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

[vsnet-grb-info 37506] GRB 250225B: VLT/FORS2 candidate optical afterglow
by GCN Circulars 26 Feb '25

26 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39494 SUBJECT: GRB 250225B: VLT/FORS2 candidate optical afterglow DATE: 25/02/26 14:07:48 GMT FROM: Benjamin Schneider at MIT <bschn(a)mit.edu> B. Schneider (LAM), A. J. Levan (Radboud and Warwick), D. B. Malesani (DAWN/NBI and Radboud), R. A. J. Eyles-Ferris (Leicester), N. R. Tanvir (Leicester), L. Izzo (INAF/OACn and DARK/NBI), A. Martin-Carrillo (UCD), P. D’Avanzo (INAF/OAB), S. D. Vergani (CNRS, Paris Obs./LUX), report on behalf of the Stargate collaboration: We observed the location of the Swift/BAT GRB 250225B (Williams et al., GCN 39473) with the FORS2 instrument on the VLT UT1. Observations began on 2025 Feb 26.40 UT (13.94 hr after the GRB), and a total of 5x50 s of observations were obtained, at large airmass ~2.3 and deep in twilight. Image subtraction against the z-band template from the Legacy Survey reveals a transient source at coordinates: RA(J2000) = 20:24:33.81 DEC(J2000) = -41:28:25.4 This source is consistent with a faint, extended object visible in the Legacy Survey (with a reported photometric redshift 1.12 +/- 0.18), and photometry suggests it has brightened by about 0.6 magnitudes from the time of the Legacy Survey observations. We consider this a candidate afterglow for GRB 250225B, although we note that detection of fading or an X-ray association will be required to robustly establish its nature. The source is offset by ~3 arcmin (65 kpc in projection) from the bright galaxy ESO 340-26. Although this is well within the range of offsets seen for merger-driven GRBs, if this transient is indeed the afterglow of GRB 250225B, the presence of an underlying source in the Legacy Survey suggests the proximity to ESO 340-26 is a chance association. Our subtraction shows no sign of any other transients within the BAT error circle, including within or close to ESO 340-26. The 5-sigma limiting magnitude for any such transient corresponds to z > 22.7 (M_z > -12 at redshift z = 0.018). We thank the staff at ESO, among which Marco Berton, for their assistance in obtaining these challenging observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39494. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37505] GRB 250225B: SVOM/GRM observation of a long burst
by GCN Circulars 26 Feb '25

26 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39493 SUBJECT: GRB 250225B: SVOM/GRM observation of a long burst DATE: 25/02/26 14:06:50 GMT FROM: yqzhang_cl(a)163.com SVOM/GRM team: Yan-Qiu Zhang, Chao Zheng, Chen-Wei Wang, Shi-Jie Zheng, Wen-Jun Tan, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Nicolas Dagoneau (CEA), Maria-Grazia Bernardini (INAF-OAB), Jean-Luc Atteia (IRAP) report on behalf of the SVOM team: SVOM/GRM was triggered on-ground by a long burst GRB 250225B at 2025-02-25T19:39:14.000 (T0), which was also observed by Swift/BAT (M.A. Williams et al., GCN #39473), Fermi/GBM (triNum #762205158) and INTEGRAL/SPI-ACS (triNum #11068). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multi-pulses with a T90 of 293.0 +/- 31.2 s in the 15-5000 keV band. In addition, the position of this burst, as determined by Swift/BAT (GCN #39473, RA: 306.145 deg, DEC: -41.4845 deg, Error: 3 arcmin), is located at about 113 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/svgrb250225B.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/39493. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37504] GRB 250226A: GECAM-B detection
by GCN Circulars 26 Feb '25

