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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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[vsnet-grb-info 37140] GRB 250129a: Liverpool Telescope optical follow-up
by GCN Circulars 03 Feb '25

03 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39131 SUBJECT: GRB 250129a: Liverpool Telescope optical follow-up DATE: 25/02/03 14:47:32 GMT FROM: A. Bochenek at Liverpool John Moores University <a.m.bochenek(a)2023.ljmu.ac.uk> A. Bochenek and D. A. Perley (LJMU) report: We observed the field of GRB250129a (Beardmore et al., GCN 39066) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 10x90s exposures in the SDSS r’ filter starting at 2025-02-02 02:53:56 UT, approximately 4.93 days after the trigger. We report a detection of the optical transient (Beardmore et al., GCN 39066) in the stacked images of r = 21.80 ± 0.11 mag. Our detection is consistent with other late-time observations (Schlekat et al., GCN39110, Gompertz et al., GCN 39114, Moskvitin et al., GCN39130), and suggests the afterglow is now decaying faster, with a temporal index of approx. -2.2 (fit to observations after 2.5 days post-trigger). The photometry was obtained using nearby PanSTARRS standards and was not corrected for extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39131. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37139] GRB 240129A: further SAO RAS optical observations
by GCN Circulars 03 Feb '25

03 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39130 SUBJECT: GRB 240129A: further SAO RAS optical observations DATE: 25/02/03 14:10:39 GMT FROM: Moskvitin Alexander at SAO RAS <mosk(a)sao.ru> A. Moskvitin, R. Uklein, Yu. Sotnikova (SAO RAS), A. Ghosh, S. Razzaque (CAPP, University of Johannesburg) report on behalf of the GRB follow-up team. We observed the field of GRB 250129A (Beardmore et al., GCN 39066; Goad et al., GCN 39082; Frederiks et al., GCN 39116) with the SAO RAS 1-m telescope Zeiss-1000 equipped with the multi-mode focal reducer MAGIC on 2025 February 2, 01:23:43--01:43:23 UT (t_mid - T0 = 3.8669 days). We obtained 3 x 300 sec. images in R band. The OT (Francile et al., GCN 39065; GCN 39075, Beardmore et al., GCN 39066, Schneider et al., GCN 39071, Belkin et al., GCN 39072; Izzo et al., GCN 39073; Izzo and Malesani, GCN 39074; Ghosh et al., GCN 39077; Schneider et al., GCN 39078; Brivio et al., GCN 39079; Siegel and Beardmore, GCN 39085; Zheng and Filippenko, GCN 39090; GCN 39102; Schlekat et al., GCN 39091; Antier et al., GCN 39096; Odeh et al., GCN 39097; Ferro et al., GCN 39098; Bochenek and Perley, GCN 39099; Malesani et al., GCN 39100; Romanov, GCN 39101; Watson et al., GCN 39104; Vinko et al., GCN 39105; Akl et al., GCN 39106; Moskvitin et al., GCN 39107; Calapai GCN 39109; Schlekat et al., GCN 39110; Gompertz et al., GCN 39114; Ror et al., GCN 39115; Lipunov et al., GCN 39119; Wu et al., GCN 39124; Paek et al., GCN 39129) is clearly detected in our stacked image with the brightness of R = 21.06 +/- 0.14 (calibrated against R2 magnitudes of nearby UNSO-B1 stars and not corrected for the MW extinction). View this GCN Circular online at https://gcn.nasa.gov/circulars/39130. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37138] GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
by GCN Circulars 03 Feb '25

03 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39129 SUBJECT: GRB 250129A: 7DT Detection and Medium-band SED of Afterglow DATE: 25/02/03 06:14:53 GMT FROM: Gregory Paek at Seoul National University <gregorypaek94(a)gmail.com> Gregory S.H. Paek (IfA, SNU ARC/SNU), Myungshin Im (SNU ARC/SNU), Hyeonho Choi (SNU ARC/SNU), Donggeun Tak (SNU ARC/SNU), Seo-Won Chang (SNU ARC/SNU), and Ji Hoon Kim (SNU ARC/SNU) report on behalf of the 7-Dimensional Telescope collaboration We detected the optical counterpart of GRB 250129A using the 7-Dimensional Telescopes (7DT). Approximately 1 hour and 14 minutes following the initial detection by Swift (Swift team, Beardmore et al., GCN #39066), we targeted the localization center provided by Swift/UVOT at RA, Dec = 198.67673 deg, +5.03063 deg with an uncertainty of 1.10 arcseconds. Observations were made with eleven 7DT units in r-band and nineteen medium-band filters, denoted as m400, m425, then through m875, in which the numeric values indicate their central wavelengths in nanometers. Each medium-band filter has a bandwidth of 25nm. Photometric flux calibration was performed using synthetic photometry based on the Gaia DR3 XP catalog (Gaia Collaboration et al. 2022) within the AB magnitude system. The optical counterpart was detected in most filters. However, only marginal detection was observed in m800, m825, m850, and m875. This is based on preliminary photometry, and no extinction correction has been applied. The 5-sigma upper limits (AB) and detections in relevant filters are summarized below. ------ Filter Mag Mag_err Date-obs[UT] Exp.time[s] Depth(5sigma) Note m425 17.3 0.0 2025-01-29T05:59:21 300 19.9 m450 17.2 0.0 2025-01-29T05:53:51 300 19.2 m475 17.2 0.0 2025-01-29T05:59:21 300 19.5 m500 17.2 0.0 2025-01-29T05:53:51 300 20.0 m525 17.2 0.0 2025-01-29T05:59:20 300 20.1 m550 17.0 0.1 2025-01-29T05:53:52 300 18.6 m575 17.0 0.0 2025-01-29T05:59:19 300 18.8 m600 16.9 0.0 2025-01-29T05:53:58 300 19.7 m625 16.9 0.0 2025-01-29T05:59:36 300 19.4 m650 16.9 0.0 2025-01-29T05:53:56 300 19.4 m675 17.1 0.1 2025-01-29T05:59:22 300 19.4 m700 16.9 0.0 2025-01-29T05:53:49 300 19.2 m725 17.0 0.0 2025-01-29T05:59:17 300 18.9 m750 17.0 0.1 2025-01-29T05:53:54 300 18.8 m775 17.0 0.1 2025-01-29T05:59:22 300 18.3 m800 2025-01-29T05:53:59 300 17.8 n/d m825 2025-01-29T05:59:32 300 17.6 n/d m850 2025-01-29T05:53:54 300 17.2 n/d m875 2025-01-29T05:59:15 300 17.1 n/d r 17.0 0.0 2025-01-29T05:59:07 600 20.9 The 7-Dimensional Telescope (7DT), located in Chile and comprising 20 wide-field telescopes equipped with 40 medium-bandwidth (~25nm) filters, aims to detect optical counterparts of GW sources and conduct the 7-Dimensional Sky Survey (7DS) of the Southern Hemisphere. Further information about the 7DT is available at http://gwuniverse.snu.ac.kr/. View this GCN Circular online at https://gcn.nasa.gov/circulars/39129. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37137] LIGO/Virgo/KAGRA S250202cu: Updated Sky localization
by GCN Circulars 03 Feb '25

03 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39128 SUBJECT: LIGO/Virgo/KAGRA S250202cu: Updated Sky localization DATE: 25/02/03 03:45:53 GMT FROM: lucy.thomas(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 S250202cu (GCN Circular 39125). 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/S250202cu For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 4768 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 5196 +/- 2273 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/39128. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37136] The EP-WXT trigger 01709131196 is likely a flaring star
by GCN Circulars 03 Feb '25

03 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39127 SUBJECT: The EP-WXT trigger 01709131196 is likely a flaring star DATE: 25/02/03 01:44:35 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Zhou (PMO, CAS), M.Q. Huang (USTC), X. Mao and Z.-X. Ling (NAOC, CAS) report on behalf of the Einstein Probe team: The EP-WXT trigger (ID: 01709131196) on 2025-02-02T21:33:52 (UTC) is likely a stellar flare associated with a M-type star RX J0916.1+0153. The preliminary X-ray luminosity (0.5-10keV) is about 5.4 x 10^29 erg/s. 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/39127. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37135] GRB 250202C: Fermi GBM Final Real-time Localization
by GCN Circulars 02 Feb '25

