Gamma-ray Burst 260101A

(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:     Thu 01 Jan 26 00:56:44 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1429608,   Seg_Num: 0
GRB_RA:           86.465d {+05h 45m 51s} (J2000),
                  87.088d {+05h 48m 21s} (current),
                  85.266d {+05h 41m 04s} (1950)
GRB_DEC:         +63.568d {+63d 34' 06"} (J2000),
                 +63.576d {+63d 34' 35"} (current),
                 +63.548d {+63d 32' 54"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       1463 [cnts]    Image_Peak=113 [image_cnts]
TRIGGER_DUR:     0.512 [sec] 
TRIGGER_INDEX:   40     E_range: 25-100 keV
BKG_INTEN:       15239 [cnts]
BKG_TIME:        3379.03 SOD {00:56:19.03} UT
BKG_DUR:         8 [sec]
GRB_DATE:        21041 TJD;     1 DOY;   26/01/01
GRB_TIME:        3390.30 SOD {00:56:30.30} UT
GRB_PHI:          44.20 [deg]
GRB_THETA:        21.14 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     13.34 [sigma]
IMAGE_SIGNIF:    8.02 [sigma]
MERIT_PARAMS:     +1  +0  +0  -1  +2  -2  +0  +0 +74  +0 
SUN_POSTN:       281.54d {+18h 46m 09s}  -23.01d {-23d 00' 40"}
SUN_DIST:        138.31 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       64.80d {+04h 19m 11s}  +26.54d {+26d 32' 09"}
MOON_DIST:        39.78 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      149.49, 17.25 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       87.94, 40.15 [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 = 309.40,14.83 [deg].
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(0.0<100sec) coincident with the FERMI_GBM event (trignum=788921795).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Thu 01 Jan 26 00:57:00 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      45
TRIGGER_NUM:     788921795
GRB_RA:          115.233d {+07h 40m 56s} (J2000),
                 115.834d {+07h 43m 20s} (current),
                 114.072d {+07h 36m 17s} (1950)
GRB_DEC:         +64.033d {+64d 01' 60"} (J2000),
                 +63.971d {+63d 58' 15"} (current),
                 +64.149d {+64d 08' 58"} (1950)
GRB_ERROR:       12.12 [deg radius, statistical plus systematic]
GRB_INTEN:       146 [cnts/sec]
DATA_SIGNIF:     8.40 [sigma]
INTEG_TIME:      1.024 [sec]
GRB_DATE:        21041 TJD;     1 DOY;   26/01/01
GRB_TIME:        3390.65 SOD {00:56:30.65} UT
GRB_PHI:         100.00 [deg]
GRB_THETA:        30.00 [deg]
DATA_TIME_SCALE: 1.0240 [sec]
HARD_RATIO:      0.86
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      96%  GRB
2nd_MOST_LIKELY:   1%  Generic Transient
DETECTORS:       1,0,0, 0,0,0, 0,0,0, 1,0,0, 0,0,
SUN_POSTN:       281.54d {+18h 46m 09s}  -23.01d {-23d 00' 40"}
SUN_DIST:        137.96 [deg]   Sun_angle= 11.0 [hr] (West of Sun)
MOON_POSTN:       64.80d {+04h 19m 12s}  +26.54d {+26d 32' 11"}
MOON_DIST:        49.58 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      152.39, 29.57 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      104.51, 41.86 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260101039/quicklook/glg_lc_medres34_bn260101039.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 2.18,-6.17 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1429608).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Thu 01 Jan 26 00:57:09 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      58
TRIGGER_NUM:     788921795
GRB_RA:           80.383d {+05h 21m 32s} (J2000),
                  81.140d {+05h 24m 34s} (current),
                  78.933d {+05h 15m 44s} (1950)
GRB_DEC:         +71.333d {+71d 19' 60"} (J2000),
                 +71.357d {+71d 21' 24"} (current),
                 +71.283d {+71d 16' 60"} (1950)
GRB_ERROR:       7.07 [deg radius, statistical plus systematic]
GRB_INTEN:       297 [cnts/sec]
DATA_SIGNIF:     13.50 [sigma]
INTEG_TIME:      1.024 [sec]
GRB_DATE:        21041 TJD;     1 DOY;   26/01/01
GRB_TIME:        3390.65 SOD {00:56:30.65} UT
GRB_PHI:         101.00 [deg]
GRB_THETA:        45.00 [deg]
DATA_TIME_SCALE: 1.0240 [sec]
HARD_RATIO:      0.94
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      97%  GRB
2nd_MOST_LIKELY:   1%  Generic Transient
DETECTORS:       1,0,0, 0,0,0, 0,0,0, 1,0,0, 0,0,
SUN_POSTN:       281.54d {+18h 46m 09s}  -23.01d {-23d 00' 40"}
SUN_DIST:        130.26 [deg]   Sun_angle= -10.6 [hr] (East of Sun)
MOON_POSTN:       64.80d {+04h 19m 13s}  +26.54d {+26d 32' 12"}
MOON_DIST:        45.75 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      141.14, 18.85 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       85.41, 48.05 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260101039/quicklook/glg_lc_medres34_bn260101039.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 2.18,-6.17 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1429608).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Thu 01 Jan 26 00:57:27 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      72
TRIGGER_NUM:     788921795
GRB_RA:           96.433d {+06h 25m 44s} (J2000),
                  97.151d {+06h 28m 36s} (current),
                  95.051d {+06h 20m 12s} (1950)
GRB_DEC:         +69.500d {+69d 30' 00"} (J2000),
                 +69.483d {+69d 28' 58"} (current),
                 +69.528d {+69d 31' 40"} (1950)
GRB_ERROR:       6.15 [deg radius, statistical plus systematic]
GRB_INTEN:       376 [cnts/sec]
DATA_SIGNIF:     24.70 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        21041 TJD;     1 DOY;   26/01/01
GRB_TIME:        3390.65 SOD {00:56:30.65} UT
GRB_PHI:         102.00 [deg]
GRB_THETA:        40.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      1.19
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      97%  GRB
2nd_MOST_LIKELY:   1%  Generic SGR
DETECTORS:       1,0,0, 0,0,0, 0,0,0, 1,0,0, 0,0,
SUN_POSTN:       281.54d {+18h 46m 09s}  -23.01d {-23d 00' 40"}
SUN_DIST:        133.45 [deg]   Sun_angle= -11.7 [hr] (East of Sun)
MOON_POSTN:       64.81d {+04h 19m 13s}  +26.54d {+26d 32' 14"}
