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

[vsnet-grb-info 37536] LIGO/Virgo/KAGRA S250226dl: Updated Sky localization
by GCN Circulars 27 Feb '25

27 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39522 SUBJECT: LIGO/Virgo/KAGRA S250226dl: Updated Sky localization DATE: 25/02/27 17:34:46 GMT FROM: ethan.payne(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 S250226dl (GCN Circular 39504). 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/S250226dl For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 1218 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 3361 +/- 1041 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/39522. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37535] GRB 250225B: VLT/Xshooter imaging
by GCN Circulars 27 Feb '25

27 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39521 SUBJECT: GRB 250225B: VLT/Xshooter imaging DATE: 25/02/27 17:12:33 GMT FROM: Yu-Han Yang at University of Rome Tor Vergata <yyang(a)roma2.infn.it> Yu-Han Yang (U Rome), Eleonora Troja (U Rome), and Rosa Becerra (U Rome) report on behalf of the ERC BHianca team: We observed the field of GRB 250225B (Williams et al., GCN 39473) with the Xshooter spectrograph on the ESO VLT UT3 (Melipal). Observations began at T+38.0 hours and, due to visibility constraints, only 2x600s spectra were acquired. Using the acquisition and guiding (A&G) camera, imaging in the I filter was carried out at an average airmass of about 2.1. No source is detected at the position of the optical and nIR candidate counterpart (Schneider et al. GCN 39494, Yang et al. GCN 39495) down to a 3-sigma limit I>22.4 AB mag calibrated using nearby stars in the Legacy Survey DR10 (Dey et al. 2019) catalogue. Compared to our previous measurement (Yang et al. GCN 39495), these observations provide tentative evidence for fading by ~0.3 mag. Further observations are planned. We thank the staff at the VLT, for the rapid execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39521. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37534] GRB 250205A / EP250205A: further radio observations with the VLA
by GCN Circulars 27 Feb '25

27 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39520 SUBJECT: GRB 250205A / EP250205A: further radio observations with the VLA DATE: 25/02/27 15:43:06 GMT FROM: Stefano Giarratana at INAF-OAB <s.giarratana(a)ira.inaf.it> S. Giarratana (INAF-OAB), M. Giroletti (INAF-IRA), G. Ghirlanda (INAF-OAB), N. Di Lalla (Stanford Univ.), N. Omodei (Stanford Univ.), O. S. Salafia (INAF-OAB) At 06:32:26 UT on 2025 Feb 8 (T_mid = 2.41 days post-burst) and at 05:58:32 UT on 2025 Feb 13 (T_mid = 7.39 days post-burst) the Karl G. Jansky VLA observed the field of GRB 250205A / EP250205A (Saccardi et al., GCN 39154; Mukherjee et al., GCN 39171) in three bands, with central frequencies of 6, 10 and 15 GHz. The standard 3C286 was used as bandpass and flux density calibrator, while J0741+3112 was used as phase calibrator. The preliminary analysis yields the following results: ================================================================ T_mid Freq Peak U.L. r.m.s. Beam PA [days] [GHz] [uJy/b] [uJy] [uJy/b] [arcsec^2] [deg] ================================================================ 2.41 6 - 21 7 0.34x0.31 47 2.41 10 38 - 8 0.23x0.20 49 2.41 15 - 21 7 0.14x0.12 34 7.39 6 - 24 8 0.38x0.31 65 7.39 10 - 21 7 1.47x0.16 68 7.39 15 - 24 8 0.16x0.12 54 ================================================================ where U.L. are the upper limits (3 sigma) for the non-detections. We would like to thank the staff of the VLA for approving, executing, and processing the observations. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. These observations were carried out as part of project SF171028, approved in the framework of the Fermi - NRAO joint program agreement. View this GCN Circular online at https://gcn.nasa.gov/circulars/39520. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37533] GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
by GCN Circulars 27 Feb '25

