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[vsnet-grb-info 41742] GRB 260208B: Fermi GBM Final Real-time Localization
by GCN Circulars 08 Feb '26

08 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43638 SUBJECT: GRB 260208B: Fermi GBM Final Real-time Localization DATE: 26/02/08 10:03:19 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 09:52:44 UT on 8 Feb 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260208B (trigger 792237169.910408 / 260208412). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 99.9, Dec = -13.1 (J2000 degrees, equivalent to J2000 06h 39m, -13d 05'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 16.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260208412/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260208412/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260208412/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43638. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41741] Fermi GRB 260208A: Global MASTER-Net observations report
by GCN Circulars 08 Feb '26

08 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43637 SUBJECT: Fermi GRB 260208A: Global MASTER-Net observations report DATE: 26/02/08 06:45:32 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-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 260208A ( Fermi GBM team, GCN 43635) errorbox 829 sec after notice time and 866 sec after trigger time at 2026-02-08 05:21:55 UT, with upper limit up to 17.9 mag. The observations began at zenith distance = 82 deg. The sun altitude is -43.2 deg. The galactic latitude b = 78 deg., longitude l = 64 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3125988 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 952 | 2026-02-08 05:21:55 | MASTER-OAFA | (13h 38m 21.97s , +33d 02m 05.7s) | C | 170 | 15.2 | 1073 | 2026-02-08 05:24:51 | MASTER-OAFA | (13h 38m 22.08s , +33d 02m 10.6s) | C | 60 | 15.9 | 1133 | 2026-02-08 05:24:51 | MASTER-OAFA | (13h 38m 22.14s , +33d 02m 11.3s) | C | 180 | 16.9 | Coadd 1139 | 2026-02-08 05:25:57 | MASTER-OAFA | (13h 38m 22.25s , +33d 02m 15.0s) | C | 60 | 16.1 | 1205 | 2026-02-08 05:27:02 | MASTER-OAFA | (13h 38m 22.38s , +33d 02m 19.9s) | C | 60 | 16.5 | 1271 | 2026-02-08 05:28:08 | MASTER-OAFA | (13h 38m 22.48s , +33d 02m 24.1s) | C | 60 | 16.6 | 1331 | 2026-02-08 05:28:08 | MASTER-OAFA | (13h 38m 22.48s , +33d 02m 24.0s) | C | 180 | 17.2 | Coadd 1336 | 2026-02-08 05:29:14 | MASTER-OAFA | (13h 38m 22.62s , +33d 02m 28.3s) | C | 60 | 16.7 | 1401 | 2026-02-08 05:30:19 | MASTER-OAFA | (13h 38m 22.73s , +33d 02m 32.6s) | C | 60 | 16.8 | 1467 | 2026-02-08 05:31:25 | MASTER-OAFA | (13h 38m 22.83s , +33d 02m 36.7s) | C | 60 | 17.0 | 1527 | 2026-02-08 05:31:25 | MASTER-OAFA | (13h 38m 22.83s , +33d 02m 36.7s) | C | 180 | 17.7 | Coadd 1532 | 2026-02-08 05:32:30 | MASTER-OAFA | (13h 38m 22.91s , +33d 02m 40.5s) | C | 60 | 17.1 | 1598 | 2026-02-08 05:33:36 | MASTER-OAFA | (13h 38m 22.99s , +33d 02m 44.5s) | C | 60 | 17.2 | 1664 | 2026-02-08 05:34:42 | MASTER-OAFA | (13h 38m 23.00s , +33d 02m 48.1s) | C | 60 | 17.2 | 1724 | 2026-02-08 05:34:42 | MASTER-OAFA | (13h 38m 23.01s , +33d 02m 48.1s) | C | 180 | 17.9 | Coadd 1730 | 2026-02-08 05:35:48 | MASTER-OAFA | (13h 38m 23.04s , +33d 02m 51.5s) | C | 60 | 17.2 | 1796 | 2026-02-08 05:36:53 | MASTER-OAFA | (13h 38m 23.05s , +33d 02m 54.5s) | C | 60 | 17.3 | 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/43637. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41740] Fermi Gamma-ray Burst Monitor trigger 792220053/260208214 is not a GRB
by GCN Circulars 08 Feb '26

08 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43636 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 792220053/260208214 is not a GRB DATE: 26/02/08 06:13:21 GMT FROM: oindabimukherjee(a)gmail.com O. Mukherjee (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 792220053/260208214 at 05:07:28.24 UT on 08 February 2026, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to distant particles." View this GCN Circular online at https://gcn.nasa.gov/circulars/43636. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41739] GRB 260208A: Fermi GBM Final Real-time Localization
by GCN Circulars 08 Feb '26

08 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43635 SUBJECT: GRB 260208A: Fermi GBM Final Real-time Localization DATE: 26/02/08 05:18:10 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 05:07:28 UT on 8 Feb 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260208A (trigger 792220053.24286 / 260208214). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 204.4, Dec = 33.0 (J2000 degrees, equivalent to J2000 13h 37m, 33d 00'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 79.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260208214/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260208214/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260208214/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43635. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41738] GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
by GCN Circulars 08 Feb '26

08 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43634 SUBJECT: GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission DATE: 26/02/08 04:24:37 GMT FROM: Rushikesh Sonawane at IISER, TVM <rushikesh23(a)iisertvm.ac.in> R. Sonawane (IISER, TVM) and S. Bala (USRA) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 13:12:10.83 UT on 07 February 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260207B (trigger 792162735/260207550). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 292.87, Dec = 50.03 (J2000 degrees, equivalent to J2000 19h 31m, +50d 1'), with a statistical uncertainty of 2.81 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 45 degrees. The GBM light curve consists of a short spike (Main Emission, ME) followed by an extended emission (EE) with a total duration (T90) of about 56 s (50-300 keV). The ME from T0-1 to T0+5 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.18 +/- 0.07 and the cutoff energy, parameterized as Epeak, is 350 +/- 65 keV. The total fluence (10-1000 keV) in this time interval is (2.7 +/- 0.1)E-06 erg/cm^2. The EE from T0+10 to T0+89 s, is best fit by a Band function with Epeak= 32 +/- 4 keV, alpha = -1.7 +/- 0.1 and beta = -2.4 +/- 0.1. The total fluence (10-1000 keV) during this time interval is (7.5 +/- 0.4)E-06 erg/cm^2. The time-averaged (ME+EE) spectrum from T0-2 to T0+89 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.83 +/- 0.05 and the cutoff energy, parameterized as Epeak, is 67 +/- 9 keV. A Band function fits this interval equally well with Epeak= 52 +/- 10 keV, alpha = -1.7 +/- 0.1 and beta = -2.2 +/- 0.1. The event fluence (10-1000 keV) in this time interval is (9.6 +/- 0.5)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.0024 s in the 10-1000 keV band is 16.6 +/- 0.3 ph/s/cm^2. 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/43634. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41737] GRB 260207A : MASTER optical counterpart discovery
by GCN Circulars 07 Feb '26

07 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43633 SUBJECT: GRB 260207A : MASTER optical counterpart discovery DATE: 26/02/07 19:42:05 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> C. Francile (OAFA), O.Gress (ISU), V.M.Lipunov (Lomonosov MSU), R.Podesta, F.Podesta (OAFA), D.Svinkin, A.Ridnaya (Ioffe Institute), I.Panchenko, P.Balanutsa, G.Antipov, A.Kuznetsov, E.Gorbovskoy, N. Tiurina, Ya.Kechin,A.Chasovnikov, V.A.Senik, D.Vlasenko, I.Ionov,Yu.Tselik(Lomonosov MSU), N.Budnev, R.Mirgazov, A.Diachok, O.Ershova (Irkutsk State University), E. Gonzalez (OAFA, San JuanUni.,Argentina); D.Buckley (SAAO), A. Sosnovskij (CrAO RAS), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino, J.Martinez, A.R.Corella, J.G. Tanori, L. F. Villalobos, L.H.Rodriguez (INAOE, Guillermo Haro AstrophysicObservatory, Mexico) V.M.Pillet, R.Rebolo Lopez (The Instituto de Astrofisica de Canarias,Spain) MASTER Global Robotic Net started (Lipunov et al. GCN 43627) Fermi GRB 260207A (GCN 43628) alert observtions at MASTER-OAFA 110 sec after notice time and 142 sec after trigger time at 2026-02-07 05:44:56 UT MASTER OT J104411.31-330936.2 discovery V.Lipunov (Lomonosov MSU), E.Gorbovskoy, N.Tiurina, P.Balanutsa, A.Kuznetsov, V.Kornilov, O.Gress, K.Ivanov, V.Vladimirov, D.Kuvshinov (Lomonosov Moscow State University, SAI) MASTER-OAFA auto-detection system ( Lipunov et al., "MASTER Global Robotic Net", Advances in Astronomy, 2010, 30L ) discovered OT source at (RA, Dec) = 10h 44m 11.31s -33d 09m 36.2s on 2026-02-07.24049 UT. The OT unfiltered magnitude was 17.3m(mlim19.8=). The OT is seen in 27 images with typical decay with different features at light curves. There is no minor planet at this place. We have reference image on 2025-02-08.36365 UT with unfiltered 20.1m. Deep photometry and spectral observations are required. We reobserved this coordinates at MASTER-SAAO at 2026-02-07 18:59:00 without object, that confirmed GRBoptical counterpart nature View this GCN Circular online at https://gcn.nasa.gov/circulars/43633. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41736] GRB 260131A/B: Mondy and Terskol optical observations
by GCN Circulars 07 Feb '26

07 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43632 SUBJECT: GRB 260131A/B: Mondy and Terskol optical observations DATE: 26/02/07 15:36:31 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. Volnova (IKI), E. Klunko (ISTP), I. Sokolov (INASAN, KIAM), N. Pankov (IKI), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN: 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; Jiang et al., GCN 43600; Li et al., GCN 43605) with the AZT-33IK 1.5m telescope of the Mondy observatory on Feb. 4 and 5, and with the 2-meter Zeiss-2000 telescope of the Terskol observatory on Feb. 4 taking several frames in the R band. The optical counterpart reported by Gompertz et al., GCN 43586; Lee et al., GCN 43587; Saccardi et al., GCN 43595; García García et al., GCN 43599, Shi et al., GCN 43601; Sanchez-Ramirez et al., GCN 43604; Jayaraman et al., GCN 43606; Zhu et al., GCN 43607; Zheng et al., GCN 43609; Adami et al., GCN 43610, is detected in the stacked frame of every epoch. Preliminary photometry and observation data are the following: Date UT start t-T0 Exp. Filter Obj. Err. UL Site/Telescope (mid,days) (n*s) (3sigma) 2026-02-04 12:10:33 4.26118 43*120 R 19.56 0.04 22.3 Mondy/AZT-33IK 2026-02-04 15:54:04 4.41278 30*150 R 19.87 0.07 22.2 Zeiss-2000/Terskol 2026-02-05 13:40:24 5.32702 49*120 R 19.83 0.04 22.5 Mondy/AZT-33IK The photometry is based on several nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43632. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41735] Fermi GRB 260207B: Global MASTER-Net observations report
by GCN Circulars 07 Feb '26

07 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43631 SUBJECT: Fermi GRB 260207B: Global MASTER-Net observations report DATE: 26/02/07 15:30:40 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 260207B ( Fermi GBM team, GCN 43629) errorbox 7553 sec after notice time and 7584 sec after trigger time at 2026-02-07 15:18:35 UT, with upper limit up to 13.0 mag. Observations started at twilight. The observations began at zenith distance = 74 deg. The sun altitude is -9.3 deg. The galactic latitude b = 14 deg., longitude l = 82 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3125301 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 7614 | 2026-02-07 15:18:35 | MASTER-Kislovodsk | (19h 15m 56.41s , +48d 54m 29.6s) | C | 60 | 13.0 | 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/43631. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41734] GRB 260206A: Swift-XRT observations
by GCN Circulars 07 Feb '26

07 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43630 SUBJECT: GRB 260206A: Swift-XRT observations DATE: 26/02/07 14:08:50 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> S. Lanava (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), J.A. Kennea (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the MAXI-detected burst GRB 260206A (Negoro et al. GCN Circ. 43624) in a series of observations tiled on the sky. The total exposure time is 1.6 ks, distributed over 5 tiles; the maximum exposure at a single sky location in the tiling was 787 s. The data were collected between T0+32.1 ks and T0+38.5 ks, and are entirely in Photon Counting (PC) mode. One uncatalogued X-ray source has been detected, with a rank of "reasonable" (i.e. a ~2 sigma detection); however, it is neither above historical upper limits nor shows evidence of fading. Therefore, at the present time we cannot say whether or not it is the afterglow. The source details are: Source 3: RA (J2000.0): 78.4839 = 05h 13m 56.13s Dec (J2000.0): -40.5311 = -40d 31' 51.8" Error: 6.7 arcsec (radius, 90% conf.) Count-rate: 0.0117 [+0.0077, -0.0055] ct s^-1 Distance: 523 arcsec from MAXI position. Two catalogued sources were also detected, including the LMXB 4U 0513-40 noted by Negoro et al. (GCN Circ. 43624); as well two 'poor' sources (~1 sigma detections). The results of the XRT-team automatic analysis of the tiled XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/xrt_products/TILED_GRB00142. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43630. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41733] GRB 260207B: Fermi GBM Final Real-time Localization
by GCN Circulars 07 Feb '26

07 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43629 SUBJECT: GRB 260207B: Fermi GBM Final Real-time Localization DATE: 26/02/07 13:22:56 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 13:12:10 UT on 7 Feb 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260207B (trigger 792162735.829288 / 260207550). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 292.9, Dec = 50.0 (J2000 degrees, equivalent to J2000 19h 31m, 50d 00'), with a statistical uncertainty of 2.8 degrees. The angle from the Fermi LAT boresight is 45.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260207550/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260207550/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260207550/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43629. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41732] GRB 260207A: Fermi GBM Final Localization
by GCN Circulars 07 Feb '26