MOON_DIST:        46.89 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      145.16, 23.09 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       93.25, 46.13 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260101039/quicklook/glg_lc_medres34_bn260101039.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 2.18,-6.17 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1429608).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Thu 01 Jan 26 00:57:19 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      57
TRIGGER_NUM:     788921795
GRB_RA:          111.470d {+07h 25m 53s} (J2000),
                 112.074d {+07h 28m 18s} (current),
                 110.304d {+07h 21m 13s} (1950)
GRB_DEC:         +63.620d {+63d 37' 12"} (J2000),
                 +63.566d {+63d 33' 59"} (current),
                 +63.719d {+63d 43' 09"} (1950)
GRB_ERROR:       10.50 [deg radius, statistical only]
DATA_SIGNIF:     11.40 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        21041 TJD;     1 DOY;   26/01/01
GRB_TIME:        3390.65 SOD {00:56:30.65} UT
GRB_PHI:         103.00 [deg]
GRB_THETA:        31.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:       281.54d {+18h 46m 09s}  -23.01d {-23d 00' 40"}
SUN_DIST:        138.84 [deg]   Sun_angle= 11.3 [hr] (West of Sun)
MOON_POSTN:       64.80d {+04h 19m 13s}  +26.54d {+26d 32' 13"}
MOON_DIST:        47.91 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      152.74, 27.89 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      102.46, 41.11 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260101039/quicklook/glg_lc_medres34_bn260101039.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_788921795.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.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1429608).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Thu 01 Jan 26 00:58:08 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      0
TRIGGER_NUM:     788921795
GRB_RA:           82.390d {+05h 29m 34s} (J2000),
                  83.124d {+05h 32m 30s} (current),
                  80.981d {+05h 23m 55s} (1950)
GRB_DEC:         +70.300d {+70d 17' 60"} (J2000),
                 +70.318d {+70d 19' 06"} (current),
                 +70.260d {+70d 15' 35"} (1950)
GRB_ERROR:       4.39 [deg radius, statistical only]
DATA_SIGNIF:     15.60 [sigma]
DATA_INTERVAL:   7.168 [sec]
GRB_DATE:        21041 TJD;     1 DOY;   26/01/01
GRB_TIME:        3390.65 SOD {00:56:30.65} UT
GRB_PHI:         102.00 [deg]
GRB_THETA:        44.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       281.54d {+18h 46m 09s}  -23.01d {-23d 00' 40"}
SUN_DIST:        131.47 [deg]   Sun_angle= -10.8 [hr] (East of Sun)
MOON_POSTN:       64.81d {+04h 19m 15s}  +26.54d {+26d 32' 18"}
MOON_DIST:        45.03 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      142.44, 18.93 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       86.25, 46.96 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260101039/quicklook/glg_lc_medres34_bn260101039.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_788921795.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
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(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1429608).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Thu 01 Jan 26 00:58:40 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      2
TRIGGER_NUM:     788921795
GRB_RA:           63.540d {+04h 14m 10s} (J2000),
                  64.149d {+04h 16m 36s} (current),
                  62.375d {+04h 09m 30s} (1950)
GRB_DEC:         +64.750d {+64d 45' 00"} (J2000),
                 +64.814d {+64d 48' 50"} (current),
                 +64.623d {+64d 37' 24"} (1950)
GRB_ERROR:       4.20 [deg radius, statistical only]
DATA_SIGNIF:     19.00 [sigma]
DATA_INTERVAL:   11.264 [sec]
GRB_DATE:        21041 TJD;     1 DOY;   26/01/01
GRB_TIME:        3390.65 SOD {00:56:30.65} UT
GRB_PHI:         110.00 [deg]
GRB_THETA:        51.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       281.54d {+18h 46m 09s}  -23.01d {-23d 00' 40"}
SUN_DIST:        131.68 [deg]   Sun_angle= -9.5 [hr] (East of Sun)
MOON_POSTN:       64.82d {+04h 19m 17s}  +26.54d {+26d 32' 22"}
MOON_DIST:        38.28 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      142.50,  9.90 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       75.02, 42.68 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260101039/quicklook/glg_lc_medres34_bn260101039.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_788921795.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
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(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1429608).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Thu 01 Jan 26 01:05:54 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     788921795
GRB_RA:           83.700d {+05h 34m 48s} (J2000),
                  84.329d {+05h 37m 19s} (current),
                  82.493d {+05h 29m 58s} (1950)
GRB_DEC:         +64.020d {+64d 01' 12"} (J2000),
                 +64.035d {+64d 02' 06"} (current),
                 +63.987d {+63d 59' 12"} (1950)
GRB_ERROR:       3.57 [deg radius, statistical only]
GRB_DATE:        21041 TJD;     1 DOY;   26/01/01
GRB_TIME:        3390.65 SOD {00:56:30.65} UT
GRB_PHI:         112.00 [deg]
GRB_THETA:        43.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       281.54d {+18h 46m 10s}  -23.01d {-23d 00' 38"}
SUN_DIST:        137.42 [deg]   Sun_angle= -10.9 [hr] (East of Sun)
MOON_POSTN:       64.90d {+04h 19m 37s}  +26.55d {+26d 33' 08"}
MOON_DIST:        39.53 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      148.48, 16.38 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       86.37, 40.66 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260101039/quicklook/glg_lc_medres34_bn260101039.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260101039/quicklook/glg_locplot_all_bn260101039.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=1429608).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 01 Jan 26 00:58:02 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     1429608,   Seg_Num: 0