26 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39492 SUBJECT: GRB 250226A: GECAM-B detection DATE: 25/02/26 14:05:27 GMT FROM: yqzhang_cl(a)163.com GRB 250226A: GECAM-B detection Yan-Qiu Zhang (IHEP), Shao-Lin Xiong (IHEP), Chen-Wei Wang (IHEP) report on behalf of the GECAM team: GECAM-B was triggered both in-flight and on-ground by a long burst, GRB 250226A, at 2025-02-26T06:34:56.000 UTC (T0), which was also detected by Fermi/GBM (Fermi GBM team, GCN #39479), EP/WXT (EP250226a/GRB 250226A, S.Q. Jiang et al., GCN #39482) and INTEGRAL/SPI-ACS (triNum #11070). According to the GECAM-B light curves in about 5-2000 keV, this burst mainly consists of multiple pulses with a duration (T90) of about 63.5 +/- 11.7 s. The GECAM light curve could be found here: https://www.bursthub.cn//admin/static/gecamgrb250226A.png We note that these results are very preliminary. Refined analysis will be reported later. Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two microsatellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/39492. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37503] GRB 250221A: EP-FXT detection of the X-ray afterglow
by GCN Circulars 26 Feb '25

26 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39491 SUBJECT: GRB 250221A: EP-FXT detection of the X-ray afterglow DATE: 25/02/26 12:12:31 GMT FROM: Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra(a)roma2.infn.it> E. Troja (U Rome), R. L. Becerra (U Rome), W. J. Zhang, T. Y. Lian, H. W. Pan (NAO, CAS), Y. Wang (PMO, CAS), and Y. -H. Yang (U Rome) report: We performed a follow-up observation of GRB 250221A detected by Swift/BAT (Caputo et al., GCN 39396) with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation began at 2025-02-23 05:16:58 (UTC), about ~ 2.1 days after the trigger, for a total exposure time of 5.2 ks. At the position of the XRT counterpart (Beardmore et al., GCN 39404), an uncatalogued X-ray source is detected by both FXT-A and FXT-B. This position is also consistent with the optical (Watson et al., GCN 39397; Cotter et al., GCN 39413; Muenter et al., GCN 39417; Shilling et al. GCN 39409; Kumar et al. GCN 39412; Pozanenko et al., GCN 39422; Ghosh et al., GCN 39425; Iskandar et al., GCN 39446) and radio afterglow (Ricci et al., GCN 39433). From a preliminary analysis we derive an observed flux of (1.7 +/- 0.2)*10^-13 erg/cm^2/s (0.3-10.0 keV), consistent with the latest Swift/XRT measurement (Salvaggio et al., GCN 39414) and indicative of a possible rebrightening (Pankov et al., GCN 39427). Further observations are planned. 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/39491. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37502] GRB 250214A: SVOM/GRM observation
by GCN Circulars 26 Feb '25

26 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39490 SUBJECT: GRB 250214A: SVOM/GRM observation DATE: 25/02/26 11:48:23 GMT FROM: zhengchao_astro(a)foxmail.com SVOM/GRM team: Chao Zheng, Shi-Jie Zheng, Shao-Lin Xiong, Yue Huang, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Frédéric Piron (LUPM), Nicolas Dagoneau (CEA), Maria-Grazia Bernardini (INAF-OAB), Jean-Luc Atteia (IRAP) report on behalf of the SVOM team: SVOM/GRM detected GRB 250214A at 2025-02-14T05:32:06 UT (T0), which was also observed by Fermi/GBM (Fermi GBM team, GCN #39320). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multi-pulses with a duration of about 6 seconds in the 15-600 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250214A.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: Chao Zheng (IHEP) (zhengchao97(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/39490. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37501] EP250226a/GRB 250226A: GSP detects optical counterpart
by GCN Circulars 26 Feb '25

26 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39489 SUBJECT: EP250226a/GRB 250226A: GSP detects optical counterpart DATE: 25/02/26 10:57:41 GMT FROM: Wenxiong Li <liwenxiong1992(a)gmail.com> W. X. Li, S. J. Xue (NAOC), M. Andrews, J. Farah, D. A. Howell, M. Newsome, E. Padilla Gonzalez, C. McCully, and G. Terreran (Las Cumbres Observatory), on behalf of a larger collaboration, report: Following the detection of the fast X-ray transient EP250226a/GRB 250226A by the Einstein Probe (Jiang et al., GCN 39482), we initiated observations of the fast X-ray transient location starting on Feb 26 at 9:23 UT (~3 hours after the EP/WXT trigger) in the i and z bands. These observations were conducted using the 1-meter telescope at the Las Cumbres Observatory node located at the Cerro Tololo Inter-American Observatory in Chile. The optical counterpart (An et al., GCN 39486; Magnani et al., GCN 39488) was detected in the co-added images with i ~19.0 and z~19.3 mag. These observations were taken as part of the Global Supernova Project. View this GCN Circular online at https://gcn.nasa.gov/circulars/39489. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37500] EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
by GCN Circulars 26 Feb '25

