very likely related to this star as initially reported by Levan et al (GCN 39218). We apologize for any confusion caused. View this GCN Circular online at https://gcn.nasa.gov/circulars/39219. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37227] EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39218 SUBJECT: EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star DATE: 25/02/07 23:22:16 GMT FROM: Andrew Levan at Radboud University <a.levan(a)astro.ru.nl> A. J. Levan (Radboud Univ and Warwick Univ.), A. van Hoof (Radboud Univ.), A. Martin-Carrillo (UCD), D.B. Malesani (DAWN/NBI and Radboud Univ.), F.E. Bauer (PUC), P.G. Jonker (Radboud Univ), G. Leloudas (DTU Space) and B. Milvang-Jensen (DAWN/NBI) report for a larger collaboration: We obtained observations of the field of the EP WXT transient (EP250207.660, trigger ID: 01709131361) with the Nordic Optical Telescope. Observations in the r-band began on 2025 Feb 7.8487 UT (4.5 hr after the EP trigger). Comparison to legacy survey observations does not reveal any plausible extragalactic counterparts to the source, consistent with earlier optical observations (Busman et al. GCN 39214), although we do note a bright galaxy at (RA=23:47:37.96, DEC=27:00:59.7) with a Legacy Survey photometric redshift of z = 0.07 +/- 0.01 (Zhou et al. 2021, MNRAS, 501, 3309) within the error box. We also note a bright flare from a high-proper motion M9 dwarf within the error box. The source is currently located at RA(J2000) = 23:47:37.44 DEC(J2000) = 27:02:06.9 It has brightened from an archival magnitude of r = 19.8+/-0.1 (Pan-STARRS) to r = 16.9+/-0.1. However, the source is identified in the Gaia DR3 catalog with a proper motion of 315.33 +/- 0.21 mas/yr. This implies it is a high proper motion, nearby star (parallax 46.76 +/- 0.16 mas) undergoing a high amplitude (+3 mag) flare. It is likely, though not conclusive, that this flare was related to the EP trigger. However, the absence of the flare in observations taken 2.5 hours earlier (Busman et al. GCN 39214) could also mean they are unrelated. We thank the observers, Fabian Mattig and Max Pritzkuleit for their excellent support in obtaining these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39218. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37226] GRB 250207A: Enhanced Swift-XRT position
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39217 SUBJECT: GRB 250207A: Enhanced Swift-XRT position DATE: 25/02/07 22:54:13 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 1772 s of XRT Photon Counting mode data and 3 UVOT images for GRB 250207A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 16.08929, -12.16479 which is equivalent to: RA (J2000): 01h 04m 21.43s Dec (J2000): -12d 09' 53.3" with an uncertainty of 2.2 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39217. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37225] CHIME/FRB source FRB 20250206A detected less than 1 minute after LIGO-Virgo-Kagra (LVK) S250206dm, however the probability of spatial coincidence is order 0.1%
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39216 SUBJECT: CHIME/FRB source FRB 20250206A detected less than 1 minute after LIGO-Virgo-Kagra (LVK) S250206dm, however the probability of spatial coincidence is order 0.1% DATE: 25/02/07 21:26:31 GMT FROM: amanda.cook(a)mcgill.ca The CHIME/FRB Collaboration reports the spatial and temporal proximity of the LIGO-Virgo-Kagra (LVK) compact-object merger candidate S250206dm (GCN 39175; likely either BH-NS or NS-NS) and the fast radio burst (FRB) 20250206A. FRB 20250206A was detected by CHIME/FRB at 2025 Feb 06, 21:26:27.956253 p/m 0.000008 UTC (topocentric at 400 MHz) about 52 seconds (having corrected for dispersive delay) after the LVK event's topocentric time. From recorded voltage data, we obtain a best-fit localization (Michilli et al. 2021) of RA, Decl. (J2000) 338.703, 12.1699 degrees, with 1-sigma uncertainties of 0.42, 0.28 arcminutes, respectively. Using LVK code for estimating the localization region of a given position(https://bit.ly/3CJsyu6) and the most updated Bilby skymap, the FRB position is at the 99.96% credible region of the Bilby localization, i.e., the FRB position is unlikely to be spatially coincident with the LVK localization. Using our raw voltage data, the burst's structure-maximized dispersion measure (DM) is 207.117 +/- 0.003 pc cm^-3. With a Galactic disk DM estimate of 40 pc cm^-3 from NE2001 and assuming a Galactic halo DM of 38 pc cm^-3, (Yamasaki & Totani 2020), the residual extragalactic DM is ~130 pc cm^-3. Using a redshift-DM relationship for the intergalactic medium of z~ DM / 800 pc cm^-3 (Connor et al. 2024), this extragalactic DM corresponds to an upper limit on the luminosity distance (i.e., assuming no DM contribution from a host galaxy) of ~800 Mpc (assuming LambdaCDM parameters from Planck Collaboration 2018), consistent with the LVK-inferred luminosity distance of 348 +/- 114 Mpc (GCN 39184). The FRB was detected with a signal-to-noise ratio of 16.4 in one CHIME/FRB beam, and 15.7 in a second beam. A preliminary baseband fluence averaged over the entire 400-800 MHz CHIME observing band is 36 +/- 4 Jy ms (1-sigma uncertainty). The source does not appear to be a repeat burst from any previously detected CHIME FRB above a signal-to-noise ratio of 8. The source has clear scattering, with a characteristic timescale of ~0.05-0.10 ms at 600 MHz (Fonseca et al. 2023). The Galactic scattering contribution in this direction using NE2001p at 600 MHz is expected to be ~1.5µs. The burst is consistent with being 100% linearly polarized and has a Faraday rotation measure (RM) of -62.07 +/- 0.05 rad m^-2, which was determined using RM-synthesis. The Galactic RM towards the FRB is estimated to be -37 +/- 11 rad m^-2(Hutschenreuter et al. 2020). The probability of chance coincidence (i.e., the likelihood that the LVK and CHIME/FRB events are temporally and spatially proximal by chance only) is difficult to estimate immediately given the large LVK uncertainty regions and CHIME/FRB's uneven exposure and sensitivity on the sky. With the strong caveat that we do not yet know the joint probability of coincidence (analysis ongoing), and that it is likely non-negligible, we are providing the above information because any potential electromagnetic counterpart will be transient. Due to on-site networking issues, this event was not sent out to the community as a VOEvent. Below, we show the multi-beam event waterfall plot, where the panels represent adjacent beams in different rows and columns. We also show an overlay of the FRB position on top of the merger event (from GraceDB, theflat-resolution FITS file created from Bilby.fits.gz,1) Multi-beam waterfall plot: https://storage.googleapis.com/chimefrb-dev.appspot.com/FRB20250206A/multib… Localization plot: https://storage.googleapis.com/chimefrb-dev.appspot.com/FRB20250206A/chime_… View this GCN Circular online at https://gcn.nasa.gov/circulars/39216. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37224] LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39215 SUBJECT: LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar DATE: 25/02/07 20:13:57 GMT FROM: kendall.ackley(a)warwick.ac.uk D. Steeghs, K. Ackley, M.Kennedy, D. O’Neill, Y.Julakanti, S. Belkin, B. P. Gompertz, B. Godson, G. Ramsay, M. Dyer, J. Lyman, K. Ulaczyk, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, L. Nuttall, E. Pallé, D. Pollacco, T. Killestein, and A. Kumar report on behalf of the GOTO collaboration: We report on optical observations and candidate vetting with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022) in response to the LIGO/Virgo/KAGRA candidate NSBH event S250206dm (The LIGO-Virgo-KAGRA Collaboration, GCN 39175). Targeted observations from both GOTO-N and GOTO-S are still ongoing. Here we report on analysis of data obtained beginning at Feb. 6 2025 21:31:11 UT, (+0.09h post trigger) and continuing through to Feb. 7 2025 18:07:58 UT (+20.71h post trigger). These cover 347 sqr. deg. within the 90% localisation contour, equivalent to 35.6% of the total 2D localisation probability. Images were processed immediately after acquisition using the GOTO pipeline with an average 5-sigma depth of 20.1 mag (L band 400-700 nm). Difference imaging was performed using deeper template observations. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real time on any candidates that passed the above checks. We report the detection of a variable transient, GOTO25aeb / AT2025bar (https://www.wis-tns.org/object/2025bar). Although individual detections are not very significant, the transient is detected multiple times and appears to be fading over the course of our observations (spanning 4 hours). It is likely associated with a host galaxy listed in the WISExSuperCOSMOS PhotoZ SVM catalogue as WISExSCOS J112243.56-453426.1 at a (photo) redshift of z ~ 0.17 (D_L = 840 Mpc). Although not necessarily matching the expectations for an EM counterpart, we believe further investigation of this transient is warranted. +--------------------------------------------------------------------------+ | Internal name | IAU name | RA(J2000) | Dec(J2000) | Mag(AB) | +--------------------------------------------------------------------------+ | GOTO25aeb | AT2025bar | 11:22:43.66, -45:34:28.58 | 20.32 +/- 0.15 | +--------------------------------------------------------------------------+ Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and not corrected for Galactic extinction. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/39215. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37223] EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39214 SUBJECT: EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations DATE: 25/02/07 19:58:43 GMT FROM: Malte Busmann at Ludwig-Maximilians-Universität München <m.busmann(a)physik.lmu.de> Malte Busmann (LMU), Daniel Gruen (LMU), Brendan O’Connor (Carnegie Mellon U.) and Antonella Palmese (Carnegie Mellon U.), Julius Gassert (LMU), Lena Schnappinger (LMU), Julian Sommer (LMU), Lei Hu (Carnegie Mellon U.), Franziska Krause (LMU), Elia Enlghard (LMU) and Yajie Zhang (LMU) report: We observed the 90% localization of EP-WXT trigger 01709131361, which lies inside of the 70% localization of S250206dm (LIGO Scientific Collaboration, GCN 39184) with the Three Channel Imager (3KK) at the Fraunhofer-Telescope Wendelstein (FTW) in the r, i and J band simultaneously for 17 x 180 s under suboptimal sky conditions. The observations started at 2025-02-07T17:52:05 UT (2.0 h after the EP-WXT trigger and 20.4 h after the NSBH/BNS merger). We performed difference imaging in the r band with templates from the DESI Legacy Surveys and do not identify any variable optical sources to a 3-sigma depth of r>20.9 AB mag calibrated to the PS1 catalog. Further observations are encouraged. We thank Christoph Ries from the Wendelstein Observatory for obtaining these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39214. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37222] GRB 250129A: ABObservatory SLOAN r’ afterglow detection
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39213 SUBJECT: GRB 250129A: ABObservatory SLOAN r’ afterglow detection DATE: 25/02/07 18:49:05 GMT FROM: A. Brosio at ABObservatory Rosarno <antonino.brosio(a)gmail.com> A. Brosio (ABObservatory), S. Savaglio (University of Calabria), S. Tosi, S. Zappatore & P. Cianfarra (University of Genoa), S. Benatti (INAF Palermo), M. Rainer (INAF Brera), D. Ricci (INAF Padova), A. Di Dato (INAF Capodimonte), S. Masiero & A. Nastasi (GAL Hassin), L. Betti (Osservatorio Polifunzionale del Chianti), D. Liguori (Osservatorio “G. Galilei” Cariati) for the NOCTIS team report: We observed the field of GRB 250129A, which was detected by Swift (Beardmore et al., GCN 39066) with the 30-cm automated telescope at ABObservatory (Rosarno, Italy) using the SLOAN r’ filter. Observations began on 2025 January 30 at 23:41:31 UT, approximately 43 hours after the Swift trigger. The observation consisted of 10 exposures of 240 seconds each, with variable conditions due to passing clouds during the session. The mid-exposure time was 00:07:31 UT, and the final exposure ended at 00:33:31 UT. From photometry, we detect the optical counterpart in our images at the position of the previously reported afterglow (Francile et al., GCN 39065; Schneider et al., GCN 39071; Belkin et al., GCN 39072; Izzo et al., GCN 39073; Izzo & Malesani, GCN 39074; Gosh et al., GCN 39077; Schneider et al., GCN 39078). The measured magnitude is: r’ = 19.32 +/- 0.13 (AB, calibrated against the Pan-STARRS catalogue on SIMBAD) at a mid-time of t - t0 = 00:12:43 after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/39213. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37221] GRB 250207A: REM IR afterglow detection
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39212 SUBJECT: GRB 250207A: REM IR afterglow detection DATE: 25/02/07 18:01:45 GMT FROM: Matteo Ferro at INAF-OAB <matteo.ferro(a)inaf.it> M. Ferro, R. Brivio, P. D’Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of GRB 250207A, detected by Fermi/GBM (Fermi GBM Team, GCN 39181) and Swift/BAT (Ferro et al., GCN 39182) with the REM 60cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, K bands, starting on 2025 February 07 at 01:17:08 UT (i.e. 61 s after the Swift trigger), and lasting for about 2 hours. From preliminary photometry we detect the counterpart in the IR images at the position of the optical afterglow (Angulo et al., GCN 39186; Kuin & Ferro, GCN 39199; Brivio et al., GCN 39202; Jelinek et al., GCN 39209) with the following magnitude: H ~ 13.3 (Vega; calibrated against the 2MASS catalogue) at a mid-time of t - t0 = 26.6 minutes after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/39212. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37220] LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39211 SUBJECT: LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap DATE: 25/02/07 17:53:35 GMT FROM: S. Srivastav at Oxford <shubhamsrivastav(a)gmail.com> K. W. Smith(QUB/Oxford), C. R. Angus, D. R. Young (QUB), S. J. Smartt (QUB/Oxford), S. Srivastav, J. Gillanders (Oxford), M. Nicholl, M. D. Fulton, T. Moore, A. Aamer, M. McCollum, S. Sim, J. Weston, X. Sheng, D. Magill, P. Ramsden (QUB), L. Shingles (GSI/QUB, H. Stevance, F. Stoppa, A. Cooper (Oxford), L. Rhodes (TSI/McGill),L. Denneau, J. Tonry, H. Weiland, R. Siverd (IfA, University of Hawaii), N. Erasmus, W. Koorts (South African Astronomical Observatory), A. Rest (STScI), T.-W. Chen (NCU), C. Stubbs (Harvard), J. Sommer (LMU), B. Schmidt (ANU) We report observations of the Bilby.fits skymap of the NSBH merger event S250206dm (The LIGO-Virgo-Kagra Collaboration, GCN 39175) by the ATLAS survey (Tonry et al., 2018, PASP, 13, 164505). ATLAS is a quadruple 0.5m optical telescope survey system (Hawaii, South Africa, Chile) employing two filters, cyan and orange. In our primary NASA mission for Near-Earth Object discovery, we cover the entire visible night sky every 24 hrs to magnitude depths m ~ 19.5, weather and Moon permitting. We targeted the accessible skymap of S250206dm with a sequence of quads (4 x 110 s images) obtained at each pointing position. Data acquisition began at MJD 60713.098 or 2024-04-22 02:21:07 (UTC), 0.8 hrs after the LVC initial alert and 5.0 hrs after the merger event (which was 60712.89). The images were processed with the ATLAS pipeline, and reference images were subtracted. Transient candidates were identified and run through our standard filtering procedures (Smith et al., 2020, PASP, 132, 1). We covered 389 square degrees of the bilby.fits skymap 90% area, and covered a sky region totalling 35% of the event's full localisation likelihood. Observations lasted between ~5 hrs to 10.5 hrs after the NSBH/BNS merger. We found no plausible new transient sources that had not been previously detected by ATLAS before the merger event or reported to the IAU Transient name server. The 5-sigma depths of our images were typically o < 19.5 +/- 0.6 AB mag. We are reporting all discoveries to the TNS, where they can be tracked, classified, searched, and commented upon. The Asteroid Terrestrial-impact Last Alert System (ATLAS) project is primarily funded to search for Near-Earth asteroids through NASA grants NN12AR55G, 80NSSC18K0284, and 80NSSC18K1575; byproducts of the NEO search include images and catalogs from the survey area. This work was partially funded by Kepler/K2 grant J1944/80NSSC19K0112 and HST GO-15889, and STFC grants ST/T000198/1 and ST/S006109/1. The ATLAS science products have been made possible through the contributions of the University of Hawaii Institute for Astronomy, University of Oxford, the Queen's University Belfast, the Space Telescope Science Institute, the South African Astronomical Observatory, and The Millennium Institute of Astrophysics (MAS), Chile. View this GCN Circular online at https://gcn.nasa.gov/circulars/39211. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37219] LIGO/Virgo/KAGRA S250206dm: Pan-STARRS survey of the skymap for optical transients
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39210 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Pan-STARRS survey of the skymap for optical transients DATE: 25/02/07 17:49:06 GMT FROM: S. Srivastav at Oxford <shubhamsrivastav(a)gmail.com> D. R. Young (QUB), J. H. Gillanders (Oxford), M. E. Huber, K. C. Chambers (IfA, Hawaii), S. J. Smartt, K. W. Smith (Oxford/QUB), S. Srivastav, F. Stoppa (Oxford), C. R. Angus, M. Nicholl, M. D. Fulton, M. McCollum, T. Moore, S. Sim, J. Weston, A. Aamer, X. Sheng (QUB), P. Ramsden (QUB/Birmingham), L. Shingles (GSI/QUB), H. Stevance,(Oxford), L. Rhodes (TSI/McGill), A. S. B. Schultz, T. de Boer, J. Fairlamb, H. Gao, C. C. Lin, T. Lowe, E. Magnier, P. Minguez, G. Paek, A. Smith, R. J. Wainscoat (IfA, Univ. Hawaii), T.-W. Chen (NCU), A. Rest (STScI), C. Stubbs (Harvard): We report observations of the Bilby.fits skymap of the NSBH merger event S250206dm (The LIGO-Virgo-Kagra Collaboration, GCN 39175) with the Pan-STARRS telescope system (Chambers et al., 2016, ArXiv e-prints, 1612.05560). The Pan-STARRS system comprises of two 1.8m telescope units located at the summit of Haleakala on the Hawaiian island of Maui, employing an SDSS-like filter system denoted as grizy, and a broad w-filter, which is a composite of the gri-filters. Tiling sequences of multiple 45-sec images were taken at each pointing position in the r-band with both Pan-STARRS1 and Pan-STARRS2. The images were processed with the Pan-STARRS pipeline. After astrometric and photometric calibration, reference images were subtracted from the target stacked images (Magnier et al., 2020a, ApJS, 251, 3; Magnier et al., 2020b, ApJS, 251, 6; Waters et al., 2020, ApJS, 251, 4). Transient candidates were identified and run through our standard filtering procedures, including rejection of artifacts with machine learning tools and cross-matching with galaxy, stellar and solar-system catalogs (e.g. Smith et al., 2020, PASP, 132, 1; Smartt et al. 2024, MNRAS 528, 2299). We covered 298 square degrees of the bilby.fits skymap 90% area, and covered a sky region totalling 32% of the event's full localisation. Data acquisition began at MJD 60713.23 or 2025-02-07 05:31:12 (UTC), 8.16 hrs after the merger event (which was on MJD 60712.89). The last image was taken at 60713.45. We found a number of plausible new extragalactic transient candidates which we have reported to the TNS. These were mostly found coincident with compact galaxies or ambiguous star/galaxy sources. We have no reason to favour any of them being a transient in a galaxy within the Bilby.fits distance of 348 +/- 114 Mpc and being a good candidate for the counterpart to S250206dm. Thus we do not highlight them here, but they can be found and matched on the TNS. The depths of these 45 sec images were typically (3.5 sigma) r < 20.0 +/- 0.4. Any transients we do find during further processing will be reported to the TNS, where they can be tracked, classified, searched, and commented upon. We encourage further information to be reported on the TNS object pages. We will re-process the 45 second exposures into deeper stacks and re-run them through the detection pipeline. Operation of the Pan-STARRS1 and Pan-STARRS2 telescopes is primarily supported by the National Aeronautics and Space Administration under Grant No. NNX12AR65G and NNX14AM74G, issued through the SSO Near-Earth Object Observations Program. Data processing is enabled by Queen's University Belfast and the University of Oxford, enabled through STFC grants ST/Y001605/1, ST/T000198/1 and ST/X001253/1, the Royal Society, and the Hintze Centre for Astrophysical Surveys. View this GCN Circular online at https://gcn.nasa.gov/circulars/39210. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37218] GRB 250207A: FRAM-Auger optical detection
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39209 SUBJECT: GRB 250207A: FRAM-Auger optical detection DATE: 25/02/07 17:00:05 GMT FROM: Martin Jelinek at Astro.Inst-AVCR,Ondrejov <martin.jelinek(a)asu.cas.cz> Martin Jelinek (ASU CAS Ondrejov, CZ), Martin Masek, Petr Janecek, Sergey Karpov, Jakub Jurysek, Jan Ebr, Ronan Cunniffe, Petr Travnicek, Michael Prouza (Institute of Physics, Prague, CZ) and Jan Strobl (ASU CAS Ondrejov, CZ) report: The 30cm robotic telescope FRAM-Auger in Malargue (Argentina) reacted robotically to the Swift/BAT and Fermi/GBM alert of GRB250207A (Fermi GBM Team, GCN 39181; Ferro et al., GCN 39182), starting with a series of 20s R-band images at 01:16:49 UT, i.e. 42s post trigger. We detect the optical afterglow at the position reported by Brivio et al. (GCN 39202), Kuin & Ferro (GCN 39199), and Angulo et al. (GCN 39186) in our initial frames. The early light curve shows a relatively steep decay with a power-law index alpha ~ 1.6. Extrapolation of this decay rate appears inconsistent with later observations by COLIBRI (Angulo et al., GCN 39186), suggesting a possible transition in the light curve slope beyond ~600s post burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/39209. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37217] LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39208 SUBJECT: LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits DATE: 25/02/07 16:57:22 GMT FROM: Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra(a)roma2.infn.it> LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits Rosa L. Becerra (U Rome), Simone Dichiara (Penn State University), Alan M. Watson (UNAM), William H. Lee (UNAM), Camila Angulo Valdez (UNAM), Eleonora Troja (U Rome), Nat Butler (ASU), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), Océlotl López (UNAM), and Margarita Pereyra (UNAM) report: We observed LIGO/Virgo/KAGRA S250206dm candidate (LVKC, GCN 39175) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir (http://ddoti.astroscu.unam.mx) on the night of 2025-02-07 UTC. We tiled the LVK localization with 5 pointings covering about 127 square degrees and including about 14% of the probability in the most recent Bilby map. We observed from 2025-02-07 02:18 UTC to 2025-02-07 12:22 UTC (from T+4.9 to T+15.0 hours after the event) obtaining a total of 2.65 hours of exposure across the fields in the w filter, with 10-sigma limiting AB magnitudes between w~18-19.5. Comparing our observations to the USNO-B1 and PanSTARRS PS1 DR2 catalogs, we identified the increase of brightness in two sources within the 95% probability region at positions: Source 1: RA, Dec= 09:59:01.76 -16:33:22.6 with w=19.1+/-0.1 Source 2: RA, Dec= 09:59:24.44 -16:29:37.4 with w=19.3+/-0.1 These positions are related to previous catalogued sources in the Legacy Survey DR10 (Dey et al. 2019). Source 1 has a reported magnitude r=21.8 (with a photo-z=0.45) whereas source 2 of r=22 (with a photo-z=0.66). Further observations are planned. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/39208. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37216] GRB 250207B: Tiled Swift observations
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39207 SUBJECT: GRB 250207B: Tiled Swift observations DATE: 25/02/07 16:37:22 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a series of observations, tiled on the sky, of the MAXI GRB 250207B. Automated analysis of the XRT data will be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00131 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. The probability of finding serendipitous sources, unrelated to the MAXI event is high: any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39207. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37215] LIGO/Virgo/KAGRA S250207bg: NED Galaxies in the Localization Volume
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39206 SUBJECT: LIGO/Virgo/KAGRA S250207bg: NED Galaxies in the Localization Volume DATE: 25/02/07 16:10:21 GMT FROM: David Cook at Caltech/IPAC-NED <dcook(a)ipac.caltech.edu> David O. Cook (Caltech/IPAC), Rick Ebert (Caltech/IPAC), George Helou (Caltech/IPAC), Joseph M. Mazzarella (Caltech/IPAC), Marion Schmitz (Caltech/IPAC), and Leo Singer (NASA/GSFC) On behalf of the NASA/IPAC Extragalactic Database (NED) Team. We spatially cross-matched the LVK S250207bg-3-Initial sky localization with the NED Local Volume Sample (NED-LVS; Cook et al. 2023), which is a subset of NED with a redshift or redshift-independent distance less than 1000 Mpc. We find 7591 galaxies within the 90% containment volume, and we list here the top 20 galaxies sorted by the joint probability of the 3D localization and the WISE W1 luminosity (an observable proxy for stellar mass). For the full or top 20 list of galaxies in the 90% volume go either to the NED Gravitational Wave Followup service at https://ned.ipac.caltech.edu/uri/NED::GWF/ or click on the following links: Full List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S250207bg/3 Top 20 List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S250207bg/3/20 The NED-GWF service provides downloadable galaxy lists and visualizations for candidate host galaxies. For each GW alert, these products are automatically generated and made available within minutes to expedite efficient electromagnetic follow-up observations. The NED top 20 list is sorted by the joint probability of the 3D localization and the WISE W1 luminosity, but users can sort on additional pre-computed prioritization metrics (star formation rate, P_3D * P_SFR; and specific star formation rate, P_3D * P_sSFR; etc.) which are available via downloading the entire galaxy list inside the event's probability volume. | objname| ra| dec|objtype| DistMpc|DistMpc_unc| m_NUV| m_NUV_unc| m_Ks| m_Ks_unc| m_W1| m_W1_unc| P_3D|P_3D_LumW1| |-------------------------|--------------|--------------|-------|-----------|-----------|------------|------------|------------|------------|------------|------------|--------|----------| |WISEA J153919.63+190427.7| 234.83187| 19.07453| G| 530.26| null| null| null| 13.627| 0.172| 10.078| 0.006|5.48e-07| 2.24e-09| |WISEA J152319.42+240611.6| 230.83105| 24.10320| G| 663.87| 0.16| null| null| 14.431| 0.157| 10.454| 0.006|3.80e-07| 1.72e-09| |WISEA J154012.34+184306.0| 235.05140| 18.71817| G| 417.30| 0.08| null| null| 13.309| 0.160| 9.114| 0.005|2.45e-07| 1.51e-09| |WISEA J153645.35+185715.6| 234.18906| 18.95426| G| 614.30| 0.14| null| null| 14.462| 0.165| 11.145| 0.006|6.31e-07| 1.29e-09| |WISEA J150631.38+283419.0| 226.63079| 28.57192| G| 515.26| 0.04| null| null| 13.286| 0.172| 10.718| 0.006|5.69e-07| 1.21e-09| |WISEA J155025.85+130154.2| 237.60767| 13.03173| G| 581.25| 0.10| null| null| 13.459| 0.155| 10.806| 0.006|4.18e-07| 1.05e-09| |WISEA J151550.70+275958.5| 228.96137| 27.99951| G| 504.04| 0.05| 20.968| 0.139| 13.749| 0.153| 10.538| 0.006|3.27e-07| 7.89e-10| | [HB89] 1552+085| 238.68574| 8.37263| QSO| 557.07| 0.06| 17.225| 0.024| 12.724| 0.045| 11.383| 0.023|5.56e-07| 7.54e-10| |WISEA J151458.01+273639.7| 228.74172| 27.61105| G| 560.27| 0.21| 22.052| 0.306| 11.568| 0.117| 11.617| 0.007|6.48e-07| 7.15e-10| |WISEA J155856.52+032444.3| 239.73542| 3.41238| G| 408.76| 0.10| null| null| 12.955| 0.169| 10.037| 0.006|2.71e-07| 6.96e-10| |WISEA J153250.52+200718.3| 233.21046| 20.12169| G| 681.89| 0.13| null| null| 13.831| 0.187| 10.888| 0.006|1.99e-07| 6.42e-10| | 3C 327| 240.61406| 1.96560| G| 486.72| 2.15| 20.654| 0.174| 12.897| 0.047| 11.037| 0.006|4.26e-07| 6.11e-10| |WISEA J155639.59+111348.0| 239.16499| 11.22994| G| 486.41| 0.14| null| null| 14.133| 0.119| 9.442| 0.006|9.76e-08| 6.04e-10| |WISEA J154320.19+143045.0| 235.83416| 14.51254| G| 622.09| 0.04| null| null| 13.890| 0.198| 11.215| 0.006|2.64e-07| 5.21e-10| |WISEA J151556.87+264556.0| 228.98694| 26.76548| G| 592.88| null| null| null| 13.560| 0.139| 12.348| 0.011|8.01e-07| 5.06e-10| |WISEA J145244.45+315248.3| 223.18524| 31.88009| G| 537.68| 0.07| null| null| 12.904| 0.040| 11.775| 0.006|5.42e-07| 4.75e-10| |WISEA J150746.48+284911.8| 226.94359| 28.81997| G| 515.60| 0.75| 20.018| 0.182| 12.395| 0.100| 12.063| 0.007|7.53e-07| 4.66e-10| |WISEA J145519.43+321511.0| 223.83099| 32.25305| G| 538.51| 0.21| null| null| 13.017| 0.046| 11.996| 0.008|5.89e-07| 4.23e-10| |WISEA J145331.46+302133.9| 223.38103| 30.35929| G| 566.40| 0.12| 22.065| 0.341| 14.897| 0.264| 9.870| 0.006|7.14e-08| 4.02e-10| |WISEA J154015.93+175229.2| 235.06642| 17.87478| G| 474.23| null| null| null| 12.689| 0.157| 11.861| 0.007|6.29e-07| 3.97e-10| Table 1: Top 20 galaxies in NED-LVS that fall in the 90% probability volume for S250207bg sorted by the joint probability of 3D position and WISE W1 luminosity (P_3D * P_LumW1). Galaxy is the NED preferred name. RA and Dec are the Equatorial coordinates in degrees (J2000). Objtype is the object type of the galaxy candidate. Distance is the distance to the galaxy in Mpc. m_NUV and mErr_NUV are the apparent magnitude and error from GALEX. m_Ks and mErr_Ks are the apparent magnitude and error from 2MASS. m_W1 and mErr_W1 are the apparent magnitude and error from AllWISE. P_3D is the probability that the galaxy is in the volume given the distance of GW event. P_3D_LumW1 is the joint probability within the volume weighted by the WISE1 luminosity of the galaxy (P_3D * P_LumW1). View this GCN Circular online at https://gcn.nasa.gov/circulars/39206. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37214] Konus-Wind detection of GRB 250204B
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39205 SUBJECT: Konus-Wind detection of GRB 250204B DATE: 25/02/07 15:46:33 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The short-duration GRB 250204B (Fermi-GBM detection: Fermi GBM team, GCN 39141; AstroSat CZTI detection: Dasgupta et al., GCN 39142; IPN triangulation: Svinkin et al., GCN 39145; SVOM/GRM observation: Zhang et al., GCN 39163) triggered Konus-Wind at T0=24073.659 s UT (06:41:13.659). The burst light curve shows a single pulse which starts at ~T0-0.1 s and has a total duration of ~1.5 s. The emission is seen up to ~2 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250204_T24073/ As observed by Konus-Wind, the burst had a fluence of 2.99(-0.29,+0.37)x10^-6 erg/cm2, and a 16-ms peak flux, measured from T0+0.008 s, of 7.51(-1.64,+1.74)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+0.256 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.85(-0.17,+0.19) and Ep = 383(-66,+92) keV (chi2 = 16/22 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.1 (chi2 = 16/21 dof). All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/39205. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37213] IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39204 SUBJECT: IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate DATE: 25/02/07 14:01:44 GMT FROM: Gianluca Masi at Virtual Telescope Project <gianluca(a)bellatrixobservatory.org> Gianluca Masi (Virtual Telescope Project) reports: Following up LIGO/Virgo/KAGRA S250206dm (LVKC, GCN 39175) at optical wavelengths, we managed to image the field centered at position RA = 149.16, Decl. =-17.94 and covering the complete 0.43 deg. error region reported by the IceCube Collaboration (GCN 39176), remotely using our 250mm-f/4.5 robotic astrograph installed at our facility in Manciano (GR), Italy. We collected 35 x 120s unfiltered exposures under significant moonlight, with a total integration of 70 minutes, centered on 22:53:35 UTC, 06 Feb. 2025, about 1.5 hours after the event. A CMOS camera based on the Sony IMX455 sensor was used. Comparing the resulting image with the POSS2, blue filter, we did not record any obvious new source, down to mag. 19. View this GCN Circular online at https://gcn.nasa.gov/circulars/39204. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37212] IceCube-250207A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39203 SUBJECT: IceCube-250207A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/02/07 13:48:55 GMT FROM: Giacomo Sommani at Ruhr-Universität Bochum <gsommani(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 2025-02-07 at 02:07:55.27 UT IceCube detected a track-like event with a high probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_BRONZE alert stream. The average astrophysical neutrino purity for bronze alerts is 30%. This alert has an estimated false alarm rate of 1.45 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/140472_78196104.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 2025-02-07 Time: 02:07:55.27 UT RA: 132.93 (+2.05, -1.89 deg 90% PSF containment) J2000 Dec: 20.66 (+1.28, -1.40 deg 90% PSF containment) J2000 Two Fermi 4FGL or 3FHL catalog sources are in the 90% uncertainty region: 4FGL J0854.8+2006 and 4FGL J0856.8+2056, located 0.9 deg and 1.2 deg away from the best-fit position, respectively. We encourage further follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu View this GCN Circular online at https://gcn.nasa.gov/circulars/39203. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37211] GRB 250207A: REM optical afterglow detection
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39202 SUBJECT: GRB 250207A: REM optical afterglow detection DATE: 25/02/07 13:23:26 GMT FROM: Riccardo Brivio at INAF-OAB <riccardo.brivio(a)inaf.it> R. Brivio, M. Ferro, P. D’Avanzo, S. Covino (INAF-OAB), A. Melandri (INAF-OAR), D. B. Malesani (DAWN/NBI and Radboud Univ.), G. Tagliaferri, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of GRB 250207A, detected by Fermi/GBM (Fermi GBM Team, GCN 39181) and Swift/BAT (Ferro et al., GCN 39182) with the REM 60cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, K bands, starting on 2025 February 07 at 01:17:08 UT (i.e. 61 s after the Swift trigger), and lasting for about 2 hours. From preliminary photometry we detect the counterpart in the optical images at the position of the optical afterglow (Angulo et al., GCN 39186; Kuin & Ferro, GCN 39199) with the following magnitude: r = 12.7 +/- 0.1 (AB; calibrated against the Pan-STARRS catalogue) at a mid-time of t - t0 = 66 s after the trigger. The analysis of the NIR data is ongoing. View this GCN Circular online at https://gcn.nasa.gov/circulars/39202. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37210] LIGO/Virgo/KAGRA S250207bg: Identification of a GW compact binary merger candidate
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39201 SUBJECT: LIGO/Virgo/KAGRA S250207bg: Identification of a GW compact binary merger candidate DATE: 25/02/07 12:27:19 GMT FROM: Luise Kranzhoff at Maastricht University <luise.kranzhoff(a)ligo.org> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S250207bg during real-time processing of data from LIGO Livingston Observatory (L1) and Virgo Observatory (V1) at 2025-02-07 11:56:45.258 UTC (GPS time: 1422964623.258). The candidate was found by the GstLAL [1] and SPIIR [2] analysis pipelines. S250207bg is an event of interest because its false alarm rate, as estimated by the online analysis, is 4.9e-36 Hz, or about one in 1e28 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250207bg After parameter estimation by RapidPE-RIFT [3], the classification of the GW signal, in order of descending probability, is BBH (>99%), NSBH (<1%), BNS (<1%), or Terrestrial (<1%). Assuming the candidate is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [4] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [4] Both HasNS and HasRemnant consider the support of several neutron star equations of state. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,0, an initial localization generated by BAYESTAR [5], distributed via GCN notice about 29 seconds after the candidate event time. * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [5], distributed via GCN notice about 5 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,1. For the bayestar.multiorder.fits,1 sky map, the 90% credible region is 110 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 546 +/- 98 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. (2023) arXiv:2305.05625 [2] Chu et al. PRD 105, 024023 (2022) doi:10.1103/PhysRevD.105.024023 [3] Rose et al. (2022) arXiv:2201.05263 and Pankow et al. PRD 92, 023002 (2015) doi:10.1103/PhysRevD.92.023002 [4] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [5] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/39201. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37209] LIGO/Virgo/KAGRA S250206dm:GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39200 SUBJECT: LIGO/Virgo/KAGRA S250206dm:GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume DATE: 25/02/07 11:45:22 GMT FROM: Maria Lisa Brozzetti at Università degli Studi di Perugia <marialisa.brozzetti(a)ligo.org> M. L. Brozzetti (UniPG/INFN), G. Dálya (L2IT/EotvosU), G. Greco (INFN), M. Bawaj (UniPG/INFN), T. Matcovich (UniPG/INFN), S. Cutini (INFN) , R. De Pietri (UniPR/INFN), Marica Branchesi (GSSI), Elahe Khalouei(IPM) On behalf of the GLADEnet Team. We analyzed the completeness of the GLADE+ [1] catalog within the 90% credible localization volume of the S250206dm event from the Update-6 alert from the GCN Circular 39175. The completeness value is 5.6e-1 in the B-band using the last released skymap : Bilby.multiorder.fits,1 , which means that the catalogue contains 56% of the total light in the B-band expected from galaxies in the localization volume. A total of 107,012 galaxies are identified within the 90% gravitational volume. The complete list of galaxies can be downloaded from the GLADEnet webpage [2] : https://virgo.pg.infn.it/gladenet/catalogs/ GLADEnet allows for the interactive visualization of the 90% localization area and its intersection with regions of high extinction as defined in GLADE+. Furthermore, the first 1000 galaxies can be explored interactively, enabling users to filter galaxies based on their 3D probability density or their absolute B magnitude. The ligo.skymap cross-match method [3,4] is used to obtain the list of galaxies. References: [1]GLADE+: An Extended Galaxy Catalogue for Multimessenger Searches with Advanced Gravitational-wave Detectors G. Dálya et al. MNRAS, 514,1, pp.1403-1411, 2022 [2] GLADEnet: A progressive web app for multi-messenger cosmology and electromagnetic follow-ups of gravitational-wave sources M. L. Brozzetti, G. Dálya, G. Greco, M. Bawaj, T. Matcovich, M. Branchesi, T. Boch, M. Baumann, S. Cutini, R. De Pietri et al. (4 more) A&A, 684, A44 (2024) [3] Singer, L. P., Chen, H.-Y., Holz, D. E., et al. 2016, Astropys. J. Lett., 829, L15. doi:10.3847/2041-8205/829/1/L15 [4] Singer, L. P., Chen, H.-Y., Holz, D. E., et al. 2016, Astropys. J. Supp., 226, 10. doi:10.3847/0067-0049/226/1/10 View this GCN Circular online at https://gcn.nasa.gov/circulars/39200. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37208] GRB 250207A: Swift/UVOT Detection
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39199 SUBJECT: GRB 250207A: Swift/UVOT Detection DATE: 25/02/07 10:42:24 GMT FROM: Paul Kuin at MSSL <npkuin(a)gmail.com> Paul Kuin (MSSL/UCL) and M. Ferro (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250207A 113 s after the BAT trigger (Ferro et al., GCN Circ. 39182). The source was also reported by Angulo et al. GCN Circ. 39186. The preliminary UVOT position is: RA (J2000) = 01:04:21.39 = 16.08912 (deg.) Dec (J2000) = -12:09:52.5 = -12.16459 (deg.) with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence). Preliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 113 263 147 15.00 +/- 0.02 v 655 674 19 16.89 +/- 0.20 b 581 600 19 16.56 +/- 0.09 u 326 575 246 15.65 +/- 0.03 uvm2 679 699 19 > 17.3 (3 sigma UL) uvw2 630 650 19 > 17.6 (3 sigma UL) The lack of detection in the UVM2 band may indicate a redshift greater than 1.3. The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.027 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/39199. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37207] LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39198 SUBJECT: LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate DATE: 25/02/07 10:37:39 GMT FROM: Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra(a)roma2.infn.it> Rosa L. Becerra (U Rome), Alan M. Watson (UNAM), William H. Lee (UNAM), Camila Angulo Valdez (UNAM), Eleonora Troja (U Rome), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), Océlotl López (UNAM), and Margarita Pereyra (UNAM) report: As part of the optical follow-up campaign for LIGO/Virgo/KAGRA S250206dm (LVKC, GCN 39175), the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir (http://ddoti.astroscu.unam.mx) observed the position RA, Dec = 149.16, -17.94, reported by the IceCube Collaboration as a track-like event spatially and temporally coincident with the gravitational-wave candidate S250206dm (IceCube Collaboration, GCN 39176). DDOTI covered the complete error region reported for this candidate (angular uncertainty of 0.43 deg, IceCube Collaboration, GCN 39176) beginning at 2025-02-07 07:07 UTC (T+9.7 hours after the event). A total exposure of 18 minutes was obtained in the w filter, reaching a 10-sigma limiting magnitude of w = 19.4. Comparing our observations with the USNO-B1 and PanSTARRS PS1 DR2 catalogs, we detect no uncatalogued sources within the observed field to our 10-sigma limit. Observations related to S250206dm are ongoing. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/39198. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37206] LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39197 SUBJECT: LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm DATE: 25/02/07 09:41:10 GMT FROM: kendall.ackley(a)warwick.ac.uk K. Ackley, S. Belkin, D. Steeghs, B. P. Gompertz, Y. Julakanti, M. Kennedy, B. Godson, G. Ramsay, D. O'Neill, M. Dyer, F. Jiménez-Ibarra, J. Lyman, K. Ulaczyk, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, L. Nuttall, E. Pallé, D. Pollacco, T. Killestein, and A. Kumar report on behalf of the GOTO collaboration: We are in the process of observing the LIGO/Virgo gravitational wave event S250206dm (GCN 39175; GCN 39178) with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022). Targeted observations with GOTO-N were performed beginning at Feb. 6 2025 21:31:11 UT, (+0.09h post trigger) and continued through to Feb. 7 2025 04:07:48 UT (+6.71h post trigger). GOTO covered the field of AT 2025azn (Hosseinzadeh et al, GCN 39191) at 22:25:45UT on 2025-02-06 (~1 hour after trigger, and 6 hours prior to the reported detection by Hosseinzadeh et al, GCN 39191) as part of the follow-up campaign for S250206dm. The observation consisted of a 4x90s exposure set in the GOTO L-band (400-700 nm). Analysis at the location of the potential optical transient does not show evidence of the source to a 3-sigma limiting AB magnitude of L > 19.8. Our previous observation of the field of AT 2025azm (Hosseinzadeh et al, GCN 39191) occurred on 2025-01-27. We do not see any evidence of excess flux down to a 3-sigma limiting AB magnitude of L > 19.0. Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations of the same pointings. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real time on any candidates that passed the above checks. Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction. Further observations are scheduled during the coming nights. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/39197. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37205] LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39196 SUBJECT: LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations DATE: 25/02/07 09:16:25 GMT FROM: Igor Andreoni at JSI/UMD/NASA <igor.andreoni(a)gmail.com> James Freeburn (Swinburne/OzGrav), Jonathan Carney (UNC), Igor Andreoni (UNC), David Cook (IPAC): We followed up the gravitational wave trigger S250206dm (GCN 39175, GCN 39178, GCN 39184) using the Goodman High Throughput Spectrograph mounted on the SOAR telescope in imaging mode via Target of Opportunity observations (PI Andreoni). We observed 33 galaxies in the highest probability region (Cook at al. GCN 39174, GCN 39177, GCN 39185) using the list produced by crossmatching the sky localization with the NED Local Volume Sample (NED-LVS; Cook et al. 2023). Specifically, we considered the galaxy list obtained using the LVK S250206dm-6-Update sky localization (Cook at al. GCN 39185), focusing on the Southern high probability area. Observations were acquired from 2025-02-07 06:18 UT until 08:48 UT. Each galaxy was observed with 60s exposures in g+i filters. A list of the observed galaxies is presented in the table below. The completed pointings were uploaded to TreasureMap: https://treasuremap.space/alerts?graceids=S250206dm Data analysis is ongoing. object_name coordinates WISEA J161708.84-674024.7 16:17:08.87 -67:40:22.49 WISEA J162759.57-693615.7 16:27:59.57 -69:36:15.71 WISEA J154439.56-665529.0 15:44:39.56 -66:55:29.08 WISEA J155633.83-693531.5 15:56:33.83 -69:35:31.55 WISEA J160843.41-685023.4 16:08:43.41 -68:50:23.44 WISEA J154441.36-665502.6 15:44:41.37 -66:55:02.61 WISEA J160915.94-690504.9 16:09:15.95 -69:05:04.94 WISEA J161332.77-674621.1 16:13:32.78 -67:46:21.13 WISEA J165614.58-695645.9 16:56:14.58 -69:56:46.00 WISEA J163330.53-670950.7 16:33:30.54 -67:09:50.72 WISEA J154538.24-703944.1 15:45:38.25 -70:39:44.12 WISEA J153057.77-694546.5 15:30:57.77 -69:45:46.58 WISEA J160838.27-700230.8 16:08:38.27 -70:02:30.85 WISEA J111435.41-485220.0 11:14:35.41 -48:52:20.02 WISEA J161213.79-710729.1 16:12:13.79 -71:07:29.14 ESO 069-IG 006N 16:38:11.94 -68:26:08.84 WISEA J165744.21-680430.9 16:57:44.21 -68:04:30.93 WISEA J165527.54-702337.9 16:55:27.54 -70:23:37.91 WISEA J110452.75-455440.5 11:04:52.76 -45:54:40.57 WISEA J163202.83-693109.0 16:32:02.84 -69:31:09.01 WISEA J164922.44-690054.7 16:49:22.44 -69:00:54.76 WISEA J161735.32-701416.0 16:17:35.32 -70:14:16.00 WISEA J163253.56-702946.2 16:32:53.57 -70:29:46.22 WISEA J164915.17-690004.8 16:49:15.17 -69:00:04.87 ESO 069- G 003 16:24:32.07 -68:49:12.91 WISEA J161946.23-690837.2 16:19:46.23 -69:08:37.26 WISEA J153854.81-680647.5 15:38:54.81 -68:06:47.55 WISEA J151821.27-691417.9 15:18:21.28 -69:14:17.93 WISEA J155653.84-695749.1 15:56:53.88 -69:57:49.18 WISEA J165438.30-670413.8 16:54:38.30 -67:04:13.82 WISEA J163224.97-700239.7 16:32:24.97 -70:02:39.78 WISEA J110509.11-450337.3 11:05:09.11 -45:03:37.38 WISEA J161822.73-683741.1 16:18:22.73 -68:37:41.20 We thank the NOIRLab and SOAR staff for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/39196. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37204] LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39195 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn DATE: 25/02/07 08:43:10 GMT FROM: James Gillanders at University of Oxford <jhgillanders.astro(a)gmail.com> M. E. Huber (IfA, Hawaii), J. H. Gillanders (Oxford), K. C. Chambers (IfA, Hawaii) S. J. Smartt, K. W. Smith (Oxford/QUB), F. Stoppa, S. Srivastav (Oxford), D. R. Young, M. Nicholl, M. D. Fulton, M. McCollum, T. Moore, S. Sim, J. Weston, A. Aamer, C. R. Angus, X. Sheng (QUB), P. Ramsden (QUB/Birmingham), L. Shingles (GSI/QUB), H. Stevance, A. Andersson (Oxford), L. Rhodes (TSI/McGill), A. S. B. Schultz, T. de Boer, J. Fairlamb, H. Gao, C. C. Lin, T. Lowe, E. Magnier, P. Minguez, G. Paek, A. Smith, R. J. Wainscoat (IfA, Univ. Hawaii), T.-W. Chen (NCU), A. Rest (STScI), and C. Stubbs (Harvard) We are currently observing the skymap of the LIGO/Virgo/KAGRA GW event S250206dm (LVK Collaboration, GCN 39175) with the twin Pan-STARRS telescope system (Chambers et al., 2016, arXiv:1612.05560) and will report detections of candidate optical transients to the TNS, and through GCNs. We also carried out targeted observations of AT2025azm and AT2025azn, two optical counterpart candidates reported by Hosseinzadeh et al., (GCN 39191). The Pan-STARRS system comprises two 1.8-m telescope units located at the summit of Haleakala on the Hawaiian island of Maui, employing an SDSS-like filter system denoted as grizy, and a broad w-filter, which is a composite of the gri-filters. The last Pan-STARRS observations of these fields was 69 days ago for AT2025azm, and 87 days ago for AT2025azn. There are no reliable historical detections at these positions in our database (typical limits of i<21, w<22). There are a few excess flux detections, but these are likely subtraction residuals in the cores of the host galaxies. Our targeted observations consisted of a sequence of 60 second exposures in griz filters for AT2025azm, and grizy filters for AT2025azn. Our observations of AT2025azm commenced at MJD 60713.27593 (2025-02-07 06:37:20.352 UTC), 9.20 hours after the merger event (LVK Collaboration, GCN 39175). Our observations of AT2025azn commenced at MJD 60713.28086 (2025-02-07 06:44:26.477 UTC), 9.31 hours after the merger event. The resultant images were processed with the Pan-STARRS pipeline. After astrometric and photometric calibration, reference images were subtracted from the target stacked images (Magnier et al., 2020a, ApJS, 251, 3; Magnier et al., 2020b, ApJS, 251, 6; Waters et al., 2020, ApJS, 251, 4). We do not detect either transient in any filter. The data were collected in poor seeing conditions (2-3 arcsec), and the 3.5 sigma limits for our 60 second exposures are: AT2025azm: g<20.1, r<20.6, i<19.9, z<19.9 AT2025azn: z<20.2, r<20.7, i<20.3, g<20.7, y<20.4 As we detect no excess flux in any of the difference images, to limits similar to (or deeper than) those reported by Hosseinzadeh et al., (GCN 39191), it suggests to us that they are not real transients. Operation of the Pan-STARRS1 and Pan-STARRS2 telescopes is primarily supported by the National Aeronautics and Space Administration under Grant No. NNX12AR65G and NNX14AM74G, issued through the SSO Near-Earth Object Observations Program. Data processing is enabled by Queen's University Belfast and the University of Oxford, enabled through STFC grants ST/Y001605/1, ST/T000198/1 and ST/X001253/1, the Royal Society, and the Hintze Centre for Astrophysical Surveys. View this GCN Circular online at https://gcn.nasa.gov/circulars/39195. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37203] LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39194 SUBJECT: LIGO/Virgo/KAGRA S250206dm: No counterpart candidates in INTEGRAL SPI-ACS prompt observation DATE: 25/02/07 08:42:39 GMT FROM: Volodymyr Savchenko at UNIGE, EPFL <volodymyr.savchenko(a)epfl.ch> V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland) J. Rodi (IAPS-Roma, Italy) A. Coleiro (APC, France) S. Mereghetti (INAF IASF-Milano, Italy) on behalf of the INTEGRAL multi-messenger collaboration: https://www.astro.unige.ch/cdci/integral-multimessenger-collaboration Using INTEGRAL/SPI-ACS realtime data (following [1]) we have performed a search for a prompt gamma-ray counterpart of S250206dm (GCN 39175). At the time of the event (2025-02-06 21:25:30 UTC, hereafter T0), INTEGRAL was operating in nominal mode. The peak of the event localization probability was at an angle of 66 deg with respect to the spacecraft pointing axis. This orientation implies strongly suppressed (14% of optimal) response of ISGRI, strongly suppressed (33% of optimal) response of IBIS/Veto, and near-optimal (79% of optimal) response of SPI-ACS. The background within +/-300 seconds around the event was rather stable (excess variance 1.2). We have performed a search for any impulsive events in INTEGRAL SPI-ACS (as described in [2]), IBIS, and IBIS/Veto data. We do not detect any significant counterparts and estimate a 3-sigma upper limit on the 75-2000 keV fluence of 2e-07 erg/cm^2 (within the 50% probability containment region of the source localization) for a burst lasting less than 1 s with a characteristic short GRB spectrum (an exponentially cut off power law with alpha=-0.5 and Ep=600 keV) occurring at any time in the interval within 300 s around T0. For a typical long GRB spectrum (Band function with alpha=-1, beta=-2.5, and Ep=300 keV), the derived peak flux upper limit is ~1.6e-07 (4.2e-08) erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range. We report for completeness and in order of FAP, all excesses identified in the search region. We find: 1 tentatively associated excess: |T-T0 | scale | S/N | flux ( x 1e-06 erg/cm2/s) | FAP | |---|---|---|---|---| |-1.41 | 0.45 | 4.6 | 0.808 +/- 0.229 +/- 0.713 | 0.00626| 5 likely background excesses: |T-T0 | scale | S/N | flux ( x 1e-06 erg/cm2/s) | FAP | |---|---|---|---|---| |37.7 | 0.05 | 11 | 6.29 +/- 0.761 +/- 5.55 | 0.0769 | |1.01 | 0.1 | 3 | 1.17 +/- 0.49 +/- 1.03 | 0.23 | |-41.4 | 1.95 | 3.1 | 0.259 +/- 0.109 +/- 0.229 | 0.363 | |-152 | 1.4 | 3.7 | 0.352 +/- 0.129 +/- 0.31 | 0.489 | |7.46 | 0.1 | 3.4 | 1.3 +/- 0.492 +/- 1.15 | 0.699 | Note that FAP estimates (especially at timescales above 2s) may be possibly further affected by enhanced non-stationary local background noise. This list excludes any excesses for which FAP is close to unity. We note that no independent IBAS alerts happened in the viscinity. SPI-ACS data can be retrieved in MMODA with [this](https://www.astro.unige.ch/mmoda/?DEC=-29.74516667&RA=265.97845833&T1=2025-02-06T21%3A24%3A30.000&T2=2025-02-06T21%3A26%3A30.000&T_format=isot&data_level=ordinary&instrument=spi_acs&product_type=spi_acs_lc&query_status=new&query_type=Real&selected_catalog=&src_name=1E+1740.7-2942&time_bin=0.05&time_bin_format=sec) link. INTEGRAL follow-up alert was distributed to SCIMMA through HERMES. All results quoted are preliminary. This circular is an official product of the INTEGRAL Multi-Messenger team. Note that we send GCNs Circulars only when one of the following conditions is met: merger contains at least one neutron star, a singificant counterpart is reported. [1] Savchenko et al. 2017, A&A 603, A46 [2] Savchenko et al. 2012, A&A 541A, 122S View this GCN Circular online at https://gcn.nasa.gov/circulars/39194. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37202] LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39193 SUBJECT: LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate DATE: 25/02/07 08:33:03 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Alan M. Watson (UNAM), Jean-Grégoire Ducoin (CPPM), Sarah Antier (OCA), Stéphane Basa (UAR Pytheas), Jean-Luc Atteia (IRAP), William H. Lee (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Rosa L. Becerra (Università degli Studi di Roma Tor Vergata), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), and Benjamin Schneider (LAM) report: We imaged the field of the AT 2025azn candidate reported by the SAGUARO team (GCN Circ. 39191) as a possible optical counterpart of the GW transient S250206dm (GCN Circ. 29175, GCN Circ. 39184) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We observed from 2025-02-07 06:39 to 07:27 UTC (9.24 to 10.04 hours after the GW transient), with a midpoint of 9.64 hours after the event, and obtained 840 seconds of exposure in the g filter and 840 seconds of exposure in the r filter in good weather conditions, albeit at airmass 2.1 to 2.8. The data were reduced and stacked using custom software and then calibrated against the PS1 catalog and analysed using STDPipe (Karpov 2021). The FWHM in both stacks is about 2.0 arcsec. At the position of AT 2025azn, and after template subtraction using Pan-STARRS DR2 reference images, we do not detect any source at a 3 sigma limiting magnitudes of: g > 21.9 r > 21.7 Our magnitude limits are not corrected for Galactic extinction. These limits are significantly fainter than the detection reported by the SAGUARO team from observation taken about 2 hours earlier. We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/39193. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37201] GRB 250129A: Continued AbAO and Mondy optical observations
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39192 SUBJECT: GRB 250129A: Continued AbAO and Mondy optical observations DATE: 25/02/07 06:03:52 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP), R. Ya. Inasaridze (AbAO) report on behalf of the IKI-GRB-FuN collaboration: We continued optical observations of the field of GRB 250129A (Beardmore et. al, GCN 39066; Lipunov et. al, GCN 39070; Schneider et. al, GCN 39071; Belkin et. al, GCN 39072; Izzo et. al, GCN 39073; Izzo et. al, GCN 39074; Ghosh et. al, GCN 39077; Schneider et. al, GCN 39078; Brivio et. al, GCN 39079; Goad et. al, GCN 39082; Siegel, GCN 39085; Osborne et. al, GCN 39089; Zheng et. al, GCN 39090; Schlekat et. al, GCN 39091; Antier et. al, GCN 39096; Odeh et. al, GCN 39097; Ferro et. al, GCN 39098; Malesani et. al, GCN 39100; Romanov, GCN 39101; Zheng et. al, GCN 39102; Watson et. al, GCN 39104; Watson et. al, GCN 39105; Akl et. al, GCN 39106; Moskvitin et. al, GCN 39107; Calapai et. al, GCN 39109; Schlekat et. al, GCN 39110; Gompertz et. al, GCN 39114; Ror et. al, GCN 39115; Frederiks et. al, GCN 39116; Wu et. al, GCN 39124; Paek et. al, GCN 39129; Moskvitin et. al, GCN 39130; Bochenek et. al, GCN 39131; Watson et. al, GCN 39136; Pankov et. al, GCN 39139; Pérez-Fournon et. al, GCN 39140; Markwardt et. al, GCN 39147) in the R filter with the 1.5-meter AZT-33IK telescope of the Sayan Solar Observatory (Mondy) and the 0.7-meter AS-32 telescope of the Abastumani Observatory (AbAO). The observations began at Mondy on 2025-02-02 at 19:46:28 UT, i.e. ~4.65 days since trigger. Using optimal image subtraction against PS1 template with apex_subtract pipeline, we detect the optical counterpart in the stacked image from Mondy, while obtaining an upper limit at AbAO. The preliminary photometry is as follows: Date UT start t-T0 Exp. Filter OT Err. UL(3sigma) Telescope (mid, days) (s) 2025-02-02 19:46:28 4.65439 41*120 R 21.63 0.18 23.1 AZT-33IK 2025-02-02 22:26:20 4.76923 93*60 R n/d n/d 21.8 AS-32 The photometry is based on nearby stars of the USNO-B1.0 catalog (R2 magnitudes) and has not been corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39192. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37200] LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39191 SUBJECT: LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts DATE: 25/02/07 05:55:46 GMT FROM: Griffin Hosseinzadeh at UC San Diego <ghosseinzadeh(a)ucsd.edu> G. Hosseinzadeh, M. Shrestha, D. J. Sand, K. A. Bostroem, J. E. Andrews, B. Subrayan, J. Pearson, J. C. Rastinejad, M. J. Lundquist, C. D. Kilpatrick, W. Fong, K. Alexander, P. N. Daly, N. Franz, K. Paterson, S. D. Wyatt, J. Hogan, A. Gibbs, C. Fuls report on behalf of the SAGUARO collaboration: We initiated observations of the localization region of the possible NSBH merger S250206dm (LVK Collaboration, GCN 39175) using the 5 square degree imager mounted on the 1.5m Catalina Sky Survey (CSS) telescope on Mt. Lemmon, AZ (Christensen et al. 2018). We observed 180 sq. deg. within the 95% confidence localization region of the Bilby map (LVK Collaboration, GCN 39178) starting at 2025-02-07 02:10:58 UTC (~5 hours after the merger). We subtract these images relative to deep reference images of each field and measure photometry calibrated to the Gaia DR2 catalog (Gaia Collaboration 2018). We performed a real-time analysis of the observations. Following the methods outlined in Rastinejad et al. (2022), we crossmatch each candidate with the TNS (Gal-Yam 2021) and point source catalogs (Tachibana and Miller 2018; Jayasinghe et al. 2019; Flesch et al. 2021; Gaia Collaboration 2023), search public ZTF photometry (Bellm et al. 2019), and run ATLAS forced photometry (Shingles et al. 2021) at the position of the candidate to rule out transients unrelated to the GW event. We determine a most likely host galaxy using the probability of chance coincidence method (Bloom et al. 2002) and search for an associated spectroscopic or photometric redshift in public galaxy catalogs (White et al. 2011; Alam et al. 2015; Beck et al. 2016, 2021; Dalya et al. 2021; DESI Collaboration et al. 2023). We discovered two possible transients in our images and reported them to the Transient Name Server. AT 2025azm (00:08:07.507 +32:33:56.70; 20.1 +/- 0.3 mag) is 1” from the center of a galaxy with a photometric redshift of z=0.07, corresponding to a distance of around 300 Mpc, in the Legacy Survey (Dey et al. 2019), SDSS (Alam et al. 2015), and Pan-STARRS1 (Chambers et al. 2016) catalogs. AT 2025azn (02:39:17.418 +49:34:21.10; 20.0 +/- 0.3 mag) is 0.5” from the center of a galaxy with a distance of 377 Mpc (z=0.08) in the GLADE catalog (Dalya et al. 2018). Both are consistent with the gravitational-wave distance within the error range. We encourage follow-up photometry and spectroscopy of both these candidates. Our analysis is ongoing. SAGUARO stands for Searches After Gravitational-waves Using ARizona's Observatories (Lundquist et al. 2019; Paterson et al. 2021; Hosseinzadeh et al. 2024). It is a partnership between the University of Arizona, Northwestern University, and the University of California, San Diego. View this GCN Circular online at https://gcn.nasa.gov/circulars/39191. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37199] GRB 250207B: MAXI/GSC detection
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39190 SUBJECT: GRB 250207B: MAXI/GSC detection DATE: 25/02/07 04:26:02 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> K. Tatano, M. Nakajima, H. Negoro (Nihon U.), M. Serino, Y. Kawakubo (AGU), Y. Kudo, H. Shibui, K. Takagi, H. Takahashi, H. Nishio (Nihon U.), T. Mihara, S. Yamada, S. Wang, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita, H. Hiramatsu, H. Nishikawa, Y. Kondo, S. Sasao, A. Yoshida (AGU), Y. Tsuboi, H. Sugai, N. Nagashima (Chuo U.), M. Shidatsu, Y. Niida (Ehime U.), I. Takahashi, M. Niwano, N. Higuchi, Y. Yatsu (Tokyo Tech), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, Y. Okada, K. Fujiwara (Kyoto U.), M. Yamauchi, Y. Otsuki, T. Hasegawa, M. Nishio (Miyazaki U.), K. Yamaoka (Nagoya U.),　 M. Sugizaki (Kanazawa U.),　W. Iwakiri (Chiba U.), T. Kawamuro (Osaka U.), report on behalf of the MAXI team: The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 02:23:36 UT on February 07, 2025. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (54.362 deg, 5.325 deg) = (03 37 26, +05 19 30) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.27 deg and 0.24 deg, respectively. The roll angle of long axis from the north direction is 124.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 218 +- 41 mCrab (4.0-10.0keV, 1 sigma error). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (R.A., Dec) = (53.893, 6.160) deg = (03 35 34, +06 09 36) (J2000) (R.A., Dec) = (53.522, 5.823) deg = (03 34 05, +05 49 22) (J2000) (R.A., Dec) = (54.372, 4.895) deg = (03 37 29, +04 53 41) (J2000) (R.A., Dec) = (54.743, 5.230) deg = (03 38 58, +05 13 48) (J2000) There was no significant excess flux in the previous transit at 00:50 UT and in the next transit at 03:56 UT with an upper limit of 20 mCrab for each. View this GCN Circular online at https://gcn.nasa.gov/circulars/39190. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37198] The EP-WXT trigger 01709131347 is likely a flaring star
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39189 SUBJECT: The EP-WXT trigger 01709131347 is likely a flaring star DATE: 25/02/07 03:52:30 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Q. C. Shui (IHEP, CAS), D. Y. Li, M. J. Liu, M. H. Zhang, W. D. Zhang (NAOC, CAS) report on behalf of the Einstein Probe team: The EP-WXT trigger (ID: 01709131347) on 2025-02-06 23:24:12 (UTC) is likely a stellar flare associated with a spectroscopic binary G 118-68. The estimated flux of the flare is around 1.0 x 10^-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 2.5 x 10^31 erg/s. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with onboard X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/39189. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37197] The EP-WXT trigger 01709131332 is likely a flaring star
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39188 SUBJECT: The EP-WXT trigger 01709131332 is likely a flaring star DATE: 25/02/07 03:50:53 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> M. H. Zhang, M. J. Liu, D. Y. Li (NAOC, CAS), Q. C. Shui (IHEP, CAS), W. D. Zhang (NAOC, CAS) report on behalf of the Einstein Probe team: The EP-WXT trigger (ID: 01709131332) on 2025-02-06 20:25:17 (UTC) is likely a stellar flare associated with a high proper motion star UPM J1217-3644. The estimated flux of the flare is around 1.2 x 10^-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 1.2 x 10^31 erg/s. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with onboard X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/39188. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37196] The EP-WXT trigger 01709131290 is likely a flaring star
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39187 SUBJECT: The EP-WXT trigger 01709131290 is likely a flaring star DATE: 25/02/07 03:34:16 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> M. J. Liu, D. Y. Li, M. H. Zhang, H. N. Yang (NAOC, CAS), Z. Y. Liu (USTC), Q. C. Shui (IHEP, CAS), W. D. Zhang, W. M. Yuan (NAOC, CAS) report on behalf of the Einstein Probe team: The EP-WXT trigger (ID: 01709131290) on 2025-02-06 09:52:08 (UTC) is likely a stellar flare associated with a star UCAC4 185-006985. The estimated flux of the flare is around 1.9 x 10^-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 5.5 x 10^31 erg/s. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with onboard X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/39187. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37195] GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39186 SUBJECT: GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection DATE: 25/02/07 03:20:08 GMT FROM: Camila Angulo Valdez at UNAM <camiangulo(a)astro.unam.mx> Camila Angulo (UNAM), Alan M. Watson (UNAM), Noémie Globus (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Jean-Luc Atteia (IRAP), Rosa L. Becerra (Università degli Studi di Roma Tor Vergata), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), and Benjamin Schneider (LAM) report: We imaged the field of GRB 250207A detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 39181) and Swift/BAT (Ferro et al., GCN Circ.39182) with the DDRAGO wide-field camera on the COLIBRÍ (SVOM/F-GFT) telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We observed from 2025-02-07 02:34 to 02:55 UTC (78 to 99 min after the burst), with a midpoint of 88.5 minutes after the event, and obtained 960 seconds of exposure in the r filter in good weather conditions. The data were reduced and stacked using custom software and then calibrated against the PS1 catalog and analysed using STDPipe (Karpov 2021). At the position of the afterglow detected by XRT and UVOT (Ferro et al., GCN Circ. 39182), we detect a source with r = 18.90 +/- 0.01 and confirm fading relative to the UVOT observation. Our magnitude is not corrected for Galactic extinction. Further observations are planned. We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/39186. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37194] LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39185 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume DATE: 25/02/07 03:18:00 GMT FROM: David Cook at Caltech/IPAC-NED <dcook(a)ipac.caltech.edu> David O. Cook (Caltech/IPAC), Rick Ebert (Caltech/IPAC), George Helou (Caltech/IPAC), Joseph M. Mazzarella (Caltech/IPAC), Marion Schmitz (Caltech/IPAC), and Leo Singer (NASA/GSFC) On behalf of the NASA/IPAC Extragalactic Database (NED) Team. We spatially cross-matched the LVK S250206dm-6-Update sky localization with the NED Local Volume Sample (NED-LVS; Cook et al. 2023), which is a subset of NED with a redshift or redshift-independent distance less than 1000 Mpc. We find 31227 galaxies within the 90% containment volume, and we list here the top 20 galaxies sorted by the joint probability of the 3D localization and the WISE W1 luminosity (an observable proxy for stellar mass). For the full or top 20 list of galaxies in the 90% volume go either to the NED Gravitational Wave Followup service at https://ned.ipac.caltech.edu/uri/NED::GWF/ or click on the following links: Full List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S250206dm/6 Top 20 List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S250206dm/6/20 The NED-GWF service provides downloadable galaxy lists and visualizations for candidate host galaxies. For each GW alert, these products are automatically generated and made available within minutes to expedite efficient electromagnetic follow-up observations. The NED top 20 list is sorted by the joint probability of the 3D localization and the WISE W1 luminosity, but users can sort on additional pre-computed prioritization metrics (star formation rate, P_3D * P_SFR; and specific star formation rate, P_3D * P_sSFR; etc.) which are available via downloading the entire galaxy list inside the event's probability volume. | objname| ra| dec|objtype| DistMpc|DistMpc_unc| m_NUV| m_NUV_unc| m_Ks| m_Ks_unc| m_W1| m_W1_unc| P_3D|P_3D_LumW1| |-------------------------|--------------|--------------|-------|-----------|-----------|------------|------------|------------|------------|------------|------------|--------|----------| |WISEA J022843.33+542030.5| 37.18021| 54.34178| G| 408.50| null| null| null| 13.098| 0.150| 9.250| 0.006|5.79e-07| 6.59e-10| |WISEA J022348.88+533854.6| 35.95371| 53.64847| G| 361.18| null| null| null| 12.653| 0.121| 10.626| 0.007|8.66e-07| 2.14e-10| |WISEA J161708.84-674024.7| 244.28700| -67.67294| G| 314.35| null| null| null| 12.878| 0.112| 9.322| 0.006|2.82e-07| 1.72e-10| |WISEA J022200.27+503737.1| 35.50117| 50.62697| G| 288.27| null| null| null| 12.566| 0.105| 9.223| 0.006|2.54e-07| 1.52e-10| |WISEA J024516.51+542758.5| 41.31871| 54.46631| G| 365.18| null| null| null| 12.190| 0.129| 10.967| 0.007|7.65e-07| 1.50e-10| | MCG -01-57-002| 335.01662| -3.45381| G| 254.69| 0.65| null| null| null| null| 9.016| 0.006|2.74e-07| 1.45e-10| |WISEA J025225.08+545415.7| 43.10437| 54.90433| G| 333.19| null| null| null| 12.932| 0.105| 10.581| 0.006|5.48e-07| 1.36e-10| |WISEA J023404.21+543420.9| 38.51758| 54.57247| G| 387.94| 0.60| null| null| 11.605| 0.091| 11.228| 0.010|6.76e-07| 1.14e-10| |WISEA J022610.54+530728.2| 36.54379| 53.12453| G| 369.10| null| null| null| 13.505| 0.153| 11.533| 0.008|9.77e-07| 1.10e-10| |WISEA J023155.31+513044.0| 37.98038| 51.51228| G| 322.72| null| null| null| 13.525| 0.153| 10.101| 0.006|3.26e-07| 1.06e-10| |WISEA J024025.00+541511.8| 40.10413| 54.25331| G| 377.15| null| null| null| 13.153| 0.114| 11.550| 0.010|8.57e-07| 1.02e-10| |WISEA J162759.57-693615.7| 246.99817| -69.60428| G| 281.76| 0.65| null| null| 12.713| 0.125| 10.256| 0.006|4.57e-07| 9.55e-11| |WISEA J021556.19+534832.3| 33.98408| 53.80906| G| 289.71| null| null| null| 12.281| 0.088| 10.334| 0.006|4.55e-07| 9.46e-11| |WISEA J154439.56-665529.0| 236.16450| -66.92469| G| 344.93| null| null| null| 12.631| 0.201| 8.871| 0.006|8.13e-08| 9.16e-11| |WISEA J023620.33+544551.7| 39.08458| 54.76433| G| 260.69| 0.40| null| null| 11.288| 0.099| 10.411| 0.006|5.59e-07| 9.04e-11| |WISEA J025232.69+543416.1| 43.13625| 54.57122| G| 251.14| null| null| null| 14.027| 0.191| 10.414| 0.007|5.55e-07| 8.88e-11| |WISEA J021942.98+525320.0| 34.92904| 52.88886| G| 471.43| null| null| null| 12.998| 0.153| 11.105| 0.012|3.29e-07| 8.85e-11| |WISEA J155633.83-693531.5| 239.14079| -69.59225| G| 320.59| null| null| null| 13.038| 0.134| 10.118| 0.007|2.65e-07| 8.10e-11| |WISEA J222605.71-063926.9| 336.52379| -6.65744| G| 305.80| null| 19.372| 0.067| 13.615| 0.206| 9.569| 0.006|1.76e-07| 8.08e-11| | 3C 445| 335.95638| -2.10357| G| 250.91| 0.79| null| null| null| null| 9.765| 0.006|2.98e-07| 7.70e-11| Table 1: Top 20 galaxies in NED-LVS that fall in the 90% probability volume for S250206dm sorted by the joint probability of 3D position and WISE W1 luminosity (P_3D * P_LumW1). Galaxy is the NED preferred name. RA and Dec are the Equatorial coordinates in degrees (J2000). Objtype is the object type of the galaxy candidate. Distance is the distance to the galaxy in Mpc. m_NUV and mErr_NUV are the apparent magnitude and error from GALEX. m_Ks and mErr_Ks are the apparent magnitude and error from 2MASS. m_W1 and mErr_W1 are the apparent magnitude and error from AllWISE. P_3D is the probability that the galaxy is in the volume given the distance of GW event. P_3D_LumW1 is the joint probability within the volume weighted by the WISE1 luminosity of the galaxy (P_3D * P_LumW1). View this GCN Circular online at https://gcn.nasa.gov/circulars/39185. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37193] LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39184 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification DATE: 25/02/07 02:51:46 GMT FROM: Will Farr <will.farr(a)stonybrook.edu> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1) and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S250206dm (GCN Circular 39175). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,1, distributed via GCN Notice, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S250206dm Based on posterior support from parameter estimation [1], under the assumption that the candidate S250206dm is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is >99%. [2] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is 15%. [2] Both HasNS and HasRemnant consider the support of several neutron star equations of state. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is 59%. For the Bilby.multiorder.fits,1 sky map, the 90% credible region is 910 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 348 +/- 114 Mpc (a posteriori mean +/- standard deviation). At the time of the candidate, the Virgo detector was being brought online and was not in observing mode. However, it was determined that the Virgo detector was sufficiently sensitive to inform our estimate of the sky localization. Investigations are ongoing to understand how the operational state of Virgo at the time of the event impacts this analysis. The estimated sky localization may change based on these studies, but this skymap represents our best understanding of the event at this time. For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. (2023) arXiv:2307.13380 [2] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe View this GCN Circular online at https://gcn.nasa.gov/circulars/39184. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37192] LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39183 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations DATE: 25/02/07 02:04:13 GMT FROM: oindabimukherjee(a)gmail.com O. Mukherjee (USRA) and R. Hamburg (USRA) report on behalf of the Fermi-GBM Team: For S250206dm (GCN 39175; GCN 39178) and using the updated Bilby skymap, Fermi-GBM was observing 35.7% of the localization probability at event time. There was no Fermi-GBM onboard trigger around the event time of the LIGO/Virgo/KAGRA (LVK) detection of GW trigger S250206dm. An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM also identified no counterpart candidates. The GBM targeted search, the most sensitive, coherent search for GRB-like signals, was run from +/-30 s around merger time, and also identified no counterpart candidates. Part of the LVK localization region is behind the Earth for Fermi, located at an RA=24.7, Dec=-4.2 with a radius of 67.9 degrees. We therefore set upper limits on impulsive gamma-ray emission for the GW localization region visible to Fermi at merger time. Using the representative soft, normal, and hard GRB-like templates described in arXiv:1612.02395, we set the following 3 sigma flux upper limits over 10-1000 keV, weighted by GW localization probability (in units of 10^-7 erg/s/cm^2): Timescale Soft Normal Hard ------------------------------------ 0.128 s: 1.5 2.4 5.1 1.024 s: 0.44 0.72 1.3 8.192 s: 0.08 0.17 0.31 Assuming the median luminosity distance of 358.7 Mpc from the GW detection, we estimate the following intrinsic luminosity upper limits over the 1 keV-10 MeV energy range (in units of 10^50 erg/s): Timescale Soft Normal Hard ------------------------------------ 0.128s: 0.71 1.02 2.95 1.024s: 0.09 0.14 0.47 8.192s: 0.02 0.02 0.04 View this GCN Circular online at https://gcn.nasa.gov/circulars/39183. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37191] GRB 250207A: Swift detection of a burst with optical counterpart
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39182 SUBJECT: GRB 250207A: Swift detection of a burst with optical counterpart DATE: 25/02/07 01:34:53 GMT FROM: Jamie Kennea at Penn State <jak51(a)psu.edu> M. Ferro (INAF-OAB), R. Gupta (NASA GSFC), J. A. Kennea (PSU), K. L. Page (U Leicester) and B. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels Swift Observatory Team: At 01:16:07 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250207A (trigger=1287821). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 16.115, -12.159 which is RA(J2000) = 01h 04m 28s Dec(J2000) = -12d 09' 30" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 30 sec. The peak count rate was ~3847 counts/sec (15-350 keV), at ~6 sec after the trigger. The XRT began observing the field at 01:17:53.2 UT, 105.9 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 16.0892, -12.1633 which is equivalent to: RA(J2000) = 01h 04m 21.41s Dec(J2000) = -12d 09' 47.9" with an uncertainty of 5.9 arcseconds (radius, 90% containment). This location is 92 arcseconds from the BAT onboard position, within the BAT error circle. Despite the onboard localisation, no X-ray source was detected in 85 s of promptly-downlinked data, suggesting that the initial centroid may equally have been a cosmic ray. This position should therefore be treated with caution. The initial flux in the 2.5 s image was 7.54e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 113 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 01:04:21.41 = 16.08919 DEC(J2000) = -12:09:52.5 = -12.16458 with a 90%-confidence error radius of about 0.74 arc sec. This position is 4.6 arc sec. from the center of the XRT error circle. The estimated magnitude is 15.04 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.027. Burst Advocate for this burst is M. Ferro (matteo.ferro AT inaf.it). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/39182. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37190] GRB 250207A: Fermi GBM Final Real-time Localization
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39181 SUBJECT: GRB 250207A: Fermi GBM Final Real-time Localization DATE: 25/02/07 01:26:45 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 01:16:03 UT on 7 Feb 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250207A (trigger 760583768.15163 / 250207053). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 11.8, Dec = -13.3 (J2000 degrees, equivalent to J2000 00h 47m, -13d 18'), with a statistical uncertainty of 3.2 degrees. The angle from the Fermi LAT boresight is 47.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250207053/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250207053/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250207053/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39181. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37189] Fermi-LAT Gamma-ray Observations of IceCube-250203A
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39180 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-250203A DATE: 25/02/07 00:54:06 GMT FROM: Simone Garrappa at Weizmann Institute of Science <simone.garrappa(a)weizmann.ac.il> S. Garrappa (Weizmann Institute of Science), C. Bartolini (INFN Bari), L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg) and P. M. Veres (Ruhr University Bochum) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC250203A neutrino event (GCN 39132) with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 2025-02-03 03:59:29.20 UTC (T0) with J2000 position RA = 253.30 (+0.49, -0.49) deg, Decl. = -1.31 (+0.48, -0.44) deg 90% PSF containment. No cataloged gamma-ray sources are found within the 90% IC250203A localization error (The Fourth Fermi-LAT catalog, 4FGL-DR4, The Fermi-LAT collaboration 2023, arXiv:2307.12546). We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) within the IC250203A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IceCube best-fit position, the >100 MeV flux upper limit (95% confidence) is <1.1e-9 ph cm^-2 s^-1 for ~16-years (2008-08-04 / T0), <7.6e-09(<1.0e-7) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. For this source, the Fermi-LAT contact person is S. Garrappa (simone.garrappa at weizmann.ac.il). The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/39180. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37188] LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39179 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations DATE: 25/02/07 00:26:56 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> N. Kawai, T. Mihara, (RIKEN), H. Negoro, M. Nakajima, K. Takagi (Nihon U.), S. Sugita, M. Serino, Y. Kawakubo, H. Hiramatsu, H. Nishikawa, Y. Kondo (AGU) report on behalf of the MAXI team: We examined MAXI/GSC all-sky X-ray images (2-20 keV) after compact binary merger candidate S250206dm at 2025-02-06 21:25:30.439 UTC (GCN #39175, 39178). At the trigger time of S250206dm, the high-voltage of MAXI/GSC was off, and it was turned on at T0+786 sec (+13.1 min). The first one-orbit (92 min) scan observation with GSC after the event covered 52% of the 90% credible region of the Bilby skymap from 21:38:56 to 22:48:26 UTC (T0+806 to T0+4976 sec). No significant new source was found in the region in the one-orbit scan observation. A typical 1-sigma averaged upper limit obtained in one scan observation is 20 mCrab at 2-20 keV. If you require information about X-ray flux by MAXI/GSC at specific coordinates, please contact the submitter of this circular by email. View this GCN Circular online at https://gcn.nasa.gov/circulars/39179. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37187] LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39178 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification DATE: 25/02/07 00:05:38 GMT FROM: Divyajyoti NLN <divyajyoti.nln(a)ligo.org> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) data around the time of the compact binary merger (CBC) candidate S250206dm (GCN Circular 39175). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S250206dm Based on posterior support from parameter estimation [1], under the assumption that the candidate S250206dm is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is >99%. [2] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is 17%. [2] Both HasNS and HasRemnant consider the support of several neutron star equations of state. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is 52%. For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 1626 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 359 +/- 125 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. (2023) arXiv:2307.13380 [2] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe View this GCN Circular online at https://gcn.nasa.gov/circulars/39178. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37186] LIGO/Virgo/KAGRA S250206dm: Updated NED Galaxies in the Localization Volume
by GCN Circulars 07 Feb '25