POINT_RA:         86.459d {+05h 45m 50s} (J2000)
POINT_DEC:       +63.563d {+63d 33' 48"} (J2000)
IMG_START_DATE:  21041 TJD;     1 DOY;   26/01/01
IMG_START_TIME:  3474.96 SOD {00:57:54.96} UT,   84.7 [sec] since BAT Trigger Time
COUNTS:          12    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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 01 Jan 26 01:01:02 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1429608,   Seg_Num: 0
GRB_RA:           86.465d {+05h 45m 51s} (J2000),
                  87.088d {+05h 48m 21s} (current),
                  85.266d {+05h 41m 04s} (1950)
GRB_DEC:         +63.568d {+63d 34' 06"} (J2000),
                 +63.576d {+63d 34' 35"} (current),
                 +63.548d {+63d 32' 54"} (1950)
GRB_DATE:        21041 TJD;     1 DOY;   26/01/01
GRB_TIME:        3390.30 SOD {00:56:30.30} UT
TRIGGER_INDEX:   40
GRB_PHI:          44.20 [deg]
GRB_THETA:        21.14 [deg]
DELTA_TIME:      -5.00 [sec]
TRIGGER_DUR:     0.512 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     13.34 [sigma]
IMAGE_SIGNIF:    8.02 [sigma]
LC_URL:          sw01429608000msb.lc
SUN_POSTN:       281.54d {+18h 46m 09s}  -23.01d {-23d 00' 39"}
SUN_DIST:        138.31 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       64.85d {+04h 19m 23s}  +26.54d {+26d 32' 37"}
MOON_DIST:        39.77 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      149.49, 17.25 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       87.94, 40.15 [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 = 309.40,14.83 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 01 Jan 26 01:03:35 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1429608,   Seg_Num: 0
POINT_RA:         86.456d {+05h 45m 49s} (J2000)
POINT_DEC:       +63.564d {+63d 33' 52"} (J2000)
POINT_ROLL:      338.952d
IMG_START_DATE:  21041 TJD;     1 DOY;   26/01/01
IMG_START_TIME:  3534.59 SOD {00:58:54.59} UT,   144.3 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.589
N_STARS:         132
X_OFFSET:        268 [pixels]
Y_OFFSET:        338 [pixels]
X_MAX:           1707 [pixels]
Y_MAX:           1777 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw01429608000msufc0144.fits
SUN_POSTN:       281.54d {+18h 46m 10s}  -23.01d {-23d 00' 39"}
SUN_DIST:        138.31 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       64.88d {+04h 19m 30s}  +26.55d {+26d 32' 53"}
MOON_DIST:        39.75 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      149.49, 17.24 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       87.94, 40.15 [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:     Thu 01 Jan 26 01:03:25 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1429608,   Seg_Num: 0
POINT_RA:         86.456d {+05h 45m 49s} (J2000)
POINT_DEC:       +63.564d {+63d 33' 52"} (J2000)
POINT_ROLL:      338.952d
IMG_START_DATE:  21041 TJD;     1 DOY;   26/01/01
IMG_START_TIME:  3534.59 SOD {00:58:54.59} UT,   144.3 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.589
N_STARS:         132
X_OFFSET:        268 [pixels]
Y_OFFSET:        338 [pixels]
X_MAX:           1707 [pixels]
Y_MAX:           1777 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw01429608000msufc0144.fits
SUN_POSTN:       281.54d {+18h 46m 10s}  -23.01d {-23d 00' 39"}
SUN_DIST:        138.31 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       64.87d {+04h 19m 30s}  +26.55d {+26d 32' 52"}
MOON_DIST:        39.75 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      149.49, 17.24 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       87.94, 40.15 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN Circular #43284
The Fermi GBM team reports the detection of a likely LONG GRB
At 00:56:30 UT on 1 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260101A (trigger 788921795.64985 / 260101039).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 83.7, Dec = 64.0 (J2000 degrees, equivalent to J2000 05h 34m, 64d 00'), with a statistical uncertainty of 3.6 degrees.
The angle from the Fermi LAT boresight is 43.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260101039/quicklook/glg_skymap_all_bn260101039.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/bn260101039/quicklook/glg_healpix_all_bn260101039.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260101039/quicklook/glg_lc_medres34_bn260101039.gif
GCN Circular #43285
S. B. Cenko (GSFC), J. J. DeLaunay (PSU), S. Dichiara (PSU), R. Gupta (NASA GSFC), N. P. M. Kuin (UCL-MSSL), A. Y. Lien (U Tampa), K. L. Page (U Leicester) and T. M. Parsotan (GSFC) report on behalf of the Neil Gehrels Swift Observatory Team:
At 00:56:30 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 260101A (trigger=1429608). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 86.465, +63.568 which is
```
   RA(J2000) = 05h 45m 51s
   Dec(J2000) = +63d 34' 06"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 40 sec. The peak count rate was ~7000 counts/sec (15-350 keV), at ~25 sec after the trigger.
The XRT began observing the field at 00:57:54.9 UT, 84.7 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 86.42741, 63.59172 which is equivalent to:
```
   RA(J2000)  = 05h 45m 42.58s
   Dec(J2000) = +63d 35' 30.2"
```
with an uncertainty of 3.5 arcseconds (radius, 90% containment). This location is 104 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 (1.60 x 10^21 cm^-2, Willingale et al. 2013), with an excess column of 3.3 (+3.30/-2.79) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 250 seconds with the U filter starting 144 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at
```
  RA(J2000)  =	05:45:42.94 =  86.42890
  DEC(J2000) = +63:35:32.1  =  63.59225
```
with a 90%-confidence error radius of about 0.61 arc sec. This position is 4.5 arc sec. from the center of the XRT error circle. The estimated magnitude is 16.03 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.179.
