Gamma-ray Burst 260208B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 08 Feb 26 09:53:14 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      45
TRIGGER_NUM:     792237169
GRB_RA:          106.250d {+07h 05m 00s} (J2000),
                 106.513d {+07h 06m 03s} (current),
                 105.747d {+07h 02m 59s} (1950)
GRB_DEC:         -27.217d {-27d 13' 00"} (J2000),
                 -27.258d {-27d 15' 27"} (current),
                 -27.140d {-27d 08' 23"} (1950)
GRB_ERROR:       25.63 [deg radius, statistical plus systematic]
GRB_INTEN:       47 [cnts/sec]
DATA_SIGNIF:     5.00 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        21079 TJD;    39 DOY;   26/02/08
GRB_TIME:        35564.91 SOD {09:52:44.91} UT
GRB_PHI:         140.00 [deg]
GRB_THETA:        15.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.81
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      97%  GRB
2nd_MOST_LIKELY:   1%  Generic Transient
DETECTORS:       0,0,0, 0,0,0, 1,1,0, 1,0,0, 0,0,
SUN_POSTN:       322.06d {+21h 28m 14s}  -14.92d {-14d 55' 26"}
SUN_DIST:        125.52 [deg]   Sun_angle= -9.6 [hr] (East of Sun)
MOON_POSTN:      213.48d {+14h 13m 55s}  -18.21d {-18d 12' 44"}
MOON_DIST:        95.93 [deg]
MOON_ILLUM:      61 [%]
GAL_COORDS:      238.83, -9.31 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      112.48,-49.40 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260208412/quicklook/glg_lc_medres34_bn260208412.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 152.10,22.68 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 08 Feb 26 09:53:23 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      58
TRIGGER_NUM:     792237169
GRB_RA:          100.900d {+06h 43m 36s} (J2000),
                 101.167d {+06h 44m 40s} (current),
                 100.388d {+06h 41m 33s} (1950)
GRB_DEC:         -25.267d {-25d 16' 00"} (J2000),
                 -25.295d {-25d 17' 39"} (current),
                 -25.215d {-25d 12' 54"} (1950)
GRB_ERROR:       4.90 [deg radius, statistical plus systematic]
GRB_INTEN:       586 [cnts/sec]
DATA_SIGNIF:     60.10 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        21079 TJD;    39 DOY;   26/02/08
GRB_TIME:        35564.91 SOD {09:52:44.91} UT
GRB_PHI:         150.00 [deg]
GRB_THETA:        10.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.47
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      95%  GRB
2nd_MOST_LIKELY:   4%  Generic Transient
DETECTORS:       0,0,0, 0,0,0, 1,1,0, 1,0,0, 0,0,
SUN_POSTN:       322.06d {+21h 28m 14s}  -14.92d {-14d 55' 26"}
SUN_DIST:        123.39 [deg]   Sun_angle= -9.3 [hr] (East of Sun)
MOON_POSTN:      213.48d {+14h 13m 55s}  -18.21d {-18d 12' 45"}
MOON_DIST:       101.10 [deg]
MOON_ILLUM:      61 [%]
GAL_COORDS:      234.97,-12.84 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      104.85,-48.15 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260208412/quicklook/glg_lc_medres34_bn260208412.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 152.10,22.68 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 08 Feb 26 09:53:33 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      69
TRIGGER_NUM:     792237169
GRB_RA:          101.217d {+06h 44m 52s} (J2000),
                 101.484d {+06h 45m 56s} (current),
                 100.704d {+06h 42m 49s} (1950)
GRB_DEC:         -25.167d {-25d 10' 00"} (J2000),
                 -25.195d {-25d 11' 42"} (current),
                 -25.114d {-25d 06' 49"} (1950)
GRB_ERROR:       4.08 [deg radius, statistical plus systematic]
GRB_INTEN:       1248 [cnts/sec]
DATA_SIGNIF:     90.60 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        21079 TJD;    39 DOY;   26/02/08
GRB_TIME:        35564.91 SOD {09:52:44.91} UT
GRB_PHI:         150.00 [deg]
GRB_THETA:        10.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      0.42