07 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43628 SUBJECT: GRB 260207A: Fermi GBM Final Localization DATE: 26/02/07 06:32:02 GMT FROM: Rushikesh Sonawane at IISER, TVM <rushikesh23(a)iisertvm.ac.in> The Fermi GBM team reports the detection of a likely LONG GRB "At 05:42:33.65 UT on 07 February 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260207A (trigger 792135758/260207238). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 160.45, Dec = -34.44 (J2000 degrees, equivalent to J2000 10h 41m, -34d 26'), with a statistical uncertainty of 3.29 degrees. The angle from the Fermi LAT boresight is 37 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260207238/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260207238/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260207238/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/43628. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41731] Fermi trigger No 792135758: Global MASTER-Net observations report
by GCN Circulars 07 Feb '26

07 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43627 SUBJECT: Fermi trigger No 792135758: Global MASTER-Net observations report DATE: 26/02/07 06:16:25 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-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB260207.24 (trigger No 792135758,10h 41m 48.00s , -34d 26m 24.0s, R=3.29) errorbox 110 sec after notice time and 142 sec after trigger time at 2026-02-07 05:44:56 UT, with upper limit up to 20.7 mag. The observations began at zenith distance = 7 deg. The sun altitude is -41.7 deg. The galactic latitude b = 21 deg., longitude l = 275 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3124959 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 158 | 2026-02-07 05:44:56 | MASTER-OAFA | (10h 51m 33.24s , -33d 38m 46.3s) | C | 30 | 19.5 | 203 | 2026-02-07 05:44:56 | MASTER-OAFA | (10h 51m 33.24s , -33d 38m 46.4s) | C | 120 | 20.0 | Coadd 198 | 2026-02-07 05:45:32 | MASTER-OAFA | (10h 51m 33.30s , -33d 38m 44.9s) | C | 40 | 19.6 | 250 | 2026-02-07 05:46:18 | MASTER-OAFA | (10h 51m 33.38s , -33d 38m 43.0s) | C | 50 | 19.7 | 311 | 2026-02-07 05:47:14 | MASTER-OAFA | (10h 51m 33.48s , -33d 38m 40.8s) | C | 60 | 19.8 | 382 | 2026-02-07 05:48:20 | MASTER-OAFA | (10h 51m 33.59s , -33d 38m 38.3s) | C | 70 | 19.8 | 644 | 2026-02-07 05:52:17 | MASTER-OAFA | (10h 42m 03.76s , -34d 05m 23.7s) | C | 120 | 19.9 | 799 | 2026-02-07 05:52:17 | MASTER-OAFA | (10h 42m 03.76s , -34d 05m 23.7s) | C | 430 | 20.7 | Coadd 781 | 2026-02-07 05:54:24 | MASTER-OAFA | (10h 42m 04.00s , -34d 05m 19.4s) | C | 140 | 19.9 | 942 | 2026-02-07 05:56:50 | MASTER-OAFA | (10h 42m 04.28s , -34d 05m 14.5s) | C | 170 | 19.9 | 1064 | 2026-02-07 05:59:47 | MASTER-OAFA | (10h 42m 04.50s , -34d 05m 10.9s) | C | 60 | 19.7 | 1129 | 2026-02-07 06:00:52 | MASTER-OAFA | (10h 42m 04.62s , -34d 05m 08.8s) | C | 60 | 19.7 | 1194 | 2026-02-07 06:01:58 | MASTER-OAFA | (10h 42m 04.73s , -34d 05m 07.0s) | C | 60 | 19.7 | 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/43627. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41730] EP260131a: VLA detection
by GCN Circulars 06 Feb '26

06 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43626 SUBJECT: EP260131a: VLA detection DATE: 26/02/06 20:32:30 GMT FROM: Genevieve Schroeder at Cornell University <genevieveschroeder(a)u.northwestern.edu> Genevieve Schroeder (Cornell), Anna Ho (Cornell), Daniel Perley (LJMU) report: We observed the position of EP260131a (Ding et al., GCN 43574, Wu et al. GCN 43583), with the Karl G. Jansky Very Large Array (VLA) under program 26A-488 (PI: Ho) beginning on 2026 February 3 at 06:37 UT (3.15 days post discovery) at a mean frequency of 10 GHz. Based on preliminary analysis, we detect a ~40 uJy (~6 sigma) radio source at the position of EP260131a. At the assumed redshift of EP260131a of z = 0.937 (Schneider et al., GCN 43582), the VLA observation corresponds to a 10 GHz luminosity of ~1e30 erg/s/Hz. This is consistent with, but on the lower end of, a typical GRB radio afterglow (Chandra & Frail 2012, ApJ, 746, 156). Additional followup is planned. We thank the VLA staff for quickly approving and executing these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/43626. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41729] GRB 260206A: Tiled Swift observations
by GCN Circulars 06 Feb '26

06 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43625 SUBJECT: GRB 260206A: Tiled Swift observations DATE: 26/02/06 17:39:59 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a series of observations, tiled on the sky, of the MAXI GRB 260206A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/xrt_products/TILED_GRB00142 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. The probability of finding serendipitous sources, unrelated to the MAXI event is high: any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43625. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41728] GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
by GCN Circulars 06 Feb '26

06 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43624 SUBJECT: GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection DATE: 26/02/06 11:14:51 GMT FROM: Hitoshi Negoro at Nihon University/MAXI team <negoro.hitoshi(a)nihon-u.ac.jp> H. Negoro, M. Nakajima, K. Saito (Nihon U.), T. Usuki (Ehime U.), K. Takagi, H. Nishio (Nihon U.), T. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, Y. Kawakubo, H. Hiramatsu, Y. Kondo, D. Iijima, A. Yoshida (AGU), Y. Tsuboi, H. Sugai, N. Nagashima, Y. Ishihara (Chuo U.), M. Shidatsu, C. Kang, T. Nakamoto, M. Uenishi, S. Yatsuzuka (Ehime U.),I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara, S. Kobayashi (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), W. Iwakiri (Chiba U.), T. Kawamuro (Osaka U.), and S. Yamada (Tohoku U), The MAXI/GSC nova alert system triggered on a bright uncatalogued hard X-ray transient source at 08:47:33 UT on February 6, 2026. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (78.322 deg, -40.534 deg) = (05 13 17, -40 32 02) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.33 deg and 0.23 deg, respectively. The roll angle of the long axis from the north direction is 38.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (77.845, -39.759) deg = (05 11 22, -39 45 32) (J2000) (77.278, -40.246) deg = (05 09 06, -40 14 45) (J2000) (79.005, -41.397) deg = (05 16 01, -41 23 49) (J2000) (79.569, -40.903) deg = (05 18 16, -40 54 10) (J2000) The X-ray flux averaged over the scan was 244 +- 33 mCrab (4.0-10.0keV, 1 sigma error). There was no significant excess flux in the previous transit at 07:36 UT and in the next transit at 10:22 UT with an upper limit of 20 mCrab for each. We note that the X-ray burster 4U 0513-40 is close to the above position, but out of the error box. If the systematic error is large this time, the burst may come from 4U 0513-40. View this GCN Circular online at https://gcn.nasa.gov/circulars/43624. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41727] GRB 260204A: SVOM/VT confirms fading of the optical afterglow
by GCN Circulars 06 Feb '26

06 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43623 SUBJECT: GRB 260204A: SVOM/VT confirms fading of the optical afterglow DATE: 26/02/06 04:13:44 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, Y. N. Ma, C. Wu, Z. H. Yao, Y. L. Qiu, L.P. Xin, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA/Irfu), R. Z. Li (YNAO), C. W. Wang (IHEP) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observation to the GRB 260204A triggered by SVOM/ECLAIRs (sb26020403, Pillas et al., GCN 43613), which was also detected by Fermi (Fermi GBM team, GCN 43618) and followed by Swift (Evan et al., GCN 43622), LCO (Turpin et al., GCN 43616; Malesani et al. GCN 43621), GOTO (Kumar et al, GCN 43617) and MASTER (Lipunov et al., GCN 43619). The observation started at 2026-02-05T07:04:40 UTC, i.e., 16.27 hour post trigger in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. By stacking images of 47*50 sec in VT_R and 44*50 sec in VT_B, the counterpart (Li et al., GCN 43620; Malesani et al. GCN 43621) was confirmed to be fading with the brightness of VT_R~23.1+/-0.3 mag and VT_B>23.3 mag at the mid time of 18.0 hours post trigger. Combined with the earlier detection (Li et al., GCN 43620), the optical decay slope was -0.90. Our photometry was in AB magnitude and not corrected for Galactic extinction. 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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/43623. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41726] GRB 260204A: Swift-XRT observations
by GCN Circulars 05 Feb '26

05 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43622 SUBJECT: GRB 260204A: Swift-XRT observations DATE: 26/02/05 13:29:09 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P.A. Evans (U. Leicester), J.A. Kennea (PSU), E. Ambrosi (INAF-IASFPA) , A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), D.N. Burrows (PSU), S. Campana (INAF-OAB), M. Capalbi (INAF-OAR), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), M. Ferro (INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the SVOM/ECLAIRs-detected GRB 260204A, collecting 1.7 ks of Photon Counting (PC) mode data between T0+23 ks and T0+25 ks after the trigger. We have detected 4 sources. These have been automatically classified as follows: * 0 likely counterparts * 0 candidate counterparts * 3 uncatalogued X-ray sources * 1 known X-ray source As already reported source 1 is consistent with an optical source (Li et al., GCN Circ. 43620; Malesani et al., GCN Circ. 43621). We note that, in the X-rays, this source is not well separated from source 3 and cannot rule out that these arise not from point sources but from a patch of diffuse emission. We note also the presence of a source in the XMM Slew survey XMMSL3 catalogue, XMMSL3 J134023.8+015613 at RA,Dec = 205.0888, +1.9370 degrees (J2000), with a 1-sigma error of 4.3" (statistical) and an estimated systematic error of ~8" (see http://xmmssc.irap.omp.eu/Catalogue/XMMSL3/XMMSL3_Catalogue_User_Guide.html… ry). This source is 33" from the position of source 1. Source 2 is consistent with the position of HD 118981, a high proper motion star, while source 4 is a known quasar. Further observations are planned. Uncatalogued X-ray sources -------------------------- Source 1 (SWIFT J134025.4+015552): ================================== RA (J2000.0): 205.1060 = 13 40 25.44 Dec (J2000.0): +1.9313 = +01 55 52.7 Error: 5.0 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 5.4 arcmin from the SVOM/ECLAIRs position. Mean rate: 0.0235 +/- 0.0046 ct s^-1 Mean flux: (8.7 +/- 1.7)e-13 erg cm^-2 s^-1 Peak rate: 0.0235 +/- 0.0046 ct s^-1 Peak flux: (8.7 +/- 1.7)e-13 erg cm^-2 s^-1 ECF: 3.71e-11 erg cm^-2 ct^-1 assuming NH=1.90e+20 cm^-2, gamma=1.76 determined from a spectral fit. RASS UL: 4.1e-02 ct s^-1 (converted to XRT; 0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. Source 2 (SWIFT J134026.9+020905): ================================== RA (J2000.0): 205.1125 = 13 40 27.00 Dec (J2000.0): +2.1515 = +02 09 05.4 Error: 5.0 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 7.9 arcmin from the SVOM/ECLAIRs position. Mean rate: 0.0136 +/- 0.0036 ct s^-1 Mean flux: (2.28 +/- 0.61)e-13 erg cm^-2 s^-1 Peak rate: 0.0136 +/- 0.0036 ct s^-1 Peak flux: (2.28 +/- 0.61)e-13 erg cm^-2 s^-1 ECF: 1.67e-11 erg cm^-2 ct^-1 assuming NH=1.30e+22 cm^-2, gamma=9.94 determined from a spectral fit. RASS UL: 3.3e-02 ct s^-1 (converted to XRT; 0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. A SIMBAD object `HD 118981' is 0.7" away. There is 1 2MASS object within the source's 3-sigma error radius. Source 4 (SWIFT J134043.1+020310): ================================== RA (J2000.0): 205.1796 = 13 40 43.10 Dec (J2000.0): +2.0530 = +02 03 10.8 Error: 6.6 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 4.2 arcmin from the SVOM/ECLAIRs position. Mean rate: (7.2 [+2.9, -2.3])e-3 ct s^-1 Mean flux: (1.49 [+0.60, -0.48])e-13 erg cm^-2 s^-1 Peak rate: (7.2 [+2.9, -2.3])e-3 ct s^-1 Peak flux: (1.49 [+0.60, -0.48])e-13 erg cm^-2 s^-1 ECF: 2.07e-11 erg cm^-2 ct^-1 assuming NH=6.90e+21 cm^-2, gamma=9.20 determined from a spectral fit. RASS UL: 2.1e-02 ct s^-1 (converted to XRT; 0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. A SIMBAD object `[VV2006] J134042.9+020307' is 4.5" away. Known X-ray sources ------------------- Source 3 (SWIFT J134023.6+015612): ================================== RA (J2000.0): 205.0984 = 13 40 23.62 Dec (J2000.0): +1.9369 = +01 56 12.8 Error: 6.1 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 5.1 arcmin from the SVOM/ECLAIRs position. Mean rate: 0.0225 +/- 0.0058 ct s^-1 Mean flux: (2.54 +/- 0.65)e-12 erg cm^-2 s^-1 Peak rate: 0.0225 +/- 0.0058 ct s^-1 Peak flux: (2.54 +/- 0.65)e-12 erg cm^-2 s^-1 ECF: 1.13e-10 erg cm^-2 ct^-1 assuming NH=1.89e+20 cm^-2, gamma=1.04 determined from a spectral fit. This matches a catalogued X-ray source XMMSL3 J134023.8+015613 in the XMM-NEWTON/XMMSLEWCLN catalogue. Details: Separation: 1.6" from the XRT source Cat Rate: 4.8e-01 +/- 2.6e-01 ct s^-1 Cat Flux: 7.7e-12 +/- 4.1e-12 erg cm^-2 s^-1 (0.3-10 keV) so the source is not above the catalogued flux. There is no evidence for fading. There is 1 2MASS object within the source's 3-sigma error radius. All fluxes are 0.3-10 keV, observed. 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-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/SVOM/SVOM_FIELD00057. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43622. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41725] GRB 260204A: LCO optical afterglow detection
by GCN Circulars 05 Feb '26

