Gamma-ray Burst 251230A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 30 Dec 25 01:21:56 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1429020,   Seg_Num: 0
GRB_RA:          179.894d {+11h 59m 35s} (J2000),
                 180.227d {+12h 00m 54s} (current),
                 179.253d {+11h 57m 01s} (1950)
GRB_DEC:         +11.415d {+11d 24' 55"} (J2000),
                 +11.271d {+11d 16' 14"} (current),
                 +11.694d {+11d 41' 37"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       819 [cnts]    Image_Peak=81 [image_cnts]
TRIGGER_DUR:     0.256 [sec] 
TRIGGER_INDEX:   123     E_range: 25-100 keV
BKG_INTEN:       15393 [cnts]
BKG_TIME:        4891.04 SOD {01:21:31.04} UT
BKG_DUR:         8 [sec]
GRB_DATE:        21039 TJD;   364 DOY;   25/12/30
GRB_TIME:        4901.22 SOD {01:21:41.22} UT
GRB_PHI:         -49.65 [deg]
GRB_THETA:        11.68 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     14.45 [sigma]
IMAGE_SIGNIF:    7.60 [sigma]
MERIT_PARAMS:     +1  +0  +0  -2  +2  -2  +0  +0 +22  +0 
SUN_POSTN:       279.35d {+18h 37m 23s}  -23.16d {-23d 09' 24"}
SUN_DIST:        102.69 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:       34.41d {+02h 17m 39s}  +18.36d {+18d 21' 40"}
MOON_DIST:       135.10 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      262.64, 70.12 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      175.31, 10.42 [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 = 17.50,20.18 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 30 Dec 25 01:23:27 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     1429020,   Seg_Num: 0
GRB_RA:          179.8963d {+11h 59m 35.1s} (J2000),
                 180.2293d {+12h 00m 55.0s} (current),
                 179.2554d {+11h 57m 01.2s} (1950)
GRB_DEC:         +11.4390d {+11d 26' 20.4"} (J2000),
                 +11.2943d {+11d 17' 39.4"} (current),
                 +11.7174d {+11d 43' 02.6"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       129 [cnts]
IMG_START_DATE:  21039 TJD;   364 DOY;   25/12/30
IMG_START_TIME:  4969.34 SOD {01:22:49.34} UT,   68.1 [sec] since BAT Trigger Time
CENTROID_X:      317.61,  raw= 318  [pixels]
CENTROID_Y:      333.90,  raw= 334  [pixels]
ROLL:            111.41 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   83.00
GRB_POS_XRT_Z:   14.17
IMAGE_URL:       sw01429020000msxps_rw.img
SUN_POSTN:       279.35d {+18h 37m 23s}  -23.16d {-23d 09' 24"}
SUN_DIST:        102.70 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:       34.43d {+02h 17m 43s}  +18.37d {+18d 22' 00"}
MOON_DIST:       135.08 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      262.61, 70.14 [deg] galactic lon,lat of the burst
ECL_COORDS:      175.30, 10.44 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 30 Dec 25 01:23:14 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1429020,   Seg_Num: 0
GRB_RA:          179.8963d {+11h 59m 35.11s} (J2000),
                 180.2293d {+12h 00m 55.04s} (current),
                 179.2554d {+11h 57m 01.28s} (1950)
GRB_DEC:         +11.4390d {+11d 26' 20.4"} (J2000),
                 +11.2943d {+11d 17' 39.4"} (current),
                 +11.7174d {+11d 43' 02.6"} (1950)
GRB_ERROR:       4.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       4.73e-09 [erg/cm2/sec]
GRB_SIGNIF:      11.35 [sigma]
IMG_START_DATE:  21039 TJD;   364 DOY;   25/12/30
IMG_START_TIME:  4969.34 SOD {01:22:49.34} UT,   68.1 [sec] since BAT Trigger Time
TAM[0-3]:        327.62 237.16 261.51 243.75
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       279.35d {+18h 37m 23s}  -23.16d {-23d 09' 24"}
SUN_DIST:        102.70 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:       34.43d {+02h 17m 43s}  +18.37d {+18d 21' 57"}
MOON_DIST:       135.08 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      262.61, 70.14 [deg] galactic lon,lat of the burst
ECL_COORDS:      175.30, 10.44 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 1.43 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 30 Dec 25 01:23:24 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     1429020,   Seg_Num: 0
GRB_RA:          179.8963d {+11h 59m 35.1s} (J2000),