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      95%  GRB
2nd_MOST_LIKELY:   4%  Generic Transient
DETECTORS:       0,0,0, 0,0,0, 1,1,0, 1,0,0, 0,0,
SUN_POSTN:       322.06d {+21h 28m 14s}  -14.92d {-14d 55' 26"}
SUN_DIST:        123.68 [deg]   Sun_angle= -9.3 [hr] (East of Sun)
MOON_POSTN:      213.48d {+14h 13m 56s}  -18.21d {-18d 12' 47"}
MOON_DIST:       100.89 [deg]
MOON_ILLUM:      61 [%]
GAL_COORDS:      234.99,-12.53 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      105.26,-48.01 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260208412/quicklook/glg_lc_medres34_bn260208412.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 152.10,22.68 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 08 Feb 26 09:53:38 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      73
TRIGGER_NUM:     792237169
GRB_RA:          101.333d {+06h 45m 20s} (J2000),
                 101.601d {+06h 46m 24s} (current),
                 100.821d {+06h 43m 17s} (1950)
GRB_DEC:         -25.133d {-25d 07' 59"} (J2000),
                 -25.162d {-25d 09' 43"} (current),
                 -25.080d {-25d 04' 46"} (1950)
GRB_ERROR:       4.03 [deg radius, statistical plus systematic]
GRB_INTEN:       1317 [cnts/sec]
DATA_SIGNIF:     135.70 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        21079 TJD;    39 DOY;   26/02/08
GRB_TIME:        35564.91 SOD {09:52:44.91} UT
GRB_PHI:         150.00 [deg]
GRB_THETA:        10.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.45
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      95%  GRB
2nd_MOST_LIKELY:   4%  Generic Transient
DETECTORS:       0,0,0, 0,0,0, 1,1,0, 1,0,0, 0,0,
SUN_POSTN:       322.06d {+21h 28m 14s}  -14.92d {-14d 55' 26"}
SUN_DIST:        123.78 [deg]   Sun_angle= -9.3 [hr] (East of Sun)
MOON_POSTN:      213.48d {+14h 13m 56s}  -18.21d {-18d 12' 48"}
MOON_DIST:       100.81 [deg]
MOON_ILLUM:      61 [%]
GAL_COORDS:      235.01,-12.42 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      105.41,-47.97 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260208412/quicklook/glg_lc_medres34_bn260208412.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 152.10,22.68 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 08 Feb 26 09:53:33 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      57
TRIGGER_NUM:     792237169
GRB_RA:           98.670d {+06h 34m 41s} (J2000),
                  98.966d {+06h 35m 52s} (current),
                  98.103d {+06h 32m 25s} (1950)
GRB_DEC:         -14.950d {-14d 56' 59"} (J2000),
                 -14.972d {-14d 58' 19"} (current),
                 -14.909d {-14d 54' 33"} (1950)
GRB_ERROR:       1.90 [deg radius, statistical only]
DATA_SIGNIF:     25.40 [sigma]
DATA_INTERVAL:   2.048 [sec]
GRB_DATE:        21079 TJD;    39 DOY;   26/02/08
GRB_TIME:        35564.91 SOD {09:52:44.91} UT
GRB_PHI:         199.00 [deg]
GRB_THETA:        14.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:       322.06d {+21h 28m 14s}  -14.92d {-14d 55' 26"}
SUN_DIST:        127.96 [deg]   Sun_angle= -9.1 [hr] (East of Sun)
MOON_POSTN:      213.48d {+14h 13m 56s}  -18.21d {-18d 12' 47"}
MOON_DIST:       107.46 [deg]
MOON_ILLUM:      61 [%]
GAL_COORDS:      224.51,-10.40 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      100.66,-38.07 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260208412/quicklook/glg_lc_medres34_bn260208412.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_792237169.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
COMMENTS:        Bright hard burst in the GBM.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 08 Feb 26 09:54:26 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      2
TRIGGER_NUM:     792237169
GRB_RA:          100.420d {+06h 41m 41s} (J2000),
                 100.719d {+06h 42m 53s} (current),
                  99.847d {+06h 39m 23s} (1950)
GRB_DEC:         -13.850d {-13d 50' 59"} (J2000),
