Gamma-ray Burst 260127A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Jan 26 17:52:30 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1444088,   Seg_Num: 0
GRB_RA:          231.857d {+15h 27m 26s} (J2000),
                 232.177d {+15h 28m 43s} (current),
                 231.242d {+15h 24m 58s} (1950)
GRB_DEC:          +6.758d {+06d 45' 30"} (J2000),
                  +6.669d {+06d 40' 09"} (current),
                  +6.932d {+06d 55' 53"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       0 [cnts]    Image_Peak=2334 [image_cnts]
TRIGGER_DUR:     104.000 [sec] 
TRIGGER_INDEX:   20000     E_range: 15-50 keV
BKG_INTEN:       0 [cnts]
BKG_TIME:        0.00 SOD {00:00:00.00} UT
BKG_DUR:         0 [sec]
GRB_DATE:        21067 TJD;    27 DOY;   26/01/27
GRB_TIME:        64234.88 SOD {17:50:34.88} UT
GRB_PHI:         -141.24 [deg]
GRB_THETA:        38.92 [deg]
SOLN_STATUS:     0x20000013
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    11.04 [sigma]
MERIT_PARAMS:     +1  +0  +0  +7  +1  +0  +0  +0 -14  +0 
SUN_POSTN:       310.22d {+20h 40m 52s}  -18.31d {-18d 18' 52"}
SUN_DIST:         80.86 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:       54.83d {+03h 39m 19s}  +24.79d {+24d 47' 18"}
MOON_DIST:       148.44 [deg]
MOON_ILLUM:      68 [%]
GAL_COORDS:       11.35, 47.78 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      227.52, 24.75 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is an image trigger.  (The RATE_SIGNIF & BKG_{INTEN, TIME, DUR
} are undefined.)  
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 = 158.75,6.11 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(33.0<100sec) coincident with the FERMI_GBM event (trignum=791229072).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 27 Jan 26 17:51:27 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      44
TRIGGER_NUM:     791229072
GRB_RA:          230.283d {+15h 21m 08s} (J2000),
                 230.610d {+15h 22m 27s} (current),
                 229.656d {+15h 18m 38s} (1950)
GRB_DEC:          +3.583d {+03d 34' 60"} (J2000),
                  +3.491d {+03d 29' 27"} (current),
                  +3.762d {+03d 45' 45"} (1950)
GRB_ERROR:       18.43 [deg radius, statistical plus systematic]
GRB_INTEN:       77 [cnts/sec]
DATA_SIGNIF:     7.40 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        21067 TJD;    27 DOY;   26/01/27
GRB_TIME:        64267.74 SOD {17:51:07.74} UT
GRB_PHI:          76.00 [deg]
GRB_THETA:        85.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.44
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      94%  GRB
2nd_MOST_LIKELY:   4%  Generic Transient
DETECTORS:       0,1,1, 0,0,0, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:       310.22d {+20h 40m 52s}  -18.31d {-18d 18' 52"}
SUN_DIST:         81.27 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:       54.82d {+03h 39m 16s}  +24.79d {+24d 47' 08"}
MOON_DIST:       151.43 [deg]
MOON_ILLUM:      68 [%]
GAL_COORDS:        6.18, 47.22 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      226.82, 21.27 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260127744/quicklook/glg_lc_medres34_bn260127744.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 93.32,13.33 [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 27 Jan 26 17:51:44 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      57
TRIGGER_NUM:     791229072
GRB_RA:          232.250d {+15h 29m 00s} (J2000),
                 232.579d {+15h 30m 19s} (current),
                 231.620d {+15h 26m 29s} (1950)
GRB_DEC:          +2.570d {+02d 34' 12"} (J2000),
                  +2.481d {+02d 28' 53"} (current),
                  +2.742d {+02d 44' 30"} (1950)
GRB_ERROR:       6.99 [deg radius, statistical only]
DATA_SIGNIF:     11.30 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        21067 TJD;    27 DOY;   26/01/27
GRB_TIME:        64267.74 SOD {17:51:07.74} UT
GRB_PHI:          74.00 [deg]
GRB_THETA:        86.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:       310.22d {+20h 40m 52s}  -18.31d {-18d 18' 52"}
SUN_DIST:         79.08 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:       54.82d {+03h 39m 17s}  +24.79d {+24d 47' 11"}
MOON_DIST:       152.65 [deg]
MOON_ILLUM:      68 [%]
GAL_COORDS:        6.72, 45.04 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      229.13, 20.81 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260127744/quicklook/glg_lc_medres34_bn260127744.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_791229072.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
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 27 Jan 26 17:52:52 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      0
TRIGGER_NUM:     791229072
GRB_RA:          226.390d {+15h 05m 34s} (J2000),
                 226.720d {+15h 06m 53s} (current),
                 225.757d {+15h 03m 02s} (1950)
GRB_DEC:          +2.190d {+02d 11' 24"} (J2000),
                  +2.090d {+02d 05' 25"} (current),
                  +2.383d {+02d 22' 59"} (1950)
GRB_ERROR:       6.62 [deg radius, statistical only]
DATA_SIGNIF:     10.60 [sigma]
DATA_INTERVAL:   12.288 [sec]
GRB_DATE:        21067 TJD;    27 DOY;   26/01/27
GRB_TIME:        64267.74 SOD {17:51:07.74} UT
GRB_PHI:          77.00 [deg]
