Gamma-ray Burst 260120B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Jan 26 18:00:53 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1442454,   Seg_Num: 0
GRB_RA:          284.666d {+18h 58m 40s} (J2000),
                 284.736d {+18h 58m 57s} (current),
                 284.529d {+18h 58m 07s} (1950)
GRB_DEC:         +61.912d {+61d 54' 42"} (J2000),
                 +61.949d {+61d 56' 55"} (current),
                 +61.842d {+61d 50' 30"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4625 [cnts]    Image_Peak=115 [image_cnts]
TRIGGER_DUR:     2.048 [sec] 
TRIGGER_INDEX:   271     E_range: 50-350 keV
BKG_INTEN:       32136 [cnts]
BKG_TIME:        64794.92 SOD {17:59:54.92} UT
BKG_DUR:         24 [sec]
GRB_DATE:        21060 TJD;    20 DOY;   26/01/20
GRB_TIME:        64826.15 SOD {18:00:26.15} UT
GRB_PHI:         -177.92 [deg]
GRB_THETA:        55.78 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     32.61 [sigma]
IMAGE_SIGNIF:    7.73 [sigma]
MERIT_PARAMS:     +1  +0  +0  +1  +3  -2  +0  +0 -11  +0 
SUN_POSTN:       302.90d {+20h 11m 36s}  -20.00d {-19d 59' 56"}
SUN_DIST:         83.22 [deg]   Sun_angle= 1.2 [hr] (West of Sun)
MOON_POSTN:      325.99d {+21h 43m 58s}  -15.25d {-15d 15' 02"}
MOON_DIST:        83.75 [deg]
MOON_ILLUM:      4 [%]
GAL_COORDS:       92.21, 22.90 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      330.67, 82.14 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 216.75,6.15 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(0.0<100sec) coincident with the
FERMI_GBM event (trignum=790624831).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 20 Jan 26 18:00:29 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      42
TRIGGER_NUM:     790624831
GRB_RA:          316.850d {+21h 07m 24s} (J2000),
                 316.951d {+21h 07m 48s} (current),
                 316.654d {+21h 06m 37s} (1950)
GRB_DEC:         +66.883d {+66d 52' 60"} (J2000),
                 +66.989d {+66d 59' 21"} (current),
                 +66.681d {+66d 40' 50"} (1950)
GRB_ERROR:       6.50 [deg radius, statistical plus systematic]
GRB_INTEN:       411 [cnts/sec]
DATA_SIGNIF:     18.90 [sigma]
INTEG_TIME:      1.024 [sec]
GRB_DATE:        21060 TJD;    20 DOY;   26/01/20
GRB_TIME:        64826.05 SOD {18:00:26.05} UT
GRB_PHI:         140.00 [deg]
GRB_THETA:        15.00 [deg]
DATA_TIME_SCALE: 1.0240 [sec]
HARD_RATIO:      0.37
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      88%  GRB
2nd_MOST_LIKELY:   8%  Cyg X-1
DETECTORS:       0,0,0, 0,0,0, 0,1,0, 1,0,0, 0,0,
SUN_POSTN:       302.90d {+20h 11m 36s}  -20.00d {-19d 59' 56"}
SUN_DIST:         87.62 [deg]   Sun_angle= -0.9 [hr] (East of Sun)
MOON_POSTN:      325.99d {+21h 43m 57s}  -15.25d {-15d 15' 07"}
MOON_DIST:        82.51 [deg]
MOON_ILLUM:      4 [%]
GAL_COORDS:      103.42, 12.95 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       22.64, 71.92 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260120750/quicklook/glg_lc_medres34_bn260120750.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 247.03,20.08 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 20 Jan 26 18:00:46 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      56
TRIGGER_NUM:     790624831
GRB_RA:          284.660d {+18h 58m 38s} (J2000),
                 284.707d {+18h 58m 50s} (current),
                 284.568d {+18h 58m 16s} (1950)
GRB_DEC:         +63.880d {+63d 52' 48"} (J2000),
                 +63.917d {+63d 55' 00"} (current),
                 +63.810d {+63d 48' 35"} (1950)