                 180.2293d {+12h 00m 55.0s} (current),
                 179.2554d {+11h 57m 01.2s} (1950)
GRB_DEC:         +11.4390d {+11d 26' 20.4"} (J2000),
                 +11.2943d {+11d 17' 39.4"} (current),
                 +11.7174d {+11d 43' 02.6"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       129 [cnts]
IMG_START_DATE:  21039 TJD;   364 DOY;   25/12/30
IMG_START_TIME:  4969.34 SOD {01:22:49.34} UT,   68.1 [sec] since BAT Trigger Time
CENTROID_X:      317.61,  raw= 318  [pixels]
CENTROID_Y:      333.90,  raw= 334  [pixels]
ROLL:            111.41 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   83.00
GRB_POS_XRT_Z:   14.17
IMAGE_URL:       sw01429020000msxps_rw.img
SUN_POSTN:       279.35d {+18h 37m 23s}  -23.16d {-23d 09' 24"}
SUN_DIST:        102.70 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:       34.43d {+02h 17m 43s}  +18.37d {+18d 21' 60"}
MOON_DIST:       135.08 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      262.61, 70.14 [deg] galactic lon,lat of the burst
ECL_COORDS:      175.30, 10.44 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 30 Dec 25 01:25:48 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1429020,   Seg_Num: 0
POINT_RA:        179.891d {+11h 59m 34s} (J2000)
POINT_DEC:       +11.416d {+11d 24' 57"} (J2000)
POINT_ROLL:      111.407d
IMG_START_DATE:  21039 TJD;   364 DOY;   25/12/30
IMG_START_TIME:  4977.40 SOD {01:22:57.40} UT,   76.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.694
N_STARS:         17
X_OFFSET:        488 [pixels]
Y_OFFSET:        544 [pixels]
X_MAX:           1447 [pixels]
Y_MAX:           1503 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    7
SL_URL:          sw01429020000msufc0076.fits
SUN_POSTN:       279.35d {+18h 37m 24s}  -23.16d {-23d 09' 24"}
SUN_DIST:        102.70 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:       34.45d {+02h 17m 49s}  +18.38d {+18d 22' 32"}
MOON_DIST:       135.06 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      262.64, 70.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      175.31, 10.42 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 30 Dec 25 01:26:01 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1429020,   Seg_Num: 0
POINT_RA:        179.891d {+11h 59m 34s} (J2000)
POINT_DEC:       +11.416d {+11d 24' 57"} (J2000)
POINT_ROLL:      111.407d
IMG_START_DATE:  21039 TJD;   364 DOY;   25/12/30
IMG_START_TIME:  4977.40 SOD {01:22:57.40} UT,   76.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.694
N_STARS:         17
X_OFFSET:        488 [pixels]
Y_OFFSET:        544 [pixels]
X_MAX:           1447 [pixels]
Y_MAX:           1503 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    7
SL_URL:          sw01429020000msufc0076.fits
SUN_POSTN:       279.35d {+18h 37m 24s}  -23.16d {-23d 09' 24"}
SUN_DIST:        102.70 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:       34.45d {+02h 17m 49s}  +18.38d {+18d 22' 35"}
MOON_DIST:       135.06 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      262.64, 70.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      175.31, 10.42 [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 30 Dec 25 01:27:18 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1429020,   Seg_Num: 0
POINT_RA:        179.891d {+11h 59m 34s} (J2000)
POINT_DEC:       +11.416d {+11d 24' 57"} (J2000)
ROLL:            111.407d
IMG_START_DATE:  21039 TJD;   364 DOY;   25/12/30
IMG_START_TIME:  4977.40 SOD {01:22:57.40} UT,   76.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     788750614
X_OFFSET:        694 [pixels]
Y_OFFSET:        743 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       854
Y_GRB_POS:       903
BINNING_INDEX:   1
IM_URL:          sw01429020000msuni0113.fits
SUN_POSTN:       279.35d {+18h 37m 24s}  -23.16d {-23d 09' 23"}
SUN_DIST:        102.70 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:       34.47d {+02h 17m 52s}  +18.38d {+18d 22' 52"}
MOON_DIST:       135.05 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      262.64, 70.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      175.31, 10.42 [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).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 30 Dec 25 01:27:32 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1429020,   Seg_Num: 0