GRB_THETA:        81.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       310.22d {+20h 40m 52s}  -18.31d {-18d 18' 51"}
SUN_DIST:         84.49 [deg]   Sun_angle= 5.6 [hr] (West of Sun)
MOON_POSTN:       54.83d {+03h 39m 20s}  +24.79d {+24d 47' 21"}
MOON_DIST:       151.99 [deg]
MOON_ILLUM:      68 [%]
GAL_COORDS:        0.86, 49.36 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      223.26, 18.84 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260127744/quicklook/glg_lc_medres34_bn260127744.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_791229072.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
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.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(33.0<100sec) coincident with the SWIFT_BAT event (trignum=1444088).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 27 Jan 26 18:00:25 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     791229072
GRB_RA:          226.890d {+15h 07m 34s} (J2000),
                 227.228d {+15h 08m 55s} (current),
                 226.242d {+15h 04m 58s} (1950)
GRB_DEC:          -2.180d {-02d 10' 47"} (J2000),
                  -2.279d {-02d 16' 43"} (current),
                  -1.989d {-01d 59' 18"} (1950)
GRB_ERROR:       5.09 [deg radius, statistical only]
GRB_DATE:        21067 TJD;    27 DOY;   26/01/27
GRB_TIME:        64267.74 SOD {17:51:07.74} UT
GRB_PHI:          73.00 [deg]
GRB_THETA:        79.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       310.22d {+20h 40m 54s}  -18.31d {-18d 18' 47"}
SUN_DIST:         82.64 [deg]   Sun_angle= 5.5 [hr] (West of Sun)
MOON_POSTN:       54.91d {+03h 39m 39s}  +24.81d {+24d 48' 27"}
MOON_DIST:       156.28 [deg]
MOON_ILLUM:      68 [%]
GAL_COORDS:      356.59, 46.03 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      225.06, 14.79 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260127744/quicklook/glg_lc_medres34_bn260127744.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260127744/quicklook/glg_locplot_all_bn260127744.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:        This is likely a Long GRB.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(33.0<100sec) coincident with the SWIFT_BAT event (trignum=1444088).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Jan 26 17:54:34 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     1444088,   Seg_Num: 0
GRB_RA:          231.8786d {+15h 27m 30.8s} (J2000),
                 232.1992d {+15h 28m 47.8s} (current),
                 231.2643d {+15h 25m 03.4s} (1950)
GRB_DEC:          +6.7632d {+06d 45' 47.5"} (J2000),
                  +6.6739d {+06d 40' 26.0"} (current),
                  +6.9362d {+06d 56' 10.4"} (1950)
GRB_ERROR:       6.5 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       25 [cnts]
IMG_START_DATE:  21067 TJD;    27 DOY;   26/01/27
IMG_START_TIME:  64440.17 SOD {17:54:00.17} UT,   205.3 [sec] since BAT Trigger Time
CENTROID_X:      299.95,  raw= 300  [pixels]
CENTROID_Y:      303.95,  raw= 304  [pixels]
ROLL:            109.78 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   12.39
GRB_POS_XRT_Z:   -27.45
IMAGE_URL:       sw01444088000msxps_rw.img
SUN_POSTN:       310.22d {+20h 40m 53s}  -18.31d {-18d 18' 50"}
SUN_DIST:         80.84 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:       54.85d {+03h 39m 24s}  +24.79d {+24d 47' 36"}
MOON_DIST:       148.43 [deg]
MOON_ILLUM:      68 [%]
GAL_COORDS:       11.37, 47.76 [deg] galactic lon,lat of the burst
ECL_COORDS:      227.54, 24.76 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Jan 26 17:54:36 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     1444088,   Seg_Num: 0
GRB_RA:          231.8786d {+15h 27m 30.8s} (J2000),
                 232.1992d {+15h 28m 47.8s} (current),
                 231.2643d {+15h 25m 03.4s} (1950)
GRB_DEC:          +6.7632d {+06d 45' 47.5"} (J2000),
                  +6.6739d {+06d 40' 26.0"} (current),
                  +6.9362d {+06d 56' 10.4"} (1950)
GRB_ERROR:       6.5 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       25 [cnts]
IMG_START_DATE:  21067 TJD;    27 DOY;   26/01/27
IMG_START_TIME:  64440.17 SOD {17:54:00.17} UT,   205.3 [sec] since BAT Trigger Time
CENTROID_X:      299.95,  raw= 300  [pixels]
CENTROID_Y:      303.95,  raw= 304  [pixels]
ROLL:            109.78 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   12.39
GRB_POS_XRT_Z:   -27.45
IMAGE_URL:       sw01444088000msxps_rw.img
SUN_POSTN:       310.22d {+20h 40m 53s}  -18.31d {-18d 18' 50"}
SUN_DIST:         80.84 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:       54.85d {+03h 39m 24s}  +24.79d {+24d 47' 36"}
MOON_DIST:       148.43 [deg]
MOON_ILLUM:      68 [%]
GAL_COORDS:       11.37, 47.76 [deg] galactic lon,lat of the burst
ECL_COORDS:      227.54, 24.76 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Jan 26 17:54:24 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1444088,   Seg_Num: 0
GRB_RA:          231.8786d {+15h 27m 30.86s} (J2000),
                 232.1992d {+15h 28m 47.80s} (current),
                 231.2643d {+15h 25m 03.42s} (1950)
GRB_DEC:          +6.7632d {+06d 45' 47.5"} (J2000),
                  +6.6739d {+06d 40' 26.0"} (current),
                  +6.9362d {+06d 56' 10.4"} (1950)