05 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43621 SUBJECT: GRB 260204A: LCO optical afterglow detection DATE: 26/02/05 10:45:38 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> D. B. Malesani (DAWN/NBI and Radboud), D. Turpin (CEA/Irfu), A. Saccardi (CEA/Irfu), B. Cordier (CEA/Irfu), M. Pillas, M. Dennefeld (IAP), report on behalf of the SVOM mission team: Following the report of an optical counterpart (Li et al., GCN 43620; see also the X-ray detection at https://www.swift.ac.uk/SVOM/SVOM_FIELD00057/) of the SVOM GRB 260204A (Pillas et al. GCN 43613), we inspected again our images taken with the LCO telescope at the Siding Spring Observatory (Turpin et al., GCN 43616). The optical counterpart is detected in our images, and we measure the following magnitudes: r = 20.26 +- 0.21 AB (mid-time 25.7 min after the trigger); z = 19.49 +- 0.25 AB (mid-time 38.4 min after the trigger). We note that these measurements are close to the sensitivity limit of our images, and consistent with the 5-sigma upper limits reported in our previous circular (Turpin et al., GCN 43616). The above measurements are not corrected for Galactic extinction. Compared to the SVOM/VT measurement (taken at a mean epoch ~74 min after the GRB), our data indicate only marginal decay between the two observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/43621. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41724] GRB 250204A: SVOM/VT optical candidate
by GCN Circulars 05 Feb '26

05 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43620 SUBJECT: GRB 250204A: SVOM/VT optical candidate DATE: 26/02/05 02:02:27 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H.L. Li , C. Wu, Y.N. Ma, Z.H. Yao, Y. L. Qiu, L.P. Xin, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA/Irfu), M. Pillas (IAP), M. Dennefeld (IAP) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observation to the field of GRB 260204A triggered by SVOM/ECLAIRs (sb26020403, Pillas et al., GCN 43613). The observation started at 2026-02-04T15:37:26UTC, i.e., 49 minutes post trigger in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. An uncatalogued source was detected within the error box of ECLAIRs (Pillas et al., GCN 43613) and source 1 of Swift-XRT (https://www.swift.ac.uk/SVOM/SVOM_FIELD00057) compared to the Legacy survey catalog. The position is at R.A., Dec. = 205.106167, 1.930114 degrees, equivalent to: R.A. (J2000) = 13:40:25.48 Dec. (J2000) = +1:55:48.41 with an uncertainty of 0.5 arcsec. The measurements in AB magnitudes are given below: Mid_time Band Exposure Time Magnitude (AB) 1.23 hour VT_R 27*50 sec 20.5+/-0.1 mag 1.23 hour VT_B 26*50 sec 21.3+/-0.1 mag Our photometry was in AB magnitude and not corrected for Galactic extinction. 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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/43620. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41723] GRB 260204A : MASTER Global robotic net optical observations
by GCN Circulars 05 Feb '26

05 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43619 SUBJECT: GRB 260204A : MASTER Global robotic net optical observations DATE: 26/02/05 01:13:33 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.M.Lipunov (Lomonosov MSU), O.A.Gress, N.M.Budnev (ISU), V.A.Senik, I.Panchenko, P.Balanutsa, A.Kuznetsov, E.Gorbovskoy, G.Antipov, N. Tiurina, Ya.Kechin,A.Chasovnikov, D.Vlasenko, I.Ionov,Yu.Tselik(Lomonosov MSU), R.Mirgazov, A.Diachok, O.Ershova (Irkutsk State University), R. Podesta, C.Francile, F. Podesta, E. Gonzalez (OAFA, San JuanUni.,Argentina); D.Buckley (SAAO), A. Sosnovskij (CrAO RAS), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino, J.Martinez, A.R.Corella, J.G. Tanori, L. F. Villalobos, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysic Observatory, Mexico) V.M.Pillet, R.Rebolo Lopez (The Instituto de Astrofisica de Canarias,Spain) At alert and notice time the error-box of SVOM GRB 260204A (Pillas et al. GCN 43613, also by Fermi-GBM GCN 43618; in optic observed by LCO (Turpin et al. GCN 43616), GOTO (Kumar et al. GCN 43617)) altitude was -8deg at MASTER-Tunka (the nearest MASTER for observation). So we started observe it several hours later. MASTER-Tunka robotic telescope [1-3] located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the SVOM GRB260204A (trigger No 1770219433,13h 40m 56.04s , +01d 58m 50.2s, R=0.0662) errorbox 12301 sec after notice time (13245 sec after trigger time) at 2026-02-04 19:17:57 UT, with upper limit up to 18.1 mag at single images and 19.9 at summary. MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the SVOM GRB 260204A errorbox 16703 sec after notice time and 17647 sec after trigger time at 2026-02-04 20:31:20 UT, with upper limit up to 17.1 mag. The observations began at zenith distance = 81 deg. The sun altitude was -60.8 deg. The galactic latitude b = 62 deg., longitude l = 331 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3122418 Observation and reduction will continue. [1] Lipunov et al. 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html [2] Lipunov et al. 2022, Universe, 8, id.271 [3] Lipunov et al. 2023, Astronomy Reports, 67, p.S140 View this GCN Circular online at https://gcn.nasa.gov/circulars/43619. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41722] Fermi GBM Sub-Threshold Detection of GRB 260204A
by GCN Circulars 04 Feb '26

04 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43618 SUBJECT: Fermi GBM Sub-Threshold Detection of GRB 260204A DATE: 26/02/04 21:43:34 GMT FROM: Matt Godwin <msg0028(a)uah.edu> Matt Godwin (UAH) reports on behalf of the Fermi-GBM Team: SVOM/ECLAIRs detected the GRB 260204A on 2026-02-04 at 14:48:49 UTC (Pillas et al. 2026, GCN 43613). There was no Fermi-GBM onboard trigger around this event time. An automated, blind search for gamma-ray bursts below the onboard triggering threshold in Fermi-GBM identified a candidate. The GBM Targeted Search [1], the most sensitive coherent search for GRB-like signals in GBM, identified a transient starting -35 seconds before the SVOM best SNR time at 2026-02-04T14:48:28 most significantly on the 16 s timescale, with a false alarm rate of 3.8e-05 Hz. The Fermi-MET of this transient is 791909278.714 s. The Targeted Search localization is found to be spatially consistent with the ECLAIRs localization Additionally, the GBM Targeted Search event was found with the highest significance using a "normal" spectrum (Band function with Epeak = 230 keV, alpha = -1.0, beta = -2.3) for a GRB. [1] Goldstein et al. 2019 arXiv:1903.12597 View this GCN Circular online at https://gcn.nasa.gov/circulars/43618. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41721] GRB 260204A: GOTO optical upper limit
by GCN Circulars 04 Feb '26

04 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43617 SUBJECT: GRB 260204A: GOTO optical upper limit DATE: 26/02/04 21:17:42 GMT FROM: Amit Kumar at The Open University, UK <amitkundu515(a)gmail.com> A. Kumar, D. O’Neill, B. P. Gompertz, R. Starling, M. Wortley, M. Kennedy, K. Ackley, M. Dyer, J. Lyman, K. Ulaczyk, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, G. Ramsay, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, B. Godson, T. Killestein, M. Pursiainen, on behalf of GOTO collaboration: We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to the SVOM/ECLAIRs GRB 260204A (Pillas et al. GCN 43613). Observations covering the localisation area began at 2026-02-04 15:39:17 UT (+0.85h post trigger) and continued through to 2026-02-04 17:08:08 UT (+2.33h post trigger) utilising GOTO-South. Each observation consisted of 4x90 s exposures in the GOTO L-band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real time on any candidates that passed the above checks. No new transients that could be credibly associated with GRB 260204A were detected down to an average 5-sigma depth of 19.3 mag (AB). GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester, the University of Birmingham and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/43617. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41720] GRB 260204A: LCO optical upper limits
by GCN Circulars 04 Feb '26

04 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43616 SUBJECT: GRB 260204A: LCO optical upper limits DATE: 26/02/04 21:16:28 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> D. Turpin (CEA/Irfu), A. Saccardi (CEA/Irfu), D. B. Malesani (DAWN/NBI and Radboud), B. Cordier (CEA/Irfu), report on behalf of the SVOM mission team: We observed the field of GRB 260204A (Pillas et al., GCN 43613) with the LCO 1-m telescope at Siding Spring Observatory equipped with the Sinistro instrument. Our observation started on 2026-02-04 at 15:10:42 UT (about 22 min after the trigger) and we obtained 3x200 s in each of the SDSS r and Pan-STARRS z filters. In the stacked image, we do not detect any new source within the SVOM/ECLAIRs error box. We measure the following upper limit calibrated against the PanSTARRS DR1 catalog, and not corrected for Galactic extinction: r > 20.3 AB (5-sigma, mid-time 25.7 min after the trigger); z > 19.4 AB (5-sigma, mid-time 38.4 min after the trigger). This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/43616. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41719] EP260110a: Late GTC/EMIR near-infrared observations
by GCN Circulars 04 Feb '26

04 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43615 SUBJECT: EP260110a: Late GTC/EMIR near-infrared observations DATE: 26/02/04 20:43:55 GMT FROM: javisansie(a)gmail.com J. Sanchez-Sierras (Radboud), A. van Hoof (Radboud), P. G. Jonker (Radboud), D. Mata-Sanchez (IAC and ULL), A. J. Levan (Radboud), D. B. Malesani (DAWN/NBI and Radboud Univ.) report on behalf of a larger collaboration: We observed the field of fast X-ray transient EP260110a (Zhang et al., GCNs 43363, 43367) with the Espectrógrafo Multiobjeto Infra-Rojo (EMIR) attached to the Gran Telescopio Canarias (GTC). The observations were performed in imaging mode and consisted of 260x5 s exposures, with a total exposure time of 1280 s in the H band, starting on 2026-02-01 at 06:08:10 UT (i.e. 21.76 days after the EP-WXT trigger). We used this observation as a template to perform image subtraction from the GTC/EMIR image reported by Corcoran et al. (observed 19.02 hr after the trigger; GCN 43391), which had the same exposure time and instrument configuration. The subtraction was made using the ZOGY algorithm (Zackay et al. 2016), as implemented in PyZOGY (Guevel et al. 2021). No new sources are detected inside the EP-FXT error circle in the subtraction, down to the limit of the least deep image, i.e. upper limiting AB magnitude of H > 23.3 (calibrated using nearby stars from the 2MASS catalog). View this GCN Circular online at https://gcn.nasa.gov/circulars/43615. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41718] GRB 260204B: Fermi GBM Final Real-time Localization
by GCN Circulars 04 Feb '26

04 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43614 SUBJECT: GRB 260204B: Fermi GBM Final Real-time Localization DATE: 26/02/04 17:00:30 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 16:50:06 UT on 4 Feb 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260204B (trigger 791916611.958652 / 260204701). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 338.5, Dec = -50.1 (J2000 degrees, equivalent to J2000 22h 33m, -50d 06'), with a statistical uncertainty of 6.4 degrees. The angle from the Fermi LAT boresight is 70.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260204701/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260204701/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260204701/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43614. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41717] GRB 260204A: SVOM detection of a burst
by GCN Circulars 04 Feb '26

04 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43613 SUBJECT: GRB 260204A: SVOM detection of a burst DATE: 26/02/04 15:09:47 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Pillas (IAP), M. Dennefeld (IAP), M. Brunet (IRAP), S. Guillot (IRAP), C. Pellouin (IAP), report on behalf of the SVOM mission team: At 2026-02-04T14:48:49 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260204A (SVOM burst-id sb26020403). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 6 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 10.87 in the [5-20] keV energy band over a time window of 40.96 seconds starting at 2026-02-04T14:48:28. The localization of the best alert is R.A., Dec. 205.1185, 2.0200 degrees: R.A. (J2000) = 13h40m28.44s Dec. (J2000) = 2d01m12.14s with a 90% confidence level (C.L.) radius of 7.36 arcmin (including systematic error of 2 arcmin added in quadrature). SVOM slewed to the burst. No X-ray observation could be performed by SVOM/MXT for the time being, due to Earth occultation. SVOM/VT observations will be reported in future circular. 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 Marion Pillas: marion.pillas(a)iap.fr. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/43613. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41716] GCN Announcement: New CHIME, DSA-110 and IceCube Notices, and Schema v6.1.1
by GCN Announcements 04 Feb '26

