GRB 260208A
GCN Circular 43952
Subject
GRB 260208A: radio detection with the VLA
Date
2026-03-10T09:40:09Z (7 months ago)
From
Stefano Giarratana at INAF-OAB <s.giarratana@ira.inaf.it>
Via
email
S. Giarratana (INAF-OAB), M. Giroletti (INAF-IRA),
G. Ghirlanda (INAF-OAB), N. Di Lalla (Stanford Univ.),
N. Omodei (Stanford Univ.), O. S. Salafia (INAF-OAB),
L. Nava (INAF-OAB)
At 05:24:16 UT on 2026 February 10 (T_mid = 2.04 days
post-burst) the Karl G. Jansky VLA observed the field of
GRB 260208A (Fermi GBM team, GCN 43635, 43673; Fermi-LAT
team, GCN 43645; GECAM team, GCN 43658; Waratkar et al.,
GCN 43674; Cheung et al., GCN 43675; Kirschner et al.,
GCN 43896) in three bands, with central frequencies of 6,
10 and 15 GHz.
The standard 3C286 was used as bandpass, flux density
and phase calibrator.
From a preliminary analysis, an unresolved radio source
is detected at a position (J2000):
RA: 13:38:55.595 +- 0.001
Dec: +33:48:06.12 +- 0.01
consistent with the X-ray (Swift-XRT team, GCN 43652) and
optical (Podesta et al., GCN 43640; GOTO collaboration,
GCN 43641; SVOM/VT team, GCN 43655; ZTF collaboration,
GCN 43657; Dimple et al., GCN 43661; Magnani et al.,
GCN 43664; Gupta et al., GCN 43665; Volnova et al., GCN
43666, 43770, 43771; Bochenek et al., GCN 43676;
Pérez-Fournon et al., GCN 43694; Swift/UVOT team, GCN
43702) position of the transient.
The preliminary analysis yields the following results:
================================================================
T_mid Freq Peak r.m.s. Beam PA
[days] [GHz] [uJy/b] [uJy/b] [arcsec^2] [deg]
================================================================
2.04 6 59 7 1.57x0.31 -60
2.04 10 90 8 1.27x0.18 -57
2.04 15 125 10 1.02x0.14 -55
================================================================
No source is detected with a >3sigma confidence level at the
aforementioned position in the VLASS. However, the r.m.s. noise
level of the survey at the GRB location is approximately 130 uJy/b.
We would like to thank the staff of the VLA for approving, executing,
and processing the observations.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc.
These observations were carried out as part of project SF181027,
approved in the framework of the Fermi - NRAO joint program agreement.
GCN Circular 43896
Subject
GRB 260208A: TERI Gamma-ray detection
Date
2026-03-02T15:52:13Z (7 months ago)
From
nicholasjkirschner@gmail.com
Via
Web form
Nicholas Kirschner (a), Daniel Shy (b), C.C. Cheung (b), Bernard Phlips (b), Michael Streicher (c), James Mason (c), Douglas M. Groves (c), Feng Zhang (c), and Willy Kaye (c)
(a) National Research Council Research Associate resident at the U.S. Naval Research Laboratory, 4555 Overlook Ave SW, Washington, DC 20375
(b) U.S. Naval Research Laboratory, 4555 Overlook Ave SW, Washington, DC 20375
(c) H3D, Inc., 812 Avis Dr., Ann Arbor, MI 48108, USA
The cadmium zinc TElluride Radiation Imager (TERI) gamma-ray telescope [1], operating on the International Space Station, reports the detection of GRB 260208A, which was also detected by Fermi/GBM (GCN 43635, 43673), Fermi/LAT (GCN 43645), GECAM-B (GCN 43658), NuSTAR (GCN 43674), and Glowbug (GCN 43675).
Using 1 Hz binning, we find a burst onset at T0 = 2026-02-08T05:07:28 and three emission peaks with excesses of 192, 165, and 130 counts per second (cps) above the 33.2 cps baseline rate observed in nearby off-source intervals, at ~T0+15.5s, 23.5s, and 35.5s, respectively. We use all counts between 40 keV and 3 MeV.
The analysis results presented here are preliminary and currently lack a detailed response function.