07 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39177 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Updated NED Galaxies in the Localization Volume DATE: 25/02/07 00:00:46 GMT FROM: David Cook at Caltech/IPAC-NED <dcook(a)ipac.caltech.edu> David O. Cook (Caltech/IPAC), Rick Ebert (Caltech/IPAC), George Helou (Caltech/IPAC), Joseph M. Mazzarella (Caltech/IPAC), Marion Schmitz (Caltech/IPAC), and Leo Singer (NASA/GSFC) On behalf of the NASA/IPAC Extragalactic Database (NED) Team. We spatially cross-matched the LVK S250206dm-4-Update sky localization with the NED Local Volume Sample (NED-LVS; Cook et al. 2023), which is a subset of NED with a redshift or redshift-independent distance less than 1000 Mpc. We find 54256 galaxies within the 90% containment volume, and we list here the top 20 galaxies sorted by the joint probability of the 3D localization and the WISE W1 luminosity (an observable proxy for stellar mass). For the full or top 20 list of galaxies in the 90% volume go either to the NED Gravitational Wave Followup service at https://ned.ipac.caltech.edu/uri/NED::GWF/ or click on the following links: Full List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S250206dm/4 Top 20 List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S250206dm/4/20 The NED-GWF service provides downloadable galaxy lists and visualizations for candidate host galaxies. For each GW alert, these products are automatically generated and made available within minutes to expedite efficient electromagnetic follow-up observations. The NED top 20 list is sorted by the joint probability of the 3D localization and the WISE W1 luminosity, but users can sort on additional pre-computed prioritization metrics (star formation rate, P_3D * P_SFR; and specific star formation rate, P_3D * P_sSFR; etc.) which are available via downloading the entire galaxy list inside the event's probability volume. | objname| ra| dec|objtype| DistMpc|DistMpc_unc| m_NUV| m_NUV_unc| m_Ks| m_Ks_unc| m_W1| m_W1_unc| P_3D|P_3D_LumW1| |-------------------------|--------------|--------------|-------|-----------|-----------|------------|------------|------------|------------|------------|------------|--------|----------| | MCG -01-57-002| 335.01662| -3.45381| G| 254.69| 0.65| null| null| null| null| 9.016| 0.006|2.10e-07| 6.30e-11| |WISEA J035607.76+573251.4| 59.03242| 57.54769| G| 410.56| null| null| null| 12.680| 0.123| 8.610| 0.006|3.52e-08| 4.62e-11| |WISEA J022843.33+542030.5| 37.18021| 54.34178| G| 408.50| null| null| null| 13.098| 0.150| 9.250| 0.006|6.32e-08| 4.06e-11| |WISEA J220219.95-113906.3| 330.58317| -11.65222| G| 302.43| null| 20.465| 0.149| 13.630| 0.229| 9.627| 0.006|1.51e-07| 3.61e-11| |WISEA J003646.96+403047.2| 9.19542| 40.51314| G| 463.14| 0.24| 20.697| 0.096| 13.700| 0.155| 9.758| 0.006|6.85e-08| 3.42e-11| |WISEA J235047.55+293551.6| 357.69817| 29.59772| G| 490.87| null| null| null| 12.766| 0.116| 9.929| 0.006|6.47e-08| 3.10e-11| |WISEA J000430.95+335502.6| 1.12883| 33.91731| G| 495.19| null| null| null| 13.425| 0.157| 9.831| 0.006|5.74e-08| 3.06e-11| | 3C 445| 335.95638| -2.10357| G| 250.91| 0.79| null| null| null| null| 9.765| 0.006|2.10e-07| 3.06e-11| |WISEA J022200.27+503737.1| 35.50117| 50.62697| G| 288.27| null| null| null| 12.566| 0.105| 9.223| 0.006|8.41e-08| 2.84e-11| |WISEA J000012.55+315927.2| 0.05233| 31.99092| G| 358.08| null| null| null| 13.272| 0.144| 10.098| 0.006|1.26e-07| 2.73e-11| |WISEA J001948.39+350244.8| 4.95154| 35.04578| G| 307.16| null| 19.804| 0.052| 12.767| 0.111| 9.747| 0.006|1.20e-07| 2.67e-11| |WISEA J000233.49+320338.6| 0.63946| 32.06067| G| 326.97| null| null| null| 13.158| 0.136| 9.964| 0.006|1.28e-07| 2.64e-11| |WISEA J215400.16-151308.9| 328.50075| -15.21903| G| 293.47| 1.21| 19.446| 0.077| 14.041| 0.269| 9.703| 0.006|1.23e-07| 2.58e-11| |WISEA J231640.26+192021.7| 349.16775| 19.33933| G| 508.89| null| null| null| 13.170| 0.139| 9.560| 0.006|3.49e-08| 2.53e-11| |WISEA J091707.96+104002.7| 139.28314| 10.66755| G| 245.27| 0.07| null| null| null| null| 9.503| 0.006|1.35e-07| 2.38e-11| |WISEA J222725.55-010758.9| 336.85677| -1.13309| G| 270.87| 0.06| 19.196| 0.022| null| null| 10.431| 0.006|2.27e-07| 2.08e-11| | UGC 12801| 357.61283| 26.14639| G| 293.42| 0.39| null| null| 10.743| 0.077| 9.562| 0.006|8.65e-08| 2.07e-11| |WISEA J002726.11+330928.2| 6.85896| 33.15783| G| 389.91| null| null| null| 13.572| 0.166| 8.826| 0.005|2.46e-08| 2.05e-11| |WISEA J045737.46+531524.9| 74.40617| 53.25697| G| 281.45| null| null| null| 12.147| 0.102| 9.130| 0.006|5.54e-08| 2.03e-11| |WISEA J015907.34+514849.0| 29.78058| 51.81344| G| 317.14| null| null| null| 13.443| 0.166| 9.943| 0.006|9.91e-08| 2.01e-11| Table 1: Top 20 galaxies in NED-LVS that fall in the 90% probability volume for S250206dm sorted by the joint probability of 3D position and WISE W1 luminosity (P_3D * P_LumW1). Galaxy is the NED preferred name. RA and Dec are the Equatorial coordinates in degrees (J2000). Objtype is the object type of the galaxy candidate. Distance is the distance to the galaxy in Mpc. m_NUV and mErr_NUV are the apparent magnitude and error from GALEX. m_Ks and mErr_Ks are the apparent magnitude and error from 2MASS. m_W1 and mErr_W1 are the apparent magnitude and error from AllWISE. P_3D is the probability that the galaxy is in the volume given the distance of GW event. P_3D_LumW1 is the joint probability within the volume weighted by the WISE1 luminosity of the galaxy (P_3D * P_LumW1). View this GCN Circular online at https://gcn.nasa.gov/circulars/39177. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37185] LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches
by GCN Circulars 06 Feb '25

