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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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[vsnet-grb-info 41699] GRB 260127A: GECAM-B observation
by GCN Circulars 02 Feb '26

02 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43596 SUBJECT: GRB 260127A: GECAM-B observation DATE: 26/02/02 03:09:30 GMT FROM: renyz16607(a)163.com Yang-Zhao Ren, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered on-ground by GRB 260127A, at 2026-01-27T17:51:07.000 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #43528) and Swift/BAT (Klingler et al., GCN #43529). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of a pulse with a duration (T90) of 6 +1/-1 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260127A.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/43596. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41698] GRB 260131A: NOT spectroscopic redshift z = 1.434
by GCN Circulars 01 Feb '26

01 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43595 SUBJECT: GRB 260131A: NOT spectroscopic redshift z = 1.434 DATE: 26/02/01 22:04:19 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> A. Saccardi (CEA/Irfu), J. An (NAOC), G. Corcoran (UCD), B. Gompertz (Birmingham), L. Izzo (INAF/OAC and DARK/NBI), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), B. Schneider (LAM), A de Ugarte Postigo (LAM), K. Valeckas (NOT and NBI), report on behalf of a larger collaboration: We observed the optical counterpart GOTO26akj / AT2026bwg (Gompertz et al., GCN 43586; Lee et al., GCN 43587) of the Fermi and MAXI GRB 260131A (Roberts, GCN 43585; a.k.a. GRB 260131B: Sugai et al., GCN 43580) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC spectrograph. We measure the afterglow brightness to be r = 18.98 +/- 0.02 (AB) at a mean epoch 2026 Feb 01 at 19:45:24 UT (37.1 hr after the burst), calibrated against nearby Pan-STARRS stars and not corrected for Galactic extinction. A spectrum consisting of 4x900 s exposures was secured starting on 2026 Feb 01 at 19:57 UT (37.3 hr after the Fermi/GBM trigger), using grism #4 which covers the wavelength range 3200-9600 AA. Based on a preliminary reduction of part of the spectra, a continuum is detected down to 3600 AA, setting an upper limit to the redshift z < 1.95 based on the lack of HI absorption. From the detection of several absorption features, among which Mg II 2804/2796, Fe II 2600, Fe II 2382, and Al III 1863/1855, we infer a redshift z = 1.434. Further analysis is ongoing. View this GCN Circular online at https://gcn.nasa.gov/circulars/43595. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41697] EP260131a: Liverpool Telescope optical upper limits
by GCN Circulars 01 Feb '26

01 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43594 SUBJECT: EP260131a: Liverpool Telescope optical upper limits DATE: 26/02/01 19:40:28 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 EP 260131a (Ding et al., GCN 43574, Wu et al. GCN 43583) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 8x150s exposures in SDSS r filter and 10x120s in SDSS z, starting at 2026-01-31 23:25:26 UT, approximately 19.9 hours after trigger. One z-band exposure had to be discarded due to telescope movement. We report non-detections in the stacked images in both filters at the position of the counterpart first reported by Li et al. GCN 43577 and Álvarez et al., GCN 43578, with 3-sigma upper limits being r > 22.05 and z > 21.90 mag. 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/43594. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41696] EP260131a: COLIBRÍ further observations
by GCN Circulars 01 Feb '26

01 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43593 SUBJECT: EP260131a: COLIBRÍ further observations DATE: 26/02/01 17:30:24 GMT FROM: globus(a)astro.unam.mx Benjamin Schneider (LAM), William H. Lee (UNAM), Alan M. Watson (UNAM), Noémie Globus (UNAM), Stéphane Basa (UAR Pytheas), Edilberto Aguilar-Ruiz (UNAM), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Jean-Luc Atteia (IRAP), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), 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 imaged the field of the EP260131a (Ding et al., GCN Circ. 43574; Wu et al, GCN Circ 43583) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-02-01 06:33 to 12:16 UTC (from 27.04 to 32.74 hours after the trigger) and obtained, respectively, 160 minutes of exposure in the r and z filters. The data were reduced and coadded with the COLIBRÍ ASU pipeline and analyzed with STDWeb/STDPipe (Karpov 2025). 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 candidate optical counterpart reported by Li et al. (GCN Circ. 43577), Sánchez Álvarez et al (GCN Circ. 43578), Malesani et al. (GCN Circ 43581), Schneider et al. (GCN Circ. 43582), Schneider et al. (GCN Circ 43584), Mu el al. (GCN Circ 43588), and Yao et al. (GCN CIrc. 43589) is clearly detected in our data, with a preliminary magnitude of r ~ 22. We find that the optical counterpart fades with an average temporal power-law index of ~ -0.5. We encourage further observations. 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/43593. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41695] Konus-Wind detection of GRB 260128A / EP260128a
by GCN Circulars 01 Feb '26