Burst Advocate for this burst is S. B. Cenko (brad.cenko AT nasa.gov). 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:     Thu 01 Jan 26 01:16:21 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1429608,   Seg_Num: 0
POINT_RA:         86.456d {+05h 45m 50s} (J2000)
POINT_DEC:       +63.565d {+63d 33' 52"} (J2000)
POINT_ROLL:      338.952d
IMG_START_DATE:  21041 TJD;     1 DOY;   26/01/01
IMG_START_TIME:  4266.11 SOD {01:11:06.11} UT,   875.8 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.319
N_STARS:         101
X_OFFSET:        268 [pixels]
Y_OFFSET:        338 [pixels]
X_MAX:           1707 [pixels]
Y_MAX:           1777 [pixels]
DET_THRESH:      6
PHOTO_THRESH:    2
SL_URL:          sw01429608000msufc0875.fits
SUN_POSTN:       281.55d {+18h 46m 12s}  -23.01d {-23d 00' 36"}
SUN_DIST:        138.31 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       65.02d {+04h 20m 05s}  +26.57d {+26d 34' 15"}
MOON_DIST:        39.69 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      149.49, 17.24 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       87.94, 40.15 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 01 Jan 26 01:16:36 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1429608,   Seg_Num: 0
POINT_RA:         86.456d {+05h 45m 50s} (J2000)
POINT_DEC:       +63.565d {+63d 33' 52"} (J2000)
POINT_ROLL:      338.952d
IMG_START_DATE:  21041 TJD;     1 DOY;   26/01/01
IMG_START_TIME:  4266.11 SOD {01:11:06.11} UT,   875.8 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.319
N_STARS:         101
X_OFFSET:        268 [pixels]
Y_OFFSET:        338 [pixels]
X_MAX:           1707 [pixels]
Y_MAX:           1777 [pixels]
DET_THRESH:      6
PHOTO_THRESH:    2
SL_URL:          sw01429608000msufc0875.fits
SUN_POSTN:       281.55d {+18h 46m 12s}  -23.01d {-23d 00' 36"}
SUN_DIST:        138.31 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       65.02d {+04h 20m 06s}  +26.57d {+26d 34' 16"}
MOON_DIST:        39.69 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      149.49, 17.24 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       87.94, 40.15 [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:     Thu 01 Jan 26 01:17:15 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1429608,   Seg_Num: 0
POINT_RA:         86.456d {+05h 45m 50s} (J2000)
POINT_DEC:       +63.565d {+63d 33' 52"} (J2000)
ROLL:            338.952d
IMG_START_DATE:  21041 TJD;     1 DOY;   26/01/01
IMG_START_TIME:  4266.11 SOD {01:11:06.11} UT,   875.8 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     788922703
X_OFFSET:        827 [pixels]
Y_OFFSET:        897 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       987
Y_GRB_POS:       1057
BINNING_INDEX:   1
IM_URL:          sw01429608000msuni0912.fits
SUN_POSTN:       281.55d {+18h 46m 12s}  -23.01d {-23d 00' 36"}
SUN_DIST:        138.31 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       65.03d {+04h 20m 08s}  +26.57d {+26d 34' 20"}
MOON_DIST:        39.69 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      149.49, 17.24 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       87.94, 40.15 [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:     Thu 01 Jan 26 01:16:46 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     1429608,   Seg_Num: 0
GRB_RA:           86.4281d {+05h 45m 42.74s} (J2000),
                  87.0523d {+05h 48m 12.55s} (current),
                  85.2287d {+05h 40m 54.87s} (1950)
GRB_DEC:         +63.5921d {+63d 35' 31.5"} (J2000),
                 +63.6003d {+63d 36' 01.1"} (current),
                 +63.5718d {+63d 34' 18.6"} (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:  21041 TJD;     1 DOY;   26/01/01
IMG_START_TIME:  3677.00 SOD {01:01:17.00} UT,   286.7 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       281.55d {+18h 46m 12s}  -23.01d {-23d 00' 36"}
SUN_DIST:        138.28 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       65.03d {+04h 20m 06s}  +26.57d {+26d 34' 17"}
MOON_DIST:        39.71 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      149.46, 17.24 [deg] galactic lon,lat of the burst
ECL_COORDS:       87.92, 40.18 [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 0.58% < P(seren) < 1.1%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 01 Jan 26 01:17:20 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1429608,   Seg_Num: 0
POINT_RA:         86.456d {+05h 45m 50s} (J2000)
POINT_DEC:       +63.565d {+63d 33' 52"} (J2000)
ROLL:            338.952d
IMG_START_DATE:  21041 TJD;     1 DOY;   26/01/01
IMG_START_TIME:  4266.11 SOD {01:11:06.11} UT,   875.8 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     788922703
X_OFFSET:        827 [pixels]
Y_OFFSET:        897 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       987
Y_GRB_POS:       1057
BINNING_INDEX:   1
IM_URL:          sw01429608000msuni0912.fits
SUN_POSTN:       281.55d {+18h 46m 12s}  -23.01d {-23d 00' 36"}
SUN_DIST:        138.31 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       65.03d {+04h 20m 08s}  +26.57d {+26d 34' 21"}
MOON_DIST:        39.69 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      149.49, 17.24 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       87.94, 40.15 [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:     Thu 01 Jan 26 01:04:47 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1429608,   Seg_Num: 0
POINT_RA:         86.456d {+05h 45m 49s} (J2000)
POINT_DEC:       +63.564d {+63d 33' 52"} (J2000)
ROLL:            338.952d
IMG_START_DATE:  21041 TJD;     1 DOY;   26/01/01
IMG_START_TIME:  3534.59 SOD {00:58:54.59} UT,   144.3 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     788921971
X_OFFSET:        827 [pixels]
Y_OFFSET:        897 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       987
Y_GRB_POS:       1057
BINNING_INDEX:   1
IM_URL:          sw01429608000msuni0181.fits
SUN_POSTN:       281.54d {+18h 46m 10s}  -23.01d {-23d 00' 38"}
SUN_DIST:        138.31 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       64.89d {+04h 19m 33s}  +26.55d {+26d 33' 01"}