TERI is an Office of Naval Research funded technology demonstrator for large-volume pixelated CdZnTe detectors developed, built, and operated by the U.S. Naval Research Laboratory (NRL) in conjunction with H3D, Inc. The pixelated CdZnTe detectors have an energy range of 40 keV to 3 MeV per pixel. It was launched on 2025 April 21 aboard the Department of Defense Space Test Program STP-H10 to the ISS. On the ISS, it is located on the SOX external payload facility on the Columbus module. Analysis of TERI data at NRL is supported by the Office of Naval Research 6.1.
[1] Shy, Daniel, et al. "Development of the cadmium zinc TElluride Radiation Imager." Journal of Astronomical Telescopes, Instruments, and Systems 10.4 (2024): 044009-044009 (arXiv:2408.04559).
Distribution Statement A: Approved for public release. Distribution is unlimited.
GCN Circular 43771
Subject
GRB 260208A: AbAO and Terskol optical upper limits
Date
2026-02-17T14:19:08Z (7 months ago)
From
Alina Volnova at IKI RAS <alinusss@gmail.com>
Via
Web form
A. Volnova (IKI), R. Ya. Inasaridze (AbAO), I. Sokolov (INASAN, KIAM), A. Pozanenko (IKI), N. Pankov (IKI) report on behalf of IKI-GRB-FuN:
We observed the field of GRB 260208A (Fermi GBM team, GCN 43635; Sonawane et al. 2026, GCN 43642; Longo et al. 2026, GCN 43645; Dichiara et al. 2026, GCN 43652; Luo et al. 2026, GCN 43658; Mukherjee & Meegan, GCN 43673; Waratkar & Grefenstette, GCN 43674; Cheung et al., GCN 43675) at z = 2.36 (Dimple et al., GCN 43662) with the 0.7-meter AS-32 telescope of Abastumani Observatory (AbAO) and with the 2-meter Zeiss-2000 telescope of the Terskol observatory on Feb. 10 taking several R-filter exposures. We do not detect the optical counterpart (Lipunov et al., GCN 43640; Wortley et al., GCN 43641; Dichiara et al., GCN 43652; Ma et al., GCN 43655; Ahumada et al., GCN 43657; Dimple et al., GCN 43661; Magnani et al., GCN 43664; Gupta et al., GCN 43665; Volnova et al., GCN 43666, 43770; Pérez-Fournon et al., GCN 43694; Kuin & Cenko, GCN 43702) in the stacked frames of both 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)
2026-02-10 21:58:14 2.77172 65*120 R n/d n/d 20.4 AbAO/AS-32
2026-02-10 23:52:31 2.81612 21*150 R n/d n/d 21.2 Terskol/Zeiss-2000
The photometry is based on nearby SDSS stars (R-magnitudes obtained using the 2005 Lupton transformation equations) and is not corrected for Galactic extinction.
GCN Circular 43770
Subject
GRB 260208A: continued Mondy optical observations
Date
2026-02-17T14:07:31Z (7 months ago)
From
Alina Volnova at IKI RAS <alinusss@gmail.com>
Via
Web form
A. Volnova (IKI), E. Klunko (ISTP), N. Pankov (IKI), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN:
We observed the field of GRB 260208A (Fermi GBM team, GCN 43635; Sonawane et al. 2026, GCN 43642; Longo et al. 2026, GCN 43645; Dichiara et al. 2026, GCN 43652; Luo et al. 2026, GCN 43658; Mukherjee & Meegan, GCN 43673; Waratkar & Grefenstette, GCN 43674; Cheung et al., GCN 43675) at z = 2.36 (Dimple et al., GCN 43662) with the AZT-33IK 1.5m telescope of the Mondy observatory on Feb. 9 and 10 taking several 120-seconds frames in the R band. The optical counterpart (Lipunov et al., GCN 43640; Wortley et al., GCN 43641; Dichiara et al., GCN 43652; Ma et al., GCN 43655; Ahumada et al., GCN 43657; Dimple et al., GCN 43661; Magnani et al., GCN 43664; Gupta et al., GCN 43665; Volnova et al., GCN 43666; Pérez-Fournon et al., GCN 43694; Kuin & Cenko, GCN 43702) is detected in the stacked frame from Feb. 09, and is not detected on the next day.