01 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43592 SUBJECT: Konus-Wind detection of GRB 260128A / EP260128a DATE: 26/02/01 16:47:41 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-duration GRB 260128A/EP260128a (Einstein Probe detection: Zhow et al., GCN 43549; Fermi-GBM Sub-Threshold Detection: Ravasio et al., GCN 43556) was detected by Konus-Wind (KW) in the waiting mode at T0=T0(KW)~23:40:00 UTC. A Bayesian block analysis of the KW data in the 20-1500 keV band reveals a >10 sigma count rate increase in the interval from ~T0-101 s to ~T0+61 s. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260128A/ The time-integrated spectrum of the burst (measured from from ~T0-101 s to ~T0+61 s) is best described in the 20 - 1500 keV range by a power law with exponential cutoff (CPL) model with alpha = -0.93 ± 0.99 and Ep = (103 ± 16) keV. The spectrum near the peak count rate (measured from ~T0-4 s to T0+14 s) is best described by a CPL model with alpha = -1.26 ± 0.30 and Ep = (178 ± 31) keV. The total burst fluence is (6.12 ± 2.89)x10^-6 erg/cm^2, and the 2.944 s peak energy flux, measured from T0+2.082 s, is (1.57 ± 0.44)x10^-7 erg/cm^2 (both in the 20 - 1500 keV energy range). 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/43592. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41694] GRB 260131A: Insight-HXMT/HE detection
by GCN Circulars 01 Feb '26

01 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43591 SUBJECT: GRB 260131A: Insight-HXMT/HE detection DATE: 26/02/01 15:06:33 GMT FROM: Xinghao Luo at IHEP <2952704891(a)qq.com> Xing-Hao Luo, Chen-Wei Wang, Chao Zheng, Hao-Xuan Guo, Xiao-Bo Li and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team: At 2026-01-31T06:39:31.400 (T0), Insight-HXMT/HE detected the long burst GRB 260131A, which is also detected by Fermi/GBM (Fermi GBM Team, GCN #43579) . The Insight-HXMT/HE light curve mainly consists of multiple pulses with a T90 of 7.0 +2.5/-1.0 s. The 1s peak rate, measured from T0+1.75 s, is 982 cnts/sec. Insight-HXMT/HE detected a total of 5366 counts form this burst. The HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb260131A.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/43591. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41693] Konus-Wind detection of GRB 260131A/B
by GCN Circulars 01 Feb '26

01 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43590 SUBJECT: Konus-Wind detection of GRB 260131A/B DATE: 26/02/01 14:06:26 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 260131A/B (Fermi-GBM detection: The Fermi GBM team, GCN 43579, Roberts, GCN 43585; MAXI/GSC detection: Sugai et al., GCN 43580) triggered Konus-Wind (KW) at T0=23972.646 s UT (06:39:32.646). The burst consists of two separated emission pulses, peaked around ~T0 and to T0+215 s, respectively. The total duration of the burst is ~250 s. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260131_T23972/ As observed by Konus-Wind, the burst had a fluence of (4.14 ± 0.91)x10^-5 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 0.384 s, of (4.33 ± 0.52)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+238 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 = -0.15 (-0.70,+1.61), the high energy photon index beta = -1.97 (-0.20,+0.14), the peak energy Ep = 124 (-40,+56) keV, chi2 = 83/97 dof. The spectrum near the peak count rate (measured from T0 to T0+8.448 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 = -1.17 (-0.15,+0.17), the high energy photon index beta = -1.98 (-0.18,+0.10), the peak energy Ep = 300 (-68,+131) keV, chi2 = 74/79 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/43590. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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