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

[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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