MOON_DIST:        39.74 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      149.49, 17.24 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       87.94, 40.15 [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:     Thu 01 Jan 26 01:07:02 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     1429608,   Seg_Num: 0
GRB_RA:           86.4288d {+05h 45m 42.91s} (J2000),
                  87.0530d {+05h 48m 12.72s} (current),
                  85.2294d {+05h 40m 55.04s} (1950)
GRB_DEC:         +63.5922d {+63d 35' 31.9"} (J2000),
                 +63.6004d {+63d 36' 01.5"} (current),
                 +63.5719d {+63d 34' 19.0"} (1950)
GRB_ERROR:       0.6 [arcsec radius, statistical only]
GRB_MAG:         16.03 +/- 0.14 [mag]
FILTER:          7, U
IMG_START_DATE:  21041 TJD;     1 DOY;   26/01/01
IMG_START_TIME:  3540.00 SOD {00:59:00.00} UT,   149.7 [sec] since BAT Trigger Time
SUN_POSTN:       281.54d {+18h 46m 11s}  -23.01d {-23d 00' 38"}
SUN_DIST:        138.28 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       64.91d {+04h 19m 40s}  +26.55d {+26d 33' 15"}
MOON_DIST:        39.75 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      149.46, 17.24 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       87.92, 40.18 [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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 01 Jan 26 01:04:17 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1429608,   Seg_Num: 0
GRB_RA:           86.4264d {+05h 45m 42.33s} (J2000),
                  87.0506d {+05h 48m 12.14s} (current),
                  85.2270d {+05h 40m 54.47s} (1950)
GRB_DEC:         +63.5917d {+63d 35' 30.1"} (J2000),
                 +63.5999d {+63d 35' 59.7"} (current),
                 +63.5714d {+63d 34' 17.1"} (1950)
GRB_ERROR:       3.7 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  21041 TJD;     1 DOY;   26/01/01
IMG_START_TIME:  3677.00 SOD {01:01:17.00} UT,   286.7 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       281.54d {+18h 46m 10s}  -23.01d {-23d 00' 39"}
SUN_DIST:        138.28 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       64.88d {+04h 19m 32s}  +26.55d {+26d 32' 58"}
MOON_DIST:        39.76 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      149.46, 17.24 [deg] galactic lon,lat of the burst
ECL_COORDS:       87.92, 40.18 [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:     Thu 01 Jan 26 01:05:02 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1429608,   Seg_Num: 0
POINT_RA:         86.456d {+05h 45m 49s} (J2000)
POINT_DEC:       +63.564d {+63d 33' 52"} (J2000)
ROLL:            338.952d
IMG_START_DATE:  21041 TJD;     1 DOY;   26/01/01
IMG_START_TIME:  3534.59 SOD {00:58:54.59} UT,   144.3 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     788921971
X_OFFSET:        827 [pixels]
Y_OFFSET:        897 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       987
Y_GRB_POS:       1057
BINNING_INDEX:   1
IM_URL:          sw01429608000msuni0181.fits
SUN_POSTN:       281.54d {+18h 46m 10s}  -23.01d {-23d 00' 38"}
SUN_DIST:        138.31 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:       64.89d {+04h 19m 34s}  +26.55d {+26d 33' 02"}
MOON_DIST:        39.74 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      149.49, 17.24 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       87.94, 40.15 [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 Circular #43286
I. Pérez-Fournon (IAC and ULL), F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz, I. Correa-Plasencia, E. Lekaroz-Urriza, M. Quintana-Ansaldo (all ULL), and A. López-Oramas (IAC and ULL)
Following the detection of the long GRB 260101A, detected by Fermi (Fermi GBM team, GCN #43284) and Swift (Cenko et al., GCN #43285), we observed the field with one of the two Las Cumbres Observatory (LCO) 1-m telescopes, equipped with Sinistro cameras, located at the LCO node at McDonald Observatory, Texas. The observation, a single exposure of 180 sec in the SDSS r' filter, started on 2026-01-01 at 01:55:13 UT, about 58.7 minutes after the Fermi and Swift triggers. The optical counterpart detected by Swift UVOT (Cenko et al., GCN #43285), is clearly detected in our image with a magnitude of r' = 17.67 +/- 0.04, calibrated against PanSTARRS-1 DR2 stars and not corrected for Galactic extinction.
This work makes use of observations from the Las Cumbres Observatory global telescope network (LCO program IAC2025B-008, SGLF and Superluminous Supernovae surveys).
This work made use of the Astro-COLIBRI platform (P. Reichherzer et al. 2021, ApJS, 256, 5).
GCN Circular #43287
A. de Ugarte Postigo (LAM), A. Martin-Carrillo (UCD), C. C. Thoene (AbAO), D. B. Malesani (DAWN/NBI and Radboud), J. F. Agui Fernandez (CAHA), M. A. Aloy (UV), J. P. U. Fynbo (DAWN/NBI), L. Galbany (IEEC-CSIC), S. Geier (GTC), L. Izzo (INAF/OACN and DARK/NBI), G. Lombardi (GTC), N. A. Rakotondrainibe (LAM), B. Schneider (LAM), N. R. Tanvir (Univ. Leicester), R. Scarpa (GTC) report:
We observed the optical counterpart of the new year burst GRB 260101A (Fermi GBM team, GCN 43284, Cenko et al. GCN ) using the Gran Telescopio Canarias (GTC) equipped with the OSIRIS+ instrument.
In the r-band 30-s acquisition image (beginning on 2026-01-01 at 02:13:40.010 UT, that is 1.286 hr after trigger), the optical afterglow is well detected with a magnitude 18.05 ± 0.10 (AB), calibrated against nearby SDSS objects, and not corrected for Galactic extinction.
A total of 2 spectra of 900 s were secured under poor conditions before clouds came in. Indeed, the second spectrum is already affected by a very high background. The first spectrum started on 2026-01-01 at 02:21:06.010 UT (1.410 hr after trigger), using grism R1000B. Continuum is visible over the range 3600-7800 AA. A number of absorption features are detected, which we interpret as due to Ly-alpha, SiII, OI, CII, SiIV, CIV, FeII and AlII, all at a common redshift z = 2.623, which we suggest to be the redshift of GRB 260101A. We note that the Ly-alpha absorption is very weak, making it a rather peculiar sight line.