GRB_ERROR:       6.5 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       4.58e-10 [erg/cm2/sec]
GRB_SIGNIF:      5.00 [sigma]
IMG_START_DATE:  21067 TJD;    27 DOY;   26/01/27
IMG_START_TIME:  64440.17 SOD {17:54:00.17} UT,   205.3 [sec] since BAT Trigger Time
TAM[0-3]:        327.69 237.15 261.53 243.87
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       310.22d {+20h 40m 53s}  -18.31d {-18d 18' 50"}
SUN_DIST:         80.84 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:       54.85d {+03h 39m 24s}  +24.79d {+24d 47' 34"}
MOON_DIST:       148.43 [deg]
MOON_ILLUM:      68 [%]
GAL_COORDS:       11.37, 47.76 [deg] galactic lon,lat of the burst
ECL_COORDS:      227.54, 24.76 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 1.34 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Jan 26 17:55:07 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1444088,   Seg_Num: 0
GRB_RA:          231.857d {+15h 27m 26s} (J2000),
                 232.177d {+15h 28m 43s} (current),
                 231.242d {+15h 24m 58s} (1950)
GRB_DEC:          +6.758d {+06d 45' 30"} (J2000),
                  +6.669d {+06d 40' 09"} (current),
                  +6.932d {+06d 55' 53"} (1950)
GRB_DATE:        21067 TJD;    27 DOY;   26/01/27
GRB_TIME:        64234.88 SOD {17:50:34.88} UT
TRIGGER_INDEX:   20000
GRB_PHI:         -141.24 [deg]
GRB_THETA:        38.92 [deg]
DELTA_TIME:      0.00 [sec]
TRIGGER_DUR:     104.000 [sec] 
SOLN_STATUS:     0x13
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    11.04 [sigma]
LC_URL:          sw01444088000msb.lc
SUN_POSTN:       310.22d {+20h 40m 53s}  -18.31d {-18d 18' 50"}
SUN_DIST:         80.86 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:       54.86d {+03h 39m 26s}  +24.79d {+24d 47' 41"}
MOON_DIST:       148.43 [deg]
MOON_ILLUM:      68 [%]
GAL_COORDS:       11.35, 47.78 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      227.52, 24.75 [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 an image 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 = 158.75,6.11 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Jan 26 17:57:02 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1444088,   Seg_Num: 0
POINT_RA:        231.870d {+15h 27m 29s} (J2000)
POINT_DEC:        +6.763d {+06d 45' 46"} (J2000)
POINT_ROLL:      109.781d
IMG_START_DATE:  21067 TJD;    27 DOY;   26/01/27
IMG_START_TIME:  64448.62 SOD {17:54:08.62} UT,   213.7 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.629
N_STARS:         76
X_OFFSET:        440 [pixels]
Y_OFFSET:        632 [pixels]
X_MAX:           1399 [pixels]
Y_MAX:           1591 [pixels]
DET_THRESH:      13
PHOTO_THRESH:    7
SL_URL:          sw01444088000msufc0213.fits
SUN_POSTN:       310.22d {+20h 40m 53s}  -18.31d {-18d 18' 49"}
SUN_DIST:         80.85 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:       54.88d {+03h 39m 30s}  +24.80d {+24d 47' 57"}
MOON_DIST:       148.42 [deg]
MOON_ILLUM:      68 [%]
GAL_COORDS:       11.37, 47.77 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      227.53, 24.76 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Jan 26 17:57:16 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1444088,   Seg_Num: 0
POINT_RA:        231.870d {+15h 27m 29s} (J2000)
POINT_DEC:        +6.763d {+06d 45' 46"} (J2000)
POINT_ROLL:      109.781d
IMG_START_DATE:  21067 TJD;    27 DOY;   26/01/27
IMG_START_TIME:  64448.62 SOD {17:54:08.62} UT,   213.7 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.629
N_STARS:         76
X_OFFSET:        440 [pixels]
Y_OFFSET:        632 [pixels]
X_MAX:           1399 [pixels]
Y_MAX:           1591 [pixels]
DET_THRESH:      13
PHOTO_THRESH:    7
SL_URL:          sw01444088000msufc0213.fits
SUN_POSTN:       310.22d {+20h 40m 53s}  -18.31d {-18d 18' 49"}
SUN_DIST:         80.85 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:       54.88d {+03h 39m 31s}  +24.80d {+24d 47' 59"}
MOON_DIST:       148.42 [deg]
MOON_ILLUM:      68 [%]
GAL_COORDS:       11.37, 47.77 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      227.53, 24.76 [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 27 Jan 26 17:59:21 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1444088,   Seg_Num: 0
POINT_RA:        231.870d {+15h 27m 29s} (J2000)
POINT_DEC:        +6.763d {+06d 45' 46"} (J2000)
ROLL:            109.781d
IMG_START_DATE:  21067 TJD;    27 DOY;   26/01/27
IMG_START_TIME:  64448.62 SOD {17:54:08.62} UT,   213.7 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     791229285
X_OFFSET:        835 [pixels]
Y_OFFSET:        817 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       995
Y_GRB_POS:       977
BINNING_INDEX:   1
IM_URL:          sw01444088000msuni0251.fits
SUN_POSTN:       310.22d {+20h 40m 53s}  -18.31d {-18d 18' 47"}
SUN_DIST:         80.85 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:       54.90d {+03h 39m 36s}  +24.80d {+24d 48' 18"}
MOON_DIST:       148.41 [deg]
MOON_ILLUM:      68 [%]
GAL_COORDS:       11.37, 47.77 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      227.53, 24.76 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        This notice was forced out after watchdog timer expiring -- most likely due to missing packet(s);  
COMMENTS:        as a consequence some of the fields may be incoorect (eg TRIGGER_NUM,RA,DEC).