26 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39488 SUBJECT: EP250226a/GRB 250226A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart DATE: 25/02/26 10:37:22 GMT FROM: Francesco <francesco.magnani.work(a)gmail.com> Francesco Magnani (CPPM), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), Benjamin Schneider (LAM), Alan M. Watson (UNAM), Kin Ocelotl López (UNAM), William H. Lee (UNAM), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Jean-Luc Atteia (IRAP), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Diego López-Cámara (UNAM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), and Antonio de Ugarte Postigo (LAM) report: We observed the field of EP250226a (Jiang et al., GCN Circ. 39482), consistent with the likely long GRB 250226A detected by Fermi/GBM (Fermi GCN Circ. 39479), with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We observed from 2025-02-26 07:56:43 to 09:14:20 UTC (82 minutes to 164 minutes after the trigger) and obtained 50 minutes of exposure in the i filter. The data were coadded with the COLIBRÍ pipeline and analyzed in STDWeb/STDPipe (Karpov 2021), with photometric calibration against Pan-STARRS DR1 and image subtraction against Pan-STARRS DR2. Our photometry is in the AB system and is not corrected for Galactic extinction. In our stacked image we detect a source at the position of the optical candidate reported by An et. al. (GCN Circ. 39486) and Zhu et. al. (GCN Circ. 39487) with magnitude: i = 19.05 +/- 0.03 We encourage continued monitoring of this source. 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/39488. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37499] EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315
by GCN Circulars 26 Feb '25

26 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39487 SUBJECT: EP250226a / GRB 250226A: VLT/X-shooter redshift of z = 3.315 DATE: 25/02/26 10:21:06 GMT FROM: Zipei Zhu at NAOC <zpzhu(a)nao.cas.cn> Z. P. Zhu (NAOC), A. Saccardi (CEA/Irfu), B. Schneider (LAM), L. Izzo (INAF-OACn and DARK/NBI), J. T. Palmerio (CEA/Irfu), D. Xu (NAOC), N. R. Tanvir (U. Leicester), D. B. Malesani (DAWN/NBI and Radboud Univ.), G. Pugliese (API-UvA), A. J. Levan (Radboud and Warwick), S. D. Vergani (CNRS, Obs. Paris/LUX) report on behalf of the Stargate collaboration: We observed the optical afterglow (An et al., GCN 39486) of EP250226a / GRB 250226A (Fermi GBM team, GCN 39479; Jiang et al., GCN 39482) using the ESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph. Our spectra cover the wavelength range 3000-25000 AA, and consist of 2x600 s. The observation mid-time was 2025 Feb. 26 at 08:43:57 (2.15 hr after the GBM trigger). In a 15 s image taken with the acquisition camera on Feb. 26 at 08:27:06 UT, we detect the optical afterglow, for which we measure a magnitude r =19.17 +/- 0.03 AB (calibrated against nearby stars from the Pan-STARRS catalogue). In a preliminary reduction of the spectra, we clearly detect a continuum down to 4000 AA. From the detection of a broad Lya absorption at ~5230 AA and multiple narrow absorption features, including O I, O I*, Si II, Si II*, C II, C II*, C IV, Si IV, Al II, Fe II, Fe II*, Al III, Ni II, Ni II*, Zn II, Cr II, Mg II, Mg I, Ca II we infer the redshift of the GRB to be z = 3.315. We acknowledge expert support from the ESO staff in Paranal, in particular Diego Parraguez and Marco Berton. View this GCN Circular online at https://gcn.nasa.gov/circulars/39487. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37498] EP250226a / GRB 250226A: TRT optical counterpart observation
by GCN Circulars 26 Feb '25