04 Feb '26

CHIME Fast Radio Burst Notices The CHIME Team and the GCN Team are pleased to announce the availability of a new CHIME Fast Radio Burst (FRB) notice type via the new GCN in JSON format. We welcome this new transient type to the GCN community and encourage follow-up observations. These notices can be streamed via Kafka. They are not available via GCN Classic. The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a transit radio telescope located in Penticton, BC, Canada. It consists of 4 semi-cylindrical reflectors, each with 2000 square meters of collecting area and 256 dual-polarization antennas. The telescope observes between 400 MHz and 800 MHz and covers an instantaneous field of view of ~200 square degrees. CHIME houses several electronic backends, which are tailored for specific scientific goals, such as generating cosmological maps of hydrogen density, detecting Fast Radio Bursts, and observing and timing pulsars. In particular, the FRB backend operates at ~1 ms time resolution and ~ 0.4 MHz frequency resolution. The new CHIME notices provide FRB detection details including ~arcminute localization with a latency of ~1 minute. The detection rate is ~600 per year. Notices will be distributed on the Kafka topic: gcn.notices.chime.frb A more extensive description of the information provided in these new notices is available at https://gcn.nasa.gov/missions/chime. ______________________________________ DSA-110 Fast Radio Burst Notices The DSA-110 Team and the GCN Team are pleased to announce the availability of DSA-110 notice types via the new GCN in JSON format. These notices can be streamed via Kafka. The Deep Synoptic Array-110 (DSA-110) is a radio interferometer purpose-built for fast radio burst (FRB) detection and direct localization. The array is located at the Owens Valley Radio Observatory (OVRO) comprised of 96 4.65-m dishes that continuously survey for FRBs at frequencies between 1280 to 1530 MHz. Over a three-year science program, the DSA-110 will deliver a sample of more than 300 FRBs, each localized to regions ~1 arcminute radius within 1 minute of detection. This is made possible by a suite of novel instrumentation, including precisely engineered antennas, ultra-low noise ambient-temperature receivers, and a powerful real-time, autonomous data-analysis system. DSA-110 notices provide FRB detection and localization distributed on the Kafka topic: gcn.notices.dsa110.frb See the DSA-110 mission page (https://gcn.nasa.gov/missions/dsa_110) for a more extensive description of the information provided in these new notices. ______________________________________ IceCube Gold/Bronze Track Alert Notices The IceCube Team and the GCN Team are pleased to announce the availability of a new IceCube Notice type via the new GCN in JSON format for Gold/Bronze Track alerts. These notices can be streamed via Kafka. The information included in the JSON-format Notices largely overlaps with that in GCN Classic with the addition of a URL for multi-order probability maps. AMON_ICECUBE_GOLD and AMON_ICECUBE_BRONZE notices remain available via GCN Classic and GCN Classic over Kafka. IceCube is a cubic-kilometer Cherenkov particle detector deployed in the Antarctic ice beneath the Amundsen-Scott South Pole Station. IceCube detects neutrinos by observing the light produced by relativistic charged particles created by neutrino interactions in or near the instrumented volume of ice. The new Gold/Bronze Notices provide high-energy (TeV-PeV) track-like alerts with radius angular resolution. Events are classified into Gold and Bronze based on their likelihood of being astrophysical. Two GCN Notices are sent for each event - one corresponding to the preliminary reconstruction and one corresponding to the revised reconstruction. Gold and Bronze events occur at a rate of 10 and 16 per year, respectively, with a latency of 0.5-1 minute from detection. These new alerts are distributed via GCN Kafka on the topic: gcn.notices.icecube.gold_bronze_track_alerts The IceCube documentation (https://gcn.nasa.gov/missions/icecube) has been extensively updated. It now includes details on the new information released with the updated schema, as well as explanations of the quantities listed in the FITS file headers for the multi-order probability maps. ______________________________________ Schema v6.1.1 GCN Schema v6.1.1 is available with recent changes including new Notice types (Release Notes; https://github.com/nasa-gcn/gcn-schema/releases/tag/v6.1.1) For more details on this new feature and an archive of GCN news and announcements, see https://gcn.nasa.gov/news. For questions, issues, or bug reports, please contact us via: - Contact form: https://gcn.nasa.gov/contact - GitHub issue tracker: https://github.com/nasa-gcn/gcn.nasa.gov/issues --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41715] GRB 260121A: 239Alferov CubeSat detection
by GCN Circulars 03 Feb '26

03 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43612 SUBJECT: GRB 260121A: 239Alferov CubeSat detection DATE: 26/02/03 16:12:40 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin (Ioffe), D. Frederiks (Ioffe), D. Kapshtan (Geoscan), M. Orlov (Geoscan), V. Bazunova (Geoscan), E. Shchepin (Geoscan), E. Meltsov (Geoscan), K. Starikov (Geoscan, SPbSU), A. Khogoev (Geoscan), A. Razdobarin (SPbAU), and D. Dolmatov (SPbSU), on behalf of the 239Alferov team, report: The long-duration GRB 260121A (IPN triangulation: Kozyrev et al., GCN 43564; Konus-Wind detection: Ridnaia et al., GCN 43611) was detected by 239Alferov 3U CubeSat at about 8552 s (02:22:32) UT. The burst light curve, as measured by 239Alferov detector, shows a single pulse with a duration of ~13 s. The emission is seen up to above ~1 MeV. The light curve recorded by 239Alferov is available at: http://www.ioffe.ru/LEA/GRBs/GRB260121_T08549/239Alferov/ 239Alferov is an educational 3U CubeSat mission at SSO combining amateur radio and space research objectives. The gamma-ray detector onboard 239Alferov contains a 64x72x15 mm NaI(Tl) scintillator read out by a SiPM array and covers the energy range from ~20 keV to ~1000 keV. The spacecraft is now at a commissioning stage, with scientific observations started in December 2025. Currently, the instrument records count rates in five energy bands: ~20-50 keV, ~50-100 keV, ~100-500 keV, 500-1000 keV, and > 1000 keV, with 1 s temporal resolution. The surveys span a couple of days with about a day-long analysis and maintenance intervals between the observations. The ground segment of the mission utilizes the SONIKS open ground station network. View this GCN Circular online at https://gcn.nasa.gov/circulars/43612. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41714] Konus-Wind detection of GRB 260121A
by GCN Circulars 03 Feb '26

03 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43611 SUBJECT: Konus-Wind detection of GRB 260121A DATE: 26/02/03 14:59:17 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 260121A (IPN triangulation: Kozyrev et al., GCN 43564) triggered Konus-Wind at T0=8549.319 s UT (02:22:29.319). The burst light curve shows a single pulse which starts at ~T0-0.5 s and has a total duration of ~21.6 s. The emission is seen up to ~4 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260121_T08549/ As observed by Konus-Wind, the burst had a fluence of 2.79(-0.46,+0.47)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+0.512 s, of 2.09(-0.31,+0.32)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+10.240 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.82(-0.11,+0.13), the high energy photon index beta = -2.07(-0.33,+0.18), the peak energy Ep = 366(-60,+75) keV (chi2 = 97/97 dof). The spectrum near the maximum count rate (measured from T0+0.256 to T0+2.304 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.75(-0.12,+0.15), the high energy photon index beta = -1.78(-0.11,+0.09), the peak energy Ep = 367(-73,+90) keV (chi2 = 123/97 dof). All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/43611. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41713] GRB 260131A/B: OHP/T193 optical observations
by GCN Circulars 03 Feb '26

03 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43610 SUBJECT: GRB 260131A/B: OHP/T193 optical observations DATE: 26/02/03 14:29:32 GMT FROM: Christophe Adami at LAM <christophe.adami(a)lam.fr> C. Adami (LAM/Pytheas/AMU), S. Basa (UAR Pytheas), N. Globus (UNAM), A. Watson (UNAM), B. Schneider (LAM), E. Le Floc'h (CEA-Saclay) report on behalf of the MISTRAL GRB collaboration: We carried out observations 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; Jiang et al., GCN 43600; Li et al., GCN 43605) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained 7 exposures for a total of 14 min in the r-band at a midtime of 2026-02-01 19:48UT, corresponding to T-T0 = 37.15 hours. The afterglow reported by Gompertz et al., GCN 43586; Lee et al., GCN 43587; Saccardi et al., GCN 43595; García García et al., GCN 43599, Shi et al., GCN 43601; Sanchez-Ramirez et al., GCN 43604; Jayaraman et al., GCN 43606; Zhu et al., GCN 43607 ; Zheng et al., GCN 43609 is well detected in r’ with a preliminary magnitude of : r’ = 19.09 +/- 0.08 The photometric calibration was performed using nearby stars from the PanSTARRS catalog, is in the AB system, and is not corrected for Galactic extinction. We acknowledge the excellent support from the Observatoire de Haute-Provence and in particular Jean Balcaen and Stephane Favard, and the SOPHIE observer Xavier Delfosse. View this GCN Circular online at https://gcn.nasa.gov/circulars/43610. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41712] GRB 260131A: KAIT optical observations
by GCN Circulars 03 Feb '26

03 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43609 SUBJECT: GRB 260131A: KAIT optical observations DATE: 26/02/03 07:55:33 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, observed the field of GRB 260131A (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; Li et al., GCN 43605) at ~0.914d and again at ~1.875d after the burst. A set of clear (roughly R) filter images were obtained. We detected the optical afterglow (Gompertz et al., GCN 43586; Lee et al., GCN 43587; Saccardi et al., GCN 43595; García García et al., GCN 43599, Shi et al. GCN 43601, Jayaraman et al., GCN 43606; Zhu et al., GCN 43607) in our coadd images and estimate the afterglow to be 17.8 +/- 0.1 and 19.2 +/- 0.2 mag (Vega) respectively. View this GCN Circular online at https://gcn.nasa.gov/circulars/43609. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41711] GRB 251230A: MeerLICHT afterglow detection
by GCN Circulars 03 Feb '26

03 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43608 SUBJECT: GRB 251230A: MeerLICHT afterglow detection DATE: 26/02/03 07:50:51 GMT FROM: Simon de Wet at DTU Space <simdewet(a)gmail.com> S. de Wet (DTU Space) and P.J. Groot (Radboud/UCT/SAAO) report on behalf of the MeerLICHT consortium: The 0.6m wide-field MeerLICHT optical telescope located in Sutherland, South Africa, obtained a repeating series of 60s exposures in the q,u,g,r,i,z filters following the detection of GRB 251230A by Swift (Lanava et al., GCN 43252). Our observations began 185 seconds after the Swift trigger and continued for approximately 26 minutes following the filter sequence quqgqrqiqz. A further four exposures were taken after a gap of approximately 30 minutes. We detect the bright optical afterglow in all of our images, and report the following first detections in each filter: q = 12.99 +/- 0.01 at 01:25:21 UT u = 13.95 +/- 0.05 at 01:26:41 UT g = 14.24 +/- 0.02 at 01:29:24 UT r = 14.43 +/- 0.01 at 01:32:07 UT i = 14.67 +/- 0.01 at 01:34:51 UT z = 14.80 +/- 0.03 at 01:37:36 UT We measure a power-law decline rate of -1.54 in the q-band. A light curve is available at the following link: https://raw.githubusercontent.com/simdewet/GRB_lightcurves/main/GRB251230A.… MeerLICHT is built and run by a consortium consisting of Radboud University, University of Cape Town, the South African Astronomical Observatory, the University of Oxford, the University of Manchester and the University of Amsterdam. View this GCN Circular online at https://gcn.nasa.gov/circulars/43608. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41710] GRB 250131A: FTW optical and NIR observations
by GCN Circulars 02 Feb '26

02 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43607 SUBJECT: GRB 250131A: FTW optical and NIR observations DATE: 26/02/02 22:00:00 GMT FROM: Ziyuan.Zhu(a)campus.lmu.de Ziyuan Zhu (LMU), Malte Busmann (LMU), Julius Gassert (LMU), Xander J. Hall (CMU), Brendan O’Connor (CMU), Daniel Gruen (LMU), and Antonella Palmese (CMU) report: We observed the counterpart of GRB 260131A (Fermi/GBM Team, GCN 43579; Frederiks et al., GCN 43590; Luo et al., GCN 43591; Li et al., GCN 43605) with the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW) in the r, i, and J bands for 15x 120s, starting at 2026-02-01T22:14:35 UT, (1.65 days after the trigger). We detect the counterpart in all bands and measure an r-band magnitude of r = 19.18 +/- 0.03 AB mag The magnitude is calibrated against the PS1 catalog and not corrected for Galactic extinction. We thank Christoph Ries from the Wendelstein Observatory for obtaining these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/43607. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[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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[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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[vsnet-grb-info 41692] EP260131a: SVOM/VT optical observation
by GCN Circulars 01 Feb '26

01 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43589 SUBJECT: EP260131a: SVOM/VT optical observation DATE: 26/02/01 08:04:28 GMT FROM: zhyao(a)bao.ac.cn Z. H. Yao, C. Wu, L. P. Xin, H. L. Li, Y. N. Ma, Y. L. Qiu, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) and S. D. Vergani (LUX-Paris Obs.) report on behalf of the SVOM/VT team. SVOM/VT performed a Target of Opportunity observation of EP260131a detected by EP/WXT (Ding et al., GCN 43574). SVOM/VT began observing the field at 2026-01-31T17:47:46.506 UTC, ~14.3 h after T0, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With X-band data available, the optical counterpart (Li et al., GCN 43577; Álvarez et al., GCN 43578; Malesani et al., GCN 43581; Schneider et al., GCN 43582; Schneider et al., GCN 43584; Mu el al., GCN 43588) was detected in both VT_B and VT_R band within EP/WXT's (Ding et al., GCN 43574) and EP/FXT's (Wu et al., GCN 43583) error box. The position of this target is R.A., Dec. = 149.902458, -3.307450 degrees, corresponding to: R.A. (J2000) = 09:59:36.59 Dec. (J2000) = -03:18:26.82 with an uncertainty of 0.5 arcsec. The photometric measurements are as follows: mid time (h) | exposure time (s) | band | mag (AB) --------------|-------------------|------|------------- 15.50 | 40*70 | VT_B | 22.38+/-0.05 15.31 | 41*70 | VT_R | 21.70+/-0.03 Our photometry was not corrected for Galactic extinction. 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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/43589. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41691] EP260131a: Xinglong optical upper limit
by GCN Circulars 01 Feb '26

01 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43588 SUBJECT: EP260131a: Xinglong optical upper limit DATE: 26/02/01 04:16:49 GMT FROM: Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong(a)nao.cas.cn> Haiyang-Mu (NAOC),Junjie-Jin (NAOC), Feng-Xiao (NAOC), Pengliang-Du (NAOC), Zhou-Fan (NAOC), Hong-Wu (NAOC) report: Following the detection of EP260131a by EP-WXT (GCN Circular 43574,GCN Circular 43577,GCN Circular 43578), we observed the field of EP260131a using the 2.16-m telescope at Xinglong Observatory, NAOC. We obtained 300s r-band frames with a median time of (2026-01-31 16:25:55(UT)) 13 hr after the EP trigger. No uncatalogued optical transient is detected in the stacked images within the 3 arcmin EP/WXT error circle (GCN Circular 43574,GCN Circular 43578), down to 5-sigma limiting magnitudes of r ~ 19.1(not good day with thin cloud and bad seeing), calibrated with Pan-STARRS sources in the field. Also there is no apparent brightening for the catalogued sources within the error circle. Based on the location of the report(GCN Circular 43574,GCN Circular 43578), the target was not observed. View this GCN Circular online at https://gcn.nasa.gov/circulars/43588. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41690] GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
by GCN Circulars 01 Feb '26