GCN Circular #43528
The Fermi GBM team reports the detection of a likely LONG GRB
At 17:51:07 UT on 27 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260127A (trigger 791229072.735026 / 260127744).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 226.9, Dec = -2.2 (J2000 degrees, equivalent to J2000 15h 07m, -2d 12'), with a statistical uncertainty of 5.1 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/bn260127744/quicklook/glg_skymap_all_bn260127744.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/bn260127744/quicklook/glg_healpix_all_bn260127744.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260127744/quicklook/glg_lc_medres34_bn260127744.gif

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Jan 26 18:17:00 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1444088,   Seg_Num: 0
POINT_RA:        231.869d {+15h 27m 29s} (J2000)
POINT_DEC:        +6.762d {+06d 45' 43"} (J2000)
POINT_ROLL:      109.782d
IMG_START_DATE:  21067 TJD;    27 DOY;   26/01/27
IMG_START_TIME:  65102.82 SOD {18:05:02.82} UT,   867.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.510
N_STARS:         124
X_OFFSET:        275 [pixels]
Y_OFFSET:        257 [pixels]
X_MAX:           1714 [pixels]
Y_MAX:           1696 [pixels]
DET_THRESH:      16
PHOTO_THRESH:    9
SL_URL:          sw01444088000msufc0867.fits
SUN_POSTN:       310.23d {+20h 40m 56s}  -18.31d {-18d 18' 36"}
SUN_DIST:         80.86 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:       55.09d {+03h 40m 21s}  +24.85d {+24d 50' 52"}
MOON_DIST:       148.35 [deg]
MOON_ILLUM:      68 [%]
GAL_COORDS:       11.37, 47.77 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      227.53, 24.76 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN Circular #43529
N. J. Klingler (GSFC/UMBC/CRESSTII), R. Gupta (NASA GSFC), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), K. L. Page (U Leicester), T. M. Parsotan (GSFC) and B. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels Swift Observatory Team:
At 17:50:34 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 260127A (trigger=1444088). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 231.857, +6.758 which is
```
   RA(J2000) = 15h 27m 26s
   Dec(J2000) = +06d 45' 30"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed no structure initially, typical of an image trigger, with a more classic pulse structure starting at ~T0+20 sec. The emission has a duration of about 50 sec. The peak count rate was ~1460 counts/sec (15-350 keV), at ~33 sec after the trigger.
The XRT began observing the field at 17:54:00.1 UT, 205.3 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source located at RA, Dec 231.87885, 6.76345 which is equivalent to:
```
   RA(J2000)  = 15h 27m 30.92s
   Dec(J2000) = +06d 45' 48.4"
```
with an uncertainty of 3.5 arcseconds (radius, 90% containment). This location is 80 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (4.07 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.2 (+2.30/-2.03) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 4.58e-10 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 213 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.049.
Burst Advocate for this burst is N. J. Klingler (noelklin AT umbc.edu). 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 27 Jan 26 18:17:16 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1444088,   Seg_Num: 0
POINT_RA:        231.869d {+15h 27m 29s} (J2000)
POINT_DEC:        +6.762d {+06d 45' 43"} (J2000)
POINT_ROLL:      109.782d
IMG_START_DATE:  21067 TJD;    27 DOY;   26/01/27
IMG_START_TIME:  65102.82 SOD {18:05:02.82} UT,   867.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.510
N_STARS:         124
X_OFFSET:        275 [pixels]
Y_OFFSET:        257 [pixels]
X_MAX:           1714 [pixels]
Y_MAX:           1696 [pixels]
DET_THRESH:      16
PHOTO_THRESH:    9
SL_URL:          sw01444088000msufc0867.fits
SUN_POSTN:       310.24d {+20h 40m 56s}  -18.31d {-18d 18' 36"}
SUN_DIST:         80.86 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:       55.09d {+03h 40m 22s}  +24.85d {+24d 50' 54"}
MOON_DIST:       148.35 [deg]
MOON_ILLUM:      68 [%]
GAL_COORDS:       11.37, 47.77 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      227.53, 24.76 [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 27 Jan 26 18:17:36 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     1444088,   Seg_Num: 0
GRB_RA:          231.8792d {+15h 27m 31.00s} (J2000),
                 232.1998d {+15h 28m 47.95s} (current),
                 231.2649d {+15h 25m 03.57s} (1950)
GRB_DEC:          +6.7626d {+06d 45' 45.3"} (J2000),
                  +6.6733d {+06d 40' 23.9"} (current),
                  +6.9356d {+06d 56' 08.2"} (1950)
GRB_ERROR:       1.9 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  21067 TJD;    27 DOY;   26/01/27
IMG_START_TIME:  64542.00 SOD {17:55:42.00} UT,   307.1 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       310.24d {+20h 40m 57s}  -18.31d {-18d 18' 35"}
SUN_DIST:         80.85 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:       55.10d {+03h 40m 23s}  +24.85d {+24d 50' 57"}
MOON_DIST:       148.35 [deg]
MOON_ILLUM:      68 [%]
GAL_COORDS:       11.37, 47.76 [deg] galactic lon,lat of the burst
ECL_COORDS:      227.54, 24.76 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.  
