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[vsnet-grb-info 41682] GRB 260131A: Fermi GBM Final Real-time Localization
by GCN Circulars 31 Jan '26

31 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43579 SUBJECT: GRB 260131A: Fermi GBM Final Real-time Localization DATE: 26/01/31 06:50:08 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 06:39:30 UT on 31 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260131A (trigger 791534375.436908 / 260131277). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 21.9, Dec = 26.9 (J2000 degrees, equivalent to J2000 01h 27m, 26d 53'), with a statistical uncertainty of 1.8 degrees. The angle from the Fermi LAT boresight is 104.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260131277/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260131277/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260131277/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43579. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41681] EP260131a: COLIBRÍ optical observations of the counterpart
by GCN Circulars 31 Jan '26

31 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43578 SUBJECT: EP260131a: COLIBRÍ optical observations of the counterpart DATE: 26/01/31 05:53:41 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Fredd Sánchez Álvarez (UNAM), Alan M. Watson (UNAM), Benjamin Schneider (LAM), Noémie Globus (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), 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), and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the EP260131a (Ding et al., GCN Circ. 43574) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-01-31 04:40 to 05:32 UTC (from 1.14 to 2.02 hours after the trigger) and obtained 39 minutes of simultaneous exposure in the r and z filters. 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. In the stacked image, detect the candidate optical counterpart reported by Li et al. (GCN Circ. 43577) at preliminary magnitudes of: r = 21.05 +/- 0.08, z = 20.69 +/- 0.09. Observations are ongoing. 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/43578. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41680] EP260131a: Las Cumbres detection of an optical counterpart
by GCN Circulars 31 Jan '26

31 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43577 SUBJECT: EP260131a: Las Cumbres detection of an optical counterpart DATE: 26/01/31 05:12:32 GMT FROM: Wenxiong Li at NAOC <liwenxiong1992(a)gmail.com> Wenxiong Li, Runduo Liang (NAOC), Iair Arcavi (TAU), Ido Keinan (TAU), David Sand (U of Arizona) We observed the position of EP260131a with a Las Cumbres 1m telescope at Cerro Tololo Inter-American Observatory, Chile, ~1 hour after the Einstein Probe WXT trigger. We took 2x300s exposures in the broad optical w band. We find a uncataloged source at RA=149.9025, Dec=-3.3073 within the EP-FXT error circle and measure the following preliminary photometry calibrated to the r band: MJD 61071.183 Mag 20.9 Additional followup is encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/43577. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41679] GRB 260127B: AstroSat CZTI detection
by GCN Circulars 31 Jan '26

31 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43576 SUBJECT: GRB 260127B: AstroSat CZTI detection DATE: 26/01/31 05:11:40 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> A. Arya (IITB), A. Goyal (IITB), M. Tembhurnikar (IUCAA), S. Salunke (IUCAA), Harsha K. H. (IUCAA), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a short GRB 260127B which was also detected by Fermi GBM (Fermi GBM Team, GCN Circ. 43533), Swift BAT (Evans et al., GCN Circ. 43542), and Konus IPN (Ridnaia et al., GCN Circ. 43559). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2026-01-27 20:02:32.605 UTC. The measured peak count rate associated with the burst is 2558 (+901, -550) counts/s above the background in the combined data of all quadrants, with a total of 233 (+42, -31) counts. The local mean background count rate was 261 (+9, -32) counts/s. Using cumulative rates, we measure a T90 of 0.17 (+0.11, -0.03) s. The source was also detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2026-01-27 20:02:32.292 UTC. The measured peak count rate associated with the burst is 602 (+68, -74) counts/s above the background in the combined data of all quadrants, with a total of 604 (+160, -170) counts. The local mean background count rate was 1239 (+7, -8) counts/s. Due to the intrinsic 1 s binning of veto data, we cannot reliably estimate a T90 for our detection. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/43576. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41678] GRB 260130A: Fermi GBM Detection
by GCN Circulars 31 Jan '26

31 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43575 SUBJECT: GRB 260130A: Fermi GBM Detection DATE: 26/01/31 05:10:32 GMT FROM: Peter Veres at University of Alabama in Huntsville <veresp(a)gmail.com> A. Jameson (UAH), C. Meegan (UAH), and M. Dafčíková (MUNI) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 13:29:20.82 UT on 30 January 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260130A (trigger 791472565/260130562). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 48.70, Dec = 64.17 (J2000 degrees, equivalent to J2000 3h 14m, +64d 10'), with a statistical uncertainty of 1.60 degrees. (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a mixture of two Gaussians, one with a radius of 1.8 degrees (52% contribution) and one with a radius of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]). The angle from the Fermi LAT boresight is 16 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 0.5 s (50-300 keV). The time-averaged spectrum from T0-0.07 to T0+0.20 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.41 +/- 0.02 and the cutoff energy, parameterized as Epeak, is 730 +/- 30 keV. The event fluence (10-1000 keV) in this time interval is (8.8 +/- 0.4)E-07 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.0 s in the 10-1000 keV band is 27 +/- 1 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 570 +/- 20 keV, alpha = -0.33 +/- 0.02 and beta = -2 +/- 0.1. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/43575. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41677] EP260131a: Einstein Probe detection of an X-ray transient
by GCN Circulars 31 Jan '26