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)
2026-02-09 17:00:51 1.51973 35*120 R 21.58 0.10 22.6 Mondy/AZT-33IK
2026-02-10 17:58:12 2.55608 30*120 R n/d n/d 22.6 Mondy/AZT-33IK
The photometry is based on nearby SDSS stars (R-magnitudes obtained using the 2005 Lupton transformation equations) and is not corrected for Galactic extinction.
GCN Circular 43702
Subject
GRB 260208A: Swift UVOT detection
Date
2026-02-11T17:42:26Z (7 months ago)
Edited On
2026-02-12T13:47:33Z (7 months ago)
From
Paul Kuin at MSSL <npkuin@gmail.com>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Paul Kuin at MSSL <npkuin@gmail.com>
Via
email
Paul Kuin (MSSL/UCL) and Brad Cenko (NSA/GSFC) reports on behalf of
the Swift/UVOT team:
The Swift/UVOT began observations of the Fermi-detected GRB 260208A
35.4 ks after the Fermi Trigger (Fermi GBM team, GCN Circ. 43635;
Longo et al., GCN Circ. 43645). We detect the afterglow at the position
given by Podesta et al., GCN Circ. 43640. Preliminary 3-sigma upper
limits using the UVOT photometric system (Breeveld et al. 2011,
AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure
and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 35662.9 41566.1 1208 20.84 +/-0.10
white 46325.8 47072.6 735 21.45 +/-0.21
u 35131.3 40857.7 1208 20.34 +/-0.14
u 45572.3 46319.1 735 20.12 +/-0.15
v 36195.1 47089.2 938 20.01 +/-0.32
GCN Circular 43694
Subject
GRB 260208A: LCO detection of the optical counterpart
Date
2026-02-11T12:33:24Z (7 months ago)
From
Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf@iac.es>
Via
Web form
I. Pérez-Fournon (IAC and ULL), F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz,
I. Correa-Plasencia, E. Lekaroz-Urriza, M. Quintana-Ansaldo (all ULL), and A. López-Oramas (IAC and ULL)
Following the detection of the bright and long GRB 260208A detected by Fermi GMB (Fermi GBM Team, GCN #43635; Mukherjee and Meegan, GCN #43673), Fermi LAT (Longo et al., GCN #43645), Swift-XRT (Dichiara et al., GCN #43652; Longo et al., GCN #43643), GECAM-B (Luo et al., GCN #43658), NuSTAR (Waratkar et al., GCN #43674), and Glowbug (Cheung et al., GCN #43675), we observed the field with one of the
three Las Cumbres Observatory (LCO) 1-m telescopes located at the LCO node at Cerro Tololo Inter-American Observatory (CTIO), Chile. The observation, a single exposure of 300 sec in the SDSS r' filter, started on 2026-02-09 at 07:48:36 UT, about 26.69 hours after the Fermi trigger. The optical counterpart AT 2026ciw (MASTER OT J133855.62+334806.9, GOTO26aob, ZTF26aafswob) first detected by Podesta et al. (MASTER, GCN #43640) and Wortley et al. (GOTO, GCN #43641) is detected in our image with an AB magnitude of r' = 20.92 +/- 0.17, calibrated against PanSTARRS-1 DR2 stars and not corrected for Galactic extinction. This result is consistent with the late evolution of the optical afterglow of this redshfit z = 2.36 GRB (Dimple et al., GCN #43662).
Optical detections have been reported by Podesta et al. (GCN #43640), Wortley et al. (GCN #43641), Ma et al. (GCN #43655), Ahumada et al. (GCN #43657), Dimple et al. (GCN #43661), Dimple et al. (GCN #43662), Magnani et al. (GCN #43664), Gupta et al. (GCN #43665), Volnova et al. (GCN #43666), and Bochenek et al. (GCN #43676).
This work makes use of observations from the Las Cumbres Observatory global telescope network (LCO program IAC2026A-011, SGLF and Superluminous Supernovae surveys).
This work made use of the Astro-COLIBRI platform (P. Reichherzer et al. 2021, ApJS, 256, 5).
