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

[vsnet-grb-info 42002] GRB 260225D: SVOM/GRM observation
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43885 SUBJECT: GRB 260225D: SVOM/GRM observation DATE: 26/03/01 08:05:24 GMT FROM: zhangjinpeng(a)ihep.ac.cn SVOM/GRM team: Jin-Peng Zhang, Zheng-Hang Yu, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Frédéric Daigne (IAP), Olivier GODET (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 260225D (SVOM trigger reference: sb26022503) at 2026-02-25T19:51:30.000 (T0), which is also detected by Konus-Wind (Trig_Time 19:51:32.84), Glowbug (C.C. Cheung et al., GCN #43856) and GRID. With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of two pulses with a T90 of 2.0 +1.0/-0.6 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260225D.png In addition, the position of this burst, according to Glowbug localization (RA = 94.7, Dec = 13.8, C.C. Cheung et al., GCN #43856), is located at about 93 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. Nevertheless, ECLAIRs detected the GRB through the shield above 50 keV. With this localization, the time-averaged spectrum from T0-2.0 to T0+4.0 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.12 +0.18/-0.15 and the cutoff energy, parameterized as Epeak, is 700 +480/-250 keV. The event fluence (10-1000 keV) in this time interval is (8.5 +0.8/-0.9)E-07 erg/cm^2. The localization of GRB 260225D in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260225D_amati.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: Jin-Peng Zhang (IHEP) (zhangjinpeng(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/43885. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42001] EP260227A: 3.6m DOT optical afterglow detection
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43884 SUBJECT: EP260227A: 3.6m DOT optical afterglow detection DATE: 26/03/01 07:52:34 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Dhruv Jain, Pankaj Pawar, Debalina Kar, and Kuntal Misra (ARIES) report: We observed the field of EP260227A detected by Einstein Probe WXT (Wang et al., GCN 43869) with the 3.6m Devasthal Optical Telescope (DOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2026-02-28 at 21:17:26 UT, i.e., ~25.08 hours after the EP/WXT trigger. We have taken multiple frames with an exposure time of 300s in the R filter. We stacked the images after the alignment. We detect an optical counterpart in our stacked image at the position given by the Eyles-Ferris et al. (GCN 43867). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (hours) Filter Exp time (s) Magnitude ================================================================== 2026-02-28 21:17:26 ~25.08 R 300s*24 22.92 +/-0.06 Our detection is consistent with Eyles-Ferris et al. (GCN 43867); Li et al. (GCN 43868); Lipunov et al. (GCN 43870); Fu et al.(GCN 43873); Mandarakas et al. (GCN 43874); Eyles-Ferris and N. R. Tanvir et al. (GCN 43875); Malesani et al. (GCN 43876); Eyles-Ferris et al. (GCN 43877); Strausbaugh et al. (GCN 43879); Bochenek et al. (GCN 43880); Gassert et al. (GCN 43881). 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 catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/43884. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 42000] GRB 260225B: SVOM/GRM observation
by GCN Circulars 01 Mar '26

01 Mar '26

TITLE: GCN CIRCULAR NUMBER: 43883 SUBJECT: GRB 260225B: SVOM/GRM observation DATE: 26/03/01 06:49:10 GMT FROM: yzh807926(a)163.com SVOM/GRM team: Zheng-Hang Yu, Chen-Wei Wang, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Frédéric Daigne (IAP), Olivier GODET (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 260225B (SVOM trigger reference: sb26022502) at 2026-02-25T15:14:10.000 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43833). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a precursor followed by a main episode showing a single peak with a T90 of 49.0 +26.0/-20.0 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260225B.png In addition, the position of this burst, as determined by Fermi/GBM (RA= 326.4, DEC= 0.9 GCN#43833), is located at about 111 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. At the time of the trigger, ECLAIRs was not collecting data. With this localization, the time-averaged spectrum from T0-5 to T0+30 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.71 +0.17/-0.22 and the cutoff energy, parameterized as Epeak, is 747 +1525/-389 keV. The event fluence (10-1000 keV) in this time interval is (1.48 +0.12/-0.13)E-05 erg/cm^2. The 1s peak spectrum, measured from T0+4 to T0+5 s, if fitted by a power law function with an exponential high-energy cutoff, the power law index is -1.54 +0.16/-0.20 and the cutoff energy, parameterized as Epeak, is 1390 +1560/-6701 keV. The flux (10-1000 keV) in this time interval is (1.86 +0.14/-0.15)E-06 erg/cm^2/s. The localization of GRB 260225B in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260225B_amati.png The localization of GRB 260225B in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260225B_yonetoku.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 point of contact for this burst is: Zheng-Hang Yu(IHEP)(zhyu(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/43883. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41999] GRB 260228A: SVOM detection of a burst