Happy 2026!!!
This work has used the GRBspec database at http://grbspec.eu (de Ugarte Postigo et al. 2014, doi:10.1117/12.2055774).
GCN Circular #43289
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team.
Using 1689 s of XRT Photon Counting mode data and 3 UVOT images for GRB 260101A, 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 = 86.42902, +63.59238 which is equivalent to:
```
RA (J2000): 05h 45m 42.96s
Dec (J2000): +63d 35' 32.6"
```
with an uncertainty of 2.4 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 #43290
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 260101A ( S. B. Cenko et al., GCN 43285) errorbox 34465 sec after notice time and 34491 sec after trigger time at 2026-01-01 10:31:22 UT, with upper limit up to 17.4 mag. Observations started at twilight. The observations began at zenith distance = 44 deg. The sun altitude is -11.9 deg.
The galactic latitude b = 18 deg., longitude l = 150 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3092325
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   34522 |        MASTER-Tunka |   C |    60 | 17.3 |  Coadd 
   34522 |        MASTER-Tunka |   C |    60 | 17.4 |        
```
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 #43291
P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), 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), E. Ambrosi (INAF-IASFPA) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 6.7 ks of XRT data for GRB 260101A, from 100 s to 28.9 ks after the trigger. The data comprise 165 s in Windowed Timing (WT) mode (the first 10 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode.
The late-time light curve (from T0+5.3 ks) can be modelled with a power-law decay with a decay index of alpha=1.65 (+/-0.17).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.02 (+0.16, -0.15). The best-fitting absorption column is 2.1 (+/-0.5) x 10^21 cm^-2, consistent with the Galactic value of 1.6 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.91 (+0.16, -0.15) and a best-fitting absorption column of 2.2 (+0.6, -0.5) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.8 x 10^-11 (5.1 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     2.2 (+0.6, -0.5) x 10^21 cm^-2
Galactic foreground: 1.6 x 10^21 cm^-2
Excess significance: 1.8 sigma
Photon index:	     1.91 (+0.16, -0.15)
```
If the light curve continues to decay with a power-law decay index of 1.65, the count rate at T+24 hours will be 3.9 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.5 x 10^-13 (2.0 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01429608.
This circular is an official product of the Swift-XRT team.
GCN Circular #43292
SVOM/GRM team: Zheng-Hang Yu, Chen-Wei Wang, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Hui Yang (IRAP)
Report on behalf of the SVOM team:
SVOM/GRM was triggered in-flight by a burst GRB 260101A (SVOM trigger reference: sb26010101) at 2026-01-01T00:56:37.000 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43284) and Swift (S. B. Cenko et al., GCN #43285).
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a precursor followed by a main episode with multiple peaks a T90 of 33.0 +5.5/-3.0 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260101A.png
In addition, the position of this burst, as determined by Swift/XRT (RA= 89.43, DEC= 63.59 GCN#43285), is located at about 53 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view.
With this localization, the time-averaged spectrum from T0-9 to T0+26 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.39 +/-0.11 and the cutoff energy, parameterized as Epeak, is 150 +48/-27 keV. The event fluence (10-1000 keV) in this time interval is (8.10 +0.83/-0.66)E-06 erg/cm^2.
The 1s peak spectrum, measured from T0+18.5 to T0+19.5 s, if fitted by a power law function with an exponential high-energy cutoff, the power law index is -0.89 +0.15/-0.16 and the cutoff energy, parameterized as Epeak, is 109 +14/-10 keV. The flux (10-1000 keV) in this time interval is (8.99 +0.63/-0.56)E-07 erg/cm^2/s.
With the redshift z = 2.623 by GTC (A. de Ugarte Postigo et al., GCN#43287), GRB 260101A is more consistent with Type II GRBs in the 'Amati' relation diagram, as shown at:https://www.bursthub.cn//admin/static/svgrb260101A_amati.png And the localization in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260101A_yonetoku.png
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS.
The SVOM point of contact for this burst is: Zheng-Hang Yu(IHEP)(zhyu@ihep.ac.cn)
GCN Circular #43293
A. Saccardi (CEA/Irfu), L. Izzo (INAF/OACN and DARK/NBI), A. Martin-Carrillo (UCD), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), K. Valeckas (NOT & NBI), report on behalf of a larger collaboration:
We observed the optical afterglow (Cenko et al., GCN 43285; Perez-Fournon et al., GCN 43286; de Ugarte Postigo et al., GCN 43287) of GRB 260101A detected by Fermi (Fermi GBM team, GCN 43284), Swift (Cenko et al., GCN 43285) and SVOM/GRM (Yu et al., GCN 43292) with the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. A spectrum using grism #4 was secured starting on 2026 Jan 1 at 01:43:54 UT (47 min after the GRB trigger).
Due to bad weather and seeing, we only got two spectra, one of which had a very short exposure time, resulting in a relatively low S/N for the stacked spectrum. The total exposure time is ~ 1500 s covering the wavelength range 3800-9300 AA.
From the unfiltered acquisition 30 s image we measure an AB magnitude of 17.30 +/- 0.07, at a mid-time of 45 minutes after the trigger. Our photometry was calibrated against nearby stars from the r-band PanSTARRS catalogue and not corrected for Galactic extinction.
In a preliminary reduction of the stacked spectrum, we detect a trace over the whole observed wavelength range. At the redshift of z = 2.623 reported by de Ugarte Postigo et al. (GCN 43287) we identify different absorption features, which we interpret as due to Si IV, C IV, and Al II. We note that we do not see a clear absorption corresponding to the weak Ly-alpha.
Further analysis is ongoing.
GCN Circular #43294
Chen-Wei Wang, Zheng-Hang Yu, Shao-Lin Xiong (IHEP) report on behalf of GECAM team:
GECAM-B was triggered in-flight by GRB 260101A at 2026-01-01T00:56:34.100 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43284), Swift (S. B. Cenko et al., GCN #43285), SVOM/GRM (Yu et al., GCN #43292).