GCN Circular 43676
Subject
GRB260208A: Liverpool Telescope optical follow-up observations
Date
2026-02-10T00:51:14Z (8 months ago)
Edited On
2026-02-10T17:39:27Z (8 months ago)
From
A. Bochenek at Liverpool John Moores University <a.m.bochenek@2023.ljmu.ac.uk>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of A. Bochenek at Liverpool John Moores University <a.m.bochenek@2023.ljmu.ac.uk>
Via
Web form
A. Bochenek, J. Wise, D. A. Perley (LJMU), report:
We observed the field of GRB260208a (Fermi GBM team, GCN 43635; Sonawane et al., GCN 43642; Longo et al., GCN 43645; Luo et al., GCN 43658; Mukherjee et al. GCN 43673; Waratkar et al., GCN 43674, Cheung et al., GCN 43675) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained two epochs of 3x100s exposures in the SDSS r, i, z filters and 4x100s in SDSS g, starting at 2026-02-09 02:49:11 UT, approximately 21.7 hours after trigger, and the second epoch at 24.4 hours after the trigger.
We report detections in stacked images in all filters at the position first reported by Lipunov et al., GCN 43640 and Wortley et al., GCN 43641, although we note some exposures were discarded due to poor seeing or telescope movement.
MJD (mid) T_mid-T_0 Filter Mag. (AB)
61080.11951 21.74 h z 20.03 ± 0.16
61080.12395 21.85 h i 20.24 ± 0.25
61080.12842 21.95 h r 20.75 ± 0.10
61080.13428 22.09 h g 21.34 ± 0.24
61080.22567 24.29 h z 20.35 ± 0.11
61080.23080 24.41 h i 20.49 ± 0.09
61080.23595 24.54 h r 20.97 ± 0.15
61080.23595 24.64 h g 21.39 ± 0.14
The photometry is consistent with measurements taken at similar time by Dimple et al., GCN 43661 and Magnani et al., GCN 43664. The photometry was obtained using nearby PanSTARRS secondary standards and was not corrected for extinction.
GCN Circular 43675
Subject
GRB 260208A: Glowbug gamma-ray detection
Date
2026-02-09T23:42:07Z (8 months ago)
From
C.C. Cheung at Naval Research Lab <Teddy.Cheung@nrl.navy.mil>
Via
Web form
C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report:
The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 260208A, which was also detected by Fermi/GBM (GCN 43635, 43673), Fermi/LAT (GCN 43645), GECAM-B (GCN 43658), and NuSTAR (GCN 43674).
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-02-08 05:07:25.856 with a duration of 53.2 s and a total significance of about 369 sigma. The Glowbug light curve comprises a triple-peaked structure as seen in the Fermi/GBM light curve (GCN 43635).
The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS.
Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12.
[1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959
[2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O
[3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108
Distribution Statement A: Approved for public release. Distribution is unlimited.
GCN Circular 43674
Subject
GRB 260208A: NuSTAR detection of prompt emission
Date
2026-02-09T21:01:46Z (8 months ago)
From
Gaurav Waratkar at Caltech <gauravwaratkar@iitb.ac.in>
Via
Web form
G. Waratkar (Caltech) and B. Grefenstette (Caltech) report on behalf of the NuSTAR Search for INteresting Gamma-ray Signals (SINGS) working group:
The NuSTAR SINGS working group reports the detection of prompt emission from the long-duration GRB 260208A in both the NuSTAR CsI anti-coincidence shields. This GRB was identified through a blind search using the CsI shield rates. Details of the search algorithm will be described in a future paper.
The NuSTAR SINGS algorithm triggered at 2026-02-08 05:07:29.00 (with a resolution ~5-seconds). This is consistent with the detections of GRB 260208A by Fermi/GBM (Fermi GBM Team, GCN Circ. 43635) and GECAM-B (Luo et al., GCN Circ. 43658).
The NuSTAR CsI shield data are recorded at 1 Hz. We detect one peak lasting for ~40-s, consistent with the detections of Fermi/GBM & GECAM-B. The peak count rate is ~4500-cps with a baseline rate of ~1000-cps during this time period. We also see marginal evidence in the signal above 100 keV in the CdZnTe detectors.
The optical counterpart (Podesta et al., GCN Circ. 43640) at RA = 204.731, Dec = 33.801 implies an offset from the NuSTAR boresight of 99-deg (i.e. from the side of the instrument) and an offset from the geocenter of 111-deg.
Lightcurves and analysis for this GRB can be found here:
https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/260208A/
Information on NuSTAR SINGS can be found here:
https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/
NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington.