                 -13.877d {-13d 52' 35"} (current),
                 -13.801d {-13d 48' 03"} (1950)
GRB_ERROR:       1.12 [deg radius, statistical only]
DATA_SIGNIF:     39.40 [sigma]
DATA_INTERVAL:   11.264 [sec]
GRB_DATE:        21079 TJD;    39 DOY;   26/02/08
GRB_TIME:        35564.91 SOD {09:52:44.91} UT
GRB_PHI:         196.00 [deg]
GRB_THETA:        16.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       322.06d {+21h 28m 14s}  -14.92d {-14d 55' 25"}
SUN_DIST:        129.98 [deg]   Sun_angle= -9.2 [hr] (East of Sun)
MOON_POSTN:      213.49d {+14h 13m 58s}  -18.22d {-18d 12' 57"}
MOON_DIST:       106.38 [deg]
MOON_ILLUM:      61 [%]
GAL_COORDS:      224.25, -8.39 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      102.67,-36.83 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260208412/quicklook/glg_lc_medres34_bn260208412.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_792237169.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
COMMENTS:        Bright hard burst in the GBM.  
COMMENTS:        This is likely a Long GRB.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 08 Feb 26 09:54:56 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      6
TRIGGER_NUM:     792237169
GRB_RA:           99.700d {+06h 38m 48s} (J2000),
                 100.001d {+06h 40m 00s} (current),
                  99.123d {+06h 36m 30s} (1950)
GRB_DEC:         -13.130d {-13d 07' 47"} (J2000),
                 -13.155d {-13d 09' 17"} (current),
                 -13.084d {-13d 05' 03"} (1950)
GRB_ERROR:       1.00 [deg radius, statistical only]
DATA_SIGNIF:     120.30 [sigma]
DATA_INTERVAL:   21.504 [sec]
GRB_DATE:        21079 TJD;    39 DOY;   26/02/08
GRB_TIME:        35564.91 SOD {09:52:44.91} UT
GRB_PHI:         200.00 [deg]
GRB_THETA:        16.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       322.06d {+21h 28m 14s}  -14.92d {-14d 55' 25"}
SUN_DIST:        129.79 [deg]   Sun_angle= -9.2 [hr] (East of Sun)
MOON_POSTN:      213.49d {+14h 13m 58s}  -18.22d {-18d 13' 03"}
MOON_DIST:       107.31 [deg]
MOON_ILLUM:      61 [%]
GAL_COORDS:      223.29, -8.71 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      101.73,-36.18 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260208412/quicklook/glg_lc_medres34_bn260208412.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_792237169.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
COMMENTS:        Bright hard burst in the GBM.  
COMMENTS:        This is likely a Long GRB.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 08 Feb 26 10:02:07 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     792237169
GRB_RA:           99.890d {+06h 39m 34s} (J2000),
                 100.191d {+06h 40m 46s} (current),
                  99.313d {+06h 37m 15s} (1950)
GRB_DEC:         -13.070d {-13d 04' 11"} (J2000),
                 -13.095d {-13d 05' 42"} (current),
                 -13.024d {-13d 01' 24"} (1950)
GRB_ERROR:       1.00 [deg radius, statistical only]
GRB_DATE:        21079 TJD;    39 DOY;   26/02/08
GRB_TIME:        35564.91 SOD {09:52:44.91} UT
GRB_PHI:         200.00 [deg]
GRB_THETA:        16.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       322.06d {+21h 28m 15s}  -14.92d {-14d 55' 19"}
SUN_DIST:        129.98 [deg]   Sun_angle= -9.2 [hr] (East of Sun)
MOON_POSTN:      213.55d {+14h 14m 12s}  -18.24d {-18d 14' 24"}
MOON_DIST:       107.21 [deg]
MOON_ILLUM:      61 [%]
GAL_COORDS:      223.32, -8.51 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      101.95,-36.10 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260208412/quicklook/glg_lc_medres34_bn260208412.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260208412/quicklook/glg_locplot_all_bn260208412.png
COMMENTS:        Fermi-GBM Final Position.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file should be available by the time this FINAL notice is produced.  