According to the GECAM-B light curve in about 70-6000 keV, this burst mainly consists of multi-pulses with a duration (T90) of 30.0 +6.0/-3.0 s.
The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260101A.png
Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS).
GCN Circular #43297
B. Hristov (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 00:56:30.65 UT on 01 January 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260101A (trigger 788921795/260101039). which was also detected by Swift (S. B. Cenko et al. 2026, GCN 43285), SVOM/GRM (Z. Yu et al. 2026, GCN 43292) and GECAM-B (C. Wang et al. 2026, GCN 43294). The Fermi GBM on-ground location is consistent with the one reported by Swift.
The angle from the Fermi LAT boresight is 43 degrees.
The GBM light curve consists of multiple emission episodes with a duration (T90) of about 27.4 s (50-300 keV). The time-averaged spectrum from T0 to T0+29.6 s s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.09 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 143.5 +/- 1.5 keV.
The event fluence (10-1000 keV) in this time interval is (6.7 +/- 0.12)e-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+25 s in the 10-1000 keV band is 9.6 +/- 0.3 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: sftp://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 #43312
Noémie Globus (UNAM), Sarah Antier (IJCLAB), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Camila Angulo (UNAM), 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), Nikos Mandarakas (LAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), 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 observed the optical counterpart of the “New Year Burst”, GRB 260101A (Fermi GBM team, GCN Circ. 43284; Cenko et al., GCN Circ. 43285; Pérez-Fournon et al., GCN Circ. 43286; de Ugarte Postigo et al., GCN Circ. 43287; Beardmore et al., GCN Circ. 43289; Lipunov et al., GCN Circ. 43290; D'Avanzo et al., GCN Circ. 43291; SVOM/GRM team et al., GCN Circ. 43292; Saccardi et al., GCN Circ. 43293; Wang et al., GCN Circ. 43294; Hristov et al., GCN Circ. 43297) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2026-01-03 03:22 to 05:47 UTC (50.4 hours to 52.9 hours after the trigger) and obtained 105 minutes of simultaneous exposure in the r and z filters.
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.
In our stacked images, we detect a source at the position of the afterglow (Cenko et al., GCN Circ. 43285) at preliminary magnitudes of:
```
r = 22.11 +/- 0.11,
z = 21.47 +/- 0.09.
```
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 #43318
N. Klingler (NASA-GSFC / UMBC / CRESST II) and S. B. Cenko (GSFC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 260101A 144 s after the BAT trigger (Cenko et al., GCN Circ. 43285). A source consistent with the enhanced XRT position (Evans et al., GCN Circ. 43289) is detected in the initial UVOT exposures.
The preliminary UVOT position is:

    RA  (J2000) =  05:45:42.96 =  86.42898 (deg.)
    Dec (J2000) = +63:35:32.1  =  63.59226 (deg.)

with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence).
Detections and 2-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the exposures are:

Filter   T_start(s)   T_stop(s)   Exp(s)    Mag

b          399.7        419.5      19.8     16.57 +/- 0.10
b          548.6        568.4      19.8     16.74 +/- 0.11
b          697.4        717.1      19.7     16.80 +/- 0.11
b          847.1        866.9      19.8     17.20 +/- 0.14
b         1031.0       1200.3     169.3     17.50 +/- 0.11
b         1329.9       1498.6     168.7     17.69 +/- 0.12
b         1628.4       1648.2      19.8     17.81 +/- 0.18
b        21638.8      22547.2     908.4     21.07 +/- 0.27

u          144.3        394.1     249.8     16.09 +/- 0.05
u          523.8        543.5      19.7     16.44 +/- 0.13
u          672.6        692.3      19.7     17.15 +/- 0.18
u          822.4        842.1      19.7     16.97 +/- 0.16
u          875.8       1025.6     149.8     17.12 +/- 0.08
u         1155.7       1324.8     169.1     17.86 +/- 0.18
u         1454.1       1623.5     169.4     17.86 +/- 0.18
u        95366.4      96053.5     687.1     >21.51

v          450.4        470.2      19.8     16.17 +/- 0.14
v          599.0        618.8      19.8     15.87 +/- 0.12
v          747.6        767.4      19.8     16.28 +/- 0.15
v         1081.4       1251.3     169.9     16.98 +/- 0.15
v         1380.2       1549.5     169.3     17.23 +/- 0.17
v        11438.4      12223.4     785.0     19.27 +/- 0.14
v        27138.9      28046.0     907.1     20.55 +/- 0.38

uvw1        499.5        816.9     317.4    >19.48
uvw1       1131.1       1599.0     467.9    >19.74
uvw1      34121.1      34973.5     852.4    >21.44

uvw2        425.8        743.0     317.2    >19.43
uvw2       1057.0       1525.2     468.2    >19.72
uvw2      10532.3      11432.0     899.7    >21.06
uvw2      22553.7      23374.5     820.8    >21.39
uvw2     100888.2     101273.5     385.3    >20.96

uvm2        474.7        643.2     168.5    >18.78
uvm2       1105.7       1424.3     318.6    >18.80
uvm2      28051.2      28842.6     791.4    >21.25

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.197 in the direction of the burst (Schlegel et al. 1998).

GCN Circular #43329
Jean-Luc Atteia (IRAP), Noémie Globus (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Dalya Akl (NYUAD), Camila Angulo (UNAM), 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), Nikos Mandarakas (LAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), 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 GRB 260101A (Fermi GBM team, GCN Circ. 43284; Cenko et al., GCN Circ. 43285; Pérez-Fournon et al., GCN Circ. 43286; de Ugarte Postigo et al., GCN Circ. 43287; Beardmore et al., GCN Circ. 43289; Lipunov et al., GCN Circ. 43290; D'Avanzo et al., GCN Circ. 43291; SVOM/GRM team et al., GCN Circ. 43292; Saccardi et al., GCN Circ. 43293; Wang et al., GCN Circ. 43294; Hristov et al., GCN Circ. 43297; Globus et al., GCN Circ. 43312; Klinger et al., GCN Circ. 43318) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2026-01-05 03:38 to 05:46 UTC (98.7 hours to 100.8 hours after the trigger) and obtained 94 minutes of simultaneous exposure in the r and z filters.
