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[vsnet-grb-info 41751] GRB 260208B: Fermi-LAT detection
by GCN Circulars 08 Feb '26

08 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43647 SUBJECT: GRB 260208B: Fermi-LAT detection DATE: 26/02/08 16:31:58 GMT FROM: A. Holzmann Airasca at University of Trento and INFN Bari <a.holzmannairasca(a)unitn.it> F. Longo (University and INFN, Trieste), D. Depalo (Politecnico and INFN Bari), A. Holzmann Airasca (UniTrento and INFN Bari) and R. Gupta (NASA/GSFC) report on behalf of the Fermi-LAT team: At 09:52:44.91 UT on February 8th, 2026 Fermi-LAT detected high-energy emission from GRB 260208B, which was also detected by Fermi-GBM (trigger 792237169 / 260208412, GCN #43638). The best LAT on-ground location is found to be RA, Dec = 99.64, -13.84 (J2000) with an error radius of 0.06 deg (90 % containment, statistical error only). This was 13 deg from the LAT boresight at the time of the trigger. The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally correlated with the trigger with high significance. The photon flux above 100 MeV in the time interval 0 - 2 ks after the GBM trigger is (8.7 ± 1.2)E-6 ph/cm2/s. The estimated photon index above 100 MeV is -2.03 ± 0.12. The highest energy photon has an energy of 2.6 GeV and occurs at 20 s after trigger time. A Swift ToO request has been sent for this burst. The Fermi-LAT point of contact for this burst is Chiara Bartolini (chiara.bartolini(a)ba.infn.it) The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/43647. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41750] GRB 260208C: Fermi GBM Final Real-time Localization
by GCN Circulars 08 Feb '26

08 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43646 SUBJECT: GRB 260208C: Fermi GBM Final Real-time Localization DATE: 26/02/08 15:22:56 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 15:12:18 UT on 8 Feb 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260208C (trigger 792256343.59123 / 260208634). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 281.3, Dec = -49.2 (J2000 degrees, equivalent to J2000 18h 45m, -49d 12'), with a statistical uncertainty of 2.3 degrees. The angle from the Fermi LAT boresight is 82.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260208634/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260208634/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260208634/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43646. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41749] GRB 260208A: Fermi-LAT detection
by GCN Circulars 08 Feb '26

08 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43645 SUBJECT: GRB 260208A: Fermi-LAT detection DATE: 26/02/08 15:21:39 GMT FROM: Davide Depalo at Politecnico and INFN Bari <davide.depalo(a)ba.infn.it> F. Longo (University and INFN, Trieste), D. Depalo (Politecnico and INFN Bari), A. Holzmann Airasca (UniTrento and INFN Bari) and R. Gupta (NASA/GSFC) report on behalf of the Fermi-LAT team: At 05:07:28.24 UT on February 8th, 2026 Fermi-LAT detected high-energy emission from GRB 260208A, which was also detected by Fermi-GBM (trigger 792220053 / 260208214, GCN #43635), MASTER (GCN #43640) and GOTO (GCN #43641). The best LAT on-ground location is found to be RA, Dec = 204.57, 33.77 (J2000) with an error radius of 0.15 deg (90 % containment, statistical error only). This was 80 deg from the LAT boresight at the time of the trigger. The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally correlated with the trigger with high significance. The photon flux above 100 MeV in the time interval 400 - 2500 s after the GBM trigger is (2.86 ± 0.65)E-6 ph/cm2/s. The estimated photon index above 100 MeV is -1.99 ± 0.19. The highest-energy photon is a 5.3 GeV event which is observed 1168 seconds after the GBM trigger. A Swift ToO request has been approved for this burst. The Fermi-LAT point of contact for this burst is Chiara Bartolini (chiara.bartolini(a)ba.infn.it) The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/43645. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41748] GRB 260207B: GECAM-B observation
by GCN Circulars 08 Feb '26

08 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43644 SUBJECT: GRB 260207B: GECAM-B observation DATE: 26/02/08 14:58:40 GMT FROM: xueyuan zao <zaoxueyuan(a)gmail.com> Xue-Yuan Zao, Xing-Hao Luo, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight and on-ground by GRB 260207B, at 2026-02-07T13:12:10.850 UTC, which is also detected by Fermi/GBM (Fermi GBM team, GCN #43629). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of a short spike (Main Emission, ME) followed by an extended emission (EE) with a total duration (T90) of 65 +23/-9.5 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260207B.png The ME from T0 - 0.07 to T0 + 0.19 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.15 +0.29/-0.32 and the cutoff energy, parameterized as Epeak, is 345 +151/-70 keV. The event fluence (10-1000 keV) in this time interval is (2.04 +/-0.22)E-06 erg/cm^2. 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/43644. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41747] GRB 260208A: Swift ToO observations
by GCN Circulars 08 Feb '26