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:        This position was enhanced using UVOT field astrometry.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.11% < P(seren) < 0.58%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Jan 26 18:20:04 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1444088,   Seg_Num: 0
POINT_RA:          0.000d {+00h 00m 00s} (J2000)
POINT_DEC:        +0.000d {+00d 00' 00"} (J2000)
ROLL:            6.762d
IMG_START_DATE:  21067 TJD;    27 DOY;   26/01/27
IMG_START_TIME:  65532.97 SOD {18:12:12.97} UT,   1298.1 [sec] since BAT Trigger Time
FILTER:          0, illegal value
EXPOSURE_ID:     65537
X_OFFSET:        911 [pixels]
Y_OFFSET:        1277 [pixels]
WIDTH:           386 [pixels]
HEIGHT:          1063 [pixels]
X_GRB_POS:       0
Y_GRB_POS:       0
BINNING_INDEX:   0
IM_URL:          sw01444088000msuni0905.fits
SUN_POSTN:       310.24d {+20h 40m 57s}  -18.31d {-18d 18' 34"}
SUN_DIST:         52.54 [deg]   Sun_angle= -3.3 [hr] (East of Sun)
MOON_POSTN:       55.12d {+03h 40m 29s}  +24.86d {+24d 51' 18"}
MOON_DIST:        58.38 [deg]
MOON_ILLUM:      68 [%]
GAL_COORDS:       96.34,-60.19 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        0.00,  0.00 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        WARNING: This Notice was received with 1 (or more) critical values out of range.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 1x1 binning (ie no compression).  
COMMENTS:        This notice was forced out after watchdog timer expiring -- most likely due to missing packet(s);  
COMMENTS:        as a consequence some of the fields may be incoorect (eg TRIGGER_NUM,RA,DEC).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Jan 26 18:20:18 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1444088,   Seg_Num: 0
POINT_RA:          0.000d {+00h 00m 00s} (J2000)
POINT_DEC:        +0.000d {+00d 00' 00"} (J2000)
ROLL:            6.762d
IMG_START_DATE:  21067 TJD;    27 DOY;   26/01/27
IMG_START_TIME:  65532.97 SOD {18:12:12.97} UT,   1298.1 [sec] since BAT Trigger Time
FILTER:          0, illegal value
EXPOSURE_ID:     65537
X_OFFSET:        911 [pixels]
Y_OFFSET:        1277 [pixels]
WIDTH:           386 [pixels]
HEIGHT:          1063 [pixels]
X_GRB_POS:       0
Y_GRB_POS:       0
BINNING_INDEX:   0
IM_URL:          sw01444088000msuni0905.fits
SUN_POSTN:       310.24d {+20h 40m 57s}  -18.31d {-18d 18' 34"}
SUN_DIST:         52.54 [deg]   Sun_angle= -3.3 [hr] (East of Sun)
MOON_POSTN:       55.12d {+03h 40m 30s}  +24.86d {+24d 51' 20"}
MOON_DIST:        58.38 [deg]
MOON_ILLUM:      68 [%]
GAL_COORDS:       96.34,-60.19 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        0.00,  0.00 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        WARNING: This Notice was received with 1 (or more) critical values out of range.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 1x1 binning (ie no compression).  
COMMENTS:        All 4 attachments are included.  
COMMENTS:        This notice was forced out after watchdog timer expiring -- most likely due to missing packet(s);  
COMMENTS:        as a consequence some of the fields may be incoorect (eg TRIGGER_NUM,RA,DEC).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Jan 26 17:59:35 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1444088,   Seg_Num: 0
POINT_RA:        231.870d {+15h 27m 29s} (J2000)
POINT_DEC:        +6.763d {+06d 45' 46"} (J2000)
ROLL:            109.781d
IMG_START_DATE:  21067 TJD;    27 DOY;   26/01/27
IMG_START_TIME:  64448.62 SOD {17:54:08.62} UT,   213.7 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     791229285
X_OFFSET:        835 [pixels]
Y_OFFSET:        817 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       995
Y_GRB_POS:       977
BINNING_INDEX:   1
IM_URL:          sw01444088000msuni0251.fits
SUN_POSTN:       310.22d {+20h 40m 53s}  -18.31d {-18d 18' 47"}
SUN_DIST:         80.85 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:       54.90d {+03h 39m 37s}  +24.81d {+24d 48' 20"}
MOON_DIST:       148.41 [deg]
MOON_ILLUM:      68 [%]
GAL_COORDS:       11.37, 47.77 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      227.53, 24.76 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.  
COMMENTS:        This notice was forced out after watchdog timer expiring -- most likely due to missing packet(s);  
COMMENTS:        as a consequence some of the fields may be incoorect (eg TRIGGER_NUM,RA,DEC).

GCN Circular #43530
A. Saccardi (CEA/Irfu), D. B. Malesani (DAWN/NBI and Radboud) report on behalf of the SVOM mission team:
We observed the field of GRB 260127A (Fermi GBM team, GCN 43528; Klingler et al., GCN 43529) with the LCO 1-m telescope at Siding Spring Observatory equipped with the Sinistro instrument.
Our observation started on 2026-01-27 at 18:12:42 (about 22 min after the trigger) and we obtained 3x200 s exposures in the SDSS r filter.
An uncatalogued optical transient is detected within the XRT error box at the following coordinates (J2000):
```
RA = 15:27:31.14
Dec = +06:45:45.49
```
with an uncertainty of 0.3". No object is visible at these coordinates in the much deeper archival images from the Legacy Survey, indicating that this object is most likely the optical afterglow of GRB 260127A.