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.
In our stacked images, the previously detected afterglow (Cenko et al., GCN Circ. 43285; Pérez-Fournon et al., GCN Circ. 43286; Globus et al., GCN Circ. 43312; Klinger et al., GCN Circ. 43318) has faded beyond our 5-sigma detection limit:
```
r > 22.96,
z > 22.42.
```
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 #43354
C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), S. B. Cenko (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), 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+1066 sec from the recent telemetry downlink, we report further analysis of BAT GRB 260101A (trigger #1429608) (Cenko, et al., GCN Circ. 43285). The BAT ground-calculated position is RA, Dec = 86.442, 63.583 deg which is
```
   RA(J2000)  =  05h 45m 46.2s
   Dec(J2000) = +63d 34' 57.2"
```
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 78%.
The mask-weighted light curve shows a complex light curve with many emission episodes. T90 (15-350 keV) is 48.00 +- 16.00 sec (estimated error including systematics).
The time-averaged spectrum from T-31.26 to T+64.74 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.28 +- 0.23, and Epeak of 109.2 +- 64.4 keV (chi squared 55.17 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 4.5 +- 0.2 x 10^-06 erg/cm2 and the 1-sec peak flux measured from T+24.24 sec in the 15-150 keV band is 4.6 +- 0.3 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.62 +- 0.06 (chi squared 62.07 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/1429608
GCN Circular #43389
D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, A. Tsvetkova, M. Ulanov, and T. Cline on behalf of the Konus-Wind team, report:
The long-duration GRB 260101A (Fermi-GBM detection: The Fermi GBM team, GCN 43284; Hristov and Meegan, GCN 43297; Swift-BAT detection: Cenko et al., GCN 43285; Markwardt et al., GCN 43354; SVOM-GRM detection: Yu et al., GCN 43292; GECAM-B detection: Wang et al., GCN 43294) triggered Konus-Wind at T0=3419.619 s UT (00:56:59.619).
The burst light curve shows a multipeaked structure which starts at ~T0-26 s and has a total duration of ~30 s. The emission is seen up to ~1 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260101_T03419/
As observed by Konus-Wind, the burst had the total fluence of 7.47(-0.65,+0.77)x10^-6 erg/cm2, and the 64-ms peak flux, measured from T0+0.210 s, of 1.95(-0.42,+0.44)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
Since the main fraction of burst counts 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 T0-26.365 s to T0+3.168 s) by a power law with exponential cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep), yields alpha = -1.50(-0.11,+0.13) and Ep = 176(-30,+45) keV.
Modelling the KW 3-channel spectrum near the maximum count rate (measured from T0-5.757 s to T0+3.168 s) by the CPL model yields alpha = -1.44(-0.15,+0.20) and Ep = 129(-18,+25) keV.
Assuming the redshift z=2.623 (de Ugarte Postigo et al., GCN 43287) and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014), we estimate the following rest-frame parameters: the isotropic energy release E_iso is 1.21(-0.11,+0.12)x10^53 erg, the peak luminosity L_iso is 1.15(-0.25,+0.26)x10^53 erg/s, the rest-frame peak energy of the time-averaged spectrum Ep,i,z is 637(-109,+162) keV and the spectrum near the maximum count rate Ep,p,z is 467(-65,+90) keV.
With the obtained estimates, GRB 260101A is inside 68% prediction bands for both the 'Amati' and the 'Yonetoku' relations derived for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021), see http://www.ioffe.ru/LEA/GRBs/GRB260101_T03419/GRB260101A_rest_frame.pdf
All the quoted errors are at the 68% confidence level. All the quoted values are preliminary.
GCN Circular #43481
D. Svinkin (Ioffe), D. Frederiks (Ioffe), D. Kapshtan (Geoscan), M. Orlov (Geoscan), V. Bazunova (Geoscan), E. Shchepin (Geoscan), E. Meltsov (Geoscan), K. Starikov (Geoscan, SPbSU), A. Khogoev (Geoscan), A. Razdobarin (SPbAU), and D. Dolmatov (SPbSU), on behalf of the 239Alferov team, report:
The long-duration GRB 260101A (Fermi-GBM detection: The Fermi GBM team, GCN 43284; Hristov and Meegan, GCN 43297; Swift-BAT detection: Cenko et al., GCN 43285; Markwardt et al., GCN 43354; SVOM-GRM detection: Yu et al., GCN 43292; GECAM-B detection: Wang et al., GCN 43294; Konus-Wind detection: Svinkin et al., GCN 43389) was detected by 239Alferov 3U CubeSat at about 00:56:30 UT.
The burst light curve, as measured by 239Alferov detector, shows a multipeaked structure very similar to that observed by other IPN instruments. The total burst duration duration is ~28 s. The emission is seen up to ~500 keV.
The light curve recorded by 239Alferov is available at: http://www.ioffe.ru/LEA/GRBs/GRB260101_T03419/239Alferov/
239Alferov is an educational 3U CubeSat mission at SSO combining amateur radio and space research objectives. The gamma-ray detector onboard 239Alferov contains a 64x72x15 mm NaI(Tl) scintillator read out by a SiPM array and covers the energy range from ~20 keV to ~1000 keV. The spacecraft is now at a commissioning stage, with scientific observations started in December 2025. Currently, the instrument records count rates in five energy bands: ~20-50 keV, ~50-100 keV, ~100-500 keV, 500-1000 keV, and > 1000 keV, with 1 s temporal resolution. The surveys span a couple of days with about a day-long analysis and maintenance intervals between the observations. The ground segment of the mission utilizes the SONIKS open ground station network.

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