POINT_RA:        179.891d {+11h 59m 34s} (J2000)
POINT_DEC:       +11.416d {+11d 24' 57"} (J2000)
ROLL:            111.407d
IMG_START_DATE:  21039 TJD;   364 DOY;   25/12/30
IMG_START_TIME:  4977.40 SOD {01:22:57.40} UT,   76.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     788750614
X_OFFSET:        694 [pixels]
Y_OFFSET:        743 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       854
Y_GRB_POS:       903
BINNING_INDEX:   1
IM_URL:          sw01429020000msuni0113.fits
SUN_POSTN:       279.35d {+18h 37m 24s}  -23.16d {-23d 09' 23"}
SUN_DIST:        102.70 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:       34.47d {+02h 17m 53s}  +18.38d {+18d 22' 55"}
MOON_DIST:       135.05 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      262.64, 70.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      175.31, 10.42 [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.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 30 Dec 25 01:28:14 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     1429020,   Seg_Num: 0
GRB_RA:          179.8976d {+11h 59m 35.42s} (J2000),
                 180.2306d {+12h 00m 55.35s} (current),
                 179.2567d {+11h 57m 01.59s} (1950)
GRB_DEC:         +11.4387d {+11d 26' 19.3"} (J2000),
                 +11.2940d {+11d 17' 38.3"} (current),
                 +11.7171d {+11d 43' 01.5"} (1950)
GRB_ERROR:       0.7 [arcsec radius, statistical only]
GRB_MAG:         13.73 +/- 0.14 [mag]
FILTER:          10, White
IMG_START_DATE:  21039 TJD;   364 DOY;   25/12/30
IMG_START_TIME:  4974.00 SOD {01:22:54.00} UT,   72.8 [sec] since BAT Trigger Time
SUN_POSTN:       279.35d {+18h 37m 24s}  -23.16d {-23d 09' 23"}
SUN_DIST:        102.70 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:       34.48d {+02h 17m 54s}  +18.38d {+18d 23' 05"}
MOON_DIST:       135.03 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      262.61, 70.14 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      175.31, 10.44 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT UVOT Position Notice.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The UVOT position is 4.3 arcsec from the XRT position.  
COMMENTS:        Result based on Genie data.  
COMMENTS:        Notice generated automatically.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 30 Dec 25 01:31:08 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1429020,   Seg_Num: 0
POINT_RA:        179.891d {+11h 59m 34s} (J2000)
POINT_DEC:       +11.416d {+11d 24' 59"} (J2000)
POINT_ROLL:      111.406d
IMG_START_DATE:  21039 TJD;   364 DOY;   25/12/30
IMG_START_TIME:  5189.45 SOD {01:26:29.45} UT,   288.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.721
N_STARS:         16
X_OFFSET:        374 [pixels]
Y_OFFSET:        423 [pixels]
X_MAX:           1333 [pixels]
Y_MAX:           1382 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    3
SL_URL:          sw01429020000msufc0288.fits
SUN_POSTN:       279.35d {+18h 37m 25s}  -23.16d {-23d 09' 23"}
SUN_DIST:        102.70 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:       34.51d {+02h 18m 01s}  +18.40d {+18d 23' 44"}
MOON_DIST:       135.01 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      262.63, 70.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      175.31, 10.42 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 30 Dec 25 01:31:19 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1429020,   Seg_Num: 0
POINT_RA:        179.891d {+11h 59m 34s} (J2000)
POINT_DEC:       +11.416d {+11d 24' 59"} (J2000)
POINT_ROLL:      111.406d
IMG_START_DATE:  21039 TJD;   364 DOY;   25/12/30
IMG_START_TIME:  5189.45 SOD {01:26:29.45} UT,   288.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.721
N_STARS:         16
X_OFFSET:        374 [pixels]
Y_OFFSET:        423 [pixels]
X_MAX:           1333 [pixels]
Y_MAX:           1382 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    3
SL_URL:          sw01429020000msufc0288.fits
SUN_POSTN:       279.35d {+18h 37m 25s}  -23.16d {-23d 09' 23"}
SUN_DIST:        102.70 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:       34.51d {+02h 18m 02s}  +18.40d {+18d 23' 46"}