COMMENTS:        This notice was generated completely by automated pipeline processing.  
COMMENTS:        In the LAT Field-of-view.  
COMMENTS:        Bright hard burst in the GBM.  
COMMENTS:        This is likely a Long GRB.

GCN Circular #43638
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/quicklook/glg_skymap_all_bn260208412.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/bn260208412/quicklook/glg_healpix_all_bn260208412.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260208412/quicklook/glg_lc_medres34_bn260208412.gif
GCN Circular #43639
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

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 08 Feb 26 14:54:13 UT
NOTICE_TYPE:     Fermi-LAT Offline Position
TRIGGER_NUM:     792237169
GRB_RA:           99.638d {+06h 38m 33s} (J2000),
                  99.937d {+06h 39m 45s} (current),
                  99.065d {+06h 36m 16s} (1950)
GRB_DEC:         -13.838d {-13d 50' 15"} (J2000),
                 -13.863d {-13d 51' 44"} (current),
                 -13.793d {-13d 47' 33"} (1950)
GRB_ERROR:       3.59 [arcmin radius, 90% containment, statistical only]
GRB_DATE:        21079 TJD;    39 DOY;   26/02/08
GRB_TIME:        35564.90 SOD {09:52:44.90} UT
TRIGGER_ID:      0x0
MISC:            0x40000000
SUN_POSTN:       322.27d {+21h 29m 04s}  -14.86d {-14d 51' 27"}
SUN_DIST:        129.22 [deg]   Sun_angle= -9.2 [hr] (East of Sun)
MOON_POSTN:      215.93d {+14h 23m 44s}  -19.14d {-19d 08' 28"}
MOON_DIST:       108.87 [deg]
MOON_ILLUM:      59 [%]
GAL_COORDS:      223.91, -9.07 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      101.73,-36.89 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi LAT Offline position.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        It is the result of human-in-the-loop processing.  
COMMENTS:        This is a human generated position of a LAT ground detection.  
COMMENTS:        This source corresponds to GBM trigger.

GCN Circular #43647
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@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 #43649
R. Sonawane (IISER, TVM) reports on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 09:52:44.91 UT on 08 February 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260208B (trigger 792237169/260208412). which was also detected by Fermi LAT (A. H. Airasca et al. 2026, GCN 43647). The Fermi GBM final real-time Localization (GCN 43638) is consistent with the Fermi LAT position.
The angle from the Fermi LAT boresight is 16 degrees.
The GBM light curve consists of two emission episodes with multiple spikes for a duration (T90) of about 145 s (50-300 keV). The time-averaged spectrum from T0-8.2 to T0+172.0 s is best fit by a Band function with Epeak = 855 +/- 61 keV, alpha = -1.0 +/- 0.02, and beta = -2.12 +/- 0.08.
The event fluence (10-1000 keV) in this time interval is (9.1 +/- 0.1)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+14 s in the 10-1000 keV band is 23 +/- 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/"
GCN Circular #43650
SVOM/GRM team: Xing-Hao Luo, Wen-Jun Tan, Chen-Wei Wang, Zheng-Hang Yu, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Hui Yang (IRAP)
Report on behalf of the SVOM team:
SVOM/GRM was triggered in-flight by GRB 260208B (SVOM trigger reference: sb26020804) at 2026-02-08T09:52:48.000 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43638) and Fermi/LAT (F. Longo et al., GCN #43647).
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multi-pulses with a T90 of 147 +1/-1 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260208B.png
In addition, the position of this burst, as determined by Fermi/GBM (RA=99.9 , DEC=-13.1, Fermi GBM team, GCN #43638), is located at about 64 degrees form the SVOM optical axis, which is outside the ECLAIRs field of view, but this burst is still clearly detected by ECLAIRs through the shield.
