February 2026 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 41709] GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
by GCN Circulars 02 Feb '26

02 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43606 SUBJECT: GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility DATE: 26/02/02 19:28:33 GMT FROM: rj438(a)cornell.edu R. Jayaraman (Cornell), X. J. Hall (CMU), A. Y. Q. Ho (Cornell), I. Andreoni (UNC), M. Coughlin (UMN), A. Jacquesson (IJCLab), G. Schroeder (Cornell) report: We report a serendipitous detection of the optical afterglow to GRB 260131A (Fermi/GBM Team, GCN 43579; Frederiks et al., GCN 43590; Luo et al., GCN 43591; Li et al., GCN 43605), which has been given the designation AT2026bwg (Gompertz et al., GCN 43586; Lee et al., GCN 43587; Malesani et al;, GCN 43595, García et al., GCN 43599; Shi et al., GCN 43601), as part of the Zwicky Transient Facility’s public survey. The transient ZTF26aaemwcb was first detected on MJD 61072.16995 (21.4h after the GRB trigger) with a magnitude of r = 18.08 ± 0.05 in ZTF alert photometry. Roughly a day later (MJD 61073.15126), the transient had faded to r = 19.13 ± 0.10. The last upper limit was approximately 2.5h before the initial trigger, with a limiting magnitude of r > 19.411. Separately, the transient was also observed at MJD 61072.13239 (20.5h after the GRB trigger) using multi-band imaging with the SED Machine on the Palomar P60 telescope. The table of photometry follows: Time (MJD) | Magnitude 61072.13239 | 18.21 ± 0.14 (sdss-g) 61072.13405 | 18.03 ± 0.20 (sdss-r) 61072.13571 | 17.80 ± 0.48 (sdss-i) These measurements from both ZTF and SEDM are consistent with a decaying afterglow, when compared to those from Gompertz et al., Lee et al., Malesani et al., and García et al. The fast rise and decay was initially flagged by a pipeline for discovering afterglows in the ZTF data (e.g., Ho et al. 2020, ApJ, 905, 98), as well as the ZTFrest filter (Andreoni et al. 2021, ApJ, 918, 63). Upon a retrospective search, we identified ZTF26aaemwcb as the afterglow to GRB 260131A. This Circular is based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Award #2407588 and a partnership including Caltech, USA; Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; University of Wisconsin at Milwaukee, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan; and OKC, University of Stockholm, Sweden. Operations are conducted by Caltech's Optical Observatory (COO), Caltech/IPAC, and the University of Washington at Seattle, USA. View this GCN Circular online at https://gcn.nasa.gov/circulars/43606. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41708] GRID detection of GRB 260131A/B
by GCN Circulars 02 Feb '26

02 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43605 SUBJECT: GRID detection of GRB 260131A/B DATE: 26/02/02 17:33:11 GMT FROM: GRID Student Team at Tsinghua University <grid(a)tsinghua.edu.cn> Longhao Li, Zirui Yang, Chenyu Wang report on behalf of the GRID Collaboration: GRID reports the detection of GRB 260131A/B, which was also reported by Fermi and MAXI (Roberts, GCN 43585; a.k.a. GRB 260131B, Sugai et al., GCN 43580). The event first triggered GRID at T0 = 2026-01-31 06:39:30 UTC, and was detected by both GRID-10B and GRID-11B, with a weaker signal observed by GRID-11B. A second trigger was recorded at 2026-01-31 06:43:02 UTC; however, the GRID signal associated with this later trigger is comparatively weak. Therefore, temporal analysis is based on the first trigger only. The measured burst duration for the first trigger is T90 = 10.5 ± 1.4 s in the 30–2000 keV energy range. The GRID light curves of this event can be found at https://mirrors.tuna.tsinghua.edu.cn/GRID/data/GRID-GCN/GRB260131A-B/. GRID is a student-led project to monitor the transient gamma-ray sky with multiple detectors onboard different nanosatellites in the era of multi-messenger astronomy. For more information about GRID, please refer to the following references: https://doi.org/10.1007/s10686-019-09636-w and https://doi.org/10.1007/s10686-021-09819-4. View this GCN Circular online at https://gcn.nasa.gov/circulars/43605. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41707] GRB 260131A/B: GTC/OSIRIS+ redshift confimation
by GCN Circulars 02 Feb '26