02 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39126 SUBJECT: GRB 250202C: Fermi GBM Final Real-time Localization DATE: 25/02/02 20:18:40 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 20:10:35 UT on 2 Feb 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250202C (trigger 760219840.823694 / 250202841). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 300.9, Dec = -54.5 (J2000 degrees, equivalent to J2000 20h 03m, -54d 30'), with a statistical uncertainty of 4.0 degrees. The angle from the Fermi LAT boresight is 25.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250202841/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250202841/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250202841/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39126. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37134] LIGO/Virgo/KAGRA S250202cu: Identification of a GW compact binary merger candidate
by GCN Circulars 02 Feb '25

02 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39125 SUBJECT: LIGO/Virgo/KAGRA S250202cu: Identification of a GW compact binary merger candidate DATE: 25/02/02 20:04:16 GMT FROM: Sivananda Thondapu <sivananda.thondapu(a)ligo.org> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S250202cu during real-time processing of data from LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) at 2025-02-02 18:49:02.510 UTC (GPS time: 1422557360.510). The candidate was found by the CWB BBH [1], GstLAL [2], and MBTA [3] analysis pipelines. S250202cu is an event of interest because its false alarm rate, as estimated by the online analysis, is 1.5e-08 Hz, or about one in 2 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250202cu The classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), NSBH (<1%), or BNS (<1%). Varying broadband noise in the LIGO Hanford detector was present at the time of the event, which may affect the parameters or the significance of the candidate. 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 4%. 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 30 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 4327 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 5526 +/- 1810 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 View this GCN Circular online at https://gcn.nasa.gov/circulars/39125. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37133] GRB 250129A: SVOM/C-GFT optical observations
by GCN Circulars 02 Feb '25

02 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39124 SUBJECT: GRB 250129A: SVOM/C-GFT optical observations DATE: 25/02/02 11:25:12 GMT FROM: Chao Wu at NAOC <cwu(a)nao.cas.cn> Chao WU (NAOC), Zhe Kang (CHO), Liping Xin(NAOC), Xuhui Han(NAOC), Pinpin Zhang (NAOC), Xiaomeng Lu (NAOC), Zhenwei Li (CHO), You Lv (CHO), Ruosong Zhang (NAOC), Yujie Xiao(NAOC), Yulei, Qiu(NAOC), Jing Wang(NAOC), Jianyan Wei (NAOC) report on behalf of the SVOM/C-GFT team: We observed the field of GRB 250129A detected by Swift/BAT (Beardmore et al., GCN 39066) with C-GFT. Our observations were started on 2025-01-30T17:51:44 UTC, ~37.11 hr after the trigger. A series of g, r and i band images were obtained with exposure time of 30s for each image. The optical counterpart (Beardmore et al., GCN 39066; Francile et al., GCN 39065; 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; Francile et al., GCN 39075; Ghosh et al., GCN 39077; Schneider et al., GCN 39078; Brivio et al.,GCN 39079; Siegel et al.,GCN 39085; Zheng et al., GCN 39090; Schlekat et al., GCN39091; Antier et al., GCN 39096; Odeh et al. GCN 39097; Ferroet al. GCN 39098; Bochenek et al., GCN 39099; Malesani et al., GCN 39100; Romanov et al., GCN 39101; Zheng et al., GCN 39102; Watson et al., GCN 39104;Vinko et al., GCN 39105; Akl et al., GCN 39106; Moskvitin et al., GCN 39107; Giovanni et al., GCN 39109; Schlekat et al., GCN 39110; Schlekat et al., GCN 39114 and Ror et al., GCN 39115) was clearly detected in stacked images of band g,r and i. The results are, (T-T0)_mid(hr) mag mag_err band ----------------------------------------- 37.73 20.08 0.22 g 37.83 19.74 0.16 r 37.92 19.32 0.11 i The photometry was calibrated with nearby Pan-STARRS1 stars. We thank the observation assistants Bowen Li and Yinghuai Hao at Jilin observatory for their excellent support. Chinese Ground Follow-up Telescope of SVOM mission is located at Jilin, Changchun Observatory, National Astronomical Observatories, CAS. It has FOV of 1.28 deg x 1.28 deg with a 4k*4k CMOS detector mounted on the primary focus of 1.2-meter-aperure telescope. View this GCN Circular online at https://gcn.nasa.gov/circulars/39124. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37132] The EP-WXT trigger 01709131153 is not a real source
by GCN Circulars 02 Feb '25

02 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39123 SUBJECT: The EP-WXT trigger 01709131153 is not a real source DATE: 25/02/02 10:50:26 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. L. Wang, W. J. Zhang, W. X. Wang, Y. Liu (NAO, CAS) report on behalf of the Einstein Probe team: Further analysis of the data suggests that the EP-WXT on-board trigger 01709131153 at 2025-02-02T09:47:53.499 (UTC) is not a real source. View this GCN Circular online at https://gcn.nasa.gov/circulars/39123. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37131] GRB 250202B: AstroSat CZTI detection of a bright long GRB
by GCN Circulars 02 Feb '25

02 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39122 SUBJECT: GRB 250202B: AstroSat CZTI detection of a bright long GRB DATE: 25/02/02 08:46:15 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> S. Srijan (IITB), 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 bright long GRB 250202B which was also detected by Fermi/GBM (Fermi-GBM Team, GCN Circ. 39120). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-02-02 03:57:18.0 UTC. The measured peak count rate associated with the burst is 485 (+14, -15) counts/s above the background in the combined data of all quadrants, with a total of 21162 (+462, -483) counts. The local mean background count rate was 262 (+2, -2) counts/s. Using cumulative rates, we measure a T90 of 91 (+2, -2) s. In the preliminary analysis, we find 2474 Compton events associated with this event. It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-02-02 03:57:24.5 UTC. The measured peak count rate is 750 (+7, -8) counts/s above the background in the combined Veto data of all quadrants, with a total of 30918 (+312, -410) counts. The local mean background count rate was 1195 (+1, -1) counts/s. We measure a T90 of 90 (+1, -1) s from the cumulative Veto light curve. 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/39122. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37130] LIGO/Virgo/KAGRA S250202ad: Retraction of GW compact binary merger candidate
by GCN Circulars 02 Feb '25

02 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39121 SUBJECT: LIGO/Virgo/KAGRA S250202ad: Retraction of GW compact binary merger candidate DATE: 25/02/02 04:44:54 GMT FROM: Souradeep Pal at IISER Kolkata <sp19rs015(a)iiserkol.ac.in> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: The trigger S250202ad is no longer considered to be a candidate of interest. This candidate was initially identified by one or more early-warning analyses by matching partial signal templates to the data. Analysis of additional data up to the putative merger time, with full signal templates, did not make a significant detection, indicating that the initial candidate was likely due to transient noise. View this GCN Circular online at https://gcn.nasa.gov/circulars/39121. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37129] GRB 250202B: Fermi GBM Final Real-time Localization
by GCN Circulars 02 Feb '25

02 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39120 SUBJECT: GRB 250202B: Fermi GBM Final Real-time Localization DATE: 25/02/02 04:07:47 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 03:57:17 UT on 2 Feb 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250202B (trigger 760161442.322744 / 250202165). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 347.8, Dec = 16.5 (J2000 degrees, equivalent to J2000 23h 11m, 16d 30'), with a statistical uncertainty of 1.4 degrees. The angle from the Fermi LAT boresight is 128.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250202165/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250202165/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250202165/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39120. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37128] Swift GRB250129A: MASTER 4 days observations report
by GCN Circulars 02 Feb '25