06 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39176 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches DATE: 25/02/06 22:36:52 GMT FROM: Jessie Thwaites at IceCube/U Wisc-Madison <thwaites(a)wisc.edu> IceCube Collaboration (http://icecube.wisc.edu/) reports: Searches for track-like muon neutrino events detected by IceCube consistent with the sky localization of gravitational-wave candidate S250206dm in a time range of 1000 seconds centered on the alert event time (2025-02-06 21:17:10.436 UTC to 2025-02-06 21:33:50.436 UTC) have been performed [1,2]. During this time period IceCube was collecting good quality data. Two hypothesis tests were conducted. The first search is a maximum likelihood analysis which searches for a generic point-like neutrino source coincident with the given GW skymap. The second uses a Bayesian approach to quantify the joint GW + neutrino event significance, which assumes a binary merger scenario and accounts for known astrophysical priors, such as GW source distance, in the significance estimate [3]. Two track-like events are found in spatial and temporal coincidence with the gravitational-wave candidate S250206dm calculated from the map circulated in the 3-Initial notice. This represents an overall p-value of 0.008 from the generic transient search and an overall p-value of 0.011 for the Bayesian search. These p-values measure the consistency of the observed track-like events with the known atmospheric backgrounds for this single map (not trials corrected for multiple GW events). The most probable multi-messenger source direction based on the neutrinos and GW skymap is RA 149.15 degrees, Dec -17.90 degrees. The two reported p-values can differ due to the estimated distance of the GW candidate. The distance is used as a prior in the Bayesian binary merger search, while it is not taken into account in the generic transient point-like source search. The false alarm rate of these coincidences can be obtained by multiplying the p-values with their corresponding GW trigger rates. Further details are available at https://gcn.nasa.gov/missions/icecube. Properties of the coincident events are shown below. We encourage follow-up observations of both locations. dt(s) RA(deg) Dec(deg) Angular uncertainty(deg) p-value(generic transient) p-value(Bayesian) ----------------------------------------------------------------------------------------------------- 289.12 149.16 -17.94 0.43 0.008 0.032 -109.85 354.59 32.79 1.42 0.222 0.018 where: dt = Time of track event minus time of GW trigger (sec) Angular uncertainty = Angular uncertainty of track event: the radius of a circle representing 90% CL containment by area. p-value = the p-value for this specific track event from each search. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu. [1] M. G. Aartsen et al 2020 ApJL 898 L10 [2] Abbasi et al. Astrophys.J. 944 (2023) 1, 80 [3] I. Bartos et al. 2019 Phys. Rev. D 100, 083017 View this GCN Circular online at https://gcn.nasa.gov/circulars/39176. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37184] LIGO/Virgo/KAGRA S250206dm: Identification of a GW compact binary merger candidate
by GCN Circulars 06 Feb '25