08 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43643 SUBJECT: GRB 260208A: Swift ToO observations DATE: 26/02/08 14:50:32 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/LAT-detected event GRB 260208A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021908 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/LAT 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/43643. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41746] GRB 260208A: Fermi GBM Classification Correction
by GCN Circulars 08 Feb '26

08 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43642 SUBJECT: GRB 260208A: Fermi GBM Classification Correction DATE: 26/02/08 14:07:05 GMT FROM: Rushikesh Sonawane at IISER, TVM <rushikesh23(a)iisertvm.ac.in> R. Sonawane (IISER, TVM), O.J. Roberts (Uni. of Galway, Ireland), and R. Hamburg (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, is in fact a GRB. The GBM localization for this GRB is valid (GCN 43635). The GRB was confirmed with an optical afterglow detection by MASTER (GCN 43640). This trigger was misclassified as a particle trigger (GCN 43636)." View this GCN Circular online at https://gcn.nasa.gov/circulars/43642. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41745] GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
by GCN Circulars 08 Feb '26

08 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43641 SUBJECT: GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob) DATE: 26/02/08 14:01:53 GMT FROM: MEW020(a)student.bham.ac.uk M. E. Wortley, D. O'Neill, A. Kumar, G. Ramsay, B. P. Gompertz, K. Ackley, M. Dyer, J. Lyman, K. Ulaczyk, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, R. Starling, 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 Fermi/GBM GRB 260208A (trigger GBM792220053; Fermi GBM team, GCN 43638). Observations covering the localisation area began at 2026-02-08 05:19:32 UT (+0.20h post trigger) and continued through to 2026-02-08 06:31:29 UT (+1.4h post trigger). All observations were performed with 90s integrations using the GOTO L-band filter (400–700 nm). Images were processed immediately after acquisition using the GOTO pipeline. 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. We detect the source reported by R. Podesta et al. (GCN 43640) with an L-band = 13.78 ± 0.01 AB mag at 2026-02-08 05:19:32 UT (t0+0.20h) before it faded to L=16.72 ± 0.01 AB mag at 2026-02-08 06:29:16 UT (t0+1.36h). We find no evidence of this source prior to the GRB trigger time in previous GOTO observations taken at 2026-02-08 03:33:31 UT (t0-1.57h pre-trigger) down to a 5-sigma depth of L>19.07 AB mag. 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/43641. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41744] GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
by GCN Circulars 08 Feb '26

08 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43640 SUBJECT: GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box DATE: 26/02/08 12:35:14 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> R.Podesta (OAFA), V.M.Lipunov (Lomonosov MSU), C. Francile, F.Podesta (OAFA), I.Panchenko (Lomonosov MSU), V.Shumkov (Ozersk), P.Balanutsa, G.Antipov, A.Kuznetsov, E.Gorbovskoy, D.Vlasenko, N. Tiurina, Ya.Kechin, A.Chasovnikov (Lomonosov MSU), D.Svinkin (Ioffe Institute), O.Gress, N.Budnev, R.Mirgazov, A.Diachok, O.Ershova (Irkutsk State University), E. Gonzalez (OAFA, San JuanUni.,Argentina); D.Buckley (SAAO), V.A.Senik, I.Ionov,Yu.Tselik(Lomonosov MSU), 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 43637) Fermi GRB 260208A (GCN 43635) MASTER OT J133855.59+334806.2 discovery MASTER-OAFA auto-detection system ( Lipunov et al., "MASTER Global Robotic Net", Advances in Astronomy, 2010, 30L ) discovered OT source at (RA, Dec) = 13h 38m 55.59s +33d 48m 06.2s during Fermi trigger 792220053 inspection (also known as GRB 260208A, retracted by Fermi team) The OT unfiltered magnitude is 15.2m at 05:33:36UT with GRB decay t^-alpha low at light curve (alpha ~ 1). We observed OT in MASTER-OAFA (Argentina) and MASTER-OAGH (Mexico) (Shumkov et al. https://www.wis-tns.org/object/2026ciw ). We have reference image on 2019-05-24.09972 UT with unfiltered 20.7m. Deep photometry and spectral observations are required. [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/43640. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41743] GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412)
by GCN Circulars 08 Feb '26

08 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43639 SUBJECT: GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412) DATE: 26/02/08 10:54:01 GMT FROM: Jochen Greiner at MPE <jcgrog(a)mpe.mpg.de> T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report: The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 792237169 at 09:52:44 on 08 Feb. 2026 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60). The best-fit position is: RA(2000.0) = 96.2 deg Decl.(2000.0) = -14.5 deg The 1 sigma statistical error radius is 0.8 deg. We estimate an additional systematic error of 1 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB260208412/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB260208412/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB260208412/json View this GCN Circular online at https://gcn.nasa.gov/circulars/43639. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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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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