We measure the following magnitude, calibrated against the Pan-STARRS catalog, and not corrected for Galactic extinction:
r = 20.45 +/- 0.20 AB (mid-time of 27.3 min after the trigger).
Further observations are planned.
This project is funded by the SVOM collaboration.
GCN Circular #43531
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-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the Swift GRB 260127A ( N. J. Klingler et al., GCN 43529) errorbox 3854 sec after notice time and 3972 sec after trigger time at 2026-01-27 18:56:47 UT, with upper limit up to 17.1 mag. The observations began at zenith distance = 77 deg. The sun altitude is -52.1 deg.
The galactic latitude b = 47 deg., longitude l = 12 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3117002
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

    3988 |        MASTER-Tunka |   C |    30 | 17.1 |        
    4030 |        MASTER-Tunka |   C |    30 | 17.1 |        
```
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 #43532
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Using 1.6 ks of promptly downlinked XRT event data for GRB 260127A, we find an enhanced XRT position of the afterglow: RA, Dec: 231.87962, 6.76262 which is equivalent to:
```
   RA (J2000)  = 15h 27m 31.11s
   Dec (J2000) = 00h 27m 03.03s
```
with an uncertainty of 1.9 arcseconds (radius, 90% confidence). Analysis of the promptly available data is online at http://www.swift.ac.uk/sper/1444088.
Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular is an official product of the Swift-XRT team.
GCN Circular #43535
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team.
Using 1612 s of XRT Photon Counting mode data and 2 UVOT images for GRB 260127A, 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 = 231.87939, +6.76215 which is equivalent to:
```
RA (J2000): 15h 27m 31.05s
Dec (J2000): +06d 45' 43.7"
```
with an uncertainty of 2.1 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 #43537
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 260127A detected by Fermi/GBM (Fermi GBM team, GCN 43528) and Swift/BAT (Klingler et al., GCN 43529) with LATIOS on SVOM/C-GFT. Observations started at 2026-01-27T19:07:40 UTC, ~76.55 min after the trigger.
The optical counterpart (Saccardiet et al., GCN 43530), consistent with XRT position (Evans et al., GCN 43532; Osborne et al., GCN 43535), was detected in our stacked i-band image. The magnitude is:
```
| Mid_t-T0(hr) | exposure time (s) | band | mag (AB) | mag_err|
|--------------|-------------------|------|----------|--------|
|  2.24        |  30x90s           | i    | 20.37    | 0.20   |
```
Our detection is deeper than the upper limit reported by Lipunov et al. (GCN 43532).
The photometry was calibrated against nearby stars from UCAC4 catalog and no correction for Galactic dust extinction was applied.
We thank the observation assistants Yin-Huai Hao Chun-Lei Guo 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 #43539
A. D'Ai (INAF-IASFPA), J.A. Kennea (PSU), D.N. Burrows (PSU), S. Lanava (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), S. Campana (INAF-OAB), A. Melandri (INAF-OAR) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 9.4 ks of XRT data for GRB 260127A, from 226 s to 51.7 ks after the trigger. The data comprise 102 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 late-time light curve (from T0+5.2 ks) is consistent with a constant source of mean count rate 3.6e+00 ct/sec. A power-law fit gives an index of 3.08 (+0.03, -3.08).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.14 (+0.20, -0.19). The best-fitting absorption column is 8.0 (+4.6, -3.9) x 10^20 cm^-2, in excess of the Galactic value of 4.1 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.75 (+/-0.06) and a best-fitting absorption column of 1.32 (+0.21, -0.20) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.0 x 10^-11 (4.8 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     1.32 (+0.21, -0.20) x 10^21 cm^-2
Galactic foreground: 4.1 x 10^20 cm^-2
Excess significance: 7.6 sigma
Photon index:	     1.75 (+/-0.06)
```
The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01444088.
This circular is an official product of the Swift-XRT team.
GCN Circular #43540
H. Hagio, I. Takahashi, M. Sasada, H. Seki, Y. Kubo, A. Ochi, R. Kato, S. Joshima, Y. Yatsu and N. Kawai (Science Tokyo) report on behalf of the MITSuME collaboration:
We observed the field of GRB 260127A detected by Fermi (Fermi GBM team et al., GCN 43528) and Swift ( Klingler et al., GCN 43529) with the optical three-color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50-cm telescope Akeno.
The observation started at 2026-01-27 17:52:58 UT (2.4 min after the trigger). We stacked the images taken under good conditions. We detected a point source in the Rc-band image at a position of the reported candidate (Saccardi et al., GCN 43530; Wu et al., GCN 43537). Here we report the preliminary magnitude of the source and the 5-sigma upper-limits as follows.
```
T0+[sec] | MID-UT | T-EXP[sec] | magnitudes
---------------------------------------------------------------------------------------------------------------
1245 | 2026-01-27 18:11:19 | 1620 |  g'>19.2,Rc=19.4+/-0.2, Ic>18.7
---------------------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the trigger
T-EXP: Total exposure time
```
We used the PS1 catalog for flux calibration. The catalog magnitudes in PS1 g, r and i bands were converted to our g', Rc and Ic band magnitudes following Tonry et al. (2012), Table 6. The magnitudes are expressed in the AB system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ; https://github.com/MNiwano/Eclaire).