01 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43587 SUBJECT: GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading DATE: 26/02/01 03:45:33 GMT FROM: William H. Lee at UNAM <wlee(a)astro.unam.mx> We observed the optical afterglow candidate AT2026bwg discovered by Gompertz et al. (GCN 43586), of GRB 260131A (Fermi/GBM Team, GCN 43579), also associated with GRB 260131B (Sugai et al., GCN 43580; Roberts et al., GCN 43585), using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-02-01 02:06 to 03:05 UTC (from 19.45 to 20.46 hours after the trigger) and obtained 23 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. The optical counterpart is clearly detected with preliminary magnitudes of: r = 17.96 +/- 0.01, z = 17.61 +/- 0.01. Since the start of our observations, the source has faded with an apparent average temporal power-law index of -2.01 +/ 0.26 (in r) and -1.50 +/- 0.33 (in z). 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/43587. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41689] GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
by GCN Circulars 31 Jan '26

31 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43586 SUBJECT: GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation DATE: 26/01/31 23:32:35 GMT FROM: Ben Gompertz at U of Birmingham <b.gompertz(a)bham.ac.uk> B. P. Gompertz, D. O’Neill, K. Ackley, M. Dyer, J. Lyman, K. Ulaczyk, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, G. Ramsay, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, R. Starling, B. Godson, T. Killestein, A. Kumar, M. Pursiainen, on behalf of GOTO collaboration: We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to GRB 260131A (Fermi/GBM Team, GCN 43579), now associated with GRB 260131B (Sugai et al., GCN 43580; Roberts et al., GCN 43585). Observations covering the initial GBM localisation area of GRB 260131A began at 2026-01-31 20:00:48 UT (+13.35h post trigger) and continued through to 2026-01-31 21:32:06 UT (+14.88h post trigger). 103 images were taken, across 10 unique pointings, covering 215.8 within the 90% localisation contour. ~89.8% of the total 2D localisation probability was covered, with an average 5-sigma depth of 19.4 mag in the GOTO-L filter (400 - 700nm). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real time on any candidates that passed the above checks. A new optical source GOTO26akj/AT2026bwg is identified at coordinates: RA,DEC (J2000) = 24.713819, 34.328119, 01:38:51.32, +34:19:41.23 This position is consistent with the MAXI localisation of GRB 260131B (Sugai et al., GCN 43580). The source was initially detected with L = 17.41 ± 0.03 AB mag (t0+13.62h) before fading to L = 17.59 ± 0.04 mag (t0+14.75h). We find no evidence of the source prior to the GRB trigger time in the most recent pre-GRB GOTO observations taken at 19:59:53 on 2026-01-28 (t0-58.66h) down to a 5-sigma depth of L > 19.55 AB mag. We also find no evidence of the source prior to the GRB in the ZTF observations provided by the Lasair broker (Smith et al. 2019) or the ATLAS forced photometry server (Shingles et al. 2021). Due to its temporal coincidence with GRB 260131A/B, apparent fading, and spatial coincidence with the relatively small MAXI localisation region, we consider GOTO26akj/AT2026bwg to be a promising candidate optical counterpart. Further observations to determine the nature of the source are strongly encouraged. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester, the University of Birmingham and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/43586. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41688] GRB 260131A/B: Fermi GBM Observation
by GCN Circulars 31 Jan '26

31 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43585 SUBJECT: GRB 260131A/B: Fermi GBM Observation DATE: 26/01/31 23:12:56 GMT FROM: oliver.roberts(a)universityofgalway.ie O.J. Roberts (Uni. of Galway, Ireland) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 06:39:30.44 UT on 31 January 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260131A/B (trigger 791534375/260131277). which was also detected by MAXI (H. Sugai et al. 2026, GCN 43580). The Fermi GBM final real-time Localization (GCN 43579) is consistent with the MAXI position. The MAXI burst triggered on the second pulse of 260131A. We note both bursts have similar locations and are likely the same event. The angle from the Fermi LAT boresight using the MAXI location is 112 degrees. The GBM light curve consists of two separated FRED emission episodes with a duration (T90) of about 257 s (50-300 keV). The time-averaged spectrum from T0-2.0 to T0+280.0 s is best fit by a Band function with an Epeak of 148 +/- 39 keV, alpha is -0.90 +/- 0.16 and beta is -1.76 +/- 0.06. The event fluence (10-1000 keV) in this time interval is (2.82 +/- 0.09)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+2.6 s in the 10-1000 keV band is 8.3 +/- 0.4 ph/s/cm^2. 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/43585. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41687] EP260131a: COLIBRÍ observations of slow optical fading
by GCN Circulars 31 Jan '26

31 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43584 SUBJECT: EP260131a: COLIBRÍ observations of slow optical fading DATE: 26/01/31 15:00:38 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Benjamin Schneider (LAM), Alan M. Watson (UNAM), Fredd Sánchez Álvarez (UNAM), Jean-Luc Atteia (IRAP), 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), 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; Wu et al, GCN CIrc 43583) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-01-31 04:40 to 11:52 UTC (from 1.14 to 8.35 hours after the trigger) and obtained, respectively, 127, 191, and 320 minutes of exposure in the g, 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. 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), and Schneider et al. (GCN Circ. 43582) is clearly detected in our data. It fades slowly from r ≈ 21.1 to r ≈ 21.4 and z ≈ 20.8 to z ≈ 21.2 during our observations with an apparent average temporal power-law index of -0.16 +/- 0.07. We observe that the g-r color is 0.14 +/- 0.06, consistent with the detection by Schneider et al. (GCN Circ. 43582) down to the atmospheric cutoff. We encourage further observations, especially over the next 24 hours. 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/43584. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41686] EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
by GCN Circulars 31 Jan '26

31 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43583 SUBJECT: EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations DATE: 26/01/31 13:33:19 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Q. Y. Wu (NAO, CAS), T. Wu , H. C. Ding (AHNU) , H. Sun (NAO,CAS) on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP260131a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Ding et al., GCN 43574). The refined analysis of the WXT data shows that the event started at T0=2026-01-31T03:28:00.15 (UTC), and lasted for approximately 340 seconds, after which the observation was interrupted due to Earth occultation. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 3.36 × 10^20 cm^-2, an intrinsic hydrogen column density of 5 (-3/+3) × 10^21 cm^-2, and a photon index of 1.9 (-0.8/+0.9). The derived average unabsorbed 0.5-4 keV flux is 6.3 (-1.5/+3.6) × 10^(-10) erg/s/cm^2. The Follow-up X-ray Telescope (FXT) on board EP autonomously observed this source a few minutes after the on board trigger. The source was initially occulated the Earth and entered the FXT field of view since 2026-01-31T04:14:01 (UTC, T0+2.7 ks). The effective exposure time of the observation is around 3 ks. On-ground analysis of the FXT data found an uncatalogued source at R.A. = 149.9017, DEC = -3.3074 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic), which is consistent with the WXT position and also the optical counterpart (Li et al., GCN 43577; Álvarez et al., GCN 43578; Malesani et al., GCN 43581; Schneider et al., GCN 43582). The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 3.36 × 10^20 cm^-2, an intrinsic hydrogen column density of 1.5 (-1.1/+1.3) × 10^21 cm^-2, and a photon index of 2.2 (-0.4/+0.4). The derived average unabsorbed 0.5-10 keV flux is 4.4 (-0.6/+0.6) × 10^(-13) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. Further FXT follow-up observations have been arranged. 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/43583. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41685] EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
by GCN Circulars 31 Jan '26

31 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43582 SUBJECT: EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937 DATE: 26/01/31 12:24:23 GMT FROM: Benjamin Schneider at MIT <bschn(a)mit.edu> B. Schneider (LAM), A. Saccardi (CEA/Irfu), J. An (NAOC), D. Xu (NAOC), D. B. Malesani (DAWN/NBI and Radboud), V. D'Elia (ASI-SSDC), S. D. Vergani (LUX-Paris Obs.), N. Habeeb (U. Leicester), N. R. Tanvir (U. Leicester), A. L. Thakur (INAF-IAPS) report on behalf of the Stargate collaboration: We observed the optical counterpart (Li et al., GCN 43577; Sánchez Álvarez et al., GCN 43578, Malesani et al, GCN 43581) of EP 260131a (Ding et al., GCN 43574) using the ESO/VLT UT3 (Melipal) equipped with the X-shooter spectrograph. Our spectra cover the wavelength range 3000-21000 AA and consist of 4 exposures of 1200 s each. Observations started on 2026 January 31 at 07:30:09 UT (3.98 hr after the burst). In a stacked image of 3x60 s secured in the r-band (3.79 after trigger), we measure r = 21.20 +/- 0.04 (AB), calibrated against nearby stars from Pan-STARRS. In a preliminary reduction of the spectra, we detect a continuum over the entire wavelength range. From detection in the blue down to 3090 AA, and the lack of hydrogen absorption, we set a redshift upper limit z < 1.54. Furthermore, we detect multiple absorption lines, which we interpret as Al II, Mn II, Fe II, Mg II doublet, and Ca II at a common redshift of z = 0.937. The non-detection of fine-structure transitions at z = 0.937 does not allow us to firmly associate this redshift with the GRB, however, the absence of unidentified features at higher redshift and the good S/N over the full continuum, support z = 0.937 as the most likely redshift. We acknowledge the excellent support of the ESO observing staff in Paranal, in particular Elisa Garro. The analysis of this spectrum was carried out with the help of the zHunter tool (https://doi.org/10.5281/zenodo.15189495) View this GCN Circular online at https://gcn.nasa.gov/circulars/43582. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41684] EP260131a: NOT early detection of the counterpart in "rapid response mode"
by GCN Circulars 31 Jan '26

31 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43581 SUBJECT: EP260131a: NOT early detection of the counterpart in "rapid response mode" DATE: 26/01/31 09:00:08 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. N. D. van Dalen (Radboud), J. A. Quirola-Vasquez (Radboud), P. G. Jonker (Radboud), K. Valeckas (NOT) report on behalf of a larger collaboration: We observed the field of the fast X-ray transient EP260131a (Ding et al., GCN 43574) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were triggered using the recently implemented automatic “Rapid Response Mode” and obtained in the SDSS r and z bands, consisting of 5x180 s and 9x150 s exposures, respectively, starting on 2026-01-31 at 04:56:50 UTC (~2.5 min after the GCN Notice, or 52 min after the WXT trigger). We detect the counterpart reported by Li et al. (GCN 43577) and Sánchez Álvarez et al. (GCN 43578). In our first frame (mid time 53.5 min after trigger), we measure r' = 21.18 +- 0.10 (AB) and from a stacked z-band image we measure z' = 20.75 +- 0.06 at time 75.2 min after the WXT trigger. The above magnitudes are calibrated against nearby stars from the Pan-STARRS catalog and are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43581. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41683] GRB 260131B: MAXI/GSC detection
by GCN Circulars 31 Jan '26

31 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43580 SUBJECT: GRB 260131B: MAXI/GSC detection DATE: 26/01/31 08:53:31 GMT FROM: Motoko Serino at Aoyama Gakuin U. <serino(a)phys.aoyama.ac.jp> H. Sugai (Chuo U.), D. Iijima, M. Serino (AGU), H. Negoro, M. Nakajima, K. Takagi, H. Takahashi, H. Nishio (Nihon U.), T. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita, Y. Kawakubo, H. Hiramatsu, Y. Kondo, A. Yoshida (AGU), Y. Tsuboi, N. Nagashima, Y. Ishihara (Chuo U.), M. Shidatsu, C. Kang, T. Nakamoto, M. Uenishi, T. Usuki, S. Yatsuzuka (Ehime U.), I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara, S. Kobayashi (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), W. Iwakiri (Chiba U.), T. Kawamuro (Osaka U.), S. Yamada (Tohoku U) The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 06:43:02 UT on January 31, 2026. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (24.348 deg, 34.351 deg) = (01 37 23, +34 21 03) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.11 deg and 0.09 deg, respectively. The roll angle of long axis from the north direction is 26.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 801 +- 56 mCrab (4.0-10.0keV, 1 sigma error). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (R.A., Dec) = (23.945, 34.685) deg = (01 35 46, +34 41 06) (J2000) (R.A., Dec) = (23.826, 34.499) deg = (01 35 18, +34 29 56) (J2000) (R.A., Dec) = (25.021, 33.970) deg = (01 40 05, +33 58 11) (J2000) (R.A., Dec) = (25.142, 34.154) deg = (01 40 34, +34 09 14) (J2000) There was no significant excess flux in the previous transit at 05:10 UT and in the next transit at 08:16 UT with an upper limit of 20 mCrab for each. View this GCN Circular online at https://gcn.nasa.gov/circulars/43580. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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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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[vsnet-grb-info 41672] GRB 260130A: Fermi GBM Final Real-time Localization
by GCN Circulars 30 Jan '26

30 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43569 SUBJECT: GRB 260130A: Fermi GBM Final Real-time Localization DATE: 26/01/30 13:39:52 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 SHORT GRB At 13:29:20 UT on 30 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260130A (trigger 791472565.82111 / 260130562). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 48.7, Dec = 64.2 (J2000 degrees, equivalent to J2000 03h 14m, 64d 12'), with a statistical uncertainty of 1.6 degrees. The angle from the Fermi LAT boresight is 16.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260130562/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260130562/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260130562/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43569. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41671] Fermi GRB 260129A: Global MASTER-Net observations report
by GCN Circulars 30 Jan '26