06 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39175 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Identification of a GW compact binary merger candidate DATE: 25/02/06 22:00:22 GMT FROM: youru.lee(a)g.ncu.edu.tw The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S250206dm during real-time processing of data from LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) at 2025-02-06 21:25:30.439 UTC (GPS time: 1422912348.439). The candidate was found by the GstLAL [1], MBTA [2], and PyCBC Live [3] analysis pipelines. S250206dm is an event of interest because its false alarm rate, as estimated by the online analysis, is 1.3e-09 Hz, or about one in 25 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250206dm The classification of the GW signal, in order of descending probability, is NSBH (55%), BNS (37%), Terrestrial (8%), or BBH (<1%). Assuming the candidate is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is >99%. [4] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is 30%. [4] Both HasNS and HasRemnant consider the support of several neutron star equations of state. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is 62%. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,0, an initial localization generated by BAYESTAR [5], distributed via GCN notice about 31 seconds after the candidate event time. * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [5], distributed via GCN notice about 5 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,1. For the bayestar.multiorder.fits,1 sky map, the 90% credible region is 1544 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 409 +/- 139 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. (2023) arXiv:2305.05625 [2] Aubin et al. CQG 38, 095004 (2021) doi:10.1088/1361-6382/abe913 [3] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [4] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [5] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/39175. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37183] LIGO/Virgo/KAGRA S250206dm: NED Galaxies in the Localization Volume
by GCN Circulars 06 Feb '25