GCN Circular #43543
D. B. Malesani (DAWN/NBI and Radboud), J. An (NAOC), L. B He (NAOC), G. Corcoran (UCD), K. Valeckas (NOT & NBI), L. Izzo (INAF/OAC and DARK/NBI), A. Martin-Carrillo (UCD), A. Saccardi (CEA/Irfu), B. Schneider (LAM) report on behalf of a larger collaboration:
We observed the optical counterpart (Saccardi & Malesani, GCN 43530; Wu et al., GCN 43537; Hagio et al., GCN 43540) of GRB 260127A (Klingler et al., GCN 43529; Fermi GBM team, GCN 43528) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were carried out in the SDSS i, z, and r filters (with exposure times 3x300, 5x200, and 3x300 s, respectively).
The optical counterpart is detected in the stacked images for all bands. We report the following magnitudes:
```
| Filter | Epoch (UT) | Time since GRB (hr) | Exp time (s) | Magnitude (AB) |
| ------ | ---------- | ------------------- | ------------ | -------------- |
| i      | Jan 28.197 | 10.88               | 3x300        | 22.30 +- 0.08  |
| z      | Jan 28.209 | 11.18               | 5x200        | 22.05 +- 0.18  |
| r      | Jan 28.243 | 12.00               | 3x300    	   | 22.30 +- 0.06  |
```
The above magnitudes are calibrated against the Pan-STARRS catalog and are not corrected for Galactic extinction. We note that at the coordinates of the optical counterpart a faint source is reported in the Legacy Survey catalogue. Considering its tabulated magnitudes (r = 23.3, i = 23.2, z = 22.3), the transient emission is thus significantly contaminated by the host flux.
GCN Circular #43544
Francesco Magnani (CPPM), Diego López-Cámara (UNAM), Jean-Grégoire Ducoin (CPPM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Nikos Mandarakas (LAM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report:
We imaged the field of the Swift/Fermi/GBM GRB 260127A (Fermi GBM Team, GCN Circ. 43528, Klingler et al., GCN Circ. 43529) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-01-28 09:48 to 13:24 UTC (from 16.0 to 19.5 hours after the trigger) and obtained 110 minutes of simultaneous exposure in the r and z filters.
The data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.
At the location of the optical counterpart reported by Saccardi et al. (GCN Circ. 43530), consistent with the X-ray counterpart reported by Evans et al. (GCN Circ. 43532) and Osborne et al. (GCN Circ. 43535), we marginally detect a source at a preliminary magnitude of:
r = 22.80 +/- 0.28
At this same position, we measure the following 3-sigma upper limit: z > 21.6
Our observations suggest the candidate has faded since the observations reported by Saccardi et al. (GCN Circ. 43530), Wu et al. (GCN Circ. 43537), and Hagio et al. (GCN CIrc. 43540).
We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams.
COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.
GCN Circular #43546
A. C. Trigg (NPP ORAU, NASA MSFC) reports on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 17:51:07.74 UT on 27 January 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260127A (trigger 791229072/260127744), which was also detected by Swift BAT and XRT (N. J. Klingler et al. 2026, GCN 43529). The Fermi GBM real-time localization (GCN 43528) is consistent with the Swift BAT position.
The angle from the Fermi LAT boresight is 88 degrees.
The GBM light curve single emission episode with a duration (T90) of about 36 s (50-300 keV). The time-averaged spectrum from T0-15 to T0+32 s is best fit by a power law function. The power law index is -1.55 +/- 0.04. A Comptonized model fits the spectra equally well with power law index is -1.29 +/- 0.06 and the cutoff energy, parameterized as Epeak, is 490 +/- 25 keV.
The event fluence (10-1000 keV) in this time interval is (3.8 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.32 s in the 10-1000 keV band is 2.7 +/- 0.5 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"

GCN Circular #43548
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 260127A ( Fermi GBM team, GCN 43528) errorbox 1 days 15723 sec after notice time and 1 days 15745 sec after trigger time at 2026-01-28 22:13:32 UT, with upper limit up to 16.8 mag. The observations began at zenith distance = 80 deg. The sun altitude is -63.0 deg.
The galactic latitude b = 45 deg., longitude l = 357 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3117030
We obtain a following upper limits.

