February 2025 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 37246] GRB 250206A: EIRSAT-1 GMOD Detection
by GCN Circulars 08 Feb '25

08 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39236 SUBJECT: GRB 250206A: EIRSAT-1 GMOD Detection DATE: 25/02/08 15:43:17 GMT FROM: Caimin McKenna at University College Dublin <caimin.mckenna(a)ucdconnect.ie> D. Murphy, C. McKenna, C. de Barra, A. Ulyanov, P. McDermott, M. Doyle, R. Dunwoody, J. Mangan, G. Finneran, G. Corcoran, L. Cotter, A. Empey, J. Fisher, F. Gibson Kiely, J. Thompson, D. McKeown, A. Martin-Carrillo, L. Hanlon, S. McBreen, on behalf of the EIRSAT-1 team: EIRSAT-1 reports the detection of the long gamma-ray burst GRB250206A by the Gamma-ray Module (GMOD) instrument, which was also detected by Fermi GBM (GCN [39172](https://gcn.nasa.gov/circulars/39172)). The detection was made starting at 2025-02-06 19:51:22.4 UTC. The GMOD light curve for GRB250206A with 1.2s binning shows a long burst with two pulses, separated by 7.2 seconds, consistent with that seen by NASA Fermi-GBM. The 3rd softer pulse is not detected by GMOD. The spacecraft location at the time of detection was 5.095 N, 35.194 E at an altitude of 439.8 km. The GMOD light curve for this event can be found here: https://grb.eirsat1.ie/250206A/250206A_LC_onboard_preliminary.png EIRSAT-1 is Ireland’s first satellite (Doyle et al. Proceedings of the 4th SSEA, 2022). It is a 2U CubeSat and carries onboard a number of experiments including the Gamma-Ray Module (GMOD), a novel, compact, gamma-ray detector (Murphy et al, Experimental Astronomy, 53, 961–990, 2022). GMOD consists of a 25 mm × 25 mm × 40 mm Cerium Bromide scintillator coupled to SiPMs and is designed to detect gamma-ray bursts in the ~ 60 keV - 1.5 MeV range. EIRSAT-1 was developed in University College Dublin with support from ESA’s Fly Your Satellite! programme and was launched on 1st December 2023. View this GCN Circular online at https://gcn.nasa.gov/circulars/39236. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37245] LIGO/Virgo/KAGRA S250206dm: (Update-7) NED Galaxies in the Localization Volume
by GCN Circulars 08 Feb '25

08 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39235 SUBJECT: LIGO/Virgo/KAGRA S250206dm: (Update-7) NED Galaxies in the Localization Volume DATE: 25/02/08 14:56:18 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-7-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 20861 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/7 Top 20 List Download: https://ned.ipac.caltech.edu/uri/NED::GWFglist/fits/S250206dm/7/20 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|2.36e-06| 4.22e-09| |WISEA J022348.88+533854.6| 35.95371| 53.64847| G| 361.18| null| null| null| 12.653| 0.121| 10.626| 0.007|2.93e-06| 1.14e-09| |WISEA J023404.21+543420.9| 38.51758| 54.57247| G| 387.94| 0.60| null| null| 11.605| 0.091| 11.228| 0.010|2.73e-06| 7.21e-10| |WISEA J022610.54+530728.2| 36.54379| 53.12453| G| 369.10| null| null| null| 13.505| 0.153| 11.533| 0.008|4.03e-06| 7.10e-10| |WISEA J024025.00+541511.8| 40.10413| 54.25331| G| 377.15| null| null| null| 13.153| 0.114| 11.550| 0.010|2.94e-06| 5.49e-10| |WISEA J024516.51+542758.5| 41.31871| 54.46631| G| 365.18| null| null| null| 12.190| 0.129| 10.967| 0.007|1.78e-06| 5.48e-10| |WISEA J022200.27+503737.1| 35.50117| 50.62697| G| 288.27| null| null| null| 12.566| 0.105| 9.223| 0.006|5.70e-07| 5.36e-10| |WISEA J023155.31+513044.0| 37.98038| 51.51228| G| 322.72| null| null| null| 13.525| 0.153| 10.101| 0.006|8.93e-07| 4.56e-10| |WISEA J023620.33+544551.7| 39.08458| 54.76433| G| 260.69| 0.40| null| null| 11.288| 0.099| 10.411| 0.006|1.75e-06| 4.45e-10| |WISEA J023712.75+540728.3| 39.30317| 54.12464| G| 281.88| null| null| null| 12.709| 0.114| 11.242| 0.006|3.18e-06| 4.38e-10| |WISEA J022430.81+525101.6| 36.12842| 52.85050| G| 400.04| null| null| null| 12.694| 0.141| 11.911| 0.010|3.00e-06| 4.37e-10| |WISEA J161708.84-674024.7| 244.28700| -67.67294| G| 314.35| null| null| null| 12.878| 0.112| 9.322| 0.006|4.41e-07| 4.23e-10| |WISEA J022614.61+524507.6| 36.56092| 52.75206| G| 429.82| null| null| null| 13.099| 0.140| 11.893| 0.009|2.42e-06| 4.21e-10| |WISEA J024335.91+531732.8| 40.89963| 53.29250| G| 351.10| null| null| null| 13.087| 0.139| 11.487| 0.011|2.44e-06| 4.19e-10| |WISEA J021942.98+525320.0| 34.92904| 52.88886| G| 471.43| null| null| null| 12.998| 0.153| 11.105| 0.012|9.81e-07| 4.14e-10| |WISEA J022523.45+533416.2| 36.34758| 53.57089| G| 544.42| null| null| null| 12.873| 0.115| 10.515| 0.006|3.76e-07| 3.68e-10| |WISEA J022425.11+524210.8| 36.10462| 52.70289| G| 303.57| null| null| null| 11.882| 0.114| 11.585| 0.019|3.24e-06| 3.67e-10| |WISEA J022226.96+515125.6| 35.61233| 51.85711| G| 338.33| null| null| null| 13.057| 0.131| 11.350| 0.009|2.10e-06| 3.67e-10| |WISEA J022553.94+515215.4| 36.47396| 51.87139| G| 340.02| null| null| null| 12.716| 0.089| 11.376| 0.007|1.97e-06| 3.42e-10| |WISEA J022458.67+520149.0| 36.24458| 52.03025| G| 255.83| 0.86| null| null| 10.779| 0.064| 10.693| 0.007|1.86e-06| 3.40e-10| 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/39235. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37244] LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
by GCN Circulars 08 Feb '25