31 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43574 SUBJECT: EP260131a: Einstein Probe detection of an X-ray transient DATE: 26/01/31 04:36:37 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. C. Ding, T. Wu (AHNU), Q. Y. Wu, H. Sun (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260131a. The transient triggered EP-WXT (ID: 01709254172) at 2026-01-31T03:31:25 (UTC). The WXT position of the source is R.A. = 149.921 deg, DEC = -3.291 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 149.9027 deg, DEC = -3.3094 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). Further information will be updated when the telemetry data is received. 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). View this GCN Circular online at https://gcn.nasa.gov/circulars/43574. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41676] GRB 260127B: Fermi GBM Detection
by GCN Circulars 30 Jan '26

30 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43573 SUBJECT: GRB 260127B: Fermi GBM Detection DATE: 26/01/30 21:27:55 GMT FROM: atrigg2(a)lsu.edu A. C. Trigg (NPP ORAU, NASA MSFC) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 20:02:32.57 UT on 27 January 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260127B (trigger 791236957/260127835). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 190.42, Dec = 56.88 (J2000 degrees, equivalent to J2000 12h 41m, +56d 52'), with a statistical uncertainty of 5.21 degrees. (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a mixture of two Gaussians, one with a radius of 1.8 degrees (52% contribution) and one with a radius of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]). The angle from the Fermi LAT boresight is 109 degrees. The GBM light curve displays a single short peak with a duration (T90) of about 1 s (50-300 keV). The time-averaged spectrum from T0-0.1 to T0+0.3 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.11 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 710 +/- 30 keV. The event fluence (10-1000 keV) in this time interval is (1.29 +/- 0.09)E-06 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.064 s in the 10-1000 keV band is 22 +/- 2 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 570 +/- 20 keV, alpha = -0.040 +/- 0.002 and beta = -2 +/- 0.1. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/43573. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41675] EP260128a / GRB 260128A: COLIBRÍ optical upper limit
by GCN Circulars 30 Jan '26

30 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43572 SUBJECT: EP260128a / GRB 260128A: COLIBRÍ optical upper limit DATE: 26/01/30 15:46:49 GMT FROM: Jean-Luc Atteia at IRAP <jean-luc.atteia(a)irap.omp.eu> Jean-Luc Atteia (IRAP), Enrique Moreno Méndez (UNAM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), 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), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the X-ray transient EP260128a / GRB 260128a (Zhou et al., GCN Circ. 43549, Ravasio et al., GCN Circ. 43556) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-01-30 04:48 to 10:12 UTC (from 29.14 to 35.53 hours after the trigger) and obtained 238 minutes of simultaneous exposure in the i and z filters. 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. In the stacked images, we do not detect any new source at the Liverpool Telescope proposed candidate position (Eyles-Ferris et al., GCN Circ. 43553) nor at the NOT proposed candidate position (He et al., GCN Circ. 43555), down to the following 3-sigma limits: i > 23.6 z > 23.1 These upper limits are consistent with the one reported by Malesani et al. (GCN Circ. 43570). 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/43572. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41674] Fermi GRB 260130A: Global MASTER-Net observations report
by GCN Circulars 30 Jan '26

30 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43571 SUBJECT: Fermi GRB 260130A: Global MASTER-Net observations report DATE: 26/01/30 15:30:22 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 260130A ( Fermi GBM team, GCN 43569) errorbox 6593 sec after notice time and 6628 sec after trigger time at 2026-01-30 15:19:49 UT, with upper limit up to 15.6 mag. Observations started at twilight. The observations began at zenith distance = 23 deg. The sun altitude is -11.2 deg. The galactic latitude b = 6 deg., longitude l = 138 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3118825 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 6659 | 2026-01-30 15:19:49 | MASTER-Kislovodsk | (03h 14m 10.80s , +65d 46m 26.8s) | C | 60 | 15.4 | 6760 | 2026-01-30 15:21:30 | MASTER-Kislovodsk | (03h 33m 51.07s , +65d 44m 38.9s) | C | 60 | 15.3 | 6860 | 2026-01-30 15:23:10 | MASTER-Kislovodsk | (03h 28m 09.77s , +63d 51m 38.5s) | C | 60 | 15.6 | 6964 | 2026-01-30 15:24:54 | MASTER-Kislovodsk | (03h 46m 28.40s , +63d 52m 21.7s) | C | 60 | 15.4 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43571. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41673] EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
by GCN Circulars 30 Jan '26

30 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43570 SUBJECT: EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits DATE: 26/01/30 14:23:44 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), J. An (NAOC), G. Corcoran (UCD), P. D’Avanzo (INAF/OAB), M. De Pasquale (U. Messina), L.B. He (NAOC), A. Martin-Carrillo (UCD), A. Melandri (INAF/OAR), D. Xu (NAOC), W. Boschin (TNG), V. Lorenzi (TNG), H. Lucio Medeiros (TNG), T. Pursimo (NOT), report on behalf of a larger collaboration: We observed the optical counterpart (He et al., GCN 43555) of the high-energy transient EP260128a / GRB 260128A (Zhou et al., GCN 43549; Ravasio et al., GCN 43556) in both the optical and infrared. Optical observations were carried out at the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera, for a total of 14x200 s in the SDSS z filter. NIR observations were carried out at the Telescopio Nazionale Galileo (TNG) equipped with the NICS camera, for a total of 40x60 s in the J filter. The afterglow (He et al., GCN 43555) is not detected in any of our stacked images. We report 3-sigma limiting magnitudes: z > 23.2, mean epoch 2026 Jan 29.961 UT (23.39 hr after the EP trigger); J > 22.0, mean epoch 2026 Jan 29.939 UT (22.88 hr after the EP trigger). The above magnitudes are in the AB system, are calibrated against nearby objects from the Pan-STARRS (z) and VHS (J) catalogs, and are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43570. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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