02 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39119 SUBJECT: Swift GRB250129A: MASTER 4 days observations report DATE: 25/02/02 03:23:05 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, N.Tiurina, P.Balanutsa, I.Panchenko, K.Zhirkov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, Ya.Kechin, V.Senik, V.Topolev, A.Chasovnikov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), D.Buckley (SAAO), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) The MASTER-OAFA All Sky Camera located in Argentina (OAFA observatory of San Juan National University) imaged SWIFT GRB 250129A (A. P. Beardmore et al., GCN 39066) errorbox with upper limit up to ~8 mag (V) at single 5-s images with _prompt_ limit ~10 mag. MASTER-OAFA Very Wide Field Camera (VWFC, MASTER-ShOK camera of Global MASTER-Net: http://observ.pereplet.ru, Lipunov, Korniov, Gorbovskoy, Tiurina & Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 626 pp.) located in Argentina (OAFA observatory of San Juan National University) was pointed to the SWIFT GRB 250129A ( A. P. Beardmore et al., GCN 39066) errorbox 185 sec after trigger time at 2025-01-29 04:48:14 UT, with upper limit up to ~15 mag. MASTER500-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru) located in Argentina (OAFA observatory of San Juan National University) was pointed to the SWIFT GRB 250129A (Francile et al., GCN 39065) errorbox 160 sec after notice time (240sec after trigger time) at 2025-01-29 04:49:09 UT, with upper limit up to 21.1 mag. The observations began at zenith distance = 73 deg. (the sun altitude was -41.0 deg.) and were condinued at 30, 31 Jan, 01, 02, 03 Feb. MASTER600-Tunka robotic telescope located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the SWIFT GRB 250129A errorbox 40114 sec after notice time (40194 sec after trigger time) at 2025-01-29 15:55:03 UT, with upper limit up to 21.0 mag. The observations began at zenith distance = 85 deg (the sun altitude was -52.8 deg.) and were continued at 30, 31 Jan, 01, 02 Feb 2025. MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the SWIFT GRB 250129A errorbox 55139 sec after notice time (55220 sec after trigger time) at 2025-01-29 20:05:29 UT, with upper limit up to 18.9 mag. The observations began at zenith distance = 83 deg. The sun altitude was -59.8 deg. Observations were continued observations at 30, 31 Jan, 01, 02 Jan. MASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) was pointed to the SWIFT GRB 250129A errorbox 62515 sec after notice time (62595 sec after trigger time) at 2025-01-29 22:08:24 UT, with upper limit up to 20.2 mag. The observations began at zenith distance = 81 deg. The sun altitude is -39.2 deg. MASTER OT J131442.41+050150.4 presents from 29 jan (240s after trigger time) up to now (~21.5m, unfiltered) all 4 days with light curve with complicated structure . The galactic latitude b = 67 deg., longitude l = 319 deg. Real time updated cover map and discovered OT are available here: https://master.sai.msu.ru/site/master2/observ.php?id=2760136 View this GCN Circular online at https://gcn.nasa.gov/circulars/39119. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37127] GRB 250202A: Fermi GBM Final Real-time Localization
by GCN Circulars 02 Feb '25

02 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39118 SUBJECT: GRB 250202A: Fermi GBM Final Real-time Localization DATE: 25/02/02 01:18:35 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 01:08:03 UT on 2 Feb 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250202A (trigger 760151288.464456 / 250202047). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 295.3, Dec = -35.0 (J2000 degrees, equivalent to J2000 19h 41m, -35d 00'), with a statistical uncertainty of 9.0 degrees. The angle from the Fermi LAT boresight is 36.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250202047/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250202047/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250202047/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39118. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37126] GRB 250201A: INTEGRAL SPI/ACS detection
by GCN Circulars 01 Feb '25

01 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39117 SUBJECT: GRB 250201A: INTEGRAL SPI/ACS detection DATE: 25/02/01 19:34:25 GMT FROM: Aishwarya L Thakur at INAF-IAPS, Rome <aishth(a)outlook.com> Patrizia Barria(a,b), Giulia Gianfagna(a), James Craig Rodi(a), Aishwarya Linesh Thakur(a), Lorenzo Natalucci(a,b), Luigi Piro(a) report: GRB 250201A was discovered by Fermi/GBM (GCN 39112) on 2025-02-01T09:59:46 (UTC). We searched for a corresponding counterpart in the INTEGRAL/SPI-ACS data. In an SPI-ACS light curve above 80 keV, we find a signal temporally coincident with the GBM detection, having an approximate duration of ~ 20 sec. The signal consists of two pulses over this duration. The approximate peak count rate in SPI-ACS is 77,500 cts/s for E>80 keV, over a median background rate of 62,800 cts/s. This work is based on observations with INTEGRAL, an ESA project with instruments and a science data centre funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, and Spain), and with the participation of Russia and the USA. The SPI-ACS detector system has been provided by MPE Garching/Germany. ----- (a) INAF/IAPS-Rome (b) ICSC National Research Centre for High-Performance Computing View this GCN Circular online at https://gcn.nasa.gov/circulars/39117. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37125] Konus-Wind detection of GRB 250129A
by GCN Circulars 01 Feb '25

01 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39116 SUBJECT: Konus-Wind detection of GRB 250129A DATE: 25/02/01 17:29:52 GMT FROM: Dmitry Frederiks at Ioffe Institute <fred(a)mail.ioffe.ru> D. Frederiks, A.Lysenko, A. Ridnaya, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long GRB 250129A (Swift detection: Beardmore et al., GCN 39066) was detected by Konus-Wind (KW) in the waiting mode. A Bayesian block analysis of the KW waiting mode data in the 20-400 keV band reveals a >6 sigma count rate increase in the interval from T0-66 s to T0+208 s where T0 = T0(BAT) = 04:45:09 UT. The KW light curve of this burst is available at http://www.ioffe.ru/LEA/GRBs/GRB250129A/ Modeling the time-integrated spectrum of the burst by a power law with exponential cutoff (CPL) model dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) yields alpha = -1.74 (-0.07, + 0.07) and Ep = 66(-8,+8) keV. In the 10 keV -10 MeV band, standard for the KW analysis, the burst fluence is (6.71 ± 0.14)x10^-6 erg/cm^2 and the 2.944 s peak energy flux is (1.46 ± 0.18)x10^-7 erg/cm^2/s. Assuming the redshift z=2.151 (Schneider et al., GCN 39071) and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014), we estimate the burst isotropic energy release E_iso to (7.7 ± 0.2)x10^52 erg, the isotropic peak luminosity L_iso to (5.3 ± 0.7)x10^51 erg/s, and the rest-frame peak spectral energy Ep,z to (207 ± 22) keV. With the obtained estimates, GRB 250129A is consistent with 68% prediction bands of 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021), see http://www.ioffe.ru/LEA/GRBs/GRB250129A/GRB250129A_rest_frame.pdf 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/39116. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37124] GRB 250129A: 1.3m DFOT Optical observations
by GCN Circulars 01 Feb '25

01 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39115 SUBJECT: GRB 250129A: 1.3m DFOT Optical observations DATE: 25/02/01 17:07:56 GMT FROM: Amit Kumar Ror at ARIES <mitturor77894(a)gmail.com> Amit K. Ror, Anshika Gupta, Kiran, Shashi B. Pandey, Kuntal Mishra (ARIES) report: We observed the field of GRB 250129A detected by the Swift Burst Alert Telescope (Swift team, Beardmore et al. 2025; GCN 39066) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2025-01-30 at 22:57:11 UT, i.e., ~ 1.76 days after the Swift-BAT trigger. We have taken multiple frames with an exposure time of 300 s in the R filter. We stacked the images after the alignment. We detected an optical afterglow in our stacked image within the error box of the enhanced Swift-XRT position by Goad et al. 2025 (GCN 39082). Further observations of the burst are still ongoing. We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (days) Filter Exp time (s) Magnitude ========================================================= 2025-01-30 22:57:11 ~1.76 R 300s*12 19.52 +/- 0.03 Our detection is consistent with Francile et al. 2025 (GCN 39065); Lipunov et al. 2025 (GCN 39070); Schneider et al. (GCN 39071); Belkin et al. 2025 (GCN 39072); Izzo et al. 2025 (GCN 39073); Izzo et al. 2025 (GCN 39074); Francile et al. 2025 (GCN 39075); Ghosh et al. 2025 (GCN 39077); Schneider et al. 2025 (GCN 39078); Brivio et al. 2025 (GCN 39079); Siegel et al. 2025 (GCN 39085); Zheng et al. 2025 (GCN 39090); Schlekat et al. 2025 (GCN 39091); Antier et al. 2025(GCN 39096); Odeh et al. 2025 (GCN 39097); Ferro et al. 2025(GCN 39098); Bochenek et al. 2025 (GCN 39099);Malesani et al. 2025 (GCN 39100); Romanov et al. 2025 (GCN 39101); Zheng et al. 2025 (GCN 39102); Zheng et al. 2025 (GCN 39102); Watson et al. 2025 (GCN 39104); Vinko et al. 2025(GCN 39105); Akl et al. 2025 (GCN 39106); Moskvitin et al. 2025 (GCN 39107); Giovanni et al. 2025 (GCN 39109); Schlekat et al. 2025 (GCN 39110) and Schlekat et al. 2025 (GCN 39114). The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalogue. This circular may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/39115. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37123] GRB 250129A: Liverpool Telescope observations suggest continued engine activity
by GCN Circulars 01 Feb '25