26 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39486 SUBJECT: EP250226a / GRB 250226A: TRT optical counterpart observation DATE: 25/02/26 08:35:09 GMT FROM: Dong Xu at NAOC/CAS <dxu(a)nao.cas.cn> J. An, S.Q. Jiang, X. Liu, S.Y. Fu, Z.P. Zhu, D. Xu (NAOC), S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), Z. Fan, W.X. Li, N.C. Sun, Y.N. Wang (NAOC) report on behalf of a large collaboration: We observed the field of EP250226a detected by EP/WXT (Jiang et al., GCN 39482), which is very likely the same event of GRB 250226A detected by Fermi/GBM (Fermi GBM team, GCN 39479), using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Cerro Tololo Inter-American Observatory, Chile. We obtained several 300 s frames in the Sloan-r filter. An uncatalogued and decaying optical source is detected within the EP/FXT error circle (Jiang et al., GCN 39482) at coordinates R.A. (J2000) = 14:57:03.63 Dec. (J2000) = +20:58:32.31 with an uncertainty of about 1.0 arcsec. The source has r ~ 17.7 mag at 21.8 min after the EP trigger, calibrated with PanSTARRS DR2 stars and not corrected for Galactic extinction. We think that the source is the optical counterpart of EP250226a / GRB 250226A. View this GCN Circular online at https://gcn.nasa.gov/circulars/39486. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37497] LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
by GCN Circulars 26 Feb '25

26 Feb '25

TITLE: GCN CIRCULAR NUMBER: 39485 SUBJECT: LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources DATE: 25/02/26 08:33:05 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P.A. Evans (U. Leicester), J.J. Delaunay (PSU), K.L. Page (U. Leicester), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), S.B. Cenko (NASA/GSFC), R.A.J. Eyles-Ferris (U. Leicester), A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), A.A. Breeveld (UCL-MSSL), S. Campana (INAF-OAB), M. De Pasquale (University of Messina), S. Dichiara (PSU), P. D’Avanzo (INAF-OAB), A. D’Aì (INAF-IASFPA) , V. D’Elia (ASI-SSDC & INAF-OAR), C. Gronwall (PSU), D. Hartmann (Clemson University), N. Klingler (NASA-GSFC / UMBC / CRESST II), N.P.M. Kuin (UCL-MSSL), S. Laha (NASA/GSFC), S.R. Oates (U. Birmingham), J.P. Osborne (U. Leicester), P. O’Brien (U. Leicester), M.J. Page (UCL-MSSL), G. Raman (PSU) S. Ronchini (PSU), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.H. Siegel (PSU), G. Tagliaferri (INAF-OAB), E. Troja (U Tor Vergata, INAF) report on behalf of the Swift team: Swift has carried out 1 observation of the combined LVK/Swift-BAT-GUANO error region for the GW trigger S250223dk, centred on the most-probable location (RA,Dec = 85.4260, -47.5420 [J2000]). We gathered 5.5 ks of data from 106 ks to 140 ks after the LVK trigger. This observations covers 73% of the probability in the combined skymap. We have detected 7 X-ray sources. Each source is assigned a rank of 1-4 which describes how likely it is to be related to the GW trigger, with 1 being the most likely and 4 being the least likely. The ranks are described at https://www.swift.ac.uk/ranks.php. We have found: * 0 sources of rank 1 * 0 sources of rank 2 * 7 sources of rank 3 * 0 sources of rank 4 RANK 3 sources ============== These are uncatalogued X-ray sources, however they are not brighter than previous upper limits, so do not stand out as likely counterparts to the GW trigger. | Source ID | RA | Dec | Err90 | | S250223dk_X1 | 05h 41m 59.75s | -47d 21' 33.8" | 6.8" | | S250223dk_X2 | 05h 42m 11.19s | -47d 23' 57.3" | 6.4" | | S250223dk_X3 | 05h 41m 58.45s | -47d 33' 26.5" | 6.5" | | S250223dk_X4 | 05h 42m 19.59s | -47d 34' 02.3" | 6.9" | | S250223dk_X5 | 05h 42m 03.87s | -47d 42' 35.1" | 6.4" | | S250223dk_X6 | 05h 42m 01.25s | -47d 43' 06.8" | 6.3" | | S250223dk_X7 | 05h 41m 25.44s | -47d 26' 58.1" | 6.4" | For all flux conversions and comparisons with catalogues and upper limits from other missions, we assumed a power-law spectrum with NH=3x10^20 cm^-2, and photon index (Gamma)=1.7, unless otherwise stated. The results of the XRT automated analysis, including details of the sources listed above, are online at https://www.swift.ac.uk/LVC/S250223dk This circular is an official product of the Swift XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39485. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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