GCN Circular 43673
Subject
GRB 260208A: Fermi GBM Observation
Date
2026-02-09T20:09:35Z (8 months ago)
Edited On
2026-02-10T16:38:08Z (8 months ago)
From
oindabimukherjee@gmail.com
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of oindabimukherjee@gmail.com
Via
Web form
O. Mukherjee (USRA) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
"At 05:07:28.24 UT on 08 February 2026, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 260208A (trigger 792220053/260208214),
which was also detected by Fermi-LAT (F. Longo et al. 2026, GCN 43645),
Swift XRT (S. Dichiara et al. 2026, GCN 43652),
and NOT (Dimple et al. 2026, GCN 43662) with a spectroscopic redshift of z = 2.36.
The Fermi GBM on-ground location is consistent with the Fermi-LAT position.
The angle from the Fermi LAT boresight is 80 degrees.
The GBM light curve consists of a single emission episode with a duration (T90)
of about 35.3 s (50-300 keV). The time-averaged spectrum
from T0-3.6 to T0+66.0 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.87 +/- 0.01 and the cutoff energy,
parameterized as Epeak, is 460 +/- 0.1 keV.
The event fluence (10-1000 keV) in this time interval is
(1.50 +/- 0.06)E-04 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+17 s in the 10-1000 keV band is 29.7 +/- 0.4 ph/s/cm^2.
A Band function fits the spectrum equally well
with Epeak= 328 +/- 1 keV, alpha = -0.76 +/- 0.01 and beta = -2 +/- 0.01.
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/"
GCN Circular 43667
Subject
GRB 260208A: Mondy optical observations (duplicate submission)
Date
2026-02-09T12:00:08Z (8 months ago)
Edited On
2026-02-09T15:18:02Z (8 months ago)
From
Alina Volnova at IKI RAS <alinusss@gmail.com>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov>
Via
Web form
This is a duplicate submission of GCN Circular 43666.
GCN Circular 43666
Subject
GRB 260208A: Mondy optical observations
Date
2026-02-09T11:57:27Z (8 months ago)
From
Alina Volnova at IKI RAS <alinusss@gmail.com>
Via
Web form
A. Volnova (IKI), E. Klunko (ISTP), N. Pankov (IKI), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN:
We observed the field of GRB 260208A (Fermi GBM team, GCN 43635; Sonawane et al. 2026, GCN 43642; Longo et al. 2026, GCN 43645; Dichiara et al. 2026, GCN 43652; Luo et al. 2026, GCN 43658) at z = 2.36 (Dimple et al., GCN 43662) with the AZT-33IK 1.5m telescope of the Mondy observatory on Feb. 8 starting at 20:54:02 UT and taking several 120-seconds frames in the R band. The optical counterpart (Lipunov et al., GCN 43640; Wortley et al., GCN 43641; Dichiara et al., GCN 43652; Ma et al., GCN 43655; Ahumada et al., GCN 43657; Dimple et al.,GCN 43661; Magnani et al., GCN 43664; Gupta et al., GCN 43665) is detected in the single frame.
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)
2026-02-08 20:54:02 0.66429 10*120 R 19.92 0.06 21.8 Mondy/AZT-33IK
2026-02-08 21:14:03 0.67819 10*120 R 20.14 0.07 21.8 Mondy/AZT-33IK
2026-02-08 21:34:04 0.69139 10*120 R 20.05 0.06 21.8 Mondy/AZT-33IK
The photometry is based on nearby SDSS stars (R-magnitudes obtained using the 2005 Lupton transformation equations) and is not corrected for Galactic extinction.