01 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39114 SUBJECT: GRB 250129A: Liverpool Telescope observations suggest continued engine activity DATE: 25/02/01 13:22:21 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), R. Brivio (INAF-OAB) and A. J. Levan (Radboud) report on behalf of a larger collaboration: We initiated follow-up observations of GRB 250129A (Beardmore et al., GCN 39066) with the IO:O camera on the 2m robotic Liverpool Telescope (LT). Observations were taken across the nights of 2025-01-30 and 2025-01-31, consisting of 5x180 s exposures in each of the SDSS r and i filters. In a preliminary analysis, we measure the following AB magnitudes: t-t0(d) exp(s) filt mag error 2.06 900 r 20.29 0.04 2.93 900 r 20.40 0.05 Magnitudes are calibrated against nearby Pan-STARRS stars and are not corrected for galactic extinction. Our measurements indicate either minimal evolution between 2 and 3 days after trigger, or a continuation of the flaring behaviour observed during the first 24 hours, as noted by Belkin et al. (GCN 39072), Francile et al. (GCN 39075), Brivio et al. (GCN 39079), Zheng & Filippenko (GCN 39090), Antier et al. (GCN 39096), and Malesani et al. (GCN 39100). View this GCN Circular online at https://gcn.nasa.gov/circulars/39114. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37122] GRB 250201A: BALROG localization (Fermi Trigger 760096791 / GRB 250201417)
by GCN Circulars 01 Feb '25

01 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39113 SUBJECT: GRB 250201A: BALROG localization (Fermi Trigger 760096791 / GRB 250201417) DATE: 25/02/01 10:53:32 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 760096791 at 09:59:46 on 01 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) = 112.5 deg Decl.(2000.0) = -54.7 deg The 1 sigma statistical error radius is 2.0 deg. We estimate an additional systematic error of 1 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB250201417/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB250201417/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB250201417/json View this GCN Circular online at https://gcn.nasa.gov/circulars/39113. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37121] GRB 250201A: Fermi GBM Final Real-time Localization
by GCN Circulars 01 Feb '25

01 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39112 SUBJECT: GRB 250201A: Fermi GBM Final Real-time Localization DATE: 25/02/01 10:10:18 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 09:59:46 UT on 1 Feb 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250201A (trigger 760096791.667376 / 250201417). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 115.8, Dec = -52.6 (J2000 degrees, equivalent to J2000 07h 43m, -52d 36'), with a statistical uncertainty of 1.1 degrees. The angle from the Fermi LAT boresight is 17.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250201417/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250201417/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250201417/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39112. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37120] LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
by GCN Circulars 01 Feb '25

01 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39111 SUBJECT: LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations DATE: 25/02/01 06:33:44 GMT FROM: Satoshi Sugita at Aoyama Gakuin U. <sugita(a)phys.aoyama.ac.jp> S. Sugita, M. Serino, Y. Kawakubo, H. Hiramatsu, H. Nishikawa, Y. Kondo (AGU) H. Negoro, M. Nakajima, K. Takagi (Nihon U.), N. Kawai, T. Mihara, (RIKEN), report on behalf of the MAXI team: We examined MAXI/GSC all-sky X-ray images (2-20 keV) after compact binary merger candidate S250201i at 2025-02-01 02:08:41.292 UTC. At the trigger time of S250201i, the high-voltage of MAXI/GSC was off, and it was turned on at T0+844 sec (+14.1 min). The first one-orbit (92 min) scan observation with GSC after the event covered 98% of the 90% credible region of the bayestar skymap from 03:09:42 to 03:22:16 UTC (T0+3661 to T0+4415 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/39111. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37119] GRB 250129A: Skynet Continued Optical Observations
by GCN Circulars 01 Feb '25

01 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39110 SUBJECT: GRB 250129A: Skynet Continued Optical Observations DATE: 25/02/01 03:46:26 GMT FROM: dschlekat(a)unc.edu Donovan Schlekat, Dylan Dutton, Daniel Reichart, Joshua Haislip, Vladimir Kouprianov, Daryl Janzen, Arie Verveer, and John Kennewell report on behalf of the Skynet Robotic Telescope Network at the University of North Carolina at Chapel Hill. We continued to observe the optical counterpart of GRB 250129A (Beardmore et al., GCN 39066) with two of Skynet’s 0.4m PROMPT telescopes at the Cerro Tololo Inter-American Observatory, Skynet’s 0.4m PROMPT telescope located in Meckering, Australia, and a 0.5m telescope at the Astronomical Observatory of the Jagiellonian University in Krakow, Poland. The observations began ~14 hours after the trigger and ended ~60 hours after the trigger. We detected the optical transient in both the V and R bands. The observed position of the optical counterpart was consistent with the coordinates described in other reports (Francile et al., GCN 39065; Beardmore et al., GCN 39066; Schneider et al., GCN 39071; Belkin et al., GCN 39072; Izzo et al., GCN 39073; Izzo & Malesani, GCN 39074; Ghosh et al., GCN 39077; Schneider et al., GCN 39078; Brivio et al., GCN 39079; Siegel et al., GCN 39085; Zheng & Filippenko, GCN 39090; Schlekat et al., 39091; Antier et al., 39096; Odeh et al., GCN 39097; Ferro et al., GCN 39098; Bochenek et al., GCN 39099; Malesani et al., GCN 39100; Romanov, GCN 39101; Zheng & Filippenko, GCN 39102; Watson et al., GCN 39104; Vinko et al., GCN 39105; Akl et al., GCN 39106; Moskvitin et al., GCN 39107; Calapai, GCN 39109). We observed the optical counterpart fading with a temporal index of ~1.75, consistent with the value reported by Akl et al. (GCN 39106). Select photometry is reported below. Tmid - T0 (days)| Telescope | Filter | Exposure (s) | Mag. | Mag Error --------------------------------------------------------------------------- 0.591 | PROMPT-MO | R | 100x80 | 17.482 | 0.051 1.191 | PROMPT-5 | R | 300 | 18.725 | 0.054 2.114 | PROMPT-5 | R | 10x300 | 19.828 | 0.057 2.566 | PROMPT-MO | R | 150x80 | 20.153 | 0.058 Our images have been calibrated using stars from the APASS catalog. Magnitudes were not corrected for dust extinction. Additional Skynet observations are ongoing. View this GCN Circular online at https://gcn.nasa.gov/circulars/39110. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37118] GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
by GCN Circulars 01 Feb '25

01 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39109 SUBJECT: GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations DATE: 25/02/01 00:21:27 GMT FROM: Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, Messina, Italy <giovannicalapai(a)tiscali.it> Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, (Messina) Italy Member of: GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. Report: We observed the field of GRB 250129A (Swift trigger=1285812, Page et al., GCN 39066) with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3. The observations were started at 2025-01-31 01:00 UT (approximately 44.25 hours after burst) stacking a set of unfiltered CCD image. The observations were carried out with clear skies and fair visibility conditions. The OT was detected at the following position: RA (J2000.0) 13h 14m 42.38s Decl. (J2000.0) +05° 01' 50.8" Photometry was obtained using nearby PanSTARRS stars as follows: Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Err. 2025-01-31 02:34:24 UT 45.82 105x60s CR 20.14 +/-0.30 Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied. Our observations are consistent with other already reported Lipunov et al. (GCN 39070), Gompertz et al. (GCN 39072), Malesani et al. (GCN 39073), Izzo et al. (GCN 39074), Lipunov et al. (GCN 39075), Ghosh et al. (GCN 39077), Schneider et al. (GCN 39078), Brivio et al. (GCN 39079), Siegel et al. (GCN 39085), 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), Bochenek et al. (GCN 39099), Malesani et al. (GCN 39100), Romanov (GCN 39101), Zheng et al. (GCN 39102), Watson et al. (GCN 39104), Vinko et al. (GCN 39105), Akl et al. (GCN 39106), Moskvitin et al. (GCN 39107). The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/39109. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37117] EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
by GCN Circulars 31 Jan '25