30 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43568 SUBJECT: Fermi GRB 260129A: Global MASTER-Net observations report DATE: 26/01/30 09:45:35 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-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 260129A ( "The Fermi GBM team, GCN 43560) errorbox 11097 sec after trigger time at 2026-01-29 07:38:10 UT, with upper limit up to 20.3 mag. The observations began at zenith distance = 14 deg. The sun altitude is -26.1 deg. MASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 260129A errorbox 11436 sec after notice time and 62790 sec after trigger time at 2026-01-29 21:59:43 UT, with upper limit up to 18.7 mag. The observations began at zenith distance = 29 deg. The sun altitude is -38.6 deg. The galactic latitude b = 10 deg., longitude l = 281 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3118323 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 11158 | 2026-01-29 07:38:10 | MASTER-OAFA | (11h 27m 13.34s , -44d 41m 02.7s) | C | 120 | 20.3 | 11292 | 2026-01-29 07:40:24 | MASTER-OAFA | (11h 27m 07.54s , -44d 41m 59.8s) | C | 120 | 20.3 | 11428 | 2026-01-29 07:42:41 | MASTER-OAFA | (11h 27m 15.05s , -44d 41m 35.1s) | C | 120 | 20.3 | 62821 | 2026-01-29 21:59:43 | MASTER-SAAO | (10h 11m 50.86s , -45d 52m 29.4s) | C | 60 | 18.4 | 62821 | 2026-01-29 21:59:43 | MASTER-SAAO | (10h 14m 26.54s , -46d 07m 36.2s) | C | 60 | 18.5 | 63446 | 2026-01-29 22:10:08 | MASTER-SAAO | (10h 11m 53.44s , -45d 51m 31.8s) | C | 60 | 18.5 | 63446 | 2026-01-29 22:10:08 | MASTER-SAAO | (10h 14m 29.91s , -46d 06m 40.7s) | C | 60 | 18.5 | 63538 | 2026-01-29 22:11:41 | MASTER-SAAO | (10h 23m 16.96s , -45d 52m 29.2s) | C | 60 | 18.5 | 63538 | 2026-01-29 22:11:41 | MASTER-SAAO | (10h 25m 53.45s , -46d 07m 38.5s) | C | 60 | 18.7 | 69831 | 2026-01-29 23:56:34 | MASTER-SAAO | (10h 11m 31.47s , -45d 50m 19.4s) | C | 60 | 18.5 | 69831 | 2026-01-29 23:56:34 | MASTER-SAAO | (10h 14m 12.48s , -46d 05m 44.3s) | C | 60 | 18.6 | 69924 | 2026-01-29 23:58:06 | MASTER-SAAO | (10h 23m 08.92s , -45d 50m 23.0s) | C | 60 | 18.5 | 69924 | 2026-01-29 23:58:06 | MASTER-SAAO | (10h 25m 49.94s , -46d 05m 48.7s) | C | 60 | 18.7 | 71379 | 2026-01-30 00:22:22 | MASTER-SAAO | (11h 35m 50.59s , -53d 50m 24.1s) | C | 60 | 18.4 | 72378 | 2026-01-30 00:39:01 | MASTER-SAAO | (11h 35m 50.52s , -53d 49m 57.6s) | C | 60 | 18.4 | 97583 | 2026-01-30 07:39:05 | MASTER- | (11h 14m 18.98s , -40d 12m 46.3s) | C | 60 | 12.5 | 98173 | 2026-01-30 07:48:55 | MASTER- | (10h 28m 29.18s , -38d 41m 20.6s) | C | 60 | 17.5 | 98173 | 2026-01-30 07:48:55 | MASTER- | (10h 29m 56.16s , -39d 15m 37.1s) | C | 60 | 17.8 | 98242 | 2026-01-30 07:50:04 | MASTER- | (10h 39m 15.98s , -39d 16m 29.4s) | C | 60 | 17.7 | 98242 | 2026-01-30 07:50:04 | MASTER- | (10h 37m 49.29s , -38d 42m 11.6s) | C | 60 | 17.4 | 98312 | 2026-01-30 07:51:14 | MASTER- | (10h 49m 27.34s , -39d 17m 20.5s) | C | 60 | 16.0 | 98312 | 2026-01-30 07:51:14 | MASTER- | (10h 48m 02.65s , -38d 43m 01.0s) | C | 60 | 16.9 | 98384 | 2026-01-30 07:52:26 | MASTER- | (10h 13m 19.68s , -40d 15m 49.2s) | C | 60 | 14.8 | 98384 | 2026-01-30 07:52:26 | MASTER- | (10h 14m 48.12s , -40d 50m 02.2s) | C | 60 | 14.8 | 98453 | 2026-01-30 07:53:36 | MASTER- | (10h 16m 32.79s , -40d 50m 27.7s) | C | 60 | 13.0 | 98453 | 2026-01-30 07:53:36 | MASTER- | (10h 14m 46.66s , -40d 16m 18.6s) | C | 60 | 12.3 | 98524 | 2026-01-30 07:54:47 | MASTER- | (10h 41m 57.54s , -37d 23m 14.9s) | C | 60 | 18.1 | 98524 | 2026-01-30 07:54:47 | MASTER- | (10h 40m 33.59s , -36d 49m 02.8s) | C | 60 | 17.6 | 98594 | 2026-01-30 07:55:56 | MASTER- | (10h 51m 59.28s , -37d 21m 24.5s) | C | 60 | 18.0 | 98594 | 2026-01-30 07:55:56 | MASTER- | (10h 50m 35.55s , -36d 47m 11.0s) | C | 60 | 17.7 | 98666 | 2026-01-30 07:57:08 | MASTER- | (10h 15m 39.98s , -40d 15m 20.6s) | C | 60 | 12.3 | 98806 | 2026-01-30 07:59:28 | MASTER- | (10h 27m 25.44s , -40d 50m 52.5s) | C | 60 | 15.6 | 98806 | 2026-01-30 07:59:28 | MASTER- | (10h 25m 56.82s , -40d 16m 28.3s) | C | 60 | 15.6 | 98950 | 2026-01-30 08:01:52 | MASTER- | (10h 28m 26.76s , -38d 43m 31.6s) | C | 60 | 17.8 | 98950 | 2026-01-30 08:01:52 | MASTER- | (10h 29m 53.21s , -39d 17m 54.3s) | C | 60 | 17.9 | 99020 | 2026-01-30 08:03:02 | MASTER- | (10h 39m 13.65s , -39d 17m 26.4s) | C | 60 | 17.9 | 99020 | 2026-01-30 08:03:02 | MASTER- | (10h 37m 47.28s , -38d 43m 02.2s) | C | 60 | 17.7 | 99090 | 2026-01-30 08:04:12 | MASTER- | (10h 47m 58.95s , -38d 41m 25.0s) | C | 60 | 17.5 | 99090 | 2026-01-30 08:04:12 | MASTER- | (10h 49m 25.13s , -39d 15m 51.5s) | C | 60 | 17.8 | 99162 | 2026-01-30 08:05:24 | MASTER- | (10h 13m 13.05s , -40d 17m 55.1s) | C | 60 | 14.9 | 99162 | 2026-01-30 08:05:24 | MASTER- | (10h 14m 41.45s , -40d 52m 16.3s) | C | 60 | 14.8 | 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/43568. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41670] GRB 260128B: LCO optical upper limits
by GCN Circulars 30 Jan '26

30 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43567 SUBJECT: GRB 260128B: LCO optical upper limits DATE: 26/01/30 09:25:29 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> C. Wu (NAOC), J. X. Cao (GXU), A. Saccardi (CEA/Irfu), D. Turpin (CEA/Irfu), report on behalf of the SVOM mission team: We observed the field of the SVOM GRB 260128B (Brunet et al., GCN 43561) with the LCO 1m telescope at Cerro Tololo Interamerican Observatory equipped with the Sinistro instrument. Our observation started on 2026-01-30 at 00:48:11 UT (about 1.75 days after the trigger) and we obtained 6x300 s exposures in the SDSS r and 5x300 s exposures in the Pan-STARRS z filters. In the stacked image, we do not detect any new source within the SVOM/ECLAIRs error box, in agreement with Méndez et al. (GCN 43566). We measure the following upper limit calibrated against the PanSTARSS DR1 catalog, and not corrected for Galactic extinction: r > 22.4 AB (3-sigma, mid-time 42.5 hr after the trigger) z > 21.3 AB (3-sigma, mid-time 42.2 hr after the trigger). This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/43567. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41669] GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
by GCN Circulars 30 Jan '26

30 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43566 SUBJECT: GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits DATE: 26/01/30 05:14:51 GMT FROM: enriquemm(a)astro.unam.mx Enrique Moreno Méndez (UNAM), Jean-Luc Atteia (IRAP), 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), N. A. Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), and Sébastien Le Stum (APC) report: We imaged the field of the SVOM GRB 260128A (Brunet et al., GCN Circ. 43561) using the DDRAGO two-channel wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-01-30 02:15 to 03:38 UTC (from 43.5 to 44.8 hours after the trigger) and obtained 60 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. WIthin the ECLAIRs 12 arcmin error circle (Brunet et al., GCN Circ. 43561), and in comparison to the corresponding PS1 images, we do not detect any new sources to preliminary 5-sigma limiting magnitudes of r > 22.3 z > 21.5 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/43566. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41668] GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
by GCN Circulars 30 Jan '26

30 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43566 SUBJECT: GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits DATE: 26/01/30 05:14:51 GMT FROM: enriquemm(a)astro.unam.mx Enrique Moreno Méndez (UNAM), Jean-Luc Atteia (IRAP), 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), N. A. Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), and Sébastien Le Stum (APC) report: We imaged the field of the SVOM GRB 260128A (Brunet et al., GCN Circ. 43561) using the DDRAGO two-channel wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-01-30 02:15 to 03:38 UTC (from 43.5 to 44.8 hours after the trigger) and obtained 60 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. WIthin the ECLAIRs 12 arcmin error circle (Brunet et al., GCN Circ. 43561), and in comparison to the corresponding PS1 images, we do not detect any new sources to preliminary 5-sigma limiting magnitudes of r > 22.3 z > 21.5 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/43566. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41667] EP260128a: J band upper limit by SYSU 80cm infrared telescope
by GCN Circulars 30 Jan '26