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43882 SUBJECT: GRB 260228A: SVOM detection of a burst DATE: 26/02/28 21:28:57 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Y. Julakanti, R. Eyles-Ferris (Univ. Leicester), S. Schanne (CEA/IRFU), H. Yang (IRAP), M.-G. Bernardini (INAF-OAB, LUPM) report on behalf of the SVOM mission team: At 2026-02-28T20:55:55 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260228A (SVOM burst-id sb26022802). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was only detected by the Image Trigger (IMT), which produced a sequence of 7 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 10.64 in the 5-20 keV energy band over a time window of 40.96 seconds starting at 2026-02-28T20:55:34 (Tb). The localization of the best alert is R.A., Dec. 237.8312, 26.3060 degrees: R.A. (J2000) = 15h51m19.50s Dec. (J2000) = 26d18m21.48s with a 90% confidence level (C.L.) radius of 7.51 arcmin (including systematic error of 2 arcmin added in quadrature). The SVOM/ECLAIRs light curve showed a single broad peak structure in the Energy bands 5-8 and 8-20 keV only. The T90 duration computed in 5-120 keV is (16.6 -3.5/+7.2) s. SVOM slewed to the burst. No X-ray observation could be performed by SVOM/MXT for the time being because of Earth occultation. No optical observation could be performed by SVOM/VT for the time being. The Space-based multi-band astronomical 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. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is Yashaswi Julakanti: skyj1(a)leicester.ac.uk. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/43882. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41998] EP260227a: FTW optical and NIR observations
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43881 SUBJECT: EP260227a: FTW optical and NIR observations DATE: 26/02/28 20:17:24 GMT FROM: Julius Gassert at Ludwig-Maximilians-Universität München <julius.gassert(a)campus.lmu.de> Julius Gassert (LMU/CMU), Malte Busmann (LMU), Christoph Ries (LMU), Xander J. Hall (CMU), Brendan O’Connor (CMU), Daniel Gruen (LMU), and Antonella Palmese (CMU) report: We observed the optical counterpart (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868; Fu et al., GCN 43873; Mandarakas et al., GCN 43874; Eyles-Ferris & Tanvir, GCN 43875; Malesani et al., GCN 43876; Eyles-Ferris et al., GCN 43877; Strausbaugh et al, GCN 43879, Bochenek et al. GCN 43880) of EP 20260227a (Wang et al., GCN 43869) with the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW) in the r, i, and J bands for 19x 180s, starting at 2026-02-28T04:21:12 (0.34 days after the trigger). We detect the counterpart in all bands and measure an r-band magnitude of r = 21.69 +/- 0.10 AB mag The magnitude is calibrated against the PS1 catalog and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43881. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41997] EP260227a: Liverpool Telescope optical observations
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43880 SUBJECT: EP260227a: Liverpool Telescope optical observations DATE: 26/02/28 20:05:03 GMT FROM: A. Bochenek at Liverpool John Moores University <a.m.bochenek(a)2023.ljmu.ac.uk> A. Bochenek, D. A. Perley (LJMU) report: We observed the field of EP260227a (Wang et al., GCN 43869) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 5x120s exposures in SDSS r and i filters and 3x100s + 2x120s in SDSS z, starting at 2026-02-28 02:54:00 UT, approximately 6.69 hours after trigger. We report detections in stacked images in all filters at the position first reported by Eyles-Ferris et al. (GCN 43867) and Li et al. (GCN 43868). MJD (mid) T_mid-T_0 Filter Mag. (AB) 61099.12483 6.79 h r 21.31 ± 0.19 61099.13319 6.99 h i 21.10 ± 0.12 61099.14035 7.16 h z 20.71 ± 0.11 Our results are consistent with the slower fading of the optical counterpart as reported by and Eyles-Ferris et al. (GCN 43875), comparing to the observations of Fu et al. (GCN 43873), Mandarakas et al. (GCN 43874) and Eyles-Ferris et al. (GCN 43875). The photometry was obtained using nearby PanSTARRS secondary standards and was not corrected for extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43880. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41996] EP260227a: LCOGT Optical Observations
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43879 SUBJECT: EP260227a: LCOGT Optical Observations DATE: 26/02/28 17:33:05 GMT FROM: Robert Strausbaugh at Eastern Illinois University <rstrausbaugh(a)eiu.edu> R. Strausbaugh (Eastern Illinois University), A. Cucchiara (NASA) report on behalf of a larger collaboration: We observed the EP260227a field (Wang et al., GCN 43869) with the LCOGT 1-meter Sinistro instrument at the Cerro Tololo Interamerican Observatory, Chile site, on February 28, from 05:39 to 06:00 UT (corresponding to 9.28 to 9.63 hours after the trigger time) with the SDSS r and i filters. We performed a series of 3x200s exposures in i-band and r-band. We marginally detect an uncatalogued sources in both bands, consistent with other optical detections (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868; Fu et al., GCN 43873; Mandarakas et al., GCN 43874; Eyles-Ferris et al., GCN 43875; Malesani et al., GCN 43876). The following magnitudes are calculated using the PanSTARRS catalog as reference: r = 20.78 +/- 0.58 i = 21.47 +/- 0.52 These magnitudes are not corrected for galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43879. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41995] GRB 260226A: Asiago r-band upper limit