31 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39108 SUBJECT: EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube DATE: 25/01/31 15:15:59 GMT FROM: Jessie Thwaites at IceCube/U Wisc-Madison <thwaites(a)wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search for track-like muon neutrino events arriving from the direction of the FBOT EP250108A in a time window of [-600, +5000] seconds from the initial trigger reported by Einstein Probe (GCN 38861), during which time IceCube was collecting good quality data (2025-01-08 12:20:28.34 UTC to 2025-01-08 13:53:48.34 UTC). Zero track-like events are found coincident with the position of the FBOT. We accordingly derive a time-integrated muon-neutrino flux upper limit for this source of E^2 dN/ dE = 0.29 GeV cm^-2 at 90% CL, under the assumption of an E^-2 power law. 90% of events IceCube would detect from a source at this declination with an E^-2 spectrum have energies in the approximate energy range between 60 TeV and 20 PeV. A subsequent search was performed with a time window of [-2, +12] days with respect to the initial trigger (2025-01-06 12:30:28.34 UTC to 2025-01-20 12:30:28.34 UTC). In this case, we report a p-value of 1.0, consistent with background expectation. We accordingly derive a time-integrated muon-neutrino flux upper limit for this source of E^2 dN/ dE = 0.34 GeV cm^-2 at 90% CL, under the assumption of an E^-2 power law. 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] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/39108. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37116] GRB 250129A: SAO RAS optical observations
by GCN Circulars 31 Jan '25

31 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39107 SUBJECT: GRB 250129A: SAO RAS optical observations DATE: 25/01/31 12:29:18 GMT FROM: Moskvitin Alexander at SAO RAS <mosk(a)sao.ru> A. Moskvitin, O. Spiridonova, Yu. Sotnikova (SAO RAS), A. Ghosh, S. Razzaque (CAPP, University of Johannesburg) We observed the field of GRB 250129A (Beardmore et al., GCN 39066) with the SAO RAS 1-m telescope Zeiss-1000 on January 30, 23:46:43 -- January 31, 00:19:22 UT (t_mid - T0 = 43.298 hours = 1.8041 days). We obtained 5 x 300 sec. images in Rc band. The OT (Francile et al., GCN 39065; GCN 39075, Beardmore et al., GCN 39066, Schneider et al., GCN 39071, Belkin et al., GCN 39072; Izzo et al., GCN 39073; Izzo and Malesani, GCN 39074; Ghosh et al., GCN 39077; Schneider et al., GCN 39078; Brivio et al., GCN 39079; Siegel and Beardmore, GCN 39085; Zheng and Filippenko, GCN 39090; GCN 39102; Schlekat et al., GCN 39091; Antier et al., GCN 39096; Odeh et al., GCN 39097; Ferro et al., GCN 39098; Bochenek and Perley, GCN 39099; Malesani et al., GCN 39100; Romanov, GCN 39101; Watson et al., GCN 39104; Vinko et al., GCN 39105; Akl et al., GCN 39106) is clearly detected in the stacked frame with the brightness of R = 19.65 +/- 0.13 (calibrated against R2 magnitudes of nearby UNSO-B1 stars and not corrected for the MW extinction). View this GCN Circular online at https://gcn.nasa.gov/circulars/39107. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37115] GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
by GCN Circulars 31 Jan '25

31 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39106 SUBJECT: GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow DATE: 25/01/31 11:10:13 GMT FROM: Dalya Akl at American Uni. SHJ <dalyaakl.d(a)gmail.com> Dalya Akl (AUS), Alan M. Watson (UNAM), Camila Angulo (UNAM), Sarah Antier (OCA/IJCLAB), Benjamin Schneider (LAM), 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), and Margarita Pereyra (UNAM) report: We continued imaging the field of the Swift GRB 250129A (Beardmore et al., GCN Circ. 39066) during the commissioning of the COLIBRÍ (SVOM/F-GFT) telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We observed with the OGSE engineering test camera in a red filter approximating SDSS r starting at 2025-01-31 07:30:00 UTC. Compared to our observations from the previous night, we see a decay with an index of about -1.8 between T+30 and T+52 hours, less steep than the very sharp decline reported by (Zheng & Filippenko, GCN Circ. 39102) from T+28.5 to T+33.5 hours. Further observations are planned. We warmly thank the COLIBRÍ engineering team and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. We warmly thank the GRANDMA IJCLAB team and S. Karpov for the access of the STDWeb service for STDPipe. View this GCN Circular online at https://gcn.nasa.gov/circulars/39106. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37114] GRB 250129A: optical photometry from Konkoly
by GCN Circulars 31 Jan '25

31 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39105 SUBJECT: GRB 250129A: optical photometry from Konkoly DATE: 25/01/31 10:23:30 GMT FROM: Jozsef Vinko at Konkoly Observator <vinko(a)konkoly.hu> GRB 250129A: optical photometry from Konkoly J. Vinko, A. Horti-David, R. Konyves-Toth, Zs. Bora, L. Kriskovics, A. Pal, R. Szakats (Konkoly Observatory, Hungary) We report detection and photometry of the optical afterglow of GRB 250129A (Beardmore et al., GCN 39066) taken with the RC80 robotic telescope at Piszkesteto Station of Konkoly Observatory, Hungary. The observations started on 2025-01-29 23:35:21 UT, 18.84 hours after the trigger. 5 sets of 300 sec frames were collected through Sloan g', r'- and i' bands. The optical afterglow (Francile et al., GCN 39065; Beardmore et al., GCN 39066; 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; Brivio et al., GCN 39079; Siegel et al., GCN 39085; Zheng et al. GCN 39090; Schlekat et al., GCN 39091; Antier et al., 39096; Odeh et al., GCN 39097; Ferro et al., GCN 39098; Bochenek et al., GCN 39099; Malesani et al., GCN 39100; Romanov, GCN 39101; Zheng & Filippenko, GCN 39102; Watson et al. GCN 39104) was detected on the stacked frames with the following magnitudes, calibrated via nearby PS1 stars: Date UT-middle t-T0(days) Exp(s) g'(AB) r'(AB) i'(AB) 2025-01-30 00:13:39 0.7849 5x300 20.32 (0.21) 19.29 (0.08) 19.12 (0.10) The magnitudes above are not corrected for galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39105. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37113] GRB 250129A: COLIBRÍ Optical Observations
by GCN Circulars 31 Jan '25

31 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39104 SUBJECT: GRB 250129A: COLIBRÍ Optical Observations DATE: 25/01/31 07:13:32 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Alan M. Watson (UNAM), Camila Angulo (UNAM), D. Akl (AUS), S. Antier (OCA), Benjamin Schneider (LAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Rosa Becerra (Università degli Studi di Roma Tor Vergata), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), J.-G. Ducoin (CPPM), Francesco Magnani (CPPM) and Margarita Pereyra (UNAM) report: We imaged the field of the Swift GRB 250129A (Beardmore et al., GCN Circ. 39066) during the commissioning of the COLIBRÍ (SVOM/F-GFT) telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We observed with the OGSE engineering test camera in a red filter that approximates SDSS r from 2025-01-30 07:01 to 12:54 UTC. In the subset of our data from 2025-01-30 12:01 to 12:54, from 31.27 to 32.15 hours after the event, with a total exposure of 2220 seconds, we clearly detect the afterglow with r = 19.38 +/- 0.04 This magnitude is not corrected for Galactic extinction. The data were reduced using custom software and then analysed and calibrated against the PS1 catalog using the STDWeb service. Further observations are planned. We warmly thank the COLIBRÍ engineering team and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. We warmly thank the GRANDMA IJCLAB team and S. Karpov for the access of the STDWeb service for STDPipe. View this GCN Circular online at https://gcn.nasa.gov/circulars/39104. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37112] GRB 250128B: VLA possible radio detection
by GCN Circulars 31 Jan '25