08 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39234 SUBJECT: LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations DATE: 25/02/08 14:29:23 GMT FROM: David Coulter at STScI <dcoulter(a)ucsc.edu> D. A. Coulter (STScI), C. D. Kilpatrick (Northwestern), P. Macias (UCSC), R. J. Foley (UCSC), K. W. Davis (UCSC), A. Villar (Harvard) reports on behalf of the Gravity Collective [1, 2]: We searched the localization region of the probable NSBH merger candidate, S250206dm (LVK Collaboration, [GCN 39175](https://gcn.nasa.gov/circulars/39175)), with the ~0.22 square degree field-of-view near IR imager NEWFIRM currently mounted on the Blanco 4-m telescope at CTIO. We observed the entire 0.43 deg confidence region reported by the IceCube Collaboration ([GCN 39176](https://gcn.nasa.gov/circulars/39176)) that overlapped with the GW localization, beginning observations at 2025-02-07 05:47 UTC (+8.3 hours after GW trigger) in J-band. We obtained 3 sequences of 22x5 second co-adds across the neutrino confidence region, with an average depth of J ~ 22 AB mag. Data were processed using standard procedures in photpipe [3], and we performed image subtraction across each field using templates constructed from VIRCAM J-band images with limiting magnitudes of J ~ 19 AB mag. After vetting sources of transient emission as being unassociated with variable stars, minor planets, and known transients in each surveyed field, we concluded that there are no likely sources of transient emission in the NEWFIRM imaging. [1] Kilpatrick, C. D. et al. 2021 [2] Coulter, D. A., et al. 2024 [3] Rest, A. et al. 2005 View this GCN Circular online at https://gcn.nasa.gov/circulars/39234. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37243] GRB 250206A: Fermi-LAT detection
by GCN Circulars 08 Feb '25

08 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39233 SUBJECT: GRB 250206A: Fermi-LAT detection DATE: 25/02/08 13:50:51 GMT FROM: Rahul Gupta at NASA GSFC <rahul.gupta(a)nasa.gov> R. Gupta (NASA GSFC), S. Lopez (CNRS / IN2P3), and A. Holzmann Airasca (UniTrento and INFN Bari) on behalf of the Fermi-LAT Collaboration: On February 06, 2025, Fermi-LAT detected high-energy emission from GRB 250206A, which was also detected by Fermi-GBM (trigger 760564296 / 250206827, GCN 39172). The best LAT on-ground location is found to be: RA, Dec = 225.31, -62.26 (J2000) with an error radius of 0.56 deg (90 % containment, statistical error only). This was 33 deg from the LAT boresight at the time of the GBM trigger (T0 = 19:51:31.93 UT). The data from the Fermi-LAT shows a significant increase in the event rate that is spatially and temporally correlated with the GBM emission with high significance. The photon flux above 100 MeV in the time interval 0 - 90 s after the GBM trigger is (2.1 ± 0.7) E-5 ph/cm2/s. The estimated photon index above 100 MeV is 2.1 ± 0.3. The highest-energy photon is a 1.4 GeV event which is observed ~ 16 seconds after the GBM trigger. A Swift ToO has been approved for this burst. The Fermi-LAT point of contact for this burst is Rahul Gupta (rahulbhu.c157(a)gmail.com). 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/39233. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37242] GRB 250207B: Swift-XRT observations
by GCN Circulars 08 Feb '25

08 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39232 SUBJECT: GRB 250207B: Swift-XRT observations DATE: 25/02/08 13:22:06 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), J.A. Kennea (PSU), D.N. Burrows (PSU), M. A. Williams (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the MAXI-detected burst GRB 250207B in a series of observations tiled on the sky. The total exposure time is 1.5 ks, distributed over 6 tiles; the maximum exposure at a single sky location in the tiling was 540 s. The data were collected between T0+51.2 ks and T0+53.6 ks, and are entirely in Photon Counting (PC) mode. No X-ray sources have been detected. The 3-sigma upper limit in the field (not including the regions where the tiles overlap) ranges from ~0.0e+00 to ~5.5e-01 ct s^-1, corresponding to a 0.3-10 keV observed flux of 0.0e+00 to 2.2e-11 erg cm^-2 s^-1 (assuming a typical GRB spectrum). The results of the XRT-team automatic analysis of the tiled XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/xrt_products/TILED_GRB00131. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39232. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37241] LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification
by GCN Circulars 08 Feb '25

08 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39231 SUBJECT: LIGO/Virgo/KAGRA S250206dm: Updated Sky localization and EM Bright Classification DATE: 25/02/08 11:14:31 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), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S250206dm (GCN Circular 39184). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.offline1.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 13%. [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 35%. For the Bilby.offline1.multiorder.fits,0 sky map, the 90% credible region is 547 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 373 +/- 104 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/39231. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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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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