GCN Circular 43665
Subject
GRB 260208A: 1.3m DFOT optical detection
Date
2026-02-09T11:24:07Z (8 months ago)
From
ANSHIKA GUPTA at ARIES <anshika05180@gmail.com>
Via
Web form
Anshika Gupta, Kuntal Misra, Dhruv Jain, Pankaj Pawar, and Debalina Kar (ARIES) report:
We observed the field of GRB 260208A detected by (Fermi GBM team, GCN 43635; Sonawane et al. 2026, GCN 43642; Longo et al. 2026, GCN 43645; Dichiara et al. 2026, GCN 43652; Luo et al. 2026, GCN 43658) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2026-02-08 at 20:52:28 UT, i.e., ~ 15.75 hours after the Fermi/GBM trigger. We detect an optical afterglow in a single 300s R-band exposure at the position reported by (Podesta et al. 2026, GCN 43640). We obtain the following preliminary magnitude in the stacked image:
Date Start_UT T_start-T0 (hour) Filter Exp time (s) Magnitude
===============================================================
2026-02-08 20:52:28 ~15.75 R 300s*1 19.89 +/-0.04
The optical detection of the burst is consistent with Lipunov et al. 2026 (GCN 43637); Podesta et al. 2026 (GCN 43640); Wortley et al. 2026 (GCN 43641); Ma et al. 2026 (GCN 43655); Ahumada et al. 2026 (GCN 43657); and Dimple et al. 2026 (GCN 43661, 43662).
The magnitude is not corrected for the Galactic extinction in the direction of the burst.
Photometric calibration is performed using the standard stars from the USNO-B1.0 catalogue.
GCN Circular 43664
Subject
GRB 260208A: COLIBRÍ optical observations
Date
2026-02-09T11:14:54Z (8 months ago)
From
F. Magnani at Aix-Marseille Université, CPPM/CNRS <francesco.magnani.work@gmail.com>
Via
Web form
Francesco Magnani (CPPM), Leonardo García García (UNAM), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (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), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), 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 Fermi GRB 260208A (43635, GCN Circ. 43642, Fermi LAT, GCN Circ. 43645, GECAM-B, GCN Circ. 43658) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. 2026-02-09T08:16:25.726 to 2026-02-09T09:37:56.715 UTC (from 27.15 to 28.51 hours after the trigger) and obtained 30 minutes of simultaneous exposure in the r, z filters.
The data were reduced and coadded and analysed with the COLIBRÍ 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.
We detected the optical counterpart Lipunov et al. (GCN Circ. 43640), Wortley et al. (GCN Circ. 43641), Dichiara et al. (GCN Circ. 43652), Ma et al. (GCN Circ. 43655), Ahumada et al. (GCN Circ. 43657), Dimple et al. (GCN Circ. 43661), with measured redshift z = 2.36 (Dimple et al. GCN Circ. 43662) at a preliminary magnitude of:
r = 21.09 +/- 0.04
z = 20.64 +/- 0.06
Further 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.
GCN Circular 43662
Subject
GRB 260208A: NOT spectroscopic redshift z = 2.36
Date
2026-02-09T10:13:18Z (8 months ago)
From
Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo@gmail.com>
Via
email
Dimple (U. Birmingham), D. B. Malesani (DAWN/NBI and Radboud), A. de Ugarte Postigo (LAM), A. Saccardi (CEA/Irfu), G. Corcoran (UCD), B. P. Gompertz (U. Birmingham), L. Izzo (INAF/OAC and DARK/NBI), A. Martin-Carrillo (UCD) and S. Bijavara Seshashayana (NOT and Malmo Univ.) report on behalf of a larger collaboration:
We observed the optical counterpart AT2026ciw (Podesta et al., GCN 43640; Wortley et al., GCN 43641; Ma et al., GCN 43655; Ahumada et al., GCN 43657, Dimple et al., GCN 43661) of the GRB 260208A detected by Fermi (Fermi GBM Team, GCN 43635; Sonawane et al., GCN 43642; Longo et al., GCN 43645) and GECAM-B (Luo et al., GCN 43658), which was also detected in X-rays (Dichiara et al., GCN 43652).
Observations started at 05:45:58 UT on 9 February 2026 (24.64 hr after the burst) and consisted of 4x1200 s exposures with grism 4, covering the wavelength range between 3200 and 9600 Å.
From a preliminary reduction of the spectrum, a trough due to Lya absorption is visible at 4080 AA. From the detection of multiple absorption features, which we interpret as due to O I, C II, Si IV, Si II, C IV, Fe II, Al II, and Al III, we infer a redshift of z = 2.36.