31 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39103 SUBJECT: GRB 250128B: VLA possible radio detection DATE: 25/01/31 01:38:41 GMT FROM: Genevieve Schroeder at Cornell University <genevieveschroeder(a)u.northwestern.edu> G. Schroeder (Cornell), T. Laskar (Utah), W. Fong, J. Rastinejad (Northwestern) report: We observed the position of the short GRB 250128B (Evans et al., GCN 39058; Fermi GBM team, GCN 39057) with the Karl G. Jansky Very Large Array (VLA) under program 25A-063 (PI: Schroeder) beginning on 2025 Jan 29 at 10:05 UT (0.74 days post-burst) for 0.75 hours at a mean frequency of 6 GHz. Based on preliminary analysis, within the enhanced XRT position (Evans et al., GCN 39069) we find a possible source with a peak flux density of ~20 uJy at the position: RA(J2000): 15:25:42.032 Dec(J2000): -00:32:22.72 with an uncertainty of 0.1 arcsec in each coordinate. This position is ~2 arcsec offset from the optical/near IR sources reported in Yang et al. (GCN 39084) and Rastinejad et al. (GCN 39088). At present we cannot determine if this possible source is associated with the burst. We note that these observations were taken 2.7 hr prior to those reported in Ricci et al. (GCN 39093). We thank the VLA staff for quickly approving and executing these observations. Further observations are planned to assess the temporal behavior of the possible source. View this GCN Circular online at https://gcn.nasa.gov/circulars/39103. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37111] GRB 250129A: continued KAIT observations indicating steep decay after 28.5h
by GCN Circulars 30 Jan '25

30 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39102 SUBJECT: GRB 250129A: continued KAIT observations indicating steep decay after 28.5h DATE: 25/01/30 22:40:51 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, continued observing the afterglow of the GRB 250129A (Francile et al., GCN 39065; Beardmore et al., GCN 39066; 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; Brivio et al., GCN 39079; Siegel et al., GCN 39085; Zheng et al. GCN 39090; Schlekat et al., GCN 39091; Antier et al., 39096; Odeh et al., GCN 39097; Ferro et al., GCN 39098; Bochenek et al., GCN 39099; Malesani et al., GCN 39100; Romanov, GCN 39101) in the clear (roughly R) band. Observation started at ~28.5h after the burst and lasted for ~5.0h. The OT was still clearly detected in every individual image. Our photometry results show that the OT was in a single power-law decay phase, decayed from ~18.6 mag (~28.5h) to ~19.5 mag (~33.5h) with a decay index of ~4.1, much steeper compared to the value of ~0.85 reported by Bochenek et al. (GCN 39099). This indicating the OT is likely in a post jet-break phase. View this GCN Circular online at https://gcn.nasa.gov/circulars/39102. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37110] GRB 250129A: iTelescope optical observation
by GCN Circulars 30 Jan '25

30 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39101 SUBJECT: GRB 250129A: iTelescope optical observation DATE: 25/01/30 20:15:55 GMT FROM: Filipp Dmitrievich Romanov at Amateur astronomer <filipp.romanov.27.04.1997(a)gmail.com> I observed the field of GRB 250129A (Beardmore et al., GCN Circ. 39066) remotely using telescope T11 (0.51-m f/6.8 reflector + CCD + f/4.5 focal reducer) of iTelescope.Net (located in Utah Desert Remote Observatory at Great Basin Desert, Beryl Junction, Utah, USA) on 2025-01-30. Five images (exposure times of 300 seconds, BINx1) were obtained with Rc filter. I detected the optical afterglow in all images in the UVOT position. I measured the magnitude of it = 19.7 +/- 0.2 in the stacked image (mid time 13:11:06 UT = 32.43 h. after the trigger) compared to r magnitudes of nearby stars from Pan-STARRS DR1 catalogue (Chambers et al., 2016). Magnitude was not corrected for Galactic extinction. Stacked image: https://www.flickr.com/photos/filipp-romanov/54297183051/ F. D. Romanov (AAVSO). View this GCN Circular online at https://gcn.nasa.gov/circulars/39101. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37109] GRB 250129A: NOT optical observations of continuining activity
by GCN Circulars 30 Jan '25

30 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39100 SUBJECT: GRB 250129A: NOT optical observations of continuining activity DATE: 25/01/30 17:47:55 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University <d.malesani(a)astro.ru.nl> D. B. Malesani (DAWN/NBI), K. E. Heintz (DAWN/NBI), B. P. Gompertz (Birmingham), A. Martin-Carrillo (UCD), A. M. Bochenek (LJMU), R. Brivio (INAF/OABr), A. M. Kadela (NOT, NBI), B. N. Hauptmann (NOT and DTU Space), report on behalf of a larger collaboration: We observed the nice optical afterglow of GRB 250129A (Beardmore et al., GCN 39066) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Seeing conditions were sub-optimal, around 2". Observations were carried out in the r and i filters (exposure time of 3x200 s each). At a mean epoch of Jan 30.0916 UT (21.44 hr after the trigger), we measure for the afterglow r = 19.24 +- 0.03 (AB), calibrated against nearby objects from the Pan-STARRS catalog. We note that this value is ~0.35 mag fainter than the measurement reported at a later epoch by Bochenek & Perley (24.1 hr after trigger; GCN 39099). Accurate relative comparison using a shared set of calibration stars confirms the rebrightening. Flaring was thus still ongoing even ~24 hr after the trigger, continuing the earlier trend highlighted by Belkin et al. (GCN 39072), Francile et al. (GCN 39075), Brivio et al. (GCN 39079), Zheng & Filippenko (GCN 39090), and Antier et al. (GCN 39096). We encourage further follow-up of this unusual event at all wavelengths. View this GCN Circular online at https://gcn.nasa.gov/circulars/39100. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37108] GRB 250129a: Liverpool Telescope optical follow-up
by GCN Circulars 30 Jan '25

30 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39099 SUBJECT: GRB 250129a: Liverpool Telescope optical follow-up DATE: 25/01/30 14:06:13 GMT FROM: A. Bochenek at Liverpool John Moores University <a.m.bochenek(a)2023.ljmu.ac.uk> A. Bochenek and D. A. Perley (LJMU) report: We observed the field of GRB250129a (Beardmore et al., GCN 39066) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 6x90s exposures in the SDSS r’ filter starting at 2025-01-30 04:53:17 UT, approximately 24.1 hours after the trigger. Three of the images had to be discarded due to autoguider issues. We report a detection in the stacked images of r = 18.91 ± 0.03 mag. Our detection is consistent with the re-brightening (Brivio et al., GCN 39079, Zheng et al., GCN 39090) and subsequent observations of the afterglow (Odeh et al., GCN39097, Ferro et al. GCN39098). This implies slow decay, approx. 2 magnitudes in r-band from (clear) R ~17.1 at 6.9h post trigger (Zheng et al., GCN 39090) to this work’s r = 18.91 at 24.1h, with the decay index of approximately ~0.85. The photometry was obtained using nearby PanSTARRS standards and was not corrected for extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39099. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37107] GRB 250129A: TNG NIR afterglow detection
by GCN Circulars 30 Jan '25

30 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39098 SUBJECT: GRB 250129A: TNG NIR afterglow detection DATE: 25/01/30 13:08:07 GMT FROM: Matteo Ferro at INAF-OAB <matteo.ferro(a)inaf.it> M. Ferro, R. Brivio, P. D'Avanzo, S. Covino (INAF-OAB), A. Rossi (INAF-OAS), D. B. Malesani (DAWN/NBI & Radboud Univ.), A. Melandri (INAF-OAR), G. Mainella e M. Cecconi (INAF-TNG) on behalf of the CIBO collaboration report: We observed the field of the GRB250129A detected by the Swift (Beardmore et al., GCNC 36556) with the Italian 3.6m TNG telescope equipped with the near-infrared camera NICS to follow up its afterglow. A series of images were obtained with the J and H filters starting on 2025-01-30T06:16:34 UT (i.e. 25.5 hours post T0). The afterglow (Lipunov et al., GCN 39070; Schneider et al., GCN 39071; Gompertz et al., GCN 39072; Izzo et al., GCN 39073; Izzo et al., GCN 39074; Francile et al., GCN 39075; Ghosh et al., GCN 39077; Schneider et al., GCN 39078; Brivio et al., GCN 39079; Heintz et al., GCN 39081; Siegel et al., GCN 39085; Zheng et al., GCN 39090; Schlekat et al., GCN 39091; Antier et al., GCN 39096; Odeh et al., GCN 39097) is detected in the co-added image with a preliminary result of H(Vega)~16.7 mag (calibrated against the 2MASS catalogue). View this GCN Circular online at https://gcn.nasa.gov/circulars/39098. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37106] GRB 250129A: AKO Optical Afterglow Detection
by GCN Circulars 30 Jan '25