02 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43604 SUBJECT: GRB 260131A/B: GTC/OSIRIS+ redshift confimation DATE: 26/02/02 11:48:03 GMT FROM: Ruben Sanchez-Ramirez at IAA-CSIC <ruben(a)iaa.es> R. Sanchez-Ramirez, A. J. Castro-Tirado, M.D. Caballero-Garcia, S. Guziy, S.-Y. Wu, I. Perez-Garcia, and E. Fernandez-Garcia (IAA-CSIC), D. Garcia-Alvarez (GTC), Y.-D. Hu (GXI), M. Gritsevich (Univ. of Helsinki), and L. Piro (INAF/IAPS), on behalf of a larger collaboration, report: Following the detection of GRB 260131A/B (Fermi/GBM Team, GCN 43579; Sugai et al., GCN 43580; Roberts et al., GCN 43585; Frederiks et al., GCN 43590; Luo et al., GCN 43591), we observed the optical afterglow detected by several facilities (Gompertz et al., GCN 43586; Lee et al., GCN 43587; Saccardi et al., GCN 43595; García García et al., GCN 43599, Jiang et al. GCN 43600, Shi et al. GCN 43601), with the 10.4m GTC telescope, at the Spanish Roque de los Muchachos Observatory, on the island of La Palma, equipped with the OSIRIS+ instrument. The spectroscopic data consisted of 3x900s exposures using grism R1000R, covering the spectral range between 5,000 and 10,000 A. The observations started on Feb 1 at 20:08 UT (i.e. ~37h after the burst trigger). From a preliminary reduction, we find the absorption system reported by Saccardi et al. (GCN 43595) at a consistent z=1.435. We note also the presence of FeII* lines. View this GCN Circular online at https://gcn.nasa.gov/circulars/43604. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41706] GRB 260130A: Insight-HXMT/HE detection
by GCN Circulars 02 Feb '26

02 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43603 SUBJECT: GRB 260130A: Insight-HXMT/HE detection DATE: 26/02/02 11:35:26 GMT FROM: zhangjinpeng(a)ihep.ac.cn Jin-Peng Zhang, Chen-Wei Wang, Chao Zheng, and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team: At 2026-01-30T13:29:20.800 (T0), Insight-HXMT/HE detected a short GRB 260130A, which is also detected by Fermi/GBM (Fermi GBM Team, GCN #43569; A. Jameson et al., GCN #43575). The Insight-HXMT/HE light curve mainly consists of a bright single pulse with a T90 of 0.08 +/- 0.02 s. The 1 ms peak rate (since this is a bright short burst with duration < 1 s, we check 1 ms peak rate instead of 1 s), measured from T0+0.019 s, is 46000 +/- 5000 cnts/sec. Insight-HXMT/HE detected a total of 1250 +/- 50 counts from this burst. The Insight-HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb260130A.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://hxmten.ihep.ac.cn View this GCN Circular online at https://gcn.nasa.gov/circulars/43603. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41705] GRB 260130A: GECAM-B observation of a short burst
by GCN Circulars 02 Feb '26

02 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43602 SUBJECT: GRB 260130A: GECAM-B observation of a short burst DATE: 26/02/02 11:34:18 GMT FROM: zhangjinpeng(a)ihep.ac.cn Jin-Peng Zhang, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by GRB 260130A, at 2026-01-30T13:29:20.850 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43569; A. Jameson et al., GCN #43575). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of a bright short pulse, with a duration (T90) of 0.083 +/- 0.009 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260130A.png The time-averaged spectrum from T0 - 0.05 to T0 + 0.02 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.52 +0.23/-0.24 and the cutoff energy, parameterized as Epeak, is 860 +190/-140 keV. The event fluence (10-1000 keV) in this time interval is (1.28 +0.11/-0.10)E-06 erg/cm^2. The 'Amati' relation diagram of GRB 260130A is shown at: https://www.bursthub.cn//admin/static/gecambgrb260130A_amati.png Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (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/43602. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41704] GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
by GCN Circulars 02 Feb '26

02 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43601 SUBJECT: GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope DATE: 26/02/02 08:39:44 GMT FROM: shiy228(a)mail2.sysu.edu.cn Yun Shi, Jin-Ji Li, Pu Lin, Hao-Nan Yang, Zhong-Nan Dong, Yan Yu, Jia-Qi Lin, Wei-Sen Huang, Chun Chen, Duo-Le Cao, P H Thomas Tam, Rong-Feng Shen, Bin Ma (Sun Yat-sen University) report on behalf of the SYSU 80cm infrared telescope team: We observed the field of GRB 260131A/B (Fermi/GBM Team, GCN 43579; Sugai et al., GCN 43580; Roberts et al., GCN 43585; Frederiks et al., GCN 43590; Luo et al., GCN 43591), using the Sun Yat-sen University (SYSU) 80cm infrared telescope. Our observations were carried out on 2026 Feb 01 14:39 UT, 31.99 hours after the GRB trigger, using stacked images in the J band. We clearly detect an infrared counterpart at the position of the optical afterglow candidate AT2026bwg / GOTO26akj (Gompertz et al., GCN 43586; Lee et al., GCN 43587; Saccardi et al., GCN 43595; García García et al., GCN 43599). The preliminary photometric results are summarized in the table below. The photometry was calibrated against nearby stars from the 2MASS catalog and is reported in the Vega system, without correction for Galactic extinction. Start Time (UTC) |Band | Exp | Mag (Vega) -------------------------|-------|---------|------------------ 2026/2/1 14:39:25 | J | 600s | 16.9+/-0.2 2026/2/1 14:49:48 | J | 600s | 17.0+/-0.2 2026/2/1 15:00:10 | J | 600s | 17.1+/-0.2 2026/2/1 15:10:33 | J | 840s | 17.0 +/-0.2 The SYSU 80cm infrared telescope is operated and managed by the Department of Astronomy, Sun Yat-sen University. View this GCN Circular online at https://gcn.nasa.gov/circulars/43601. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41703] GRB 260131A/B: EP/FXT X-ray afterglow detection
by GCN Circulars 02 Feb '26