GCN Circular 43661
Subject
GRB 260208A: Liverpool Telescope optical detection
Date
2026-02-09T10:00:09Z (8 months ago)
From
Dimple at University of Birmingham <dimplepanchal96@gmail.com>
Via
Web form
Dimple (U. Birmingham), B. P. Gompertz (U. Birmingham), D. O'Neill (U. Birmingham), and D. B. Malesani (DAWN/NBI and Radboud) report on behalf of a larger collaboration:
We conducted follow-up observations of GRB 260208A (Fermi GBM team, GCN 43635; Sonawane et al., GCN 43642; Longo et al., GCN 43645; Luo et al., GCN 43658) with the IO:O camera on the 2m robotic Liverpool Telescope (LT). Observations began at 03:49:38 UT on 2026-02-09, ~22.8 hr after the Fermi trigger, and consisted of 5 x 180 s exposures in each of the SDSS r and i filters.
We detect the optical counterpart (Podesta et al., GCN 43640; Wortley et al., GCN 43641; Ma et al., GCN 43655; Ahumada et al., GCN 43657; also detected in X-rays, Dichiara et al., GCN 43652) in both filters, and measure an AB magnitude of r = 20.63 ± 0.04.
Magnitudes are calibrated against nearby Pan-STARRS stars and are not corrected for Galactic extinction.
GCN Circular 43658
Subject
GRB 260208A: GECAM-B observation of a bright burst
Date
2026-02-09T05:50:39Z (8 months ago)
Edited On
2026-02-09T14:28:41Z (8 months ago)
From
Xinghao Luo at IHEP <2952704891@qq.com>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Xinghao Luo at IHEP <2952704891@qq.com>
Via
Web form
Xing-Hao Luo, Zheng-Hang Yu, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team:
GECAM-B was triggered in-flight by GRB 260208A, at 2026-02-08T05:07:30.550 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43635) and Fermi/LAT (Fermi LAT team, GCN #43645).
According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 38 +2/-1 s.
The GECAM-B light curve can be found here:
https://www.bursthub.cn//admin/static/gecambgrb260208A.png
The time-averaged spectrum from T0-11.5 s to T0+147.5 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.29 +0.10/-0.08 and the cutoff energy, parameterized as Epeak, is 651 +175/-134 keV. The event fluence (10-1000 keV) in this time interval is (1.62 +0..050/-0.066)E-04 erg/cm^2. Thus GRB 260208A is consistent with Type II GRBs in the 'Amati' relation diagram, as shown at:
https://www.bursthub.cn//admin/static/gecambgrb260208A_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).
GCN Circular 43657
Subject
GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
Date
2026-02-09T03:44:52Z (8 months ago)
From
Tomas Ahumada <tomas.ahumada@noirlab.edu>
Via
Web form
Tomas Ahumada (NOIRLab), Robert Stein (UMD), Theophile du Laz (CIT), Igor Andreoni (UNC), Michael Coughlin (UMN), Mansi Kasliwal (CIT), Shreya Anand (Stanford), report on behalf of the ZTF collaboration:
We observed the localization region of the long GRB 260208A (trigger 792220053.24286 / 260208214, Fermi GBM team, GCN 43635) detected by the Gamma-Ray Burst Monitor (GBM) on the Fermi satellite with the Palomar 48 inch telescope equipped with the 47 square degree Zwicky Transient Facility (ZTF) camera. We obtained a series of g- and r-band images covering 130 square degrees beginning at 2026-02-08T10:43:17 (5.6 hours after the burst trigger time). This corresponds to 93% of the probability enclosed in the Earth-occultation corrected GRB localization map. Each exposure was 300 seconds, reaching g-band and r-band median depths of 21.2 mag and 21.2 mag respectively.
The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC (Masci et al. 2019).
We queried the ZTF alert stream using Kowalski (Duev et al. 2019) through Fritz (Coughlin et al. 2023). We required at least 2 detections separated by at least 15 minutes to select against moving objects. Furthermore, we cross-match our candidates with the Minor Planet Center to flag known asteroids, reject stellar sources (Tachibana and Miller 2018), and apply machine learning algorithms (Mahabal et al. 2019). We require that no spatially coincident ZTF alerts were issued before the detection time of the GBM trigger.
We detect the afterglow candidate AT 2026ciw (Podesta et al. GCN 43640, Wortley et al. GCN 43641) as ZTF26aafswob. This is the only source that passed our filtering scheme (Ahumada et al. 2022). The most recent ZTF visit to the field was 3 days prior to the detection. The ZTF detections are reported in the following table:
Time (MJD) | Filter | Magnitude
61079.44815970 | g | 19.05 ± 0.05
61079.52940970 | r | 19.11 ± 0.05
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.