30 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39097 SUBJECT: GRB 250129A: AKO Optical Afterglow Detection DATE: 25/01/30 11:41:15 GMT FROM: Mohammad Odeh at Al Khatim Observatory M44 <mshodeh(a)gmail.com> Mohammad Odeh (Al-Khatim Observatory, AKO, operated by the International Astronomical Center in Abu Dhabi, UAE), and Shaikha Alshamsi, Nuha Manal Pattani, and Nidhal Guessoum (American University of Sharjah, UAE), report: We observed the field of GRB 250129A (Beardmore et al., GCN 39066) using our 0.36m f/7.7 robotic telescope. The observation session began on 29 January 2025 at 21:07 UT and continued until 22:02 UT, with a midpoint at 21:36 UT, approximately 16.8 hours after the trigger. We obtained multiple 180-second exposures using the Ic filter. The optical afterglow was clearly detected at: R.A. (J2000): 13:14:42.40 Dec. (J2000): +05:01:50.4 Our detection is consistent with the results of Francile et al., GCN 39065; Beardmore et al., GCN 39066; Schneider et al., GCN 39071; Belkin et al., GCN 39072; Izzo et al., GCN 39073; Izzo & Malesani, GCN 39074; Ghosh et al., GCN 39077; Schneider et al., GCN 39078; Brivio et al., GCN 39079; Siegel et al., GCN 39085; Zheng et al., GCN 39090; Schlekat et al., GCN 39091; Antier et al., GCN 39096. The following observation was calculated using the Atlas catalogue as a reference: ---------------------------------------------------------------------------- - ObsTime (mid), Exposure (sec), Filter, Mag ---------------------------------------------------------------------------- - 2025-01-29T21:35:48Z, 18 x 180s (stacked), Ic, 18.7 +/- 0.22 ---------------------------------------------------------------------------- - The magnitude is not corrected for galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39097. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37105] GRB 250129A: GRANDMA/TAROT optical afterglow detection
by GCN Circulars 30 Jan '25

30 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39096 SUBJECT: GRB 250129A: GRANDMA/TAROT optical afterglow detection DATE: 25/01/30 10:05:34 GMT FROM: Patrice Hello at IJCLAB, Orsay <patrice.hello(a)ijclab.in2p3.fr> S. Antier (OCA/IJCLAB), P. Hello (IJCLAB), P. Gokuldass (ERAU), A. Klotz (IRAP), C. Limonta, M. Boer, Q. Andre, A. Durroux (OCA), N. Guessoum (AUS), Haowei Peng (Tsinghua), C. Andrade, M. Coughlin (UMN), P-A Duverne (APC), S. Karpov (FZU), T. Pradier (Unistra/IPHC), D. Turpin (CEA-Saclay/Irfu) on behalf of the GRANDMA collaboration: we observed the field of GRB 250129A, detected by Swift (Beardmore et al., GCN 39066) using TAROT/TCH and TAROT/TCA. Observations began 1 min after T0 without filter, and we took a series of images with various exposure times from 1.76 min to 73 min post T0. We detected the optical afterglow candidate in he first (earliest) measurement with TAROT/TCH (5x30s exposure time) at T0+2.96min with mag=17.48 +/- 0.08 (in R band). The data were reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022), using Skymapper for reference. Processing of remaining data is ongoing. Our measurements are compatible with early measurements, GCNs 39070, 39072, 39073, 39074, 39078, 39079. GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/). View this GCN Circular online at https://gcn.nasa.gov/circulars/39096. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37104] GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
by GCN Circulars 30 Jan '25

30 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39095 SUBJECT: GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading DATE: 25/01/30 09:08:18 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> Y.-H. I. Yin (NJU), Y. L. Wang, H. N. Yang, H. Y. Liu (NAO, CAS), Z. Y. Liu, M. Q. Huang (USTC), Z. X. Ling, Y. Liu (NAO, CAS), B. Cordier, D. Turpin (CEA) on behalf of the Einstein Probe team: We performed a second follow-up observation of GRB 250127A (SVOM, Wu et al., GCN 39041) with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation started at 2025-01-29 09:55:45 (UTC) with ~ 4.9 ks of exposure in total. The uncatalogued x-ray source detected by both Swift/XRT (Source 2, Kennea et al., GCN 39056) and EP-FXT (Yin et al. GCN 39053) is no longer detected in our second EP-FXT epoch. Assuming Galactic equivalent hydrogen column density of 4.52 x 10^20 cm^-2 and a photon index of 2.0, the upper limit of the 0.5-10 keV flux is estimated to be 1.93 x 10^-14 erg/s/cm^2. The fading behavior of the x-ray source identified by Yin et al. GCN 39053 and Kennea et al., GCN 39056, confirms it as being the afterglow of GRB 250127A. 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/39095. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37103] GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
by GCN Circulars 30 Jan '25

30 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39094 SUBJECT: GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits DATE: 25/01/30 07:15:01 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> A. S. Moskvitin (SAO RAS), N. Pankov (HSE, IKI), O. Spiridonova (SAO RAS), V. Rumyantsev (CrAO), A. Volnova (IKI), A. Pozanenko (IKI) report on behalf of the collaboration between IKI-GRB-FuN and the GRB follow-up team. We observed the field of GRB 250128B (Fermi GBM team, GCN 39057; Evans et al., GCN 39058; Myers and Meegan, GCN 39063; Osborne et al., GCN 39064) with the 1-meter Zeiss-1000 telescope at the Special Astrophysical Observatory (SAO RAS) and the 2.6-meter Shajn telescope (ZTSh) at Crimean Astrophysical Observatory (CrAO). The observations began on 2025-01-29 00:57:27 at the SAO RAS, i.e. ~0.38 days since the burst. We obtained 12 x 300 sec images in the Rc-filter with Zeiss-1000 and 44 x 120 sec images in the R-filter with ZTSh. The stacked images from both telescopes have not revealed any new optical source located within the enhanced XRT circle (Evans et al., GCN 39069). The preliminary upper limits are as follows: Date UT start t-T0 Exp. Filter UL(3sigma) Telescope (mid, days) (s) 2025-01-29 00:57:27 0.38090 12*300 Rc 23.5 Zeiss-1000 2025-01-29 01:33:22 0.41284 44*120 R 23.1 ZTSh The photometry is based on nearby stars of the USNO-B1.0 catalog (R2 magnitudes) and have not been corrected for the Galactic extinction. Our results are consistent with the upper limits obtained by other teams (Izzo & Malesani, GCN 39059; Lipunov et al., GCN 39061; GCN 39067; Ulaczyk et al., GCN 39062; Adami et al., GCN 39076; Becerra et al., GCN 39080; Heintz et al., GCN 39081; Yang et. al, GCN 39084; Rossi et. al, GCN 39086). View this GCN Circular online at https://gcn.nasa.gov/circulars/39094. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37102] GRB 250128B: VLA radio upper limit
by GCN Circulars 30 Jan '25

30 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39093 SUBJECT: GRB 250128B: VLA radio upper limit DATE: 25/01/30 06:35:37 GMT FROM: Eleonora Troja <nora.gsfc(a)gmail.com> Roberto Ricci (U Rome), Muskan Yadav (U Rome), Rosa L. Becerra (U Rome), Yu-Han Yang (U Rome) and Eleonora Troja (U Rome) report: We observed the field of the short GRB 250128B discovered by Fermi/GBM (Fermi GMB team, GCN 39057) and Swift/BAT (Evans et al. GCN 39058) with the Very Large Array at the centre frequency of 6 GHz (C band) with a bandwidth 4 GHz. The observations started on 2025-01-29 at 12:48 UT and lasted for 47 mins, resulting in a mid elapsed time of 20.8 hours after trigger. The primary calibrator was 3C286 and the phase calibrator J1546+0026. Within the enhanced Swift/XRT position (Evans et al., GCN 39069) no counterpart is found down to a 3-sigma upper limit of 15 microJy. Additional follow-up is planned. We thank the VLA staff for promptly observing the target. View this GCN Circular online at https://gcn.nasa.gov/circulars/39093. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37101] Ep250125A: 1.3m DFOT optical upper limit
by GCN Circulars 30 Jan '25