GRB_ERROR:       1.49 [deg radius, statistical only]
DATA_SIGNIF:     28.10 [sigma]
DATA_INTERVAL:   2.048 [sec]
GRB_DATE:        21060 TJD;    20 DOY;   26/01/20
GRB_TIME:        64826.05 SOD {18:00:26.05} UT
GRB_PHI:         203.00 [deg]
GRB_THETA:        10.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:       302.90d {+20h 11m 36s}  -20.00d {-19d 59' 56"}
SUN_DIST:         85.10 [deg]   Sun_angle= 1.2 [hr] (West of Sun)
MOON_POSTN:      325.99d {+21h 43m 58s}  -15.25d {-15d 15' 03"}
MOON_DIST:        85.27 [deg]
MOON_ILLUM:      4 [%]
GAL_COORDS:       94.28, 23.40 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      343.21, 83.32 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260120750/quicklook/glg_lc_medres34_bn260120750.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_790624831.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
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:     Tue 20 Jan 26 18:09:35 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     790624831
GRB_RA:          282.170d {+18h 48m 41s} (J2000),
                 282.210d {+18h 48m 50s} (current),
                 282.093d {+18h 48m 22s} (1950)
GRB_DEC:         +64.250d {+64d 15' 00"} (J2000),
                 +64.281d {+64d 16' 50"} (current),
                 +64.191d {+64d 11' 29"} (1950)
GRB_ERROR:       1.50 [deg radius, statistical only]
GRB_DATE:        21060 TJD;    20 DOY;   26/01/20
GRB_TIME:        64826.05 SOD {18:00:26.05} UT
GRB_PHI:         206.00 [deg]
GRB_THETA:        11.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       302.91d {+20h 11m 37s}  -20.00d {-19d 59' 51"}
SUN_DIST:         85.79 [deg]   Sun_angle= 1.4 [hr] (West of Sun)
MOON_POSTN:      326.06d {+21h 44m 15s}  -15.22d {-15d 13' 07"}
MOON_DIST:        86.25 [deg]
MOON_ILLUM:      4 [%]
GAL_COORDS:       94.41, 24.54 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      341.10, 84.44 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260120750/quicklook/glg_lc_medres34_bn260120750.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260120750/quicklook/glg_locplot_all_bn260120750.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:        This is likely a Long GRB.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1442454).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Jan 26 18:04:08 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1442454,   Seg_Num: 0
GRB_RA:          284.666d {+18h 58m 40s} (J2000),
                 284.736d {+18h 58m 57s} (current),
                 284.529d {+18h 58m 07s} (1950)
GRB_DEC:         +61.912d {+61d 54' 42"} (J2000),
                 +61.949d {+61d 56' 55"} (current),
                 +61.842d {+61d 50' 30"} (1950)
GRB_DATE:        21060 TJD;    20 DOY;   26/01/20
GRB_TIME:        64826.15 SOD {18:00:26.15} UT
TRIGGER_INDEX:   271
GRB_PHI:         -177.92 [deg]
GRB_THETA:        55.78 [deg]
DELTA_TIME:      77.00 [sec]
TRIGGER_DUR:     2.048 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     32.61 [sigma]
IMAGE_SIGNIF:    7.73 [sigma]
LC_URL:          sw01442454000msb.lc
SUN_POSTN:       302.90d {+20h 11m 36s}  -20.00d {-19d 59' 54"}
SUN_DIST:         83.22 [deg]   Sun_angle= 1.2 [hr] (West of Sun)
MOON_POSTN:      326.02d {+21h 44m 04s}  -15.24d {-15d 14' 19"}
MOON_DIST:        83.74 [deg]
MOON_ILLUM:      4 [%]
GAL_COORDS:       92.21, 22.90 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      330.67, 82.14 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Lightcurve.  