With this localization, the time-averaged spectrum from T0-12 to T0+166 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.01 +0.04/-0.04 and the cutoff energy parameterized as Epeak, is 830 +105/-89 keV. The event fluence (10-1000keV) in this time interval is (1.09 +0.024/-0.025)E-04 erg/cm^2.
The 1s peak spectrum, measured from T0+11 to T0+12 s, is also best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.81 +0.03/-0.03 and the cutoff energy, parameterized as Epeak, is 1520 +130/-120 keV. The flux (10-1000 keV) in this time interval is (1.011 + 0.019/-0.019)E-05 erg/cm^2/s.
The localization of GRB 260208B in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260208B_amati.png The localization of GRB 260208B in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260208B_yonetoku.png
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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS.
The SVOM point of contact for this burst is: Xing-Hao Luo (luoxh@ihep.ac.cn)
GCN Circular #43651
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 260208B. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021909 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 #43659
H. L. Li, C. W. Wang, Y. L. Qiu, Y. N. Ma, Z. H. Yao, C. Wu, 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) report on behalf of the SVOM/VT team.
SVOM/VT performed ToO observation to GRB 260208B detected by Fermi-GBM (The Fermi GBM team, GCN 43638; Preis & Greiner, GCN 43639; Sonawane et al., GCN 43649), Fermi-LAT (Longo et al., GCN 43647) and SVOM/GRM (Luo et al., GCN 43650). The observation started at 2026-02-08T18:13:53 UTC, i.e., 8.359 hours 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 source 1 detected by Swift-XRT (Evans et al., GCN 43651). The position is at R.A., Dec. = 99.619042, -13.774177 degrees, equivalent to:
```
    R.A. (J2000) =  +06:38:28.57
    Dec. (J2000) = -13:46:27.04
```
with an uncertainty of 0.5 arcsec.
The measurements in AB magnitudes are given below:
```
    Mid_time       Band        Exposure Time     Magnitude (AB)
   10.341 hour     VT_R         53*50 sec        22.3+/-0.2 mag
   10.341 hour     VT_B         57*50 sec         > 23.5 mag
```
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 #43663
S. Q. Jiang, H. N. Yang, Y. L. Wang, Y. Liu (NAO, CAS), Z. H. Yang, Q. C. Zhao (IHEP, CAS) on behalf of the Einstein Probe (EP) team:
EP-FXT performed a follow-up observation on GRB 260208B detected by Fermi/GBM (The Fermi GBM team, GCN 43638; Preis & Greiner, GCN 43639; Sonawane et al., GCN 43649), Fermi/LAT (Longo et al., GCN 43647) and SVOM/GRM (Luo et al., GCN 43650) at 2026-02-09T06:37:35 (UTC), about 20.748 hours after the Fermi/GBM trigger.
Two uncatalogued X-ray sources are detected around the Fermi/LAT error circle. Preliminary informations are listed as follows:
Source 1: EPF_J063834.1-135348
```
RA (J2000): 99.6419
Dec (J2000): -13.8965
Flux: 1.12 x 10^-13 erg/cm^2/s (observed, 0.5-10 keV)
```
Source 2: EPF_J063827.9-134635
```
RA (J2000): 99.6162
Dec (J2000): -13.7764
Flux: 0.96 x 10^-13 erg/cm^2/s (observed, 0.5-10 keV)
The position is consistent with the source 1 detected by Swift-XRT (Evans et al., GCN 43651) and the optical candidate detected by SVOM/VT (Li et al., GCN 43659).
```
The position uncertainties of the above sources are about 20 arcsec in radius (90% C.L. statistical and systematic). The current result is based on the FXT on-board alert and will be updated when the telemetry data are 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).
GCN Circular #43668
Francesco Magnani (CPPM), Leonardo García García (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), 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 bright Fermi GRB 260208B (Fermi GBM Team, GCN Circ. 43638), also detected by SVOM/GRM (L. Xing-Hao, GCN Circ. 43650), using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-02-09T05:10:25 to 2026-02-09T06:30:45 UTC (from 19.3 to 20.6 hours after the trigger) and obtained 30 minutes of simultaneous exposure in the r, 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.