06 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39174 SUBJECT: LIGO/Virgo/KAGRA S250206dm: NED Galaxies in the Localization Volume DATE: 25/02/06 21:55:45 GMT FROM: David Cook at Caltech/IPAC-NED <dcook(a)ipac.caltech.edu> David O. Cook (Caltech/IPAC), Rick Ebert (Caltech/IPAC), George Helou (Caltech/IPAC), Joseph M. Mazzarella (Caltech/IPAC), Marion Schmitz (Caltech/IPAC), and Leo Singer (NASA/GSFC) On behalf of the NASA/IPAC Extragalactic Database (NED) Team. We spatially cross-matched the LVK S250206dm-3-Initial sky localization with the NED Local Volume Sample (NED-LVS; Cook et al. 2023), which is a subset of NED with a redshift or redshift-independent distance less than 1000 Mpc. We find 52020 galaxies within the 90% containment volume, and we list here the top 20 galaxies sorted by the joint probability of the 3D localization and the WISE W1 luminosity (an observable proxy for stellar mass). For the full or top 20 list of galaxies in the 90% volume go either to the NED Gravitational Wave Followup service at https://ned.ipac.caltech.edu/uri/NED::GWF/ or click on the following links: Full List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S250206dm/3 Top 20 List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S250206dm/3/20 The NED-GWF service provides downloadable galaxy lists and visualizations for candidate host galaxies. For each GW alert, these products are automatically generated and made available within minutes to expedite efficient electromagnetic follow-up observations. The NED top 20 list is sorted by the joint probability of the 3D localization and the WISE W1 luminosity, but users can sort on additional pre-computed prioritization metrics (star formation rate, P_3D * P_SFR; and specific star formation rate, P_3D * P_sSFR; etc.) which are available via downloading the entire galaxy list inside the event's probability volume. | objname| ra| dec|objtype| DistMpc|DistMpc_unc| m_NUV| m_NUV_unc| m_Ks| m_Ks_unc| m_W1| m_W1_unc| P_3D|P_3D_LumW1| |-------------------------|--------------|--------------|-------|-----------|-----------|------------|------------|------------|------------|------------|------------|--------|----------| |WISEA J035607.76+573251.4| 59.03242| 57.54769| G| 410.56| null| null| null| 12.680| 0.123| 8.610| 0.006|5.19e-08| 6.11e-11| |WISEA J022843.33+542030.5| 37.18021| 54.34178| G| 408.50| null| null| null| 13.098| 0.150| 9.250| 0.006|9.06e-08| 5.22e-11| | MCG -01-57-002| 335.01662| -3.45381| G| 254.69| 0.65| null| null| null| null| 9.016| 0.006|1.75e-07| 4.70e-11| |WISEA J220219.95-113906.3| 330.58317| -11.65222| G| 302.43| null| 20.465| 0.149| 13.630| 0.229| 9.627| 0.006|1.87e-07| 4.02e-11| |WISEA J231640.26+192021.7| 349.16775| 19.33933| G| 508.89| null| null| null| 13.170| 0.139| 9.560| 0.006|5.70e-08| 3.72e-11| |WISEA J003646.96+403047.2| 9.19542| 40.51314| G| 463.14| 0.24| 20.697| 0.096| 13.700| 0.155| 9.758| 0.006|7.37e-08| 3.31e-11| |WISEA J215400.16-151308.9| 328.50075| -15.21903| G| 293.47| 1.21| 19.446| 0.077| 14.041| 0.269| 9.703| 0.006|1.64e-07| 3.10e-11| |WISEA J000430.95+335502.6| 1.12883| 33.91731| G| 495.19| null| null| null| 13.425| 0.157| 9.831| 0.006|6.26e-08| 3.00e-11| |WISEA J091707.96+104002.7| 139.28314| 10.66755| G| 245.27| 0.07| null| null| null| null| 9.503| 0.006|1.80e-07| 2.84e-11| |WISEA J235047.55+293551.6| 357.69817| 29.59772| G| 490.87| null| null| null| 12.766| 0.116| 9.929| 0.006|6.50e-08| 2.79e-11| |WISEA J090906.84+134338.0| 137.27863| 13.72719| G| 246.54| 0.03| 19.109| 0.048| null| null| 9.635| 0.006|1.91e-07| 2.71e-11| |WISEA J023348.85+553955.6| 38.45375| 55.66506| G| 554.10| null| null| null| 13.376| 0.194| 8.753| 0.005|1.44e-08| 2.47e-11| |WISEA J213220.13-230609.5| 323.08396| -23.10275| G| 152.92| 0.65| 20.276| 0.135| 12.046| 0.022| 9.287| 0.006|3.19e-07| 2.39e-11| | 3C 445| 335.95638| -2.10357| G| 250.91| 0.79| null| null| null| null| 9.765| 0.006|1.61e-07| 2.11e-11| | 2MFGC 07267| 140.43463| 7.28237| G| 239.49| null| null| null| 12.026| 0.087| 9.803| 0.006|1.77e-07| 2.03e-11| |WISEA J103204.15-302813.3| 158.01758| -30.47050| G| 526.75| 0.65| null| null| 12.749| 0.140| 9.417| 0.005|2.55e-08| 2.03e-11| |WISEA J111625.30-474423.2| 169.10533| -47.74000| G| 541.68| null| null| null| 13.677| 0.237| 9.277| 0.006|2.05e-08| 1.97e-11| |WISEA J004546.18+394932.4| 11.44258| 39.82569| G| 605.36| 0.24| 20.160| 0.035| 13.845| 0.185| 9.381| 0.005|1.82e-08| 1.97e-11| |WISEA J153057.77-694546.5| 232.74150| -69.76292| G| 373.52| null| null| null| 13.645| 0.271| 9.044| 0.006|3.31e-08| 1.87e-11| |WISEA J034501.09+571427.1| 56.25442| 57.24086| G| 395.20| null| null| null| 12.710| 0.124| 10.274| 0.007|7.34e-08| 1.75e-11| Table 1: Top 20 galaxies in NED-LVS that fall in the 90% probability volume for S250206dm sorted by the joint probability of 3D position and WISE W1 luminosity (P_3D * P_LumW1). Galaxy is the NED preferred name. RA and Dec are the Equatorial coordinates in degrees (J2000). Objtype is the object type of the galaxy candidate. Distance is the distance to the galaxy in Mpc. m_NUV and mErr_NUV are the apparent magnitude and error from GALEX. m_Ks and mErr_Ks are the apparent magnitude and error from 2MASS. m_W1 and mErr_W1 are the apparent magnitude and error from AllWISE. P_3D is the probability that the galaxy is in the volume given the distance of GW event. P_3D_LumW1 is the joint probability within the volume weighted by the WISE1 luminosity of the galaxy (P_3D * P_LumW1). View this GCN Circular online at https://gcn.nasa.gov/circulars/39174. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37182] GRB 250206A: BALROG localization (Fermi Trigger 760564296 / GRB 250206827)
by GCN Circulars 06 Feb '25

06 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39173 SUBJECT: GRB 250206A: BALROG localization (Fermi Trigger 760564296 / GRB 250206827) DATE: 25/02/06 20:26:24 GMT FROM: Jochen Greiner at MPE <jcgrog(a)mpe.mpg.de> T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report: The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 760564296 at 19:51:31 on 06 Feb. 2025 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60). The best-fit position is: RA(2000.0) = 222.4 deg Decl.(2000.0) = -63.8 deg The 1 sigma statistical error radius is 2.6 deg. We estimate an additional systematic error of 1 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB250206827/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB250206827/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB250206827/json View this GCN Circular online at https://gcn.nasa.gov/circulars/39173. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37181] GRB 250206A: Fermi GBM Final Real-time Localization
by GCN Circulars 06 Feb '25

06 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39172 SUBJECT: GRB 250206A: Fermi GBM Final Real-time Localization DATE: 25/02/06 20:02:04 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 19:51:31 UT on 6 Feb 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250206A (trigger 760564296.928588 / 250206827). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 222.1, Dec = -65.0 (J2000 degrees, equivalent to J2000 14h 48m, -65d 00'), with a statistical uncertainty of 1.7 degrees. The angle from the Fermi LAT boresight is 33.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250206827/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250206827/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250206827/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39172. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37180] GRB 250205A: Fermi GBM Observation
by GCN Circulars 06 Feb '25