COMMENTS:           
COMMENTS:        The next comments were copied from the BAT_POS Notice:  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 216.75,6.15 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Jan 26 18:02:57 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     1442454,   Seg_Num: 0
POINT_RA:        284.673d {+18h 58m 41s} (J2000)
POINT_DEC:       +61.914d {+61d 54' 52"} (J2000)
IMG_START_DATE:  21060 TJD;    20 DOY;   26/01/20
IMG_START_TIME:  64971.63 SOD {18:02:51.63} UT,   145.5 [sec] since BAT Trigger Time
COUNTS:          4    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        1    Max_iter_allowed= 4
ERROR_CODE:      1
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        No source found in the image.

GCN Circular #43477
The Fermi GBM team reports the detection of a likely LONG GRB
At 18:00:26 UT on 20 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260120B (trigger 790624831.046372 / 260120750).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 282.2, Dec = 64.2 (J2000 degrees, equivalent to J2000 18h 48m, 64d 12'), with a statistical uncertainty of 1.5 degrees.
The angle from the Fermi LAT boresight is 11.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260120750/quicklook/glg_skymap_all_bn260120750.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/bn260120750/quicklook/glg_healpix_all_bn260120750.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260120750/quicklook/glg_lc_medres34_bn260120750.gif
GCN Circular #43478
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB260120.75 (trigger No 1442454,18h 58m 39.84s , +61d 54m 43.2s, R=0.05) errorbox 277 sec after notice time and 308 sec after trigger time at 2026-01-20 18:05:34 UT, with upper limit up to 17.0 mag. The observations began at zenith distance = 72 deg. The sun altitude is -43.2 deg.
The galactic latitude b = 23 deg., longitude l = 92 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3109829
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

     399 |   MASTER-Kislovodsk |   C |   180 | 12.3 |        
     399 |   MASTER-Kislovodsk |   C |   180 | 17.0 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
[1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html
GCN Circular #43479
M. Ferro (INAF-OAB), R. Gupta (NASA GSFC), A. Y. Lien (U Tampa), K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 18:00:26 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 260120B (trigger=1442454). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 284.666, +61.912 which is
```
   RA(J2000) = 18h 58m 40s
   Dec(J2000) = +61d 54' 42"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 10 sec. The peak count rate was ~1700 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 18:02:51.6 UT, 145.5 seconds after the BAT trigger. No source was detected in the 2.5-s promptly available image. We are waiting for the full dataset to detect and localise the XRT counterpart.
No UVOT data are available at this time.
Burst Advocate for this burst is M. Ferro (matteo.ferro AT inaf.it). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Jan 26 18:21:49 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1442454,   Seg_Num: 0
POINT_RA:        284.673d {+18h 58m 41s} (J2000)
POINT_DEC:       +61.914d {+61d 54' 50"} (J2000)
POINT_ROLL:      162.774d
IMG_START_DATE:  21060 TJD;    20 DOY;   26/01/20
IMG_START_TIME:  64975.27 SOD {18:02:55.27} UT,   149.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.696
N_STARS:         53
X_OFFSET:        494 [pixels]
Y_OFFSET:        567 [pixels]
X_MAX:           1453 [pixels]
Y_MAX:           1526 [pixels]
DET_THRESH:      20
PHOTO_THRESH:    12
SL_URL:          sw01442454000msufc0149.fits
SUN_POSTN:       302.91d {+20h 11m 39s}  -20.00d {-19d 59' 44"}
SUN_DIST:         83.22 [deg]   Sun_angle= 1.2 [hr] (West of Sun)