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43878 SUBJECT: GRB 260226A: Asiago r-band upper limit DATE: 26/02/28 12:43:06 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> A. Reguitti (INAF/OAPd), P. D'Avanzo (INAF/OAB), D. B. Malesani (DAWN/NBI and Radboud), L. Tomasella (INAF/OAPd) report on behalf of the CIBO collaboration: We observed the field of the bright GRB 260226A (Depalo et al., GCN 43850; Bissaldi et al., GCN 43851; Harsha et al., GCN 43846; Waratkar & Grefenstette, GCN 43854; Woolf et al.. GCN 43855; Kobayashi et al., GCN 43860; Svinkin et al., GCN 43864; Yu et al., GCN 43865) using the 67/92 Schmidt Telescope located at the Asiago observatory (Italy). Observations consisted of five r-band exposures of 240 s each, with a mid time Feb 26.766 UT (7.77 hr after the Fermi/GBM trigger). Image subtraction was carried out using the DESI Legacy survey (Dey et al. 2019, doi:10.3847/1538-3881/ab089d) as template. No new source is detected within the revised Fermi/LAT error circle (Depalo et al., GCN 43850) down to a limiting magnitude r > 20.4 AB (calibrated against nearby objects from the Pan-STARRS catalog). Our non detection is consistent with other reports from the literature (Konno et al., GCN 43852; Saikia et al., GCN 43853; Strausbaugh & Cucchiara, GCN 43858; Angulo et al., GCN 43859). View this GCN Circular online at https://gcn.nasa.gov/circulars/43878. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41994] EP260227a: Thai National Telescope observations
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43877 SUBJECT: EP260227a: Thai National Telescope observations DATE: 26/02/28 12:41:42 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris (Leicester), S. Littlefair (Sheffield), V. Dhillon (Sheffield), I. Pelisoli (Warwick), J. van Dalen (Radboud), P. G. Jonker (Radboud), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), D. Mata-Sanchez (IAC and ULL), report on behalf of a larger collaboration: We observed the position of the fast X-ray transient EP260227a (Wang et al., GCN 43869) with the 2.4m Thai National Telescope equipped with the ULTRASPEC instrument. Observations were conducted in the KG5 wideband filter which approximately covers the wavebands of the SDSS ugr filters (https://tinyurl.com/kg5filter; Hardy et al. 2017). The total exposure time was 62 minutes with a mid time of 2026-02-27 22:28:00 UT (2.52 hr after trigger). We clearly detect the optical counterpart (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868; Fu et al., GCN 43873; Mandarakas et al., GCN 43874; Eyles-Ferris & Tanvir, GCN 43875; Malesani et al., GCN 43876) at a magnitude m_KG5 = 23.57 +/- 0.07 (AB) calibrated to Pan-STARRS and not corrected for Galactic extinction. The faint magnitude compared to other photometry is likely attributable to the peak response of the adopted filter in the blue and the red colour of the source, broadly consistent with the DLA suggested by Malesani et al (GCN 43876). View this GCN Circular online at https://gcn.nasa.gov/circulars/43877. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 41993] EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43876 SUBJECT: EP260227a: likely GTC/OSIRIS+ redshift z = 2.714 DATE: 26/02/28 12:12:32 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> D. B. Malesani (DAWN/NBI and Radboud), P. G. Jonker (Radboud), A. Martin-Carrillo (UCD), R. A. J. Eyles-Ferris (Leicester), J. van Dalen (Radboud), D. Mata-Sanchez (IAC and ULL), A. de Ugarte Postigo (LAM), N. Castro Rodríguez (GTC), A. L. Cabrera Lavers (GTC) report on behalf of a larger collaboration: We observed the optical counterpart (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868; Fu et al., GCN 43873; Mandarakas et al., GCN 43874; Eyles-Ferris & Tanvir, GCN 43875) of EP260227a (Wang et al., GCN 43869) using the Gran Telescopio Canarias (GTC) equipped with the OSIRIS+ spectrograph. Our observations consisted of 4 exposures of 900 s each, using grism R1000B which covers the wavelength range 3670 - 7700 Å. The observation start time was 2026-02-28 at 03:16 UT (~7.1 hr after the trigger). In the acquisition magnitude, we measure r = 21.55 +/- 0.07 AB at mid time 6.89 hr after trigger (consistent with the NOT measurement; Fu et al., GCN 43873). This value is calibrated against nearby objects from the Pan-STARRS catalog and not corrected for Galactic extinction. A faint trace is detected down to ~4000 Å, with an apparent spectral break around 4500 Å which is interpreted as due to H I and the onset of the Lyman forest. A few weak, narrow features, due to Si II 1259, Si II 1304, C II 1334, C IV 1548/1550, allow us to measure a redshift z = 2.714. View this GCN Circular online at https://gcn.nasa.gov/circulars/43876. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0