30 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43565 SUBJECT: EP260128a: J band upper limit by SYSU 80cm infrared telescope DATE: 26/01/30 04:42:48 GMT FROM: linp(a)mail2.sysu.edu.cn Pu Lin, Jin-Ji Li, 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 EP260128a (Zhou et al., GCN 43549) using the Sun Yat-sen University 80cm infrared telescope with 167 x 20 s exposures in J band. The calculated position is RA = 128.32533 deg, DEC = -10.27565 deg J2000, from EP/FXT observation (Zhou et al., GCN 43554). Our observations began at 2026-1-29 20:00:00 UTC, 20.33 hours after the EP trigger. We do not detect any counterpart at the position of the optical afterglow (H. L. Li et al., GCN 43551, J. A. Quirola-Vasquez et al., GCN 43552, R. A. J. Eyles-Ferris et al., GCN 43553, L.B. He et al., GCN 43555), down to a 5-sigma depth of J~ 18.5 Vega magnitudes. 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/43565. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41666] IPN triangulation of GRB 260121A
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43564 SUBJECT: IPN triangulation of GRB 260121A DATE: 26/01/29 23:10:15 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the MGNS/BepiColombo team, J. Benkhoff on behalf of the BepiColombo team, D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, A. Goldstein, M. S. Briggs, C. Wilson-Hodge, M. Hui, and E. Burns on behalf of the Fermi GBM team, G. Waratkar, J.Joshi, V. Bhalerao, D. Bhattacharya, A. Arya, and S. Vadawale, on behalf of the Astrosat-CZTI team, E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, A. Tohuvavohu, and J. DeLaunay on behalf of the Swift-BAT team, and D. Kapshtan, M. Orlov, V. Bazunova, E. Shchepin, E. Meltsov, K. Starikov, A. Khogoev, on behalf of the 239Alferov team, report: The long-duration GRB 260121A was detected by Fermi (GBM; in continuous TTE data), Konus-Wind, Astrosat (CZTI), INTEGRAL (SPI-ACS), 239Alferov CubeSat, and BepiColombo-MGNS at about 8552 s UT (02:22:32). We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 213.591 (14h 14m 22s) -62.629 (-62d 37' 45") Corners: 212.178 (14h 08m 43s) -65.088 (-65d 05' 17") 212.129 (14h 08m 31s) -64.984 (-64d 59' 01") 214.879 (14h 19m 31s) -60.111 (-60d 06' 38") 214.922 (14h 19m 41s) -60.220 (-60d 13' 11") --------------------------------------------- The error box area is 855 sq. arcmin, and its maximum dimension is 5.13 deg (the minimum one is 3 arcmin). The Sun distance was 72 deg. The localization may be improved. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB260121_T08549/IPN/ The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/43564. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41665] GRB 260127A: Swift-BAT refined analysis
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43563 SUBJECT: GRB 260127A: Swift-BAT refined analysis DATE: 26/01/29 21:16:56 GMT FROM: D. R. Sadaula at NASA GSFC <dev.r.sadaula(a)nasa.gov> T. Parsotan (GSFC), S. D. Barthelmy (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team) Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 260127A (trigger #1444088) (Kilingler et al., GCN Circ. 43529). The BAT ground-calculated position is RA, Dec = 231.879, 6.758 deg which is RA(J2000) = 15h 27m 30.9s Dec(J2000) = +06d 45' 28.4" with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 40%. The classic pulse has a single peak that started around T+20 sec and has a structure before it at ~T+5 sec. The duration of the burst is ~100 sec. T90 (15-350 keV) is 104.06 +- 19.41 sec (estimated error including systematics). The time-averaged spectrum using multiple GTIs from T-2.68 to T+7.62, T+9.00 to T+84.43 sec, and T+86.00 to T+117.04 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.76 +- 0.15. The fluence in the 15-150 keV band is 2.3 +- 0.2 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+33.36 sec in the 15-150 keV band is 2.1 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1444088 View this GCN Circular online at https://gcn.nasa.gov/circulars/43563. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41664] GRB 260129B: Fermi GBM Final Localization
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43562 SUBJECT: GRB 260129B: Fermi GBM Final Localization DATE: 26/01/29 19:56:51 GMT FROM: Christian Malacaria at INAF-OAR <cmalacaria.astro(a)gmail.com> "The Fermi GBM team reports the detection of a likely Long GRB. At 10:06:57 UT on 29 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260129B (trigger 791374022 / 260129421). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 0.36, Dec = -67.05 (J2000 degrees, equivalent to J2000 00h 01m, -67d 03'), with a statistical uncertainty of 10.6 degrees. The angle from the Fermi LAT boresight is 129.9 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260129421/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260129421/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260129421/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/43562. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41663] GRB 260128B: SVOM detection of a burst through offline search
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43561 SUBJECT: GRB 260128B: SVOM detection of a burst through offline search DATE: 26/01/29 19:08:31 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Brunet (IRAP), S. Le Stum, A. Coleiro (APC), O. Godet (IRAP),report on behalf of the SVOM team: The SVOM/ECLAIRs telescope detected a transient source, labelled GRB 260128B, starting at 2026-01-28T06:48:34.72 UTC (T0), through an offline search with the event-by-event data downloaded through the X-band ground station. The burst was detected within several energy ranges and timescales. The best detection is obtained by the Image Trigger with a signal-to-noise ratio of 7.5 within 4-20 keV over a time window of 10.24 seconds starting at T0-10.24s. The lightcurve shows a single peaked structure lasting around 4s. The localization of the source is RA, Dec = 27.734, -25.867 degrees: RA (J2000) = 01h50m56.16s Dec (J2000) = -25d52m01.20s with a 90% C.L. radius of 12.0 arcmin (including systematic error of 6 arcmin added in quadrature). We note that no bright catalogued X-ray sources are found in the error box. The Space 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. ECLAIRs was developed jointly by APC, CEA, CNES, and IRAP. The SVOM point of contact for this event is : Sébastien Le Stum : lestum at apc.in2p3.fr Please contact him by email if you require additional information regarding the SVOM follow-up of this burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/43561. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41662] GRB 260129A: Fermi GBM Final Localization
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43560 SUBJECT: GRB 260129A: Fermi GBM Final Localization DATE: 26/01/29 18:53:30 GMT FROM: Christian Malacaria at INAF-OAR <cmalacaria.astro(a)gmail.com> "The Fermi GBM team reports the detection of a likely Long GRB. At 04:33:12 UT on 29 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260129A (trigger 791353997 / 260129190). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 160.4, Dec = -46.8 (J2000 degrees, equivalent to J2000 10h 41m, -46d 48'), with a statistical uncertainty of 9.7 degrees. The angle from the Fermi LAT boresight is 20.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260129190/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260129190/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260129190/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/43560. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41661] IPN triangulation of GRB 260127B (short)
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43559 SUBJECT: IPN triangulation of GRB 260127B (short) DATE: 26/01/29 18:13:36 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, and A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi GBM team, report: The short-duration GRB 260127B (Fermi-GBM detection: The Fermi GBM team, GCN 43533) was detected by Fermi (GBM trigger 791236957) and Konus-Wind at about 72153 s UT (20:02:33). We have triangulated it to a Konus-GBM annulus centered at RA(2000)=104.669 deg (06h 58m 40s) Dec(2000)=+21.845 deg (+21d 50' 41"), whose radius is 72.490 +/- 0.104 deg (3 sigma). The annulus combined with the Fermi-GBM final position (GCN 43533; glg_healpix_all_bn260127835_v00) gives ~6.8 sq. deg (3 sigma) localization region. The the optical source detected by GOTO (GOTO26aih/AT2026bnn, GCN 43538) is outside the IPN annulus. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB260127_T72154/IPN/ View this GCN Circular online at https://gcn.nasa.gov/circulars/43559. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41660] GRB 260127B: Swift-XRT observations
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43558 SUBJECT: GRB 260127B: Swift-XRT observations DATE: 26/01/29 15:59:58 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> D.N. Burrows (PSU), S. Lanava (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), S. Campana (INAF-OAB), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Fermi/GBM-detected burst GRB 260127B (The Fermi GBM team, GCN Circ. 43533), collecting 985 s of Photon Counting (PC) mode data between T0+70.4 ks and T0+71.4 ks. No X-ray sources have been detected consistent with the tentative GOTO optical afterglow candidate (O’Neill et al, GCN Circ. 43538). The 3-sigma upper limit in the field ranges from ~0.01 to ~0.02 ct s^-1, corresponding to a 0.3-10 keV observed flux of 5.0e-13 to 6.9e-13 erg cm^-2 s^-1 (assuming a typical GRB spectrum). The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/ToO_GRBs/00021900. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43558. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41659] GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43557 SUBJECT: GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations DATE: 26/01/29 15:04:48 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. Volnova (IKI), A. Moskvitin (SAO RAS), N. Pankov (IKI), A. Tarasenkov (INASAN), I. Sokolov (INASAN, KIAM), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN collaboration: We observed the field of the Swift/Fermi/GBM GRB 260127A (Fermi GBM Team, GCN Circ. 43528; Klingler et al., GCN Circ. 43529; Osborne et al., GCN 43535; D'Ai et al, GCN 43539; Trigg, GCN 43546) in R-band with the RC500 telescope of the INASAN-Kislovodsk observatory starting on 2026-01-27 (UT) 23:20:50, in Rc-band with the Zeiss-1000 of the SAO RAS starting on 2026-01-28 (UT) 01:01:40, and in clear light with the 0.8-meter K-800 telescope of the Terskol observatory of INASAN 2026-01-28 (UT) 01:46:18. The optical counterpart reported previously (Saccardi & Malesani, GCN 43530; Lipunov et al., GCNs 43531, 43548; Wu et al., GCN 43537; Hagio et al., GCN 43540; Malesani et al, GCN 43543; Magnani et al., GCN 43544) is clearly detected in the stacked frame of the Zeiss-1000 and is not detected in the stacked frames of the RC500 and K-800 telescopes. Preliminary photometry and observational details are the following: Date UT start t-T0 Exp. Filter Obj. Err. UL Site/Telescope (mid,days) (n*s) (3sigma) 2026-01-27 23:20:50 0.30822 110*120 R n/d n/d 21.9 INASAN-Kislovodsk/RC500 2026-01-28 01:01:40 0.32599 15*300 Rc 22.00 0.22 22.7 SAO RAS/Zeiss-1000 2026-01-28 01:46:18 0.35748 94*30 Clear n/d n/d 21.2 Terskol/K800 The photometry is based on several nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction. We would like to thank the SAO RAS engineering team: Afanasieva I. V., Pritychenko M. A., Egorov V. A., Shaldyrvan I. V. for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/43557. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41658] GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43556 SUBJECT: GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection DATE: 26/01/29 14:50:07 GMT FROM: mariaedvige.ravasio(a)ru.nl M. E. Ravasio (ICE-CSIC and Radboud Univ.), P.G. Jonker (Radboud Univ.) and E. Burns (LSU), C. Malacaria (INAF-OAR) report on behalf of the Fermi-GBM Team: Fermi-GBM had full spatial and temporal coverage of the transient EP260128a detected by EP-WXT (H. Zhou et al., GCN 43549; H. Zhou et al., GCN 43554). There was no Fermi-GBM onboard trigger around the refined EP starting time at T0 = 2026-01-28T23:38:19 UTC (H. Zhou et al., GCN 43554). The GBM Targeted Search [1], the most sensitive, coherent search for GRB-like signals, was run in the time interval [-50;+500] s from T0, seeking signals between 64 ms and 32.768 s in duration. A transient was found, with the most significant signal at T0+145 s on a 16 s timescale, with a false alarm rate of 1.1e-05 Hz, although there is significant evidence of an earlier start of the emission. The light curve is multi-peaked, and a significant signal is also found at T0+70 s with FAR of 6.5e-05 Hz. The localisation is consistent with the EP one, with a spatial association probability of 99.3%. Among the three spectral templates tested, the transient was best-fit with a “normal” spectral template (Band function with Epeak = 230 keV, alpha = -1.0, beta = -2.3) for a GRB. [1] Goldstein et al. 2019 arXiv:1903.12597 View this GCN Circular online at https://gcn.nasa.gov/circulars/43556. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41657] EP260128a: NOT optical counterpart candidate
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43555 SUBJECT: EP260128a: NOT optical counterpart candidate DATE: 26/01/29 11:54:22 GMT FROM: L. B. He at NAOC <helb(a)bao.ac.cn> L.B. He, J. An, X. Liu, S.Q. Jiang, Z.P. Zhu, D. Xu (NAOC), S.Y. Fu (HUST), J.P.U. Fynbo (DAWN/NBI), N. Pyykkinen (NOT) report on behalf of a large collaboration: We observed the field of EP260128a (Zhou et al., GCN 43549) using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations started at 00:13:10 UT on 2026-01-29, i.e., 33.18 minutes after the EP trigger, and we obtained 9 x 90 s frames in the Sloan r-band and 9 x 100 s frames in the Sloan z- band. The stacked r- and z- band images have 3-sigma depth of r ~ 24.1 and z ~ 23.5, calibrated with nearby Pan-STARRS1 DR2 stars and not corrected for Galactic extinction. A new optical source is detected in the stacked z-band image within the EP/FXT error circle (Zhou et al., GCN 43554) at coordinates RA = 08:33:18.08 (128.32533) DEC = -10:16:32.3 (-10.27565) to ~ 4.2-sigma and we measured z = 23.07 +/- 0.26 (AB) at 1.004 hrs post-trigger. This source is not present in the z-band Legacy Survey DR11 early image v2, which is a bit deeper than the z-band NOT image. This source is also not present in the stacked r-band NOT image, as well as the r-band Legacy Survey image that is deeper than the NOT image. Considering the r-band non-detection and the z-band (weak) detection for the NOT candidate, EP260128a might be a high-redshift (i.e., z > ~5) event. We also note that the counterpart candidate by Liverpool Telescope (Eyles-Ferris et al., GCN 43553) is not present in neither r-band nor z-band stacked NOT image. Further optical and near-infrared follow-ups are encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/43555. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41656] EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43554 SUBJECT: EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations DATE: 26/01/29 10:01:54 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Zhou (PMO, CAS), T. Wu, H.-C. Ding (AHNU), Z.-X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP260128a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Zhou et al., GCN 43549). The refined analysis of the WXT data shows that the event started at T0=2026-01-28T 23:38:19(UTC), and lasted for approximately 100 seconds, after which the WXT light curve was interrupted due to the autonomous follow-up observation. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 5.84×10^20 cm^-2 and a photon index of 0.05 +/- 0.73. The derived average unabsorbed 0.5-4 keV flux is 6.98(-4.40/+11.93)×10^(-9) erg/s/cm^2. The Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously at 2026-01-28T23:43:01(UTC, T0+282 s). The exposure time of this observation is 2102s. On-ground analysis of the FXT data found an uncatalogued source at R.A. = 128.3253, DEC = -10.2750 (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic), which is consistent with the WXT position. The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 5.84×10^20 cm^-2 and a photon index of 1.99 +/-0.06. The derived average unabsorbed 0.5-10 keV flux is (2.76 +/- 0.15)×10^(-11) erg/s/cm^2. The best-fitted FXT spectra show no additional absorption is required. Further FXT follow-up observations have been arranged. Although a faint counterpart of EP260128a has been reported (Lipunov et al., GCN 43550; Quirola-Vasquez et al., GCN 43552; Eyles-Ferris et al., GCN 43553), further multi-band follow-up observations are encouraged to explore the nature of EP260128a. 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/43554. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41655] EP260128a: Liverpool Telescope optical observations and possible counterpart
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43553 SUBJECT: EP260128a: Liverpool Telescope optical observations and possible counterpart DATE: 26/01/29 09:33:37 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris and R. L. C. Starling (Leicester) report on behalf of a larger collaboration: We observed the field of EP260128a (Zhou et al., GCN 43549) with the 2m Liverpool Telescope on La Palma using the IO:O instrument. We obtained 6x150s exposures in each of the SDSS r’ and SDSS g’ filters starting at 2026-01-28 23:56:39 UT, approximately 16.6 minutes after the X-ray detection. We performed image subtraction on the stacked images using reference images from Pan-STARRS and Legacy DR11 and also compared the stacked and reference images manually. In the r’ stack and within the EP/FXT localisation, we tentatively identify a low significance source at a position RA 08:33:18.17 (128.32569 deg) Dec -10:16:19.3 (-10.27202 deg) The source is detected to ~2.6-sigma and we measure r’ = 22.92 +/- 0.38. The source is not visible in the g’ stack (started ~18 minutes later). We derive 3-sigma upper limits for our stacked images of r’ > 22.8 and g’ > 22.5 with AB photometry calibrated to Pan-STARRS and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43553. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41654] EP260128a: LCO optical upper limits
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43552 SUBJECT: EP260128a: LCO optical upper limits DATE: 26/01/29 07:47:19 GMT FROM: Jonathan Quirola at Radboud University <jaquirola1990(a)gmail.com> J. A. Quirola-Vasquez (Radboud), J. N. D. van Dalen (Radboud), J. Chacón(PUC), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud), A. J. Levan (Radboud), D. B. Malesani (DAWN/NBI and Radboud), and F. E. Bauer (SSI and UTA) report on behalf of a larger collaboration: We observed the field of the fast X-ray transient EP260128a (Zhou et al., GCN 43549) using an LCO 1m telescope located at the Cerro Tololo Inter-American Observatory (Chile) equipped with the SINISTRO instrument. A series of 6x300 s exposures was taken in each of the SDSS-r filter, starting on 2026-01-29 at 02:05:48 UT (2.43 hr after the trigger). No new source is detected within or at the border of the EP/FXT uncertainty region (Zhou et al., GCN 43549) compared to Legacy DR11. From the stacked images, we obtain the following 3-sigma upper limits:  r > 22.5 These upper limits are in AB magnitudes, calibrated using nearby stars from the Pan-STARRS catalog, and are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43552. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41653] EP260126a: SVOM/VT optical upperlimit
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43551 SUBJECT: EP260126a: SVOM/VT optical upperlimit DATE: 26/01/29 07:03:18 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Y. N. Ma, Z. H. Yao, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM/VT performed ToO osbervation on EP260126a (Fu et al., GCN 43520). The observation started on 2026-01-26T16:14:40 UT (i.e. 11.837 hour after trigger) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously. No uncatalogued sources are detected in single or stacked images within error box of EP-FXT (Fu et al., GCN 43520). The 3 sigma limit magnitudes are derived as below: Mid time | Band | Exposure Time | 3 sigma limit magnitude 13.907 hour VT_B 29*70 sec >23.4 mag 13.907 hour VT_R 29*70 sec >22.9 mag Our non-detection is consistent with earlier reports from other telescopes (Zhu et al., GCN 43521; Globus et al., GCN 43522; Eyles-Ferris et al., GCN 43523; Eyles-Ferris & Habeeb, GCN 43524; Lee et al., GCN 43525; Taguchi et al., GCN 43541). 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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/43551. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41652] EP260128a: Global MASTER-Net observations report
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43550 SUBJECT: EP260128a: Global MASTER-Net observations report DATE: 26/01/29 06:54:20 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-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP260128a ( EP Team et al., GCN 43549) errorbox 9549 sec after notice time and 17258 sec after trigger time at 2026-01-29 04:27:37 UT, with upper limit up to 19.9 mag. The observations began at zenith distance = 21 deg. The sun altitude is -40.7 deg. The galactic latitude b = 18 deg., longitude l = 235 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3117956 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 17289 | 2026-01-29 04:27:37 | MASTER-OAFA | (08h 29m 07.40s , -10d 15m 51.1s) | C | 60 | 18.7 | 17364 | 2026-01-29 04:28:53 | MASTER-OAFA | (08h 29m 12.43s , -10d 16m 52.4s) | C | 60 | 13.8 | 25520 | 2026-01-29 06:44:48 | MASTER-OAFA | (08h 33m 35.30s , -09d 55m 35.4s) | C | 60 | 19.9 | 25597 | 2026-01-29 06:46:06 | MASTER-OAFA | (08h 33m 42.32s , -09d 56m 34.0s) | C | 60 | 19.9 | 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/43550. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41651] EP260128a: Einstein Probe detection of an X-ray transient
by GCN Circulars 29 Jan '26