MOON_POSTN:      326.17d {+21h 44m 40s}  -15.17d {-15d 10' 24"}
MOON_DIST:        83.73 [deg]
MOON_ILLUM:      4 [%]
GAL_COORDS:       92.21, 22.89 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      330.70, 82.14 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Jan 26 18:21:56 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1442454,   Seg_Num: 0
POINT_RA:        284.673d {+18h 58m 41s} (J2000)
POINT_DEC:       +61.914d {+61d 54' 50"} (J2000)
POINT_ROLL:      162.774d
IMG_START_DATE:  21060 TJD;    20 DOY;   26/01/20
IMG_START_TIME:  64975.27 SOD {18:02:55.27} UT,   149.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.696
N_STARS:         53
X_OFFSET:        494 [pixels]
Y_OFFSET:        567 [pixels]
X_MAX:           1453 [pixels]
Y_MAX:           1526 [pixels]
DET_THRESH:      20
PHOTO_THRESH:    12
SL_URL:          sw01442454000msufc0149.fits
SUN_POSTN:       302.91d {+20h 11m 39s}  -20.00d {-19d 59' 44"}
SUN_DIST:         83.22 [deg]   Sun_angle= 1.2 [hr] (West of Sun)
MOON_POSTN:      326.17d {+21h 44m 41s}  -15.17d {-15d 10' 23"}
MOON_DIST:        83.73 [deg]
MOON_ILLUM:      4 [%]
GAL_COORDS:       92.21, 22.89 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      330.70, 82.14 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Jan 26 18:22:19 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1442454,   Seg_Num: 0
POINT_RA:        284.673d {+18h 58m 41s} (J2000)
POINT_DEC:       +61.914d {+61d 54' 50"} (J2000)
ROLL:            162.774d
IMG_START_DATE:  21060 TJD;    20 DOY;   26/01/20
IMG_START_TIME:  64975.27 SOD {18:02:55.27} UT,   149.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     790625012
X_OFFSET:        813 [pixels]
Y_OFFSET:        886 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       973
Y_GRB_POS:       1046
BINNING_INDEX:   1
IM_URL:          sw01442454000msuni0187.fits
SUN_POSTN:       302.91d {+20h 11m 40s}  -20.00d {-19d 59' 44"}
SUN_DIST:         83.22 [deg]   Sun_angle= 1.2 [hr] (West of Sun)
MOON_POSTN:      326.17d {+21h 44m 41s}  -15.17d {-15d 10' 18"}
MOON_DIST:        83.72 [deg]
MOON_ILLUM:      4 [%]
GAL_COORDS:       92.21, 22.89 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      330.70, 82.14 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Jan 26 18:22:28 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1442454,   Seg_Num: 0
GRB_RA:          284.6593d {+18h 58m 38.23s} (J2000),
                 284.7301d {+18h 58m 55.22s} (current),
                 284.5227d {+18h 58m 05.45s} (1950)
GRB_DEC:         +61.9048d {+61d 54' 17.2"} (J2000),
                 +61.9416d {+61d 56' 29.7"} (current),
                 +61.8347d {+61d 50' 04.7"} (1950)
GRB_ERROR:       3.9 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  21060 TJD;    20 DOY;   26/01/20
IMG_START_TIME:  65022.00 SOD {18:03:42.00} UT,   195.8 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       302.91d {+20h 11m 40s}  -20.00d {-19d 59' 44"}
SUN_DIST:         83.21 [deg]   Sun_angle= 1.2 [hr] (West of Sun)
MOON_POSTN:      326.17d {+21h 44m 42s}  -15.17d {-15d 10' 16"}
MOON_DIST:        83.72 [deg]
MOON_ILLUM:      4 [%]
GAL_COORDS:       92.20, 22.90 [deg] galactic lon,lat of the burst
ECL_COORDS:      330.62, 82.14 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See https://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Jan 26 18:22:12 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1442454,   Seg_Num: 0
POINT_RA:        284.673d {+18h 58m 41s} (J2000)
POINT_DEC:       +61.914d {+61d 54' 50"} (J2000)
ROLL:            162.774d
IMG_START_DATE:  21060 TJD;    20 DOY;   26/01/20
IMG_START_TIME:  64975.27 SOD {18:02:55.27} UT,   149.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     790625012
X_OFFSET:        813 [pixels]
Y_OFFSET:        886 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       973