30 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39092 SUBJECT: Ep250125A: 1.3m DFOT optical upper limit DATE: 25/01/30 05:24:36 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Amit K. Ror, Divyanshu, Kuntal Mishra, and Shashi B. Pandey (ARIES) report: We observed the field of Ep250125A detected by EP-WXT trigger ( Wu et al. 2025, GCN 39028) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2025-01-25 at 22:27:28 UT, i.e., ~ 19.83 hours after the EP-WXT trigger. We have taken multiple frames with an exposure time of 300 s in the R filter. We stacked the images after the alignment. We could not detect the optical emission in our stacked image within the error box of the EP-WXT telescope (Wu et al. 2025, GCN 39028) and Swift-XRT (Kennea et al. 2025, GCN 39029). We obtain the following 3-sigma upper limit in the stacked image: Date Start_UT T_start-T0 (hour) Filter Exp time (s) Magnitude ========================================================= 2025-01-25 22:27:28 ~19.83 R 300s*24 >22.8 The non-detection of the burst is consistent with the upper limits reported by Aryan et al. 2025, GCN 39032. The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalogue. This circular may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/39092. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37100] GRB 250129A: Skynet optical observations
by GCN Circulars 29 Jan '25

29 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39091 SUBJECT: GRB 250129A: Skynet optical observations DATE: 25/01/29 23:18:26 GMT FROM: dschlekat(a)unc.edu Donovan Schlekat, Dylan Dutton, Daniel Reichart, Joshua Haislip, and Vladimir Kouprianov report on behalf of the Skynet Robotic Telescope Network at the University of North Carolina at Chapel Hill. We observed the field of GRB 250129A with two of Skynet's PROMPT telescopes located at the Cerro Tololo Inter-American Observatory. The observation began at 05:12:20 UT on January 29 2025, roughly 27 minutes after the Swift-BAT trigger (Beardmore et al., GCN 39066). Observations were performed in the B, V, R, and I bands. Exposure lengths were calculated using our automated exposure length scaling model. We detect the optical afterglow consistent with the coordinates reported by other facilities (Francile et al., GCN 39065; Beardmore et al., GCN 39066; Schneider et al., GCN 39071; Belkin et al., GCN 39072; Izzo et al., GCN 39073; Izzo & Malesani, GCN 39074; Ghosh et al., GCN 39077; Schneider et al., GCN 39078; Brivio et al., GCN 39079; Siegel et al., GCN 39085; Zheng et al., GCN 39090). The coordinates are: R.A. (J2000): 13:14:42.39 Dec. (J2000): 05:01:50.22 We detect the object in the B, V, R, and I band. The initial detection photometry for each band is reported below. Additional Skynet observations are ongoing. Tmid - T0 (s)| Telescope | Filter | Exposure (s) | Mag | Mag Error ------------------------------------------------------------------ 1674.49 | PROMPT-5 | B | 59 | 17.525 | 0.051 1678.99 | PROMPT-6 | V | 34 | 16.902 | 0.054 1711.99 | PROMPT-6 | R | 22 | 16.628 | 0.057 1938.49 | PROMPT-6 | I | 19 | 16.111 | 0.095 Our images have been calibrated using stars from the APASS catalog. Magnitudes were not corrected for dust extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39091. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37099] GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
by GCN Circulars 29 Jan '25

29 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39090 SUBJECT: GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours DATE: 25/01/29 22:21:18 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, responded to GRB 250129A detected by Swift (Beardmore et al., GCN 39066) starting at 09:25 UT, ~4.68h after the bust. Observations were performed in the clear (roughly R) filter with a set of 60s exposures and lasted for ~2.2h. The optical afterglow (Francile et al., GCN 39065; Beardmore et al., GCN 39066; 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; Brivio et al., GCN 39079; Siegel et al., GCN 39085) was clearly detected in every individual image. Our photometry results show that the OT rebrightened since ~4.68h (~16.7 mag) and reached a double peak at ~4.99h (~16.3 mag) and again at 5.2h (~16.3 mag), then decayed afterword, with small flares during decay phase, till ~17.1 mag at ~6.90h. View this GCN Circular online at https://gcn.nasa.gov/circulars/39090. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37098] GRB 250129A: Swift-XRT refined Analysis
by GCN Circulars 29 Jan '25

29 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39089 SUBJECT: GRB 250129A: Swift-XRT refined Analysis DATE: 25/01/29 22:15:26 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), A. D'Ai (INAF-IASFPA), M. A. Williams (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), A.P. Beardmore (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 10 ks of XRT data for GRB 250129A, from 147 s to 46.4 ks after the BAT trigger. The data comprise 10 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=3.64 (+1.35, -0.10). At T+1185 s the decay flattens to an alpha of 0.15 (+/-0.07) before breaking again at T+23.0 ks to a final decay with index alpha=2.2 (+0.7, -0.6). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.92 (+0.16, -0.10). The best-fitting absorption column is consistent with the Galactic value of 2.4 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.4 x 10^-11 (3.6 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Galactic foreground: 2.4 x 10^20 cm^-2 Intrinsic column: 2 (+/-38) x 10^20 cm^-2 at z=2.151 Photon index: 1.92 (+0.16, -0.10) If the light curve continues to decay with a power-law decay index of 2.2, the count rate at T+24 hours will be 0.011 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.8 x 10^-13 (4.0 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/01285812. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39089. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37097] GRB 250128B: Gemini-North optical extended source detection
by GCN Circulars 29 Jan '25

29 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39088 SUBJECT: GRB 250128B: Gemini-North optical extended source detection DATE: 25/01/29 21:19:48 GMT FROM: Jillian Rastinejad at Northwestern Univ. <jillianrastinejad2024(a)u.northwestern.edu> Jillian Rastinejad, Wen-fai Fong (Northwestern), Genevieve Schroeder (Cornell), Harsh Kumar (CfA), Benjamin Gompertz (Birmingham) and Andrew Levan (Radboud) report on behalf of a larger collaboration: We observed the location of the X-ray counterpart of the short GRB 250128B (Evans et al., GCN 39058) with the Gemini Multi-Object Spectrograph (GMOS) mounted on Gemini-North under Program GN-2024B-Q-111 (PI: Fong). We obtained 13x120-sec imaging in r-band at a mid-time of 2025-01-29 14:43:45.0 UT (0.93 days post-burst), at a median airmass of 1.3 and seeing of 1’’. Within the enhanced XRT localization (Evans et al., GCN 39069), we detect a faint extended source, or possibly a blend of two unrelated sources. This source complex is centered at R.A. = 15:25:42.07, Decl. = -00:32:20.3 (J2000) with an approximate visual angular size of 2”, and is consistent with the position of the candidate near-IR source reported by Yang et al., GCN 39084. Both positions are consistent with the enhanced XRT localization (Evans et al., GCN 39069). Calibrated to SDSS, we measure a preliminary brightness for this source complex of r = 25.4 +/- 0.2 AB mag, not corrected for Galactic extinction. We do not detect any other sources within or adjacent to the XRT localization to a 3-sigma limiting magnitude of r > 25.8 AB mag. At this stage, we cannot make any determination if there is any contribution to the observed light from an afterglow component. Further observations are planned to monitor the variability of the source. We thank Jennifer Andrews and additional Gemini staff for the rapid planning and execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39088. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37096] The EP-WXT trigger 01709131085: KAIT confirmation of the stellar flare
by GCN Circulars 29 Jan '25

29 Jan '25

TITLE: GCN CIRCULAR NUMBER: 39087 SUBJECT: The EP-WXT trigger 01709131085: KAIT confirmation of the stellar flare DATE: 25/01/29 20:04:00 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, automatically responded to the EP-WXT trigger (ID= 01709131085; Li et al., GCN 39068) starting at 05:09 UT, Jan. 29th, ~20 minutes after the trigger. A set of images with 20s exposure time were obtained in B, V, R I and clear (roughly R) filters. Observations lasted for about 3 hours. The high proper motion star RX J0448.7+1003 reported by Li et al. (GCN 39068) was covered by KAIT images. Photometry of the star show that its brightness is at B~13.2 mag in our first B band image at 26.7 minutes, increased to a peak of B~12.9 mag at 43.6 minutes, then decreased afterward with B~13.6 mag at 187 minutes. We therefore confirm that this EP-WXT trigger event is truly associated with this stellar flare. View this GCN Circular online at https://gcn.nasa.gov/circulars/39087. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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