27 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39519 SUBJECT: GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection DATE: 25/02/27 14:32:17 GMT FROM: Aishwarya L Thakur at INAF-IAPS, Rome <aishth(a)outlook.com> James Craig Rodi(a), Aishwarya Linesh Thakur(a), Patrizia Barria(a,b), Giulia Gianfagna(a), Lorenzo Natalucci(a,b), Luigi Piro(a), report: GRB 250226B was discovered by Fermi/GBM (GCN 39503) at 2025-02-26T22:30:23 (UTC). In a 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 multiple pulses over this duration. The strongest pulse of this signal is also detected in the IBIS/PICsIT data. The approximate peak count rate in SPI-ACS is 95,000 cts/s for E>80 keV, over a median background rate of 63,000 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/39519. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37532] GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection
by GCN Circulars 27 Feb '25

27 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39519 SUBJECT: GRB 250226B: INTEGRAL SPI-ACS and PICsIT detection DATE: 25/02/27 14:32:17 GMT FROM: Aishwarya L Thakur at INAF-IAPS, Rome <aishth(a)outlook.com> James Craig Rodi(a), Aishwarya Linesh Thakur(a), Patrizia Barria(a,b), Giulia Gianfagna(a), Lorenzo Natalucci(a,b), Luigi Piro(a), report: GRB 250226B was discovered by Fermi/GBM (GCN 39503) at 2025-02-26T22:30:23 (UTC). In a 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 multiple pulses over this duration. The strongest pulse of this signal is also detected in the IBIS/PICsIT data. The approximate peak count rate in SPI-ACS is 95,000 cts/s for E>80 keV, over a median background rate of 63,000 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/39519. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37531] EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection
by GCN Circulars 27 Feb '25

27 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39518 SUBJECT: EP250226a/GRB 250226A: INTEGRAL SPI-ACS and PICsIT detection DATE: 25/02/27 14:31:11 GMT FROM: Aishwarya L Thakur at INAF-IAPS, Rome <aishth(a)outlook.com> Aishwarya Linesh Thakur(a), James Craig Rodi(a), Patrizia Barria(a,b), Giulia Gianfagna(a), Luigi Piro(a), Lorenzo Natalucci(a,b) report: EP250226a/GRB 250226A was discovered by Fermi/GBM (GCN 39479) and EP-WXT (GCN 39482) at 2025-02-26T06:34:57 (UTC) and has also been detected by GECAM-B (GCN 39492) In a SPI-ACS light curve above 80 keV, we find a signal temporally coincident with the GBM and EP-WXT detections, having an approximate duration of ~ 15 sec. The signal consists of a single pulse over this duration. This signal is also detected marginally in the IBIS/PICsIT data. The approximate peak count rate in SPI-ACS is 74,000 cts/s for E>80 keV, over a median background rate of 67,600 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/39518. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37530] GRB 250225B: INTEGRAL SPI-ACS detection
by GCN Circulars 27 Feb '25

27 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39517 SUBJECT: GRB 250225B: INTEGRAL SPI-ACS detection DATE: 25/02/27 14:29:04 GMT FROM: Aishwarya L Thakur at INAF-IAPS, Rome <aishth(a)outlook.com> Aishwarya Linesh Thakur(a), Patrizia Barria(a,b), James Craig Rodi(a), Giulia Gianfagna(a), Luigi Piro(a), Lorenzo Natalucci(a,b) report: GRB 250225B was discovered by Swift/BAT (GCN 39479) at 2025-02-25T19:39:13 (UTC) and has also been detected by SVOM/GRM (GCN 39493), Konus Wind (GCN 39498) and Fermi/GBM (GCN 39502). In a SPI-ACS light curve above 80 keV, we find a signal temporally coincident with these detections, having an approximate duration of ~ 3 sec. The signal consists of a single pulse over this duration. The approximate peak count rate in SPI-ACS is 90,000 cts/s for E>80 keV, over a median background rate of 70,800 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/39517. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37529] EP250225a: NOT optical candidate counterpart
by GCN Circulars 27 Feb '25