Y_GRB_POS:       1046
BINNING_INDEX:   1
IM_URL:          sw01442454000msuni0187.fits
SUN_POSTN:       302.91d {+20h 11m 40s}  -20.00d {-19d 59' 44"}
SUN_DIST:         83.22 [deg]   Sun_angle= 1.2 [hr] (West of Sun)
MOON_POSTN:      326.17d {+21h 44m 41s}  -15.17d {-15d 10' 19"}
MOON_DIST:        83.72 [deg]
MOON_ILLUM:      4 [%]
GAL_COORDS:       92.21, 22.89 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      330.70, 82.14 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Jan 26 18:24:54 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     1442454,   Seg_Num: 0
GRB_RA:          284.6600d {+18h 58m 38.40s} (J2000),
                 284.7308d {+18h 58m 55.39s} (current),
                 284.5234d {+18h 58m 05.62s} (1950)
GRB_DEC:         +61.9052d {+61d 54' 18.7"} (J2000),
                 +61.9420d {+61d 56' 31.1"} (current),
                 +61.8351d {+61d 50' 06.2"} (1950)
GRB_ERROR:       0.6 [arcsec radius, statistical only]
GRB_MAG:         18.29 +/- 0.14 [mag]
FILTER:          10, White
IMG_START_DATE:  21060 TJD;    20 DOY;   26/01/20
IMG_START_TIME:  64981.00 SOD {18:03:01.00} UT,   154.8 [sec] since BAT Trigger Time
SUN_POSTN:       302.92d {+20h 11m 40s}  -20.00d {-19d 59' 43"}
SUN_DIST:         83.21 [deg]   Sun_angle= 1.2 [hr] (West of Sun)
MOON_POSTN:      326.19d {+21h 44m 47s}  -15.16d {-15d 09' 43"}
MOON_DIST:        83.72 [deg]
MOON_ILLUM:      4 [%]
GAL_COORDS:       92.20, 22.90 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      330.62, 82.14 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT UVOT Position Notice.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        Result based on Genie data.  
COMMENTS:        Notice generated automatically.

GCN Circular #43483
C. Wu (NAOC), Z. Kang (CHO), L.P. Xin, X.H. Han, P.P. Zhang, X.M. Lu (NAOC), Z.W. Li, Y. Lv (CHO), R.S. Zhang, Y.J. Xiao, Y.L. Qiu, J. Wang, J.S. Deng, L. Huang, J.Y. Wei (NAOC) report on behalf of the SVOM/C-GFT team:
We observed the field of GRB 260120B detected by Fermi/GBM(Fermi GBM team, GCN 43477) and Swift/BAT (Ferro et al., GCN 43479) with LATIOS on SVOM/C-GFT. Observa-tions started at 2026-01-20T18:01:29 UTC, ~63 seconds after the trigger.
An uncatalogued optical source, compared to Legacy Surveys DR10 Source Catalog, is detected in our images within the localization error circle (Ferro et al., GCN 43479) at:
RA (J2000) = 18h58m38.35s = 284.65980 degrees
Dec (J2000) = +61d54m18s = 61.90508 degrees
with an uncertainty of ~0.5 arcsec.
The magnitudes are:
```
| Mid_t-T0(s) | exposure time (s) | band | mag (AB) | mag_err|
|-------------|-------------------|------|----------|--------|
|  68         |  1x10             |  i    | 15.74   | 0.04   |
|  634        |  6x30             |  g   | 19.18  | 0.12  |
|  854        |  6x30             |  r    | 19.03   | 0.12   |
```
The brightness decays very rapidly, with the source fading by ~3.4 mag in the i band over 1000 s starting at T0+68 s.
The photometry was calibrated against nearby stars in UCAC4 catalogue and no correction for Galactic dust extinction was applied.
We thank the observation assistants Hong-Xv Xue and Bo-Wen Li at Jilin observatory for their excellent support.
The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcsec x 21 arcsec FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching.
GCN Circular #43484
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 609 s of XRT Photon Counting mode data and 1 UVOT images for GRB 260120B, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 284.65977, +61.90497 which is equivalent to:
```
RA (J2000): 18h 58m 38.34s
Dec (J2000): +61d 54' 17.9"
```
with an uncertainty of 2.3 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest position can be viewed at https://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the Swift-XRT team.