06 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39171 SUBJECT: GRB 250205A: Fermi GBM Observation DATE: 25/02/06 15:42:40 GMT FROM: oindabimukherjee(a)gmail.com O. Mukherjee (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 21:25:33.72 UT on 05 February 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250205A (trigger 760483538/250205893). which was also detected by SVOM (Saccardi et al. 2025, GCN 39154), Swift XRT (Kennea et al. 2025, GCN 39161), and OSIRIS+/GTC with z = 3.55 (Postigo et al. 2025, GCN 39160). The Fermi GBM on-ground location is consistent with the SVOM position. The angle from the Fermi LAT boresight is 59 degrees. The GBM light curve consists of multiple peaks with a duration (T90) of about 105 s (50-300 keV). The time-averaged spectrum from T0-63 to T0+75 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.2 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 83 +/- 3 keV. A Band function with Epeak = 80 +/- 5 keV, alpha = -0.2 +/- 0.16 and beta = -3.11 +/- 0.39 fits the spectrum equally well. The event fluence (10-1000 keV) in this time interval is (6.6 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.38 s in the 10-1000 keV band is 2 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/39171. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37179] GRB 250205A: REM NIR upper limit
by GCN Circulars 06 Feb '25

06 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39170 SUBJECT: GRB 250205A: REM NIR upper limit DATE: 25/02/06 13:36:20 GMT FROM: Matteo Ferro at INAF-OAB <matteo.ferro(a)inaf.it> M. Ferro, R. Brivio, P. D’Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of GRB 250205A detected by SVOM (Saccardi et al., GCN 39154) and Einstein Probe (Liu et al., GCN 39165) with the REM 60cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the J, H, K bands, starting on 2025 February 06 at 00:34:51 UT (i.e. 3.17 hours after the trigger), and lasting for about 1 hour. From preliminary photometry we do not detect any NIR counterpart consistent with the candidate optical/NIR afterglow (Gompertz et al., GCN 39156; Schneider et al., GCN 39157; Palmerio et al., GCN 39159; de Ugarte Postigo et al., GCN 39160; Watson et al., GCN 39162; Busmann et al., GCN 39169), down to the following 3sigma magnitude upper limit: H > 16.5 (Vega; calibrated against the 2MASS catalogue) at a mid-time of t - t0 = 3.6 hr after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/39170. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37178] EP250205a/GRB 250205A: FTW optical and NIR observations of the counterpart
by GCN Circulars 06 Feb '25

06 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39169 SUBJECT: EP250205a/GRB 250205A: FTW optical and NIR observations of the counterpart DATE: 25/02/06 13:31:09 GMT FROM: Malte Busmann at Ludwig-Maximilians-Universität München <m.busmann(a)physik.lmu.de> Malte Busmann (LMU), Daniel Gruen (LMU), Brendan O’Connor (Carnegie Mellon U.) and Antonella Palmese (Carnegie Mellon U.) report: We observed the counterpart of EP250205a/GRB 250205A (Saccardi et al., GCN 39154; Gompertz et al., GCN 39156; Schneider and Adami, GCN 39157; Gompertz et al., GCN 39158; Palmerio et al., GCN 39159; de Ugarte Postigo et al., GCN 39160; Kennea et al., GCN 39161; Watson et al., GCN 39162; Liu et al., GCN 39165; Breeveld et al., GCN 39168) with the Three Channel Imager (3KK) at the Fraunhofer Telescope Wendelstein (FTW) in the r, i and J band simultaneously for 40 x 180 s starting at 2025-02-05T23:04:26 UT (1.66 hours after the trigger). We detect the counterpart in the single exposures. In the first exposure at r = (21.95 +/- 0.17) mag i = (21.26 +/- 0.13) mag J = (20.25 +/- 0.16) mag. The r- and i-band manitudes are calibrated against the PS1 catalog and the J-band is calibrated with the 2MASS Catalog. All magnitudes are provided in the AB system and are not corrected for Galactic extinction. We thank Christoph Ries from the Wendelstein Observatory for obtaining these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39169. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37177] GRB 250205A: Swift/UVOT Upper Limits
by GCN Circulars 06 Feb '25

06 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39168 SUBJECT: GRB 250205A: Swift/UVOT Upper Limits DATE: 25/02/06 12:21:23 GMT FROM: Alice Breeveld at MSSL-UCL <a.breeveld(a)ucl.ac.uk> A. A. Breeveld (UCL-MSSL) and R. Brivio (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of SVOM/ECLAIRs detected burst GRB 250205A 4593 s after the trigger (Saccardi et al., GCN Circ. 39154). The afterglow reported by Gompertz et al., GCN Circ. 39156, Schneider & Adami, GCN Circ. 39157, Palmerio et al., GCN Circ. 39159, de Ugarte Postigo et al., GCN Circ. 39160, Kennea et al., GCN Circ. 39161 and Watson et al., GCN Circ. 39162, is not detected in the single U-band exposure. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposure is: Filter T_start(s) T_stop(s) Exp(s) Mag u 4593 6243 1625 >20.9 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.046 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/39168. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37176] LIGO/Virgo/KAGRA S250205ee: Updated Sky localization and Source Classification
by GCN Circulars 06 Feb '25

06 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39167 SUBJECT: LIGO/Virgo/KAGRA S250205ee: Updated Sky localization and Source Classification DATE: 25/02/06 10:35:25 GMT FROM: Divyajyoti NLN <divyajyoti.nln(a)ligo.org> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) data around the time of the compact binary merger (CBC) candidate S250205ee (GCN Circular 39155). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S250205ee After parameter estimation by RapidPE-RIFT [2], the updated classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), NSBH (<1%), or BNS (<1%). For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 1574 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 2493 +/- 889 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. (2023) arXiv:2307.13380 [2] Rose et al. (2022) arXiv:2201.05263 and Pankow et al. PRD 92, 023002 (2015) doi:10.1103/PhysRevD.92.023002 View this GCN Circular online at https://gcn.nasa.gov/circulars/39167. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37175] EP250205a/GRB 250205A: correction to the source localization
by GCN Circulars 06 Feb '25

06 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39166 SUBJECT: EP250205a/GRB 250205A: correction to the source localization DATE: 25/02/06 10:07:31 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Z. Y. Liu (USTC), M. H. Zhang, M. J. Liu, H. N. Yang, W. Yuan (NAO, CAS) report on behalf of the Einstein Probe team The EP-FXT observation source localization given in GCN 39165 is incorrect. The correct source localization should be R.A. = 113.5107, DEC = 32.3718 (J2000). We apologize for the mistake. View this GCN Circular online at https://gcn.nasa.gov/circulars/39166. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37174] EP250205a/GRB 250205A: Einstein Probe observation
by GCN Circulars 06 Feb '25

06 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39165 SUBJECT: EP250205a/GRB 250205A: Einstein Probe observation DATE: 25/02/06 09:14:37 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Z. Y. Liu (USTC), M. H. Zhang, M. J. Liu, H. N. Yang, W. Yuan (NAO, CAS) report on behalf of the Einstein Probe team We report on the detection of an X-ray transient, designated EP250205a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, which triggered the on-board processing unit at 2025-02-05 21:32:08 (UTC) (trigger ID: 01709131283). The source position is R.A. = 113.522 deg, DEC = 32.363 deg (J2000) with an uncertainty of about 2.5 arcmin (radius, 90% C.L. statistical and systematic). An autonomous follow-up observation of EP250205a was performed by the Follow-up X-ray Telescope (FXT) on board EP, 256s after the WXT trigger. An uncatalogued X-ray source was detected at R.A. = 113.509 deg, DEC = 32.373 deg (J2000) with an uncertainty of less than 10 arcsec (radius, 90% C.L. statistical and systematic), consistent with the WXT position of EP250205a. The 0.5-4.0 keV WXT spectrum can be fitted with an absorbed power law with a fixed Galactic absorption with column density 4.4 x 10^20 cm^-2 and an intrinsic absorber with a redshift of 3.55. The fitted equivalent hydrogen column density of the intrinsic absorber is 6.5(+9.8/-6.5) x 10^22 cm^-2, the photon index 2.5(+1.7/-1.2), and the unabsorbed 0.5-4 keV flux 4.2 (+1.1/-1.1) x 10^-10 erg/s/cm^2. The average 0.5-10 keV spectrum of the follow-up observation obtained by EP-FXT can be fitted with an absorbed power law with a photon index of 2.82 (+0.06/-0.04) (with a galactic column density fixed at 4.4 x 10^20 cm^-2), yielding an average unabsorbed 0.5-10 keV flux of 3.65 (+0.07/-0.09) x 10^-11 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. EP250205a is spatially and temporally consistent with GRB 250205A (Saccardi et al. GCN 39154) at a redshift of 3.55 (de Ugarte Postigo et al. GCN 39160). EP250205a was first detected by WXT at 2025-02-05T21:31:28 (UTC), about 410 seconds after the SVOM/ECLAIRs trigger time (2025-02-05T21:24:38), due to Earth obscuration of the WXT FoV from 2025-02-05T20:26:42 to 2025-02-05T21:31:28. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES. View this GCN Circular online at https://gcn.nasa.gov/circulars/39165. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37173] GRB 250127C: SVOM/GRM observation of a burst
by GCN Circulars 06 Feb '25

06 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39164 SUBJECT: GRB 250127C: SVOM/GRM observation of a burst DATE: 25/02/06 07:00:22 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Jean-Luc Atteia (IRAP), Stéphane Schanne (CEA), Frédéric Piron (LUPM) report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a long burst GRB 250127C (SVOM trigger reference: sb25012702) at 2025-01-27T05:34:47.500 UTC (T0). With the event-by-event data downloaded through the X-band ground station, the GRM light curve of 15 to 600 keV shows that this burst consists of multi-pulses with a T90 of 28.6 +2.7/-9.9 s. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250127C.png The SVOM/GRM on-ground localization of this burst is (J2000): RA: 274.5 deg DEC: 25.0 deg Error: 1.94 deg (1sigma, statistical only) We caution that the calibration of SVOM/GRM is undergoing and this localization is subject to systematic errors. In addition, the position of this burst, as determined by GRM, is located at about 159 degrees from the SVOM optical axis, and outside the ECLAIRs field of view. This burst was detected by the Count-Rate Trigger onboard ECLAIRs, as an increase in counts over background, but it was not localized by the coded-mask imaging process, which confirms that the burst occurred outside the ECLAIRs field of view. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Chen-Wei Wang (IHEP) (cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/39164. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37172] GRB 250204B: SVOM/GRM observation of a likely short burst
by GCN Circulars 06 Feb '25

06 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39163 SUBJECT: GRB 250204B: SVOM/GRM observation of a likely short burst DATE: 25/02/06 06:08:28 GMT FROM: yqzhang_cl(a)163.com SVOM/GRM team: Yan-Qiu Zhang, Wen-Jun Tan, Chen-Wei Wang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Nicolas Dagoneau(CEA), Maria-GraziaBernardini (INAF-OAB), Jean-Luc Atteia (IRAP) report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a likely short burst GRB 250204B (sb25020402) at 2025-02-04T06:41:14.100 UTC (T0), which was also observed by Fermi/GBM (Fermi GBM team, GCN #39141) and AstroSat CZTI (A. Dasgupta et al., GCN #39142). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a single pulse with a T90 of 2.92 +/- 0.08 s in the 15-300 keV band. In addition, the position of this burst, as determined by Fermi/GBM (GCN #39141, RA: 2.35 deg, DEC: 29.70 deg, Error: 2.80 deg), is located at about 137 degrees from the SVOM optical axis, and outside the ECLAIRs field of view. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250204B.png The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Yan-Qiu Zhang (IHEP) (zhangyanqiu(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/39163. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37171] GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
by GCN Circulars 06 Feb '25

06 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39162 SUBJECT: GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection DATE: 25/02/06 05:06:58 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Sarah Antier (OCA), Jean-Luc Atteia (IRAP), Rosa L. Becerra (Università degli Studi di Roma Tor Vergata), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Jean-Grégoire Ducoin (CPPM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), and Benjamin Schneider (LAM) report: We imaged the field of the SVOM/ECLAIRs GRB 250205A (Saccardi et al., GCN Circ. 39154) with the DDRAGO wide-field camera on the COLIBRÍ (SVOM/F-GFT) telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We observed from 2025-02-06 03:01 to 04:48 UTC, with a midpoint of 6.34 hours after the event, and obtained 3840 seconds of exposure in the r filter in good weather conditions. The data were reduced and stacked using custom software and then calibrated against the PS1 catalog and analysed using STDPipe (Karpov 2021). We detect the afterglow (Gompertz et al., GCN Circ. 39156, and Schneider & Adami, GCN Circ. 39157) with r = 22.89 +/- 0.11 This magnitude is not corrected for Galactic extinction. Our measurement is significantly fainter than the earlier r magnitudes reported by Gompertz et al. (GCN Circ. 39156), Schneider & Adami (GCN Circ. 39157), Palmerio et al. (GCN Circ. 39159), and de Ugarte Postigo et al. (GCN Circ. 39160), confirming that this is the afterglow. Compared to the magnitude reported by de Ugarte Postigo et al., our measurement implies a temporal index of -0.80 +/- 0.08 between 1.76 and 6.34 hours. Further observations are planned. We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/39162. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37170] GRB 250205A: Swift/XRT detection
by GCN Circulars 06 Feb '25

06 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39161 SUBJECT: GRB 250205A: Swift/XRT detection DATE: 25/02/06 00:52:30 GMT FROM: Jamie Kennea at Penn State <jak51(a)psu.edu> J. A. Kennea (PSU), B. Sbarufatti (INAF-OAB) and P. A. Evans (Leicester) report on behalf of the Swift/XRT team: At 22:38:21UT Swift began a target of opportunity observation of GRB 250205A (GCN #39154), approximately 74 minutes after the trigger. We detect a bright previously uncatalogued X-ray source at the following coordinates: RA/Dec(J2000) = 113.51144, 32.37196, which is equivalent to: RA (J2000): 07h 34m 02.75s, Dec (J2000): +32d 22' 19.1", with an estimated error of 3.8 arc-seconds radius (90% confidence). This position lies 69 arc-seconds from the SVOM/MXT position reported in GCN #39154, and 1.7 arc-seconds from the SVOM.VT optical counterpart (GCN #39159). The mean flux during the 1.4 ks XRT observation was 4.9 (±0.4) x 10^-12 erg cm^-2 s^-1 (0.3-10 keV). Further observations of GRB 250205A with Swift are planned. View this GCN Circular online at https://gcn.nasa.gov/circulars/39161. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37169] GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55
by GCN Circulars 06 Feb '25

06 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39160 SUBJECT: GRB 250205A: Redshift from OSIRIS+/GTC z = 3.55 DATE: 25/02/06 00:28:38 GMT FROM: Antonio de Ugarte Postigo at LAM/OCA, CNRS <deugarte(a)oca.eu> A. de Ugarte Postigo (LAM), D. B. Malesani (DAWN/NBI and Radboud Univ.), A. Martin-Carrillo (UCD), C. C. Thoene (AbAO), J. F. Agui Fernandez (CAHA), N. R. Tanvir (Univ. Leicester), L. Izzo (INAF/OACn and DARK/NBI), J. P. U. Fynbo (DAWN/NBI), S. Geier (GTC), G. Lombardi (GTC), N. A. Rakotondrainibe (LAM), A. M. Garcia Rodriguez (GTC), D. González González (GTC) report, We have observed the counterpart of GRB 250205A (Saccardi et al. GCN 39154, also detected by EP as trigger id 01709131283), also discovered in parallel by Gompertz et al. (GCN 39156) and Schneider et al. (GCN 39157) and detected by SVOM/VT (Palmerio et al. GCN 39159), with OSIRIS+ on the 10.4 m GTC, located at the Roque de los Muchachos Observatory in the island of La Palma (Spain). Our observation consisted of a 30 s acquisition in r-band followed by 4x900s of spectroscopy using grism R1000B, which covers the spectral range between 3600 and 7800 AA. The optical counterpart is well detected in the acquisition obtained at 23:10:36 UT (mean epoch 1.7661 hrs after the burst) with an r-band AB magnitude of 21.78 +/- 0.06 mag, as compared with 4 field stars from the Sloan catalogue. The spectra show a faint trace with clear absorption features. In a preliminary reduction, we identify features of Ly-alpha, SII, SiII, SiII*, OI, CII, SiIV, CIV, FeII, FeII* at a common redshift of 3.55, which we identify as the redshift of the GRB. Further analysis is ongoing. View this GCN Circular online at https://gcn.nasa.gov/circulars/39160. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37168] GRB250205A: SVOM/VT optical afterglow detection
by GCN Circulars 05 Feb '25

05 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39159 SUBJECT: GRB250205A: SVOM/VT optical afterglow detection DATE: 25/02/05 23:50:19 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> GRB 250205A: SVOM/VT optical counterpart confirmation J. T. Palmerio (CEA), S. Vergani (Obs.Paris), L.P. Xin, Y. L. Qiu (NAOC), A. Saccardi (CEA), H.L. Li., C. Wu, Z.H. Yao, Y.N. Ma, X.H. Han, H.B. Cai, J.Y. Wei (NAOC), report on behalf of the SVOM team: After the trigger by SVOM/ECLAIRs at 2025-02-05T21:24:38 UTC (Tb), SVOM performed an automatic slew on the burst. The VT observing time reported in (Saccardi et al. GCN 39154) is incorrect, rather SVOM/VT began observing the field at 2025-02-05T21:32:08, 449 seconds after the SVOM trigger, in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. An uncatalogued source was detected within the error box of SVOM/MXT (Saccardi et al. GCN 39154) using the VT VHF pipeline at ra=113.51107, dec=32.37187 (J2000), corresponding to: RA (J2000) = 07h34m02.7s Dec (J2000) = +32d22m18.7s with an uncertainty of 1 arcsec. consistent with the optical afterglow reported by Gompertz et al. (GCN 39156) and Schneider et al. (GCN 39157). The source was detected in both VT_R and VT_B, though the presence of light bloom from a bright source in the image prevents the determination of the VT_R magnitude from the VHF pipeline. The source was fading between the first 2 VT observing sequences, the magnitudes are given below: mag(AB) VT_B | mag err | mid-observing time since trigger (minutes) 20.91 | 0.06 | 8.75 21.18 | 0.05 | 12.5 The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC),CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/39159. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37167] GRB 250205A: GOTO optical upper limits
by GCN Circulars 05 Feb '25

05 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39158 SUBJECT: GRB 250205A: GOTO optical upper limits DATE: 25/02/05 23:30:43 GMT FROM: Ben Gompertz at U of Birmingham <b.gompertz(a)bham.ac.uk> B. P. Gompertz, S. Belkin, D. O'Neill, G. Ramsay, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, F. Jimenez-Ibarra, A. Kumar, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Pall'e and D. Pollacco report on behalf of the GOTO collaboration: We report on observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to GRB 250205A, detected by EP and SVOM (Saccardi et al., GCN 39154). Targeted observations were performed by GOTO-North (La Palma) at 21:43:59 on 2025-02-05 (19 minutes after the ECLAIRs trigger time). The observation consisted of 4x90s exposures in the GOTO L-band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline. The optical counterpart reported by Gompertz et al. (GCN 39156) and Schneider et al. (GCN 39157) is not detected to a 3-sigma limiting AB magnitude of L > 19.7 mags. Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/39158. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37166] GRB 250205A: OHP/T193 optical counterpart candidate
by GCN Circulars 05 Feb '25

05 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39157 SUBJECT: GRB 250205A: OHP/T193 optical counterpart candidate DATE: 25/02/05 23:18:19 GMT FROM: Benjamin Schneider at MIT <bschn(a)mit.edu> B. Schneider (LAM) and C. Adami (LAM/Pytheas/AMU) We observed the field of the GRB 250205A (Saccardi et al., GCN 39154) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained three exposures (300 s + 2x500 s) in the r-band starting at 22:06:27UT on 2025-02-05 (42 min after the trigger). In the stacked image, we clearly detected a new source not visible in the Legacy Survey and consistent with the MXT error at: RA(J200) = 7:34:02.62 DEC(J200) = +32:22:18.98 with an uncertainty of 0.5 arcsec. The preliminary magnitude derived for that source is r = 21.01 +/- 0.07 mag (AB) The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the magnitude is not corrected for Galactic extinction. This source is consistent with the one reported by Gompertz et al. GCN 39156. Further observations are ongoing. We acknowledge the excellent support from Observatoire de Haute-Provence and in particular Jean-Pierre Troncin for the MISTRAL observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39157. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37165] GRB 250205A: Liverpool Telescope optical counterpart candidate detection
by GCN Circulars 05 Feb '25