29 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43549 SUBJECT: EP260128a: Einstein Probe detection of an X-ray transient DATE: 26/01/29 01:47:47 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Zhou (PMO, CAS), T. Wu, H.-C. Ding (AHNU), Z.-X. Ling (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 EP260128a. The transient triggered EP-WXT (ID: 01709253190) at 2026-01-28T23:39:59 (UTC). The WXT position of the source is R.A. = 128.303 deg, DEC = -10.281 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. = 128.3233 deg, DEC = -10.2767 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/43549. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41650] Fermi GRB 260127A: Global MASTER-Net observations report
by GCN Circulars 28 Jan '26

28 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43548 SUBJECT: Fermi GRB 260127A: Global MASTER-Net observations report DATE: 26/01/28 23:15:22 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 260127A ( Fermi GBM team, GCN 43528) errorbox 1 days 15723 sec after notice time and 1 days 15745 sec after trigger time at 2026-01-28 22:13:32 UT, with upper limit up to 16.8 mag. The observations began at zenith distance = 80 deg. The sun altitude is -63.0 deg. The galactic latitude b = 45 deg., longitude l = 357 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3117030 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 102175 | 2026-01-28 22:13:32 | MASTER-Kislovodsk | (14h 51m 08.24s , +02d 48m 33.2s) | C | 60 | 16.6 | 102578 | 2026-01-28 22:20:15 | MASTER-Kislovodsk | (15h 05m 19.35s , +04d 43m 03.8s) | C | 60 | 16.6 | 102789 | 2026-01-28 22:23:46 | MASTER-Kislovodsk | (15h 03m 14.11s , +02d 50m 18.9s) | C | 60 | 16.5 | 102901 | 2026-01-28 22:25:38 | MASTER-Kislovodsk | (14h 49m 55.15s , -00d 58m 21.9s) | C | 60 | 16.8 | 103234 | 2026-01-28 22:31:11 | MASTER-Kislovodsk | (15h 02m 06.17s , +00d 55m 55.7s) | C | 60 | 16.8 | 103454 | 2026-01-28 22:34:51 | MASTER-Kislovodsk | (14h 50m 37.84s , -02d 52m 07.1s) | C | 60 | 16.5 | 103569 | 2026-01-28 22:36:46 | MASTER-Kislovodsk | (15h 15m 11.23s , +02d 50m 27.3s) | C | 60 | 16.5 | 103928 | 2026-01-28 22:42:46 | MASTER-Kislovodsk | (15h 13m 59.01s , +00d 56m 55.7s) | C | 60 | 16.6 | 104040 | 2026-01-28 22:44:38 | MASTER-Kislovodsk | (14h 52m 27.85s , -04d 45m 35.0s) | C | 60 | 16.6 | 104156 | 2026-01-28 22:46:33 | MASTER-Kislovodsk | (15h 02m 42.73s , -02d 51m 50.3s) | C | 60 | 16.6 | 104268 | 2026-01-28 22:48:25 | MASTER-Kislovodsk | (15h 27m 17.10s , +02d 49m 26.6s) | C | 60 | 16.5 | 104390 | 2026-01-28 22:50:27 | MASTER-Kislovodsk | (15h 13m 49.40s , -00d 57m 33.9s) | C | 60 | 16.6 | 104620 | 2026-01-28 22:54:17 | MASTER-Kislovodsk | (15h 26m 00.01s , +00d 54m 54.2s) | C | 60 | 16.5 | 104726 | 2026-01-28 22:56:03 | MASTER-Kislovodsk | (15h 04m 25.84s , -04d 43m 38.4s) | C | 60 | 16.7 | 104959 | 2026-01-28 22:59:56 | MASTER-Kislovodsk | (14h 55m 16.13s , -06d 36m 58.7s) | C | 60 | 16.7 | 105183 | 2026-01-28 23:03:40 | MASTER-Kislovodsk | (15h 25m 53.63s , -00d 56m 48.2s) | C | 60 | 16.7 | 105413 | 2026-01-28 23:07:30 | MASTER-Kislovodsk | (15h 07m 22.73s , -06d 39m 00.3s) | C | 60 | 16.6 | 105526 | 2026-01-28 23:09:23 | MASTER-Kislovodsk | (15h 16m 34.84s , -04d 44m 35.6s) | C | 60 | 16.8 | 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/43548. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41649] IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
by GCN Circulars 28 Jan '26

28 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43547 SUBJECT: IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility DATE: 26/01/28 21:37:15 GMT FROM: Robert David Stein at JSI <rdstein(a)umd.edu> Robert Stein (JSI), Jannis Necker (Leiden University), Akshay Eranhalodi (DESY), and Anna Franckowiak (Ruhr University Bochum) report, On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: As part of the ZTF neutrino follow up program (Stein et al. 2023), we observed the localization region of the neutrino event IceCube-260125A (Zegarelli et. al, GCN 43512) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started observations in the g- and r-band beginning at 2026-01-25 11:15 UTC, approximately 1.1 hours after event time. We covered 100.0% (1.3 sq deg) of the reported localization region. This estimate accounts for chip gaps. Each exposure was 300s with a typical depth of 21.0 mag. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019, Stein et al. 2021) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019). No candidate counterparts were detected. 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. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019). Alert filtering is performed with the nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ). View this GCN Circular online at https://gcn.nasa.gov/circulars/43547. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41648] GRB 260127A: Fermi GBM Observation
by GCN Circulars 28 Jan '26

28 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43546 SUBJECT: GRB 260127A: Fermi GBM Observation DATE: 26/01/28 18:26:39 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 17:51:07.74 UT on 27 January 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260127A (trigger 791229072/260127744), which was also detected by Swift BAT and XRT (N. J. Klingler et al. 2026, GCN 43529). The Fermi GBM real-time localization (GCN 43528) is consistent with the Swift BAT position. The angle from the Fermi LAT boresight is 88 degrees. The GBM light curve single emission episode with a duration (T90) of about 36 s (50-300 keV). The time-averaged spectrum from T0-15 to T0+32 s is best fit by a power law function. The power law index is -1.55 +/- 0.04. A Comptonized model fits the spectra equally well with power law index is -1.29 +/- 0.06 and the cutoff energy, parameterized as Epeak, is 490 +/- 25 keV. The event fluence (10-1000 keV) in this time interval is (3.8 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.32 s in the 10-1000 keV band is 2.7 +/- 0.5 ph/s/cm^2. 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/43546. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41647] IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 28 Jan '26

28 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43545 SUBJECT: IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube DATE: 26/01/28 17:45:24 GMT FROM: Sam Hori at IceCube/U Wisc-Madison <sahori(a)wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-260125A (https://gcn.nasa.gov/circulars/43512) in a time range of 1000 seconds centered on the alert event time (2026-01-25 10:01:19.880 UTC to 2026-01-25 10:17:59.880 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-260125A. We report a p-value of 1.00 in this time window. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, ranges from 1.3e-01 to 1.4e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-260125A in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 3e+02 GeV and 1e+05 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2026-01-24 10:09:39.880 UTC to 2026-01-26 10:09:39.880 UTC). In this case, we report a p-value of 1.00, consistent with no significant excess of track events. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, is 1.5e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-260125A in a 2 day time window. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/43545. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41646] GRB 260127A: COLIBRÍ optical observations
by GCN Circulars 28 Jan '26

28 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43544 SUBJECT: GRB 260127A: COLIBRÍ optical observations DATE: 26/01/28 17:12:02 GMT FROM: F. Magnani at Aix-Marseille Université, CPPM/CNRS <francesco.magnani.work(a)gmail.com> Francesco Magnani (CPPM), Diego López-Cámara (UNAM), Jean-Grégoire Ducoin (CPPM), 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), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Nikos Mandarakas (LAM), Enrique Moreno Méndez (UNAM), 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 Swift/Fermi/GBM GRB 260127A (Fermi GBM Team, GCN Circ. 43528, Klingler et al., GCN Circ. 43529) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-01-28 09:48 to 13:24 UTC (from 16.0 to 19.5 hours after the trigger) and obtained 110 minutes of simultaneous exposure in the r and z filters. The data were reduced and coadded with the COLIBRÍ pipeline and analysed 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. At the location of the optical counterpart reported by Saccardi et al. (GCN Circ. 43530), consistent with the X-ray counterpart reported by Evans et al. (GCN Circ. 43532) and Osborne et al. (GCN Circ. 43535), we marginally detect a source at a preliminary magnitude of: r = 22.80 +/- 0.28 At this same position, we measure the following 3-sigma upper limit: z > 21.6 Our observations suggest the candidate has faded since the observations reported by Saccardi et al. (GCN Circ. 43530), Wu et al. (GCN Circ. 43537), and Hagio et al. (GCN CIrc. 43540). 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/43544. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41645] GRB 260127A: NOT optical observations
by GCN Circulars 28 Jan '26

28 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43543 SUBJECT: GRB 260127A: NOT optical observations DATE: 26/01/28 16:53:18 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), L. B He (NAOC), G. Corcoran (UCD), K. Valeckas (NOT & NBI), L. Izzo (INAF/OAC and DARK/NBI), A. Martin-Carrillo (UCD), A. Saccardi (CEA/Irfu), B. Schneider (LAM) report on behalf of a larger collaboration: We observed the optical counterpart (Saccardi & Malesani, GCN 43530; Wu et al., GCN 43537; Hagio et al., GCN 43540) of GRB 260127A (Klingler et al., GCN 43529; Fermi GBM team, GCN 43528) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were carried out in the SDSS i, z, and r filters (with exposure times 3x300, 5x200, and 3x300 s, respectively). The optical counterpart is detected in the stacked images for all bands. We report the following magnitudes: | Filter | Epoch (UT) | Time since GRB (hr) | Exp time (s) | Magnitude (AB) | | ------ | ---------- | ------------------- | ------------ | -------------- | | i | Jan 28.197 | 10.88 | 3x300 | 22.30 +- 0.08 | | z | Jan 28.209 | 11.18 | 5x200 | 22.05 +- 0.18 | | r | Jan 28.243 | 12.00 | 3x300 | 22.30 +- 0.06 | The above magnitudes are calibrated against the Pan-STARRS catalog and are not corrected for Galactic extinction. We note that at the coordinates of the optical counterpart a faint source is reported in the Legacy Survey catalogue. Considering its tabulated magnitudes (r = 23.3, i = 23.2, z = 22.3), the transient emission is thus significantly contaminated by the host flux. View this GCN Circular online at https://gcn.nasa.gov/circulars/43543. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41644] GRB 260127B: Swift ToO observations
by GCN Circulars 28 Jan '26

28 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43542 SUBJECT: GRB 260127B: Swift ToO observations DATE: 26/01/28 15:34:04 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the Fermi/GBM-detected event GRB 260127B. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021900 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the Fermi/GBM event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43542. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41643] EP260126a: Seimei/TriCCS optical upper limit
by GCN Circulars 28 Jan '26

28 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43541 SUBJECT: EP260126a: Seimei/TriCCS optical upper limit DATE: 26/01/28 14:52:16 GMT FROM: Kenta Taguchi <kentagch(a)kusastro.kyoto-u.ac.jp> Kenta Taguchi (Kyoto University) reports on behalf of a larger collaboration: We observed the field of EP260126a detected by the Einstein Probe (Fu et al., GCN 43520) using the Tricolor CMOS Camera and Spectrograph (TriCCS) on the 3.8-m Seimei Telescope at the Okayama Observatory of Kyoto University. Our observation started at 13:30:04 UT on 2026-01-26 (MJD = 61066.5625). For each band, we took 30-second exposures 62 times (i.e., the total exposure time is 1860 s = 31 min). From our preliminary analysis, the 5-sigma limiting magnitudes are 21.74, 21.36, and 21.33 AB mag for g, r, and i-band, respectively. We detected no transient sources in the FXT error circle. View this GCN Circular online at https://gcn.nasa.gov/circulars/43541. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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