02 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43600 SUBJECT: GRB 260131A/B: EP/FXT X-ray afterglow detection DATE: 26/02/02 08:14:51 GMT FROM: sqjiang at NAOC <sqjiang(a)bao.ac.cn> S.Q. Jiang, D. Xu (NAOC), B.P. Gompertz (U. Birmingham), H.W. Pan (NAOC), K.R. Ni (CCNU), C.Y. Dai (NJU), B.T. Wang (YNAO) report: EP/FXT performed a follow-up observation on GRB 260131A/B detected by Fermi (Fermi/GBM team, GCN 43579; Roberts et al., GCN 43585), MAXI (Sugai et al., GCN 43580), Konus-Wind (Frederiks et al., GCN 43590), and Insight-HXMT (Luo et al., GCN 43591) at 2026-02-01T16:45:27 (UTC), about 34.1 hrs after the Fermi/GBM trigger. An uncatalogued source is detected at R.A. = 24.7137, Dec. = 34.3284 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic), which is consistent with the optical counterpart GOTO26akj/AT2026bwg (Gompertz et al., GCN 43586). The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 4.81 × 10^20 cm^-2, an intrinsic hydrogen column density upper limit of 4.66 × 10^21 cm^-2 at the redshift of 1.434 (Saccardi et al., GCN 43595), and a photon index of 2.01 (-0.09/+0.12). The derived average unabsorbed 0.5-10 keV flux is 3.35 (-0.19/+0.23) × 10^(-12) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. View this GCN Circular online at https://gcn.nasa.gov/circulars/43600. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41702] GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
by GCN Circulars 02 Feb '26

02 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43599 SUBJECT: GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations DATE: 26/02/02 04:28:39 GMT FROM: Leonardo Enrique García García <lgarcia(a)astro.unam.mx> Leonardo García García (UNAM), Benjamin Schneider (LAM), Noémie Globus (UNAM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Ramandeep Gill (UNAM), Asuka Kuwata (UNAM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), and Antonio de Ugarte Postigo (LAM) report: We observed the optical afterglow candidate AT2026bwg (Gompertz et al., GCN 43586) of GRB 260131A/B (Fermi/GBM Team, GCN 43579; Sugai et al., GCN 43580; Roberts et al., GCN 43585; Frederiks et al., GCN 43590; Luo et al., GCN 43591) with the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-02-01 02:10 to 03:07 UTC (from 43.52 to 44.48 hours after the trigger) in the g/r/i/y/z bands and obtained 13 minutes of exposure in the r band. The data were reduced, coadded, calibrated, and analyzed with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. The optical counterpart (Gompertz et al., GCN 43586; Lee et al., GCN 43587; Saccardi et al., GCN 43595) is clearly detected in all filters, and has a preliminary magnitude of: r = 19.24 +/- 0.02. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/43599. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41701] GRB 260127B: Insight-HXMT/HE detection
by GCN Circulars 02 Feb '26

02 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43598 SUBJECT: GRB 260127B: Insight-HXMT/HE detection DATE: 26/02/02 03:28:19 GMT FROM: renyz16607(a)163.com Yang-Zhao Ren, Chen-Wei Wang, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng (IHEP) report on behalf of the Insight-HXMT team: At 2026-01-27T20:02:32.500 (T0), Insight-HXMT/HE detected a short burst, GRB 260127B, which is also detected by Fermi/GBM (Fermi GBM team, GCN #43533), AstroSat/CZTI (Arya et al., GCN #43576), and GECAM-B (Ren et al., GCN #43597). The Insight-HXMT/HE light curve mainly consists of multi-pulses with T90 of 0.17 +0.04/-0.02 s. The 1s peak rate, measured from T0+0.01 s, is 2733 cnts/sec. Insight-HXMT/HE detected a total of 2735 counts from this burst. The Insight-HXMT /HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb260127B.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://hxmten.ihep.ac.cn/ View this GCN Circular online at https://gcn.nasa.gov/circulars/43598. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41700] GRB 260127B: GECAM-B observation of a short burst
by GCN Circulars 02 Feb '26

02 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43597 SUBJECT: GRB 260127B: GECAM-B observation of a short burst DATE: 26/02/02 03:20:39 GMT FROM: renyz16607(a)163.com Yang-Zhao Ren, Chen-Wei Wang, Chao Zheng, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by GRB 260127B, at 2026-01-27T20:02:32.650 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #43533), and AstroSat/CZTI (Arya et al., GCN #43576). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 0.13 +0.11/-0.02 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260127B.png Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (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/43597. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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