MOON_DIST:       135.01 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      262.63, 70.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      175.31, 10.42 [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 30 Dec 25 01:32:18 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1429020,   Seg_Num: 0
POINT_RA:        179.891d {+11h 59m 34s} (J2000)
POINT_DEC:       +11.416d {+11d 24' 59"} (J2000)
ROLL:            111.406d
IMG_START_DATE:  21039 TJD;   364 DOY;   25/12/30
IMG_START_TIME:  5189.45 SOD {01:26:29.45} UT,   288.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     788750826
X_OFFSET:        694 [pixels]
Y_OFFSET:        743 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       854
Y_GRB_POS:       903
BINNING_INDEX:   1
IM_URL:          sw01429020000msuni0325.fits
SUN_POSTN:       279.35d {+18h 37m 25s}  -23.16d {-23d 09' 23"}
SUN_DIST:        102.70 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:       34.52d {+02h 18m 04s}  +18.40d {+18d 23' 59"}
MOON_DIST:       135.00 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      262.63, 70.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      175.31, 10.42 [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).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 30 Dec 25 01:32:34 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1429020,   Seg_Num: 0
POINT_RA:        179.891d {+11h 59m 34s} (J2000)
POINT_DEC:       +11.416d {+11d 24' 59"} (J2000)
ROLL:            111.406d
IMG_START_DATE:  21039 TJD;   364 DOY;   25/12/30
IMG_START_TIME:  5189.45 SOD {01:26:29.45} UT,   288.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     788750826
X_OFFSET:        694 [pixels]
Y_OFFSET:        743 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       854
Y_GRB_POS:       903
BINNING_INDEX:   1
IM_URL:          sw01429020000msuni0325.fits
SUN_POSTN:       279.35d {+18h 37m 25s}  -23.16d {-23d 09' 23"}
SUN_DIST:        102.71 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:       34.52d {+02h 18m 05s}  +18.40d {+18d 24' 03"}
MOON_DIST:       135.00 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      262.63, 70.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      175.31, 10.42 [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.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 30 Dec 25 01:39:06 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1429020,   Seg_Num: 0
POINT_RA:        179.891d {+11h 59m 34s} (J2000)
POINT_DEC:       +11.416d {+11d 24' 59"} (J2000)
POINT_ROLL:      111.406d
IMG_START_DATE:  21039 TJD;   364 DOY;   25/12/30
IMG_START_TIME:  5768.71 SOD {01:36:08.71} UT,   867.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.697
N_STARS:         50
X_OFFSET:        134 [pixels]
Y_OFFSET:        183 [pixels]
X_MAX:           1573 [pixels]
Y_MAX:           1622 [pixels]
DET_THRESH:      16
PHOTO_THRESH:    9
SL_URL:          sw01429020000msufc0867.fits
SUN_POSTN:       279.36d {+18h 37m 26s}  -23.16d {-23d 09' 22"}
SUN_DIST:        102.71 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:       34.58d {+02h 18m 20s}  +18.43d {+18d 25' 30"}
MOON_DIST:       134.94 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      262.63, 70.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      175.31, 10.42 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 30 Dec 25 01:39:21 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1429020,   Seg_Num: 0
POINT_RA:        179.891d {+11h 59m 34s} (J2000)
POINT_DEC:       +11.416d {+11d 24' 59"} (J2000)
POINT_ROLL:      111.406d
IMG_START_DATE:  21039 TJD;   364 DOY;   25/12/30
IMG_START_TIME:  5768.71 SOD {01:36:08.71} UT,   867.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.697
N_STARS:         50
X_OFFSET:        134 [pixels]
Y_OFFSET:        183 [pixels]
X_MAX:           1573 [pixels]
Y_MAX:           1622 [pixels]
DET_THRESH:      16
PHOTO_THRESH:    9
SL_URL:          sw01429020000msufc0867.fits
SUN_POSTN:       279.36d {+18h 37m 26s}  -23.16d {-23d 09' 21"}
SUN_DIST:        102.71 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:       34.59d {+02h 18m 21s}  +18.43d {+18d 25' 34"}