GCN Circular #43486
Noémie Globus (UNAM), Antonio de Ugarte Postigo (LAM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Asuka Kuwata (UNAM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), and Benjamin Schneider (LAM):
We imaged the field of the Swift GRB 260120B (Ferro at al., GCN Circ. 43479; Goad et al., GCN Circ. 43484), also detected by Fermi (Fermi GBM team, GCN Circ. 43477) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-01-21 02:00 to 02:19 UTC (from 8.01 to 8.31 hours after the trigger) and obtained 16 minutes of simultaneous exposure in the r and z filters during evening twilight.
The data were reduced and coadded with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.
We do not detect any source within the enhanced XRT error circle (Goad et al., GCN Circ 43484) down to the following 3-sigma limits:
```
r > 22.87,
z > 22.12.
```
We do not detect the afterglow candidate reported by Wu et al (GCN Circ. 43483). This is consistent with the source having faded below our detection limit by the time of our observation, and indicates a temporal index steeper than -1.0.
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 #43487
A.A. Breeveld (UCL-MSSL) and M. Ferro (INAF-OAB) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 260120B 149 s after the BAT trigger (Ferro et al., GCN Circ. 43479). A fading source consistent with the optical counterpart position given by Wu et al., (GCN Circ. 43483) and also the enhanced XRT position (Goad et al., GCN Circ. 43484) is detected in the initial UVOT exposures.
Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white              149          299          147         18.38 ± 0.06
white              588          776           35        >19.4
v                  637          657           19        >17.4
b                  563          755           39        >18.7
u                  307          557          246         18.80 ± 0.14
w1                 686          705           19        >17.4
m2                 661          681           19        >17.1
w2                 613          633           19        >17.5
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.063 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #43489
Matt Godwin (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 18:00:26.05 UT on 20 January 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260120B (trigger 790624831/260120750), which was also detected by Swift BAT (Ferro et al. 2026, GCN 43479), Swift XRT (Goad et al. 2026, GCN 43484), and SVOM/C-GFT (Wu et al. 2026, GCN 43483). The Fermi GBM real-time localization (GCN 43477) is consistent with the Swift BAT position.
The angle from the Fermi LAT boresight is 10 degrees.
The GBM light curve consists of a single emission episode with a duration (T90) of about 7 s (50-300 keV). The time-averaged spectrum from T0-1.1 to T0+9.9 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.19 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 214 +/- 4 keV.
The event fluence (10-1000 keV) in this time interval is (3.1 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.38 s in the 10-1000 keV band is 5.8 +/- 0.3 ph/s/cm^2.
A Band function fits the spectrum equally well with Epeak= 152 +/- 2 keV, alpha = 0.36 +/- 0.02 and beta = -2.26 +/- 0.05.
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 #43492
M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), A. D'Ai (INAF-IASFPA), S. Lanava (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 5.6 ks of XRT data for GRB 260120B, from 130 s to 29.5 ks after the trigger. The data comprise 13 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode.
The light curve can be modelled with a power-law decay with a decay index of alpha=0.84 (+/-0.06).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.97 (+0.29, -0.27). The best-fitting absorption column is 2.1 (+1.2, -1.0) x 10^21 cm^-2, in excess of the Galactic value of 7.4 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.7 x 10^-11 (5.1 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     2.1 (+1.2, -1.0) x 10^21 cm^-2
Galactic foreground: 7.4 x 10^20 cm^-2
Excess significance: 2.4 sigma
Photon index:	     1.97 (+0.29, -0.27)
```
The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01442454.
This circular is an official product of the Swift-XRT team.
GCN Circular #43493
D. M. Palmer (LANL), S. D. Barthelmy (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team):
Using the data set from T-769 to T+303 sec from the recent telemetry downlink, we report further analysis of BAT GRB 260120B (trigger #1442454) (Ferro et al., GCN Circ. 43479). The BAT ground-calculated position is RA, Dec = 284.701, 61.905 deg which is
```
   RA(J2000)  =  18h 58m 48.3s 
   Dec(J2000) = +61d 54' 19.2" 
```
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 9%.
The BAT light curve showed a single-peaked structure with a duration of about 10 sec. T90 (15-350 keV) is 4.48 +- 0.94 sec (estimated error including systematics).