We detect a source at the position of the SVOM/VT candidate (Li et al., GCN Circ. 43659), with the following preliminary magnitudes :
```
r = 22.61 +/- 0.14
z = 21.99 +/- 0.25
```
Further analysis 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 #43671
A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA), J.A. Kennea (PSU), D.N. Burrows (PSU), S. Lanava (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 260208B, collecting 1.6 ks of Photon Counting (PC) mode data between T0+33.1 ks and T0+44.4 ks.
One uncatalogued X-ray source has been detected within the estimated 3-sigma Fermi/LAT error region (354 arcsec), it is below the RASS limit and shows no definitive signs of fading. Details of this source are given below:
Source 1:
```
  RA (J2000.0):  99.6189  =  06h 38m 28.55s
  Dec (J2000.0): -13.7743  =  -13d 46' 27.4"
  Error: 3.1 arcsec (radius, 90% conf. [Enhanced position])
  Count-rate: 0.0338 +/- 0.0067 ct s^-1   
  Distance: 238 arcsec from Fermi/LAT position.
  Flux: (1.63 +/- 0.32)e-12 erg cm^-2 s^-1 (observed, 0.3-10 keV)
```
The flux reported by EP-WXT for this source at 74.7 ks after the trigger (GCN Circ. 43663) is about a factor of 10 fainter than this XRT measurement, however, which suggests it is indeed the GRB afterglow.
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/00021909. We note that the large number of spurious sources was due to unusually high background.
This circular is an official product of the Swift-XRT team.
GCN Circular #43677
Harsha K. H. (IUCAA), M. Tembhurnikar (IUCAA), S. Salunke (IUCAA), U. Pathak (IITB), A. Arya (IITB), A. Goyal (IITB), 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 ML pipeline (Abraham et al., 2021, MNRAS, 504, 3084) and the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long, bright GRB 260208B which was also detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 43638), Fermi/LAT (F. Longo et al., GCN Circ. 43647), and SVOM/GRM (SVOM GRM Team, GCN Circ. 43650). We also see a relatively faint burst episode about 100 s after the initial bright burst in both CZT & CsI detectors.
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-02-08 09:52:59.50 UTC. The measured peak count rate associated with the burst is 1334 (+64, -68) counts/s above the background in the combined data of all quadrants, with a total of 14112 (+381, -416) counts. The local mean background count rate was 272 (+2, -3) counts/s. Using cumulative rates, we measure a T90 of 24 (+6, -2) s. In the preliminary analysis, we find 2125 Compton events associated with this event.
The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-02-08 09:52:58.95 UTC. The measured peak count rate associated with the burst is 3595 (+111, -118) counts/s above the background in the combined data of all quadrants, with a total of 32443 (+740, -736) counts. The local mean background count rate was 1199 (+4, -5) counts/s. We measure a T90 of 22 (+1, -1) s from the cumulative Veto light curve.
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
GCN Circular #43682
S. Q. Jiang, H. N. Yang, Y. L. Wang, Y. Liu (NAO, CAS), Z. H. Yang, Q. C. Zhao (IHEP, CAS) on behalf of the Einstein Probe (EP) team:
EP-FXT performed a follow-up observation on GRB 260208B (The Fermi GBM team, GCN 43638; Preis & Greiner, GCN 43639; Longo et al., GCN 43647; Sonawane et al., GCN 43649; Luo et al., GCN 43650; Harsha et al., GCN 43677) at 2026-02-09T06:37:35 (UTC), about 20.748 hours after the Fermi/GBM trigger. With a 4.6 ks exposure, the afterglow (Li et al., GCN 43659; Magnani et al., GCN 43668; Beardmore et al., GCN 43671) is clearly detected by EP-FXT.
The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 4.3 × 10^21 cm^-2, and a photon index of 2.01 (-0.21/+0.21). The derived average unabsorbed 0.5-10 keV flux is 7.28 (-0.81/+0.97) × 10^(-13) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters.
Compared to the flux reported by Swift/XRT (Beardmore et al., GCN 43671), the temporal decay index is approximately -1.4.
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).

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