MOON_DIST:       134.93 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      262.63, 70.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      175.31, 10.42 [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 30 Dec 25 01:39:30 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     1429020,   Seg_Num: 0
GRB_RA:          179.8974d {+11h 59m 35.37s} (J2000),
                 180.2304d {+12h 00m 55.30s} (current),
                 179.2565d {+11h 57m 01.55s} (1950)
GRB_DEC:         +11.4381d {+11d 26' 17.1"} (J2000),
                 +11.2934d {+11d 17' 36.1"} (current),
                 +11.7165d {+11d 42' 59.3"} (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:  21039 TJD;   364 DOY;   25/12/30
IMG_START_TIME:  5338.00 SOD {01:28:58.00} UT,   436.8 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       279.36d {+18h 37m 26s}  -23.16d {-23d 09' 21"}
SUN_DIST:        102.71 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:       34.59d {+02h 18m 21s}  +18.43d {+18d 25' 36"}
MOON_DIST:       134.92 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      262.61, 70.14 [deg] galactic lon,lat of the burst
ECL_COORDS:      175.31, 10.44 [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:     Tue 30 Dec 25 01:40:35 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1429020,   Seg_Num: 0
POINT_RA:        179.891d {+11h 59m 34s} (J2000)
POINT_DEC:       +11.416d {+11d 24' 59"} (J2000)
ROLL:            111.406d
IMG_START_DATE:  21039 TJD;   364 DOY;   25/12/30
IMG_START_TIME:  5768.71 SOD {01:36:08.71} UT,   867.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     788751405
X_OFFSET:        693 [pixels]
Y_OFFSET:        742 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       853
Y_GRB_POS:       902
BINNING_INDEX:   1
IM_URL:          sw01429020000msuni0904.fits
SUN_POSTN:       279.36d {+18h 37m 26s}  -23.16d {-23d 09' 21"}
SUN_DIST:        102.71 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:       34.60d {+02h 18m 24s}  +18.43d {+18d 25' 50"}
MOON_DIST:       134.92 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      262.63, 70.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      175.31, 10.42 [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 Circular #43252
S. Lanava (PSU), S. Dichiara (PSU) and R. Gupta (NASA GSFC) report on behalf of the Neil Gehrels Swift Observatory Team:
At 01:21:41 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 251230A (trigger=1429020). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 179.894, +11.415 which is
```
   RA(J2000) = 11h 59m 35s
   Dec(J2000) = +11d 24' 55"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multiple-peaked structure with a duration of about 80 sec. The peak count rate was ~5000 counts/sec (15-350 keV), at ~30 sec after the trigger.
The XRT began observing the field at 01:22:49.3 UT, 68.1 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source with an enhanced position: RA, Dec 179.89781, 11.43828 which is equivalent to:
```
   RA(J2000)  = 11h 59m 35.47s
   Dec(J2000) = +11d 26' 17.8"
```
with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 84 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 (1.88 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.4 (+1.47/-1.34) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 4.73e-09 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 76 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at
```
  RA(J2000)  =	11:59:35.42 = 179.89760
  DEC(J2000) = +11:26:19.3  =  11.43870
```
with a 90%-confidence error radius of about 0.74 arc sec. This position is 4.7 arc sec. from the center of the XRT error circle. The estimated magnitude is 13.74 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.024.
Burst Advocate for this burst is S. Lanava (sml7284 AT psu.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 Circular #43255
Wenxiong Li, Runduo Liang (NAOC), Iair Arcavi (TAU), Ido Keinan (TAU), David Sand (U of Arizona) We observed the position of EP-WXT trigger 01709250693/GRB 251230a with a Las Cumbres 1m telescope at Sutherland Observatory, South Africa, 9 mins after the Einstein Probe WXT trigger. We took 2x300s exposures in the broad optical w band.