The time-averaged spectrum from T-0.34 to T+4.59 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index -0.93 +- 1.35, and Epeak of 103.9 +- 38.6 keV (chi squared 48.41 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.2 +- 0.1 x 10^-06 erg/cm2 and the 1-sec peak flux measured from T+0.48 sec in the 15-150 keV band is 3.1 +- 0.8 ph/cm2/sec. A fit to a simple power law gives a photon index of 0.95 +- 0.21 (chi squared 57.22 for 57 d.o.f.). All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1442454
GCN Circular #43504
A. Goyal (IITB), A. Arya (IITB), M. Tembhurnikar (IUCAA), S. Salunke (IUCAA), Harsha K. H. (IUCAA), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long GRB 260120B which was also detected by Swift BAT (M. Ferro et. ala, GCN Circ. 43479), Fermi GBM (Fermi GBM Team, GCN Circ. 43477), Swift XRT (Goad et al., GCN Circ. 43484), and SVOM/C-GFT (Wu et al., GCN Circ. 43483).
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2026-01-20 18:00:23.85 UTC. The measured peak count rate associated with the burst is 312 (+129, -23) counts/s above the background in the combined data of three quadrants (out of four), with a total of 622 (+153, -176) counts. The local mean background count rate was 174 (+4, -6) counts/s. Using cumulative rates, we measure a T90 of 5.0 (+1.5, -1.5) s.
The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2026-01-20 18:00:22.68 UTC. The measured peak count rate associated with the burst is 333 (+65, -44) counts/s above the background in the combined data of all quadrants, with a total of 1026 (+266, -251) counts. The local mean background count rate was 1065 (+7, -9) counts/s. We measure a T90 of 4.3 (+1.6, -1.8) 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 #43506
SVOM/GRM team: Yang-Zhao Ren, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Sebastien Guillot(IRAP)
Report on behalf of the SVOM team:
SVOM/GRM was triggered on-ground by GRB 260120B at 2026-01-20T18:00:26.200 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #43477) and Swift/BAT (Ferro et al., GCN #43479).
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a pulse with a T90 of 8.5 +5.0/-3.5 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260120B.png
In addition, the position of this burst, as determined by Swift/BAT (RA = 284.666, Dec = 61.912, GCN #43479), is located at about 89 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view.
With this localization, the time-averaged spectrum from T0 to T0+5 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.16 +0.16/-0.18 and the cutoff energy, parameterized as Epeak, is 307 +106/-62 keV. The event fluence (10-1000 keV) in this time interval is (3.78 +0.32/-0.33)E-06 erg/cm^2.
The localization of GRB 260120B in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260120B_amati.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: Yang-Zhao Ren (IHEP)(renyz@ihep.ac.cn)
GCN Circular #43517
A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report:
The long-duration GRB 260120B (Fermi GBM detection: Fermi GBM team, GCN 43477; Godwin & Meegan, GCN 43489; Swift-BAT detection: Ferro et al., GCN 43479; Palmer et al., GCN 43493; AstroSat CZTI detection: Goyal et al., GCN 43504) triggered Konus-Wind at T0=64826.649 s UT (18:00:26.649).
The burst light curve shows a single pulse, which starts at ~T0-3.2 s and has a total duration of ~5.9 s.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260120_T64826/
As observed by Konus-Wind, the burst had a fluence of 3.41(-0.52,+0.58)x10^-6 erg/cm2, and a 64-ms peak flux, measured from T0-0.064 s, of 1.97(-0.58,+0.60)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
Since a major part of the burst emission was detected before the trigger, the spectral analysis was performed using the KW 3-channel light curve data.
Modelling the KW 3-channel time-integrated spectrum (measured from T0-3.173 s to T0+2.720 s) by a power law with exponential cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep), yields alpha = -0.56(-0.23,+0.30) and Ep = 246(-53,+67) keV.
All the quoted errors are at the 68% confidence level. All the quoted values are preliminary.

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Jochen Greiner, last update: 26-Jan-2026 [Disclaimer]