05 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39156 SUBJECT: GRB 250205A: Liverpool Telescope optical counterpart candidate detection DATE: 25/02/05 22:53:06 GMT FROM: Ben Gompertz at U of Birmingham <b.gompertz(a)bham.ac.uk> B. P. Gompertz (U. Birmingham), D. B. Malesani (DAWN/NBI and Radboud) and A. J. Levan (Radboud) report on behalf of a larger collaboration: We initiated follow-up observations of GRB 250205A (Saccardi et al., GCN 39154) with the IO:O camera on the 2m robotic Liverpool Telescope (LT). Observations began at 21:56:04, 32 minutes after the ECLAIRS trigger, and consisted of 5x120 s exposures in the SDSS r filter. A new optical source, not present in archival PS1 imaging, is detected at RA = 07:34:02.64, Dec +32:22:18.79 (J2000). In a preliminary analysis, we measure an AB magnitude of r = 20.91 +/- 0.06, calibrated against nearby Pan-STARRS stars and not corrected for galactic extinction. Follow-up observations to assess the evolution of the candidate are encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/39156. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37164] LIGO/Virgo/KAGRA S250205ee: Identification of a GW compact binary merger candidate
by GCN Circulars 05 Feb '25

05 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39155 SUBJECT: LIGO/Virgo/KAGRA S250205ee: Identification of a GW compact binary merger candidate DATE: 25/02/05 22:42:56 GMT FROM: youru.lee(a)g.ncu.edu.tw The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S250205ee during real-time processing of data from LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) at 2025-02-05 21:52:15.879 UTC (GPS time: 1422827553.879). The candidate was found by the CWB [1], CWB BBH [2], GstLAL [3], MBTA [4], and PyCBC Live [5] analysis pipelines. S250205ee is an event of interest because its false alarm rate, as estimated by the online analysis, is 1.8e-09 Hz, or about one in 17 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250205ee After parameter estimation by RapidPE-RIFT [6], the classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), NSBH (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [7] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [7] Both HasNS and HasRemnant consider the support of several neutron star equations of state. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,0, an initial localization generated by BAYESTAR [8], distributed via GCN notice about 32 seconds after the candidate event time. * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [8], distributed via GCN notice about 5 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,1. For the bayestar.multiorder.fits,1 sky map, the 90% credible region is 2350 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 2885 +/- 925 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Klimenko et al. PRD 93, 042004 (2016) doi:10.1103/PhysRevD.93.042004 [2] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018 [3] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. (2023) arXiv:2305.05625 [4] Aubin et al. CQG 38, 095004 (2021) doi:10.1088/1361-6382/abe913 [5] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [6] Rose et al. (2022) arXiv:2201.05263 and Pankow et al. PRD 92, 023002 (2015) doi:10.1103/PhysRevD.92.023002 [7] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [8] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/39155. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37163] GRB 250205A: SVOM detection of a burst
by GCN Circulars 05 Feb '25

05 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39154 SUBJECT: GRB 250205A: SVOM detection of a burst DATE: 25/02/05 22:18:47 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> A. Saccardi, T. Sadibekova, N. Dagoneau, H. Goto, S. Schanne (CEA), Ch. Van Hove (IJCLab) report on behalf of the SVOM mission team: The SVOM/ECLAIRs telescope triggered and located the long duration GRB 250205A (sb25020504) starting at 2025-02-05T21:24:38 UTC (Tb). The following trigger information was received on the ground with low-latency by the SVOM VHF Alert Network. The burst was detected by both the on-board Count-Rate Trigger (CRT) and Image Trigger (IMT) and 8 alerts were received. The best detection is obtained by IMT with a signal-to-noise ratio of 19.3 in the 8-120 keV energy band over a time window of 40.96 s starting at Tb. The localization of the best Alert is RA, Dec = 113.459, 32.365 (J2000). The uncertainty on this position is 4.5 arcminutes at 90% C.L. which includes 2 arcminutes of systematic uncertainty in quadrature. SVOM performed an automatic slew on this burst. MXT began observing the field at 2025-02-05T21:34:32, 593 seconds after the SVOM trigger. Using onboard processed data we found an uncatalogued X-ray source located in J2000 at RA, Dec 113.534, 32.370 degrees RA (J2000) = 7h34m08s Dec (J2000) = 32d22m14s with an uncertainty radius at 90% C.L. of 80 arcseconds. This location is 3.8 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received. VT began observing the field at 2025-02-05T21:41:52, 1033 seconds after the SVOM trigger. The analysis of the recorded images will be published in a future circular gathering information on the follow-up of the SVOM optical instruments. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. The Burst Advocates (BAs) on shift for this burst are Andrea Saccardi, Tatyana Sadibekova (andrea.saccardi(a)cea.fr). Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/39154. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37162] LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume
by GCN Circulars 05 Feb '25

05 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39153 SUBJECT: LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume DATE: 25/02/05 16:24:42 GMT FROM: David Cook at Caltech/IPAC-NED <dcook(a)ipac.caltech.edu> David O. Cook (Caltech/IPAC), Rick Ebert (Caltech/IPAC), George Helou (Caltech/IPAC), Joseph M. Mazzarella (Caltech/IPAC), Marion Schmitz (Caltech/IPAC), and Leo Singer (NASA/GSFC) On behalf of the NASA/IPAC Extragalactic Database (NED) Team. We spatially cross-matched the LVK S250205bk-4-Update sky localization with the NED Local Volume Sample (NED-LVS; Cook et al. 2023), which is a subset of NED with a redshift or redshift-independent distance less than 1000 Mpc. We find 2528 galaxies within the 90% containment volume, and we list here the top 20 galaxies sorted by the joint probability of the 3D localization and the WISE W1 luminosity (an observable proxy for stellar mass). For the full or top 20 list of galaxies in the 90% volume go either to the NED Gravitational Wave Followup service at https://ned.ipac.caltech.edu/uri/NED::GWF/ or click on the following links: Full List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S250205bk/4 Top 20 List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S250205bk/4/20 The NED-GWF service provides downloadable galaxy lists and visualizations for candidate host galaxies. For each GW alert, these products are automatically generated and made available within minutes to expedite efficient electromagnetic follow-up observations. The NED top 20 list is sorted by the joint probability of the 3D localization and the WISE W1 luminosity, but users can sort on additional pre-computed prioritization metrics (star formation rate, P_3D * P_SFR; and specific star formation rate, P_3D * P_sSFR; etc.) which are available via downloading the entire galaxy list inside the event's probability volume. | objname| ra| dec|objtype| DistMpc|DistMpc_unc| m_NUV| m_NUV_unc| m_Ks| m_Ks_unc| m_W1| m_W1_unc| P_3D|P_3D_LumW1| |-------------------------|--------------|--------------|-------|-----------|-----------|------------|------------|------------|------------|------------|------------|--------|----------| |WISEA J093844.45+005715.7| 144.68526| 0.95433| G| 824.18| 0.23| 21.253| 0.083| 11.774| 0.018| 10.243| 0.023|1.80e-07| 4.17e-09| |WISEA J092856.47-021335.7| 142.23530| -2.22658| G| 710.26| 0.65| null| null| 12.461| 0.067| 11.321| 0.023|4.40e-07| 2.79e-09| |WISEA J093341.13-003004.3| 143.42148| -0.50123| G| 673.85| 0.10| null| null| 14.214| 0.130| 11.563| 0.006|3.58e-07| 1.64e-09| |WISEA J091951.25-073541.7| 139.96363| -7.59489| G| 818.16| 0.65| null| null| 13.410| 0.148| 11.982| 0.023|3.24e-07| 1.48e-09| |WISEA J091742.69-081416.0| 139.42792| -8.23772| G| 542.17| 0.65| null| null| 13.284| 0.131| 10.986| 0.006|2.82e-07| 1.42e-09| |WISEA J093439.55+002752.0| 143.66484| 0.46446| G| 703.82| 0.09| 19.820| 0.033| 13.392| 0.182| 11.618| 0.022|2.88e-07| 1.37e-09| |WISEA J092442.24-043058.7| 141.17604| -4.51631| G| 689.17| null| null| null| 13.275| 0.172| 12.531| 0.017|6.76e-07| 1.33e-09| |WISEA J091817.00-080516.1| 139.57088| -8.08781| G| 630.66| null| null| null| 13.763| 0.181| 11.982| 0.009|4.12e-07| 1.12e-09| |WISEA J093252.21-032932.6| 143.21754| -3.49244| G| 631.45| null| null| null| 13.036| 0.174| 11.604| 0.007|2.65e-07| 1.03e-09| |WISEA J092320.48-045941.1| 140.83533| -4.99478| G| 729.41| 0.65| null| null| 13.622| 0.205| 12.955| 0.023|6.62e-07| 9.83e-10| |WISEA J092952.72-015714.7| 142.46970| -1.95410| G| 845.32| null| null| null| 13.348| 0.154| 12.605| 0.014|2.92e-07| 8.03e-10| |WISEA J093249.74-032936.8| 143.20729| -3.49361| G| 756.36| null| null| null| 13.293| 0.155| 12.100| 0.010|2.20e-07| 7.73e-10| |WISEA J092004.03-082300.2| 140.01683| -8.38336| G| 650.64| null| null| null| 13.494| 0.163| 12.090| 0.009|2.85e-07| 7.47e-10| |WISEA J092631.89-043419.8| 141.63296| -4.57217| G| 645.03| null| null| null| 13.754| 0.131| 13.015| 0.018|6.66e-07| 7.32e-10| |WISEA J092955.58-003402.7| 142.48160| -0.56755| G| 712.37| 0.13| null| null| 12.886| 0.138| 12.029| 0.014|2.18e-07| 7.24e-10| |WISEA J091833.08-082916.7| 139.63783| -8.48797| G| 660.03| null| null| null| 12.957| 0.126| 12.362| 0.017|3.38e-07| 7.10e-10| |WISEA J091745.56-072447.9| 139.43988| -7.41339| G| 654.29| null| 22.017| 0.284| 13.320| 0.145| 12.674| 0.011|4.37e-07| 6.77e-10| |WISEA J093033.14-034338.7| 142.63804| -3.72744| G| 647.19| null| 20.508| 0.159| 13.665| 0.191| 12.865| 0.013|4.95e-07| 6.29e-10| |WISEA J093042.67-014550.9| 142.67791| -1.76427| G| 607.80| null| 21.811| 0.330| 12.959| 0.125| 12.547| 0.014|4.10e-07| 6.15e-10| |WISEA J092150.45-071954.1| 140.46029| -7.33178| G| 661.45| null| null| null| 13.083| 0.146| 12.922| 0.018|4.54e-07| 5.73e-10| Table 1: Top 20 galaxies in NED-LVS that fall in the 90% probability volume for S250205bk sorted by the joint probability of 3D position and WISE W1 luminosity (P_3D * P_LumW1). Galaxy is the NED preferred name. RA and Dec are the Equatorial coordinates in degrees (J2000). Objtype is the object type of the galaxy candidate. Distance is the distance to the galaxy in Mpc. m_NUV and mErr_NUV are the apparent magnitude and error from GALEX. m_Ks and mErr_Ks are the apparent magnitude and error from 2MASS. m_W1 and mErr_W1 are the apparent magnitude and error from AllWISE. P_3D is the probability that the galaxy is in the volume given the distance of GW event. P_3D_LumW1 is the joint probability within the volume weighted by the WISE1 luminosity of the galaxy (P_3D * P_LumW1). View this GCN Circular online at https://gcn.nasa.gov/circulars/39153. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37161] Konus-Wind detection of GRB 250201A
by GCN Circulars 05 Feb '25

05 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39152 SUBJECT: Konus-Wind detection of GRB 250201A DATE: 25/02/05 16:18:27 GMT FROM: Dmitry Frederiks at Ioffe Institute <fred(a)mail.ioffe.ru> D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long GRB 250201A (Fermi-GBM detection: Fermi GBM team, GCN 39112; BALROG localization: Preis & Greiner, GCN 39113; INTEGRAL SPI/ACS detection: Barria et al., GCN 39117; IPN triangulation: Kozyrev et al., GCN 39151) triggered Konus-Wind (KW) at T0=35989.814 s UT (09:59:49.814). The burst light curve shows a double-peaked emission pulse with the total duration of ~21 s. The emission is seen up to ~8 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250201_T35989/ As observed by Konus-Wind, the burst had a fluence of (1.21 ± 0.08)x10^-5 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 12.160 s, of (2.97 ± 0.34)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+16.640 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.72 (-0.12,+0.13), the high energy photon index beta = -3.07 (-0.54,+0.27), the peak energy Ep = 134 (-7,+8) keV, chi2 = 118/97 dof. The spectrum near the peak count rate (measured from T0+8.448 s to T0+16.640 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.76 (-0.11,+0.13), the high energy photon index beta = -2.95 (-0.34,+0.23), the peak energy Ep = 138 (-8,+8) keV, chi2 = 94/78 dof. All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/39152. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37160] IPN triangulation of GRB 250201A
by GCN Circulars 05 Feb '25

05 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39151 SUBJECT: IPN triangulation of GRB 250201A DATE: 25/02/05 15:21:26 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the HEND/Mars Odyssey team, A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi GBM team, E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu on behalf of the Swift-BAT team, and W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr, and A.S. Gardner on on behalf of the GRS-Odyssey GRB team, report: The long-duration GRB 250201A (Fermi-GBM detection: Fermi GBM team, GCN 39112; BALROG localization: Preis & Greiner, GCN 39113; INTEGRAL SPI/ACS detection: Barria et al., GCN 39117) was detected by Fermi (GBM), Konus-Wind, INTEGRAL (SPI-ACS), Swift (BAT), and Mars-Odyssey (HEND) at about 35987 s UT (09:59:47). The burst was outside the coded field of view of the BAT. We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: ------------------------------- RA(2000), deg Dec(2000), deg ------------------------------- Center: 115.287 -54.293 Corners: 137.464 -51.378 137.379 -51.074 93.570 -52.488 93.601 -52.814 ------------------------------- The error box area is 6.8 sq. deg, and its maximum dimension is 26.3 deg (the minimum one is 21 arcmin). The Sun distance was 101 deg. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB250201_T35989/IPN The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/39151. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37159] LIGO/Virgo/KAGRA S250205bk: Updated Sky localization
by GCN Circulars 05 Feb '25

05 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39150 SUBJECT: LIGO/Virgo/KAGRA S250205bk: Updated Sky localization DATE: 25/02/05 13:44:16 GMT FROM: Will Farr <will.farr(a)stonybrook.edu> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S250205bk (GCN Circular 39148). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S250205bk For the Bilby.multiorder.fits,0 sky map, the 90% credible region is well fit by an ellipse with an area of 66 deg2 described by the following DS9 region (right ascension, declination, semi-major axis, semi-minor axis, position angle of the semi-minor axis): icrs; ellipse(09h27m, -03d55m, 10.95d, 1.92d, 118.01d) Marginalized over the whole sky, the a posteriori luminosity distance estimate is 748 +/- 160 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. (2023) arXiv:2307.13380 View this GCN Circular online at https://gcn.nasa.gov/circulars/39150. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37158] Konus-Wind detection of GRB 250202B
by GCN Circulars 05 Feb '25

05 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39149 SUBJECT: Konus-Wind detection of GRB 250202B DATE: 25/02/05 13:40:11 GMT FROM: Dmitry Frederiks at Ioffe Institute <fred(a)mail.ioffe.ru> D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long GRB 250202B (Fermi-GBM detection: The Fermi GBM team, GCN 39120; Bala et al., GCN 39133; AstroSat-CZTI detection: Srijan et al., GCN 39122; NuSTAR-ACS detection: Grefenstette, GCN 39135; IPN triangulation: Svinkin et al., GCN 39144) triggered Konus-Wind (KW) at T0=14235.288 s UT (03:57:15.288). The burst light curve consists of multiple multi-peaked emission pulses. The total duration of the burst is ~100 s. The emission is seen up to ~10 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250202_T14235/ As observed by Konus-Wind, the burst had a fluence of (2.05 ± 0.07)x10^-4 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 2.112 s, of (1.62 ± 0.10)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+106.240 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.87 (-0.05,+0.06), the high energy photon index beta = -2.67 (-0.12,+0.09), the peak energy Ep = 273 (-8,+9) keV, chi2 = 121/97 dof. The spectrum near the peak count rate (measured from T0 to T0+2.560 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.38 (-0.07,+0.08), the high energy photon index beta = -3.40 (-0.72,+0.33), the peak energy Ep = 413 (-21,+21) keV, chi2 = 63/60 dof. All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/39149. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37157] LIGO/Virgo/KAGRA S250205bk: Identification of a GW compact binary merger candidate
by GCN Circulars 05 Feb '25

05 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39148 SUBJECT: LIGO/Virgo/KAGRA S250205bk: Identification of a GW compact binary merger candidate DATE: 25/02/05 11:12:59 GMT FROM: Lorenzo Asprea at INFN Torino <lorenzo.asprea(a)to.infn.it> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S250205bk during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2025-02-05 10:35:41.575 UTC (GPS time: 1422786959.575). The candidate was found by the CWB-BBH [1], GstLAL [2], MBTA [3], PyCBC Live [4], and SPIIR [5] analysis pipelines. S250205bk is an event of interest because its false alarm rate, as estimated by the online analysis, is 9.5e-10 Hz, or about one in 33 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250205bk The classification of the GW signal, in order of descending probability, is BBH (98%), NSBH (1%), Terrestrial (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [6] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [6] Both HasNS and HasRemnant consider the support of several neutron star equations of state. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. Two sky maps are available at this time and can be retrieved from the GraceDB event page: bayestar.multiorder.fits,0, an initial localization generated by BAYESTAR [7], distributed via GCN notice about 39 seconds after the candidate event time. bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [7], distributed via GCN notice about 5 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,1. For the bayestar.multiorder.fits,1 sky map, the 90% credible region is well fit by an ellipse with an area of 101 deg2 described by the following DS9 region (right ascension, declination, semi-major axis, semi-minor axis, position angle of the semi-minor axis): icrs; ellipse(09h24m, -06d08m, 14.43d, 2.23d, 119.13d) Marginalized over the whole sky, the a posteriori luminosity distance estimate is 794 +/- 191 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018 [2] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. (2023) arXiv:2305.05625 [3] Aubin et al. CQG 38, 095004 (2021) doi:10.1088/1361-6382/abe913 [4] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [5] Chu et al. PRD 105, 024023 (2022) doi:10.1103/PhysRevD.105.024023 [6] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [7] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/39148. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37156] GRB 250129A: Swift-BAT refined analysis
by GCN Circulars 04 Feb '25

04 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39147 SUBJECT: GRB 250129A: Swift-BAT refined analysis DATE: 25/02/04 20:36:28 GMT FROM: Rahul Gupta at NASA GSFC <rahul.gupta(a)nasa.gov> C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-571 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250129A (trigger #1285812) (Beardmore, et al., GCN Circ. 39066). The BAT ground-calculated position is RA, Dec = 198.708, 5.029 deg which is RA(J2000) = 13h 14m 49.8s Dec(J2000) = +05d 01' 44.9" with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 84%. The mask-weighted BAT light curve exhibits a multi-peaked and complex structure, with the most prominent peak occurring at approximately T0 + 184 seconds. T90 (15-350 keV) is 262.25 +- 23.71 sec (estimated error including systematics). The time-averaged spectrum from T-64.39 to T+302.62 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.17 +- 0.09. The fluence in the 15-150 keV band is 5.0 +- 0.2 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+184.12 sec in the 15-150 keV band is 1.4 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1285812 View this GCN Circular online at https://gcn.nasa.gov/circulars/39147. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37155] EP 250108A: Upper limits from Fermi-GBM Observations
by GCN Circulars 04 Feb '25

04 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39146 SUBJECT: EP 250108A: Upper limits from Fermi-GBM Observations DATE: 25/02/04 19:53:01 GMT FROM: mariaedvige.ravasio(a)ru.nl M. E. Ravasio (Radboud Univ.), E. Burns (LSU), Colleen Wilson-Hodge (NASA Marshall Space Flight Center) and P.G. Jonker (Radboud Univ.) report on behalf of the Fermi-GBM Team: The location of the EP-WXT event EP250108A (Li et al., GCN 38861) was occulted by the Earth for Fermi at the EP trigger time T0=2025-01-08T12:30:28.34 UTC. There was no Fermi-GBM onboard trigger around EP-WXT times. The location becomes visible at around ~T0+415 s. The GBM targeted search [1], the most sensitive, coherent search for GRB-like signals, was run in the time interval [-50;+500] s centred at different times, from T0 up to T0+2500s, to cover the whole reported duration of the EP transient, seeking signals between 64 ms and 32.768 s in duration. A transient was found at ~T0+500 s, but its localization is consistent with the Crab nebula, which exited Earth occultation at that time. No signal consistent with the EP transient both temporally and spatially is identified, as confirmed by visual inspection of the data. Assuming a “soft” spectral template (Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7), and a duration of 8.192 s, the most conservative sky-averaged upper limit is found in the time interval [T0+1450; T0+2000] s, corresponding to a flux of 2.6e-08 erg/cm2/s in the energy band 10-1000 keV. [1] Goldstein et al. 2019 arXiv:1903.12597 View this GCN Circular online at https://gcn.nasa.gov/circulars/39146. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37154] IPN triangulation of GRB 250204B (short/hard)
by GCN Circulars 04 Feb '25