27 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39516 SUBJECT: EP250225a: NOT optical candidate counterpart DATE: 25/02/27 12:49:18 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University <d.malesani(a)astro.ru.nl> Daniele B. Malesani (DAWN/NBI and Radboud Univ.), Andrew J. Levan (Radboud Univ. and DAWN/NBI), Antonio Martin-Carrillo (UCD), Franz E. Bauer (PUC), Peter G. Jonker (Radboud Univ.), Maria E. Ravasio (Radboud Univ.), M. Alejandra Diaz Teodori (NOT and Turku Univ.), Roar H. Rasmussen (NOT), report on behalf of a larger collaboration: We observed the field of the fast X-ray transient EP250225a (Jiang et al., GCN 39475) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were carried out in the r and z filters, with mean times 2025 Feb 26.98 and 27.00 UT (1.47 and 1.49 days after the trigger, respectively). Template subtraction of the NOT images using the Legacy Survey as reference yields a potential faint candidate at the edge of the EP/WXT error circle, located at coordinates: RA(J2000) = 09:25:04.07 Dec(J2000) = -04:53:40.2 This position is consistent with an object in the Legacy Survey (with magnitudes g = 23.22, r = 22.48, i = 21.53, z = 21.57). The object looks point-like both in our data (PSF 0.75" in the z band) and in the Legacy Survey. Photometry confirms a brightening of 0.50 +- 0.05 and 0.33 +- 0.10 mag in the r and z bands, respectively, when compared to the archival fluxes in the Legacy Survey. The point-like nature of the source suggests either a transient on top of a compact host galaxy or stellar variability. Further observations are planned (and encouraged) to establish the nature of this object and its association with EP250225a. View this GCN Circular online at https://gcn.nasa.gov/circulars/39516. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37528] EP250226a/GRB 250226A:Xinglong optical follow-up observations
by GCN Circulars 27 Feb '25

27 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39515 SUBJECT: EP250226a/GRB 250226A:Xinglong optical follow-up observations DATE: 25/02/27 12:36:12 GMT FROM: Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong(a)nao.cas.cn> Junjie-Jin (NAOC), Haiyang-Mu (NAOC), Sen-Liu (NAOC), JinLei-Zhang (NAOC), Pengliang-Du (NAOC), Zhou-Fan (NAOC), Hong-Wu (NAOC) report: We observed the field of the fast X-ray transient EP250226a/GRB 250226a (Jiang et al., GCN #39482; The Fermi team, GCN #39479) using the the Xinglong 2.16-m telescope located at Xinglong, Hebei, China. We obtained 3600 s R and I-band with the time of 2025-02-26T17:04:55 . The optical object reported by An et al. (GCN #39486) is detected in our image. We measure a preliminary magnitude of R = 21.19 +/- 0.07 and I = 21.68 +/- 0.05 mag (AB), calibrated against nearby stars from the Pan-STARRS catalog. We summarize our observation results as follows: Obs. No. | Time (UTC) | Exposure Time (s) | Filter | Apparent mag (AB) | Telescope Name 1 | 2025-02-26T17:04:55 | 3600 s | R |21.19 +/- 0.07| Xinglong 2.16-cm Telescope 2 | 2025-02-26T18:05:21 | 3600 s | I | 21.68 +/- 0.0 | Xinglong 2.16-m Telescope View this GCN Circular online at https://gcn.nasa.gov/circulars/39515. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37527] EP250226a / GRB 250226A: SVOM/VT optical observations
by GCN Circulars 27 Feb '25

27 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39514 SUBJECT: EP250226a / GRB 250226A: SVOM/VT optical observations DATE: 25/02/27 11:48:14 GMT FROM: Xuhui Han at NAOC/SVOM <hxh(a)nao.cas.cn> R. Z. Li (YNAO), Z. Q. Wang (GXU), W. K. Zheng (UCB), X. H. Han, L. P. Xin, Y. L. Qiu, H. L. Li, C. Wu, Z. H. Yao, Y. N. Ma, H. B. Cai, J. Wang, Y. Xu, J. Y. Wei (NAOC), J. T. Palmerio (CEA/Irfu) report on behalf of the SVOM team: The SVOM/VT conducted a ToO follow-up observation of the EP250226a/GRB 250226A (Jiang et al., GCN 39482; Fermi GBM team, GCN 39479; Zhang et al., GCN 39492; INTEGRAL/SPI-ACS (triNum #11070)) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously with an exposure time of 18*100 seconds. The afterglow (An et. al., GCN 39486; Zhu et. al., GCN 39487; Magnani et al., GCN 39488; Li et. al., GCN 39489; Aryan et al., GCN 39509; Zou et al., GCN 39511; Zhu et al., GCN 39487) was detected with a brightness of 22.58+/-0.14 mag (AB) in VT_B and 21.56+/-0.10 mag (AB) in VT_R, at the mid-time of 20.45 hours post the burst. 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/39514. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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