GCN Circular 43655
Subject
GRB 260208A: SVOM/VT optical observation
Date
2026-02-09T02:31:49Z (8 months ago)
From
Yinuo Ma <mayn@bao.ac.cn>
Via
Web form
Y. N. Ma, L. P. Xin, Y. L. Qiu, C. Wu, H. L. Li, 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. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team.
SVOM/VT performed a Target of Opportunity observation of GRB 260208A detected by Fermi/GBM and Fermi/LAT (Fermi GBM Team, GCN 43635; Sonawane et al., GCN 43642; Longo et al., GCN 43645). SVOM/VT began observing the field at 2026-02-08T13:57:59 UTC, 8.842 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
With X-band data available, the optical counterpart (Lipunov et al., GCN 43637; Podesta et al., GCN 43640; Wortley et al., GCN 43641) within Swift/XRT Source 1 errorbox (Dichiara et al., GCN 43652) was clearly detected in both VT_B and VT_R bands. The magnitudes are:
mid time (h) | exposure time (s) | band | mag (AB) | mag err
-------------|-------------------|------|----------|--------
10.306 | 23*70 | VT_B | 21.15 | 0.06
10.170 | 19*70 | VT_R | 20.40 | 0.04
Our photometry was not corrected for Galactic extinction.
Further SVOM/VT ToO observations are scheduled.
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.
GCN Circular 43652
Subject
GRB 260208A: Swift-XRT observations
Date
2026-02-08T21:51:33Z (8 months ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
S. Dichiara (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U.
Leicester), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), M.G.
Bernardini (INAF-OAB), J.A. Kennea (PSU), D.N. Burrows (PSU) and P.A.
Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the
Fermi/LAT-detected burst GRB 260208A, collecting 3.4 ks of Photon
Counting (PC) mode data between T0+35.1 ks and T0+42.2 ks.
Six uncatalogued X-ray sources have been detected, with Source 1
located 2.2 arcsec from the new optical source seen by MASTER and GOTO
(GCN Circ. 43640 and 43641) and, therefore, consistent with that
source. The details of this new X-ray source are:
RA (J2000.0): 204.73150 = 13h 38m 55.56s
Dec (J2000.0): +33.80112 = +33d 48' 04.0"
Error: 2.5 arcsec (radius, 90% conf. [Enhanced position])
Count-rate: 0.0488 +/- 0.0045 ct s^-1
Flux: (1.55 +/- 0.14)e-12 erg cm^-2 s^-1 (observed, 0.3-10 keV)
However, we cannot presently determine if the source is fading.
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/00021908.
This circular is an official product of the Swift-XRT team.
GCN Circular 43645
Subject
GRB 260208A: Fermi-LAT detection
Date
2026-02-08T15:21:39Z (8 months ago)
From
Davide Depalo at Politecnico and INFN Bari <davide.depalo@ba.infn.it>
Via
Web form
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@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.
GCN Circular 43643
Subject
GRB 260208A: Swift ToO observations
Date
2026-02-08T14:50:32Z (8 months ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
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.
GCN Circular 43642
Subject
GRB 260208A: Fermi GBM Classification Correction
Date
2026-02-08T14:07:05Z (8 months ago)
From
Rushikesh Sonawane at IISER, TVM <rushikesh23@iisertvm.ac.in>
Via
Web form
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)."
GCN Circular 43641
Subject
GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
Date
2026-02-08T14:01:53Z (8 months ago)
From
MEW020@student.bham.ac.uk
Via
Web form
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).
GCN Circular 43640
Subject
GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
Date
2026-02-08T12:35:14Z (8 months ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
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
GCN Circular 43637
Subject
Fermi GRB 260208A: Global MASTER-Net observations report
Date
2026-02-08T06:45:32Z (8 months ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
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
GCN Circular 43635
Subject
GRB 260208A: Fermi GBM Final Real-time Localization
Date
2026-02-08T05:18:10Z (8 months ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
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/quicklook/glg_skymap_all_bn260208214.png
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/quicklook/glg_healpix_all_bn260208214.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260208214/quicklook/glg_lc_medres34_bn260208214.gif