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

  102175 | 2026-01-28 22:13:32 |   MASTER-Kislovodsk | (14h 51m 08.24s , +02d 48m 33.2s) |   C |    60 | 16.6 |        
  102578 | 2026-01-28 22:20:15 |   MASTER-Kislovodsk | (15h 05m 19.35s , +04d 43m 03.8s) |   C |    60 | 16.6 |        
  102789 | 2026-01-28 22:23:46 |   MASTER-Kislovodsk | (15h 03m 14.11s , +02d 50m 18.9s) |   C |    60 | 16.5 |        
  102901 | 2026-01-28 22:25:38 |   MASTER-Kislovodsk | (14h 49m 55.15s , -00d 58m 21.9s) |   C |    60 | 16.8 |        
  103234 | 2026-01-28 22:31:11 |   MASTER-Kislovodsk | (15h 02m 06.17s , +00d 55m 55.7s) |   C |    60 | 16.8 |        
  103454 | 2026-01-28 22:34:51 |   MASTER-Kislovodsk | (14h 50m 37.84s , -02d 52m 07.1s) |   C |    60 | 16.5 |        
  103569 | 2026-01-28 22:36:46 |   MASTER-Kislovodsk | (15h 15m 11.23s , +02d 50m 27.3s) |   C |    60 | 16.5 |        
  103928 | 2026-01-28 22:42:46 |   MASTER-Kislovodsk | (15h 13m 59.01s , +00d 56m 55.7s) |   C |    60 | 16.6 |        
  104040 | 2026-01-28 22:44:38 |   MASTER-Kislovodsk | (14h 52m 27.85s , -04d 45m 35.0s) |   C |    60 | 16.6 |        
  104156 | 2026-01-28 22:46:33 |   MASTER-Kislovodsk | (15h 02m 42.73s , -02d 51m 50.3s) |   C |    60 | 16.6 |        
  104268 | 2026-01-28 22:48:25 |   MASTER-Kislovodsk | (15h 27m 17.10s , +02d 49m 26.6s) |   C |    60 | 16.5 |        
  104390 | 2026-01-28 22:50:27 |   MASTER-Kislovodsk | (15h 13m 49.40s , -00d 57m 33.9s) |   C |    60 | 16.6 |        
  104620 | 2026-01-28 22:54:17 |   MASTER-Kislovodsk | (15h 26m 00.01s , +00d 54m 54.2s) |   C |    60 | 16.5 |        
  104726 | 2026-01-28 22:56:03 |   MASTER-Kislovodsk | (15h 04m 25.84s , -04d 43m 38.4s) |   C |    60 | 16.7 |        
  104959 | 2026-01-28 22:59:56 |   MASTER-Kislovodsk | (14h 55m 16.13s , -06d 36m 58.7s) |   C |    60 | 16.7 |        
  105183 | 2026-01-28 23:03:40 |   MASTER-Kislovodsk | (15h 25m 53.63s , -00d 56m 48.2s) |   C |    60 | 16.7 |        
  105413 | 2026-01-28 23:07:30 |   MASTER-Kislovodsk | (15h 07m 22.73s , -06d 39m 00.3s) |   C |    60 | 16.6 |        
  105526 | 2026-01-28 23:09:23 |   MASTER-Kislovodsk | (15h 16m 34.84s , -04d 44m 35.6s) |   C |    60 | 16.8 |

Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
[1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html

GCN Circular #43557
A. Volnova (IKI), A. Moskvitin (SAO RAS), N. Pankov (IKI), A. Tarasenkov (INASAN), I. Sokolov (INASAN, KIAM), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN collaboration:
We observed the field of the Swift/Fermi/GBM GRB 260127A (Fermi GBM Team, GCN Circ. 43528; Klingler et al., GCN Circ. 43529; Osborne et al., GCN 43535; D'Ai et al, GCN 43539; Trigg, GCN 43546) in R-band with the RC500 telescope of the INASAN-Kislovodsk observatory starting on 2026-01-27 (UT) 23:20:50, in Rc-band with the Zeiss-1000 of the SAO RAS starting on 2026-01-28 (UT) 01:01:40, and in clear light with the 0.8-meter K-800 telescope of the Terskol observatory of INASAN 2026-01-28 (UT) 01:46:18. The optical counterpart reported previously (Saccardi & Malesani, GCN 43530; Lipunov et al., GCNs 43531, 43548; Wu et al., GCN 43537; Hagio et al., GCN 43540; Malesani et al, GCN 43543; Magnani et al., GCN 43544) is clearly detected in the stacked frame of the Zeiss-1000 and is not detected in the stacked frames of the RC500 and K-800 telescopes. Preliminary photometry and observational details are the following:
```
Date           UT start  t-T0       Exp.    Filter Obj.   Err.   UL       Site/Telescope
                        (mid,days)  (n*s)                       (3sigma)
2026-01-27     23:20:50  0.30822    110*120 R      n/d    n/d    21.9     INASAN-Kislovodsk/RC500
2026-01-28     01:01:40  0.32599    15*300  Rc     22.00  0.22   22.7     SAO RAS/Zeiss-1000
2026-01-28     01:46:18  0.35748    94*30   Clear  n/d    n/d    21.2     Terskol/K800
```
The photometry is based on several nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction.
We would like to thank the SAO RAS engineering team: Afanasieva I. V., Pritychenko M. A., Egorov V. A., Shaldyrvan I. V. for their excellent support.
GCN Circular #43563
T. Parsotan (GSFC), S. D. Barthelmy (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team)
Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 260127A (trigger #1444088) (Kilingler et al., GCN Circ. 43529). The BAT ground-calculated position is RA, Dec = 231.879, 6.758 deg which is
```
   RA(J2000)  =  15h 27m 30.9s 
   Dec(J2000) = +06d 45' 28.4" 
```
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 40%.
The classic pulse has a single peak that started around T+20 sec and has a structure before it at ~T+5 sec. The duration of the burst is ~100 sec. T90 (15-350 keV) is 104.06 +- 19.41 sec (estimated error including systematics).
The time-averaged spectrum using multiple GTIs from T-2.68 to T+7.62, T+9.00 to T+84.43 sec, and T+86.00 to T+117.04 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.76 +- 0.15. The fluence in the 15-150 keV band is 2.3 +- 0.2 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+33.36 sec in the 15-150 keV band is 2.1 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1444088
GCN Circular #43596
Yang-Zhao Ren, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team:
GECAM-B was triggered on-ground by GRB 260127A, at 2026-01-27T17:51:07.000 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #43528) and Swift/BAT (Klingler et al., GCN #43529).
According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of a pulse with a duration (T90) of 6 +1/-1 s.
The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260127A.png
Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS).

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Jochen Greiner, last update: 02-Feb-2026 [Disclaimer]