04 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39145 SUBJECT: IPN triangulation of GRB 250204B (short/hard) DATE: 25/02/04 17:51:38 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi GBM team, E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, G. Waratkar, J.Joshi, V. Bhalerao, D. Bhattacharya, and S. Vadawale, on behalf of the Astrosat-CZTI team, report: The short-duration GRB 250204B (Fermi-GBM detection: The Fermi GBM team, GCN 39141; AstroSat-CZTI detection: Dasgupta et al., GCN 39142) was detected by Fermi (GBM trigger 760344078), AstroSat (CZTI), Swift (BAT), Konus-Wind, and INTEGRAL (SPI-ACS) at about 24074 s UT (06:41:14). We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 1.945 (00h 07m 47s) +35.469 (+35d 28' 07") Corners: 4.715 (00h 18m 52s) +29.985 (+29d 59' 08") 6.110 (00h 24m 26s) +29.936 (+29d 56' 11") 358.613 (23h 54m 27s) +40.986 (+40d 59' 08") 356.896 (23h 47m 35s) +41.060 (+41d 03' 34") --------------------------------------------- The error box area is 13.4 sq. deg, and its maximum dimension is 13.4 deg (the minimum one is 1 deg). The Sun distance was 64 deg. This localization may be improved. The IPN localization is consistent with, but reduces the area of, the Fermi-GBM localization (GCN 39141). A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB250204_T24073/IPN/ The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/39145. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37153] IPN triangulation of GRB 250202B
by GCN Circulars 04 Feb '25

04 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39144 SUBJECT: IPN triangulation of GRB 250202B DATE: 25/02/04 17:46:35 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi GBM team, E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, G. Waratkar, J.Joshi, V. Bhalerao, D. Bhattacharya, and S. Vadawale, on behalf of the Astrosat-CZTI team, and S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu on behalf of the Swift-BAT team, report: The bright long-duration GRB 250202B (Fermi-GBM detection: The Fermi GBM team, GCN 39120; Bala et al., GCN 39133; AstroSat-CZTI detection: Srijan et al., GCN 39122; NuSTAR-ACS detection: Grefenstette, GCN 39135) was detected by Fermi (GBM trigger 760161442), AstroSat (CZTI), Swift (BAT), Konus-Wind, and INTEGRAL (SPI-ACS) at about 14237 s UT (03:57:17). The burst was outside the coded field of view of the BAT. We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 344.999 (22h 60m 00s) +19.593 (+19d 35' 35") Corners: 343.557 (22h 54m 14s) +22.051 (+22d 03' 04") 347.168 (23h 08m 40s) +17.149 (+17d 08' 56") 346.317 (23h 05m 16s) +17.129 (+17d 07' 44") 342.644 (22h 50m 34s) +22.024 (+22d 01' 27") --------------------------------------------- The error box area is 4.1 sq. deg, and its maximum dimension is 6.5 deg (the minimum one is 41.5 arcmin). The Sun distance was 45 deg. This localization may be improved. The IPN localization is consistent with, but reduces the area of, the Fermi-GBM (GCN 39120) localization. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB250202_T14235/IPN The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/39144. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37152] LIGO/Virgo/KAGRA S250204ax: Updated Sky localization
by GCN Circulars 04 Feb '25

04 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39143 SUBJECT: LIGO/Virgo/KAGRA S250204ax: Updated Sky localization DATE: 25/02/04 17:06:49 GMT FROM: Will Farr <will.farr(a)stonybrook.edu> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S250204ax (GCN Circular 39137). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S250204ax For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 318 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 2056 +/- 690 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. (2023) arXiv:2307.13380 View this GCN Circular online at https://gcn.nasa.gov/circulars/39143. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37151] GRB 250204B: AstroSat CZTI detection of a short burst
by GCN Circulars 04 Feb '25

04 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39142 SUBJECT: GRB 250204B: AstroSat CZTI detection of a short burst DATE: 25/02/04 16:30:31 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> A. Dasgupta (BITS Pilani, Hyderabad), G. Waratkar (IITB), J. Joshi (IUCAA), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a short-duration GRB 250204B which was also detected by Fermi/GBM (Fermi-GBM Team, GCN Circ. 39141). Inspection of INTEGRAL/SPI-ACS data also showed the detection of the burst. The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-02-04 06:41:14.050 UTC. The measured peak count rate associated with the burst is 446 (+149, -49) counts/s above the background in the combined data of two (out of four) quadrants, with a total of 237 (+60, -71) counts. The local mean background count rate was 116 (+6, -8) counts/s. Using cumulative rates, we measure a T90 of 1.1 (+0.3, -0.5) s. It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-02-04 06:41:13.502 UTC. The measured peak count rate is 300 (+70, -41) counts/s above the background in the combined Veto data of all quadrants, with a total of 659 (+172, -189) counts. The local mean background count rate was 1265 (+8, -8) counts/s. Due to the intrinsic 1 s binning of veto data, we cannot reliably estimate a T90 from it. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/39142. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37150] GRB 250204B: Fermi GBM Final Localization
by GCN Circulars 04 Feb '25

04 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39141 SUBJECT: GRB 250204B: Fermi GBM Final Localization DATE: 25/02/04 14:58:59 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> The Fermi GBM team reports the detection of a likely LONG GRB At 06:41:14.00 UT on 04 February 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250204B (trigger 760344078/250204279). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 2.35, Dec = 29.70 (J2000 degrees, equivalent to J2000 0h 9m, +29d 41'), with a statistical uncertainty of 2.80 degrees. The angle from the Fermi LAT boresight is 124 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250204279/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250204279/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250204279/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39141. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37149] GRB 250129A: LCO late afterglow detection
by GCN Circulars 04 Feb '25

04 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39140 SUBJECT: GRB 250129A: LCO late afterglow detection DATE: 25/02/04 11:47:57 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> I. Pérez-Fournon (IAC and ULL), F. Poidevin (IAC and ULL), D. Cano-Morales (ULL), I. Correa-Plasencia (ULL), and A.E. Hernández-Díaz (ULL) We observed the field of the Swift GRB 250129A (Beardmore et al., GCN Circ. 39066) with one of the Las Cumbres Observatory Global Telescope network (LCOGT) 1-m telescopes equipped with a Sinistro camera at the LCOGT node at the Cerro Tololo Inter-American Observatory (Chile). We obtained a single 300-sec image in the SDSS-r' filter starting at 2025-02-03 07:35:39 UT, approximately 5.118 days after the trigger. The optical transient detected by Swift UVOT (Beardmore et al., GCN Circ. 39066) is clearly detected with a magnitude of r' = 22.04 +/- 0.21, calibrated against PanSTARRS stars and not corrected for extinction. The optical brightness of the afterglow is consistent with the results of late-time observations by Bochenek and Perley (GCN Circ. 39131) and Watson et al. (GCN Circ. 39136). This work makes use of observations from the Las Cumbres Observatory global telescope network (LCOGT observing programme IAC2025A-009, SGLF). View this GCN Circular online at https://gcn.nasa.gov/circulars/39140. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37148] GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
by GCN Circulars 04 Feb '25

04 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39139 SUBJECT: GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations DATE: 25/02/04 07:44:31 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP), R. Ya. Inasaridze (AbAO) report on behalf of the IKI-GRB-FuN collaboration: We performed optical observations of the field of GRB 250129A (Beardmore et. al, GCN 39066; Lipunov et. al, GCN 39070; Schneider et. al, GCN 39071; Belkin et. al, GCN 39072; Izzo et. al, GCN 39073; Izzo et. al, GCN 39074; Ghosh et. al, GCN 39077; Schneider et. al, GCN 39078; Brivio et. al, GCN 39079; Goad et. al, GCN 39082; Siegel, GCN 39085; Osborne et. al, GCN 39089; Zheng et. al, GCN 39090; Schlekat et. al, GCN 39091; Antier et. al, GCN 39096; Odeh et. al, GCN 39097; Ferro et. al, GCN 39098; Malesani et. al, GCN 39100; Romanov, GCN 39101; Zheng et. al, GCN 39102; Watson et. al, GCN 39104; Watson et. al, GCN 39105; Akl et. al, GCN 39106; Moskvitin et. al, GCN 39107; Calapai et. al, GCN 39109; Schlekat et. al, GCN 39110; Gompertz et. al, GCN 39114; Ror et. al, GCN 39115; Frederiks et. al, GCN 39116; Wu et. al, GCN 39124; Paek et. al, GCN 39129) in the R filter with the 1.5-meter AZT-33IK telescope of the Sayan Solar Observatory (Mondy) and the 0.7-meter AS-32 telescope of the Abastumani Observatory (AbAO). The observations began on 2025-01-30 at 22:16:50 UT, i.e. ~1.76 days since trigger. The optical counterpart is well detected in the stacked images from both observatories. The preliminary photometry is as follows: Date UT start t-T0 Exp. Filter OT Err. UL(3sigma) Telescope (mid, days) (s) 2025-01-30 22:16:50 1.76610 103*60 R 19.46 0.21 22.0 AS-32 2025-01-31 19:38:51 2.65188 45*120 R 20.38 0.08 23.0 AZT-33IK 2025-02-01 19:32:02 3.64507 42*120 R 20.82 0.11 22.9 AZT-33IK The photometry is based on nearby stars of the USNO-B1.0 catalog (R2 magnitudes) and have not been corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39139. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37147] GRB 250204A: Fermi GBM Final Real-time Localization
by GCN Circulars 04 Feb '25

04 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39138 SUBJECT: GRB 250204A: Fermi GBM Final Real-time Localization DATE: 25/02/04 07:38:50 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 07:28:17 UT on 4 Feb 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250204A (trigger 760346902.4098 / 250204311). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 108.2, Dec = -23.8 (J2000 degrees, equivalent to J2000 07h 12m, -23d 48'), with a statistical uncertainty of 1.1 degrees. The angle from the Fermi LAT boresight is 9.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250204311/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250204311/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250204311/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39138. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37146] LIGO/Virgo/KAGRA S250204ax: Identification of a GW compact binary merger candidate
by GCN Circulars 04 Feb '25

04 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39137 SUBJECT: LIGO/Virgo/KAGRA S250204ax: Identification of a GW compact binary merger candidate DATE: 25/02/04 06:47:05 GMT FROM: Allen1711449(a)gmail.com The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S250204ax during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2025-02-04 05:52:59.004 UTC (GPS time: 1422683597.004). The candidate was found by the CWB [1], CWB BBH [2], GstLAL [3], PyCBC Live [4], and SPIIR [5] analysis pipelines. S250204ax is an event of interest because its false alarm rate, as estimated by the online analysis, is 3.2e-10 Hz, or about one in 1e2 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250204ax After parameter estimation by RapidPE-RIFT [6], the classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), NSBH (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that the lighter compact object is consistent with a neutron star mass (HasNS) is <1%. [7] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [7] Both HasNS and HasRemnant consider the support of several neutron star equations of state. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,0, an initial localization generated by BAYESTAR [8], distributed via GCN notice about 2 minutes after the candidate event time. * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [8], distributed via GCN notice about 7 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,1. For the bayestar.multiorder.fits,1 sky map, the 90% credible region is 814 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 2533 +/- 744 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Klimenko et al. PRD 93, 042004 (2016) doi:10.1103/PhysRevD.93.042004 [2] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018 [3] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. (2023) arXiv:2305.05625 [4] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [5] Chu et al. PRD 105, 024023 (2022) doi:10.1103/PhysRevD.105.024023 [6] Rose et al. (2022) arXiv:2201.05263 and Pankow et al. PRD 92, 023002 (2015) doi:10.1103/PhysRevD.92.023002 [7] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [8] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/39137. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37145] GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
by GCN Circulars 03 Feb '25

03 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39136 SUBJECT: GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection DATE: 25/02/03 20:10:36 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Alan M. Watson (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Sarah Antier (OCA), Rosa L. Becerra (Università degli Studi di Roma Tor Vergata), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Jean-Grégoire Ducoin (CPPM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), Benjamin Schneider (LAM) and the DDRAGO engineering team: Luis Carlos Álvarez (UNAM), Fernando Angeles, Salvador Cuevas (UNAM), François Dolon (OHP), Alejandro Farah (UNAM), Johan Floriot (LAM), Jorge Fuentes-Fernández (UNAM), Arthur Langios (IRAP), Rosalía Langarica (UNAM), Simona Lombarda (LAM), Jaime Ruíz Díaz-Soto (UNAM), Samuel Ronayette (CEA), Silvio Tinoco (UNAM), and Hervé Valentín (IRAP) report: We imaged the field of the Swift GRB 250129A (Beardmore et al., GCN Circ. 39066) with the COLIBRÍ (SVOM/F-GFT) telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We observed with the DDRAGO wide-field science camera (Langarica et al., 2024, Proc SPIE 13096, 130963D) in a filter that closely approximates Pan-STARRS r, from 2025-02-03 07:45 to 08:00 UTC, at a midpoint of 5.20 days after the event, and obtained 600 seconds of exposure at a median airmass of 2.25 and good weather conditions. The data were reduced using custom software and then analysed and calibrated against the PS1 catalog using STDPipe (Karpov 2021). We clearly detect the afterglow with r = 22.10 +/- 0.15 This magnitude is not corrected for Galactic extinction. Our measurement is consistent with the magnitude reported by Bochenek & Perley (GCN Circ. 39131) at 4.93 days after the event. Further observations are planned. The DDRAGO camera is still being commissioned, and these are its first science observations. We warmly thank the COLIBRÍ engineering team and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/39136. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37144] GRB 250202B: NuSTAR detection of the prompt emission
by GCN Circulars 03 Feb '25

03 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39135 SUBJECT: GRB 250202B: NuSTAR detection of the prompt emission DATE: 25/02/03 19:37:50 GMT FROM: Brian Grefenstette at Caltech/NuSTAR <bwgref(a)srl.caltech.edu> B. Grefenstette (Caltech) reports on behalf of the NuSTAR Search for INteresting Gamma-ray Signals (SINGS) working group: The NuSTAR SINGS working group reports the detection of prompt emission from the Long GRB 250202B in both the NuSTAR CsI anti-coincidence shields. This GRB was identified through a blind search using the CsI shield rates. Details of the search algorithm will be described in a future paper. The NuSTAR SINGS algorithm triggered at 2025-02-02 03:57:12.000 (with a resolution ~5-seconds). This is consistent with the detections by Fermi (Fermi GBM Team, GCN circ. 39120, 39133) and the Astrosat CTZI detection (Waratkar et al, GCN circ. 39122). The NuSTAR CsI shield data are recorded at 1 Hz. The GRB appears to be composed of multiple, significantly-detected peaks, including a second significant set of bursts roughly 90-s after the initial trigger. The total duration for the event is at least 100-s. The largest individual burst peaks at 5,000 cps, with other bursts between 2,000 and 3,000 cps. The baseline rate is a ~1,000 cps during this time period. We do not see a clear signal in the CdZnTe detectors. Using the localization from Fermi at RA = 347.8, Dec = 16.5 implies an offset from the NuSTAR boresight of 115 deg (e.g., through the side of the instrument) and the offset from the geocenter of 114-deg Lightcurves and analysis for this GRB can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2025/250202B/ Information on NuSTAR SINGS can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/ NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA’s Science Mission Directorate in Washington. View this GCN Circular online at https://gcn.nasa.gov/circulars/39135. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37143] GRB 250202C: GRBAlpha detection
by GCN Circulars 03 Feb '25

03 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39134 SUBJECT: GRB 250202C: GRBAlpha detection DATE: 25/02/03 17:34:25 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> M. Dafcikova, J. Ripa, M. Kolar (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner (Masaryk U.), M. Ohno, H. Takahashi (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), N. Husarikova, F. Munz, M. Topinka, M. Duriskova, L. Szakszonova, J.-P. Breuer, F. Hroch (Masaryk U.), T. Urbanec, M. Kasal, A. Povalac (Brno U. of Technology), J. Hudec, J. Kapus, M. Frajt (Spacemanic s.r.o), R. Laszlo, M. Koleda (Needronix s.r.o), M. Smelko, P. Hanak, P. Lipovsky (Technical U. of Kosice), G. Galgoczi (Wigner Research Center/Eotvos U.), Y. Uchida, H. Poon, H. Matake (Hiroshima U.), N. Uchida (ISAS/JAXA), T. Bozoki (Eotvos U.), G. Dalya (Eotvos U.), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), G. Friss (Eotvos U.), Y. Fukazawa, K. Hirose (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), K. Kapas (Eotvos U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), J. Takatsy (Eotvos U.), K. Torigoe (Hiroshima U.), N. Kogiso, M. Yoneyama (Osaka Metropolitan U.), M. Moritaki (U. Tokyo), T. Kano (U. Michigan) -- the GRBAlpha collaboration. The long-duration GRB 250202C (Fermi/GBM detection: GCN 39126) was observed by the GRBAlpha 1U CubeSat (Pal et al. 2023, A&A, 677, 40; https://ui.adsabs.harvard.edu/abs/2023A%26A...677A..40P/abstract). The detection was confirmed at the peak time 2025-02-02 20:10:36.5 UTC. The T90 duration measured by GRBAlpha is 6.0 s and the overall significance during T90 reaches 8.5 sigma. The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB250202C_GCN.pdf All GRBAlpha detections are listed at: https://monoceros.physics.muni.cz/hea/GRBAlpha/ GRBAlpha, launched on 2021 March 22, is a demonstration mission for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). The detector of GRBAlpha consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~50 keV to ~1000 keV. To increase the duty cycle and the downlink rate, the upgrade of the on-board data acquisition software stack is in progress. The ground segment is also supported by the radio amateur community and it takes advantage of the SatNOGS network for increased data downlink volume. View this GCN Circular online at https://gcn.nasa.gov/circulars/39134. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37142] GRB 250202B: Fermi GBM Detection
by GCN Circulars 03 Feb '25

03 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39133 SUBJECT: GRB 250202B: Fermi GBM Detection DATE: 25/02/03 17:22:25 GMT FROM: sumanbala2210(a)gmail.com S. Bala (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 03:57:17.32 UT on 02 February 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250202B (trigger 760161442/250202165). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 347.80, Dec = 16.48 (J2000 degrees, equivalent to J2000 23h 11m, +16d 29'), with a statistical uncertainty of 1.43 degrees. (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a mixture of two Gaussians, one with a radius of 1.8 degrees (52% contribution) and one with a radius of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]). The angle from the Fermi LAT boresight is 128 degrees. The GBM light curve consists of many bright peaks with a duration (T90) of about 89 s (50-300 keV). The time-averaged spectrum from T0-0.1 to T0+109.4 s is best fit by a Band function with Epeak = 252 +/- 5 keV, alpha = -0.81 +/- 0.01, and beta = -2.56 +/- 0.05. The event fluence (10-1000 keV) in this time interval is (1.77 +/- 0.01)E-04 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1.7 s in the 10-1000 keV band is 43.4 +/- 0.7 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/39133. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37141] IceCube-250203A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 03 Feb '25

03 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39132 SUBJECT: IceCube-250203A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/02/03 15:40:47 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 2025-02-03 03:59:29.20 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_Bronze alert stream. The average astrophysical neutrino purity for Bronze alerts is 30%. This alert has an estimated false alarm rate of 3.7051 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/140436_11917698.amon), more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 2025-02-03 Time: 03:59:29.20 UT RA: 253.30 (+0.49, -0.49 deg 90% PSF containment) J2000 Dec: -1.31 (+0.48, -0.44 deg 90% PSF containment) J2000 We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino. No known gamma-ray sources listed in the Fermi 4FGL-DR4 or 3FHL catalogs are located within the 90% uncertainty region of the event. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu View this GCN Circular online at https://gcn.nasa.gov/circulars/39132. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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