We find an uncataloged source at RA=179.8972, Dec=11.4383 within the EP-WXT error circle and measure the following preliminary photometry calibrated to the r band: MJD 61039.063 Mag 15.1 The position of the counterpart is consistent with that reported by Lanava et al. (GCN 43252).
GCN Circular #43256
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-SAAO robotic telescope [1] located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB 251230A ( S. Lanava et al., GCN 43252) errorbox 1907 sec after notice time and 1930 sec after trigger time at 2025-12-30 01:53:52 UT, with upper limit up to 19.7 mag. The observations began at zenith distance = 53 deg. The sun altitude is -18.1 deg.
The galactic latitude b = 70 deg., longitude l = 265 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3090261
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

    2021 |         MASTER-SAAO |   C |   180 | 19.7 |        
    2021 |         MASTER-SAAO |   C |   180 | 14.4 |        
```
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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 30 Dec 25 01:40:49 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1429020,   Seg_Num: 0
POINT_RA:        179.891d {+11h 59m 34s} (J2000)
POINT_DEC:       +11.416d {+11d 24' 59"} (J2000)
ROLL:            111.406d
IMG_START_DATE:  21039 TJD;   364 DOY;   25/12/30
IMG_START_TIME:  5768.71 SOD {01:36:08.71} UT,   867.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     788751405
X_OFFSET:        693 [pixels]
Y_OFFSET:        742 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       853
Y_GRB_POS:       902
BINNING_INDEX:   1
IM_URL:          sw01429020000msuni0904.fits
SUN_POSTN:       279.36d {+18h 37m 26s}  -23.16d {-23d 09' 21"}
SUN_DIST:        102.71 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:       34.60d {+02h 18m 24s}  +18.43d {+18d 25' 53"}
MOON_DIST:       134.92 [deg]
MOON_ILLUM:      75 [%]
GAL_COORDS:      262.63, 70.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      175.31, 10.42 [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 #43258
Malte Busmann (LMU), Xander J. Hall (CMU), Brendan O'Connor (CMU), Daniel Gruen (LMU), and Antonella Palmese (CMU) report:
We observed the counterpart of Swift GRB 251230A (Lanava et al. GCN 43252, Li et al. GCN 43255) which is spacially and temporally consistent with EP trigger 01709250693 (likely EP251230a) with the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW) in the r, i, and J-band simultaneously for 2 x 180 s starting at 2025-12-30T01:50:41 UT (28.3 minutes after the trigger). We detect the counterpart in all bands and measure an r-band magnitude of
r = 16.30 +/- 0.05 AB mag.
The magnitude is calibrated against the PS1 catalog and not corrected for Galactic extinction.
We thank Christoph Ries from the Wendelstein Observatory for the rapid response in obtaining these observations.
GCN Circular #43259
B.T. Wang (YNAO, CAS), J. P. Chen (SYSU), D. Zhu, K. J. Zhang (YNU),and Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team:
We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP251230a. The transient triggered EP-WXT (ID: 01709250693) at 2025-12-30T01:22:21 (UTC). The WXT position of the source is R.A. = 179.881 deg, DEC = 11.427 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic).
A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 179.8996 deg, DEC = 11.4361 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). No significant X-ray source is detected within the 20 arcsec radius of the EP-FXT position. The position of FXT is 10.1 arcsec from Swift/XRT detection of GRB 251230A (Lanava et al., GCN 43252), and 11.6 arcsec from its optical counterpart (Li et al., GCN 43255).
Further information will be updated when the telemetry data is received.
Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).
GCN Circular #43260
Gianluca Masi, Virtual Telescope Project (Italy), reports:
We attempted to observe the optical counterpart of GRB 251230A (Lanava et al., GCN 43252) with the 17” robotic unit available at the Virtual Telescope Project facility in Manciano, Italy, equipped with a KAF-6303E based CCD camera, its QE peaking (68%) in the red part of the spectrum.
We collected four, 120-second unfiltered exposures, then we averaged them. The central time of the resulting stack was 30 Dec., 02:58:46 UTC, that is about 1.6 hours after the burst.
We detected a bright object at the following position (J2000.0):
```
R.A.: 11 59 35.38
Decl.: + 11 26 18.5
```
mean residuals < 0.1” on both axes R= 18.4 (assuming R-mags from Gaia DR2 for the reference stars).
This position is consistent with Lanava et al. (GCN 43252), Li et al. (GCN 43255) and Busmann et al. (GCN 43258).
GCN Circular #43262
Ankur Ghosh, Soebur Razzaque (CAPP, University of Johannesburg), Rahul Gupta (NASA GSFC), Alexander Moskvitin, Yulia Sotnikova (SAO RAS), Naveen Dukiya (ARIES) on behalf of a larger collaboration.
We observed the field of the GRB 251230A triggered by Swift (Lanava et al., GCN 43252) in B, V, and r filter of the 1-m Sinistro telescope and 0.4-m SCICAM QHY600 at the Las Cumbres Observatory Global Telescope (LCOGT) node located at South African Astronomical Observatory (SAAO). The 1-m Sinistro telescope is equipped with a 4K x 4K CCD (FOV: 26 x 26 arcmin, scale: 0.39 arcsec/pixel) and the 0.4 m SCICAM QHY600 is equipped with 9576 x 6388 pixel CCD (FOV: 1.9 x 1.2 degrees, scale: 0.74 arcsec/pixel). Observations began on October 13, 2025, starting from 0.84 hours after the GRB trigger. Further observations are still ongoing.
We clearly detect the optical transient (OT) reported by GCNs (Lanava et al., GCN 43252, Li et al., GCN 43255, Masi et al., GCN 43260).
```
----------------------------------------------------------------------------------------------------- 
|Date|		|JDstart|	|t-T0 (hours)|	|Exp (sec)|	|Filter|	|Magnitude| 
-----------------------------------------------------------------------------------------------------      
2025-12-30	2461039.59159	0.84		1 x 300 	r		r = 17.20 +/- 0.01
2025-12-30	2461039.60333	1.12		2 x 300 	r		r = 17.64 +/- 0.11
-----------------------------------------------------------------------------------------------------
```
The field was calibrated against nearby APASS stars, with magnitudes converted using Lupton (2005) equations, and has not been corrected for Galactic extinction.
GCN Circular #43263
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team.
Using 1379 s of XRT Photon Counting mode data and 1 UVOT images for GRB 251230A, 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 = 179.89737, +11.43831 which is equivalent to:
```
RA (J2000): 11h 59m 35.37s
Dec (J2000): +11d 26' 17.9"
```
with an uncertainty of 2.2 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 #43265
Y. N. Ma, L. P. Xin, Y. L. Qiu, C. Wu, H. L. Li, Z. H. Yao, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), J. X. Cao (GXU), W. L. Zhang (PMO) report on behalf of the SVOM/VT team.
SVOM/VT performed a Target of Opportunity observation of GRB 251230A / EP251230a detected by Swift/BAT and EP/WXT (Lanava et al., GCN 43252; Wang et al., GCN 43259; Osborne et al., GCN 43263). SVOM/VT began observing the field at 2025-12-30T03:13:20 UTC, 1.861 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
With X-band data available, the optical counterpart (Li et al., GCN 43255; Busmann et al., GCN 43258; Masi, GCN 43260; Ghosh et al., GCN 43262) was clearly detected in both VT_B and VT_R bands. The magnitudes are:
```
mid time (s) | exposure time (s) | band | mag (AB) | mag err
-------------|-------------------|------|----------|--------
     6874    |         50        | VT_B |  19.11   |  0.04 
     8174    |         50        | VT_B |  19.53   |  0.05 
     6874    |         50        | VT_R |  18.57   |  0.03 
     8174    |         50        | VT_R |  19.07   |  0.05 
```
Our photometry was not corrected for Galactic extinction.
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.
GCN Circular #43267
R. Starling, A. Kumar, G. Ramsay, D. O’Neill, B. P. Gompertz, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, S. Belkin, B. Godson, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares report on behalf of the GOTO collaboration:
We report on observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) that serendipitously covered the field of GRB 251230A detected by Swift (Lanava et al., GCN 43252; Osborne et al., GCN 43263) and likely coincident with an Einstein Probe trigger (Wang et al., GCN 43259). Two sets of observations were performed by GOTO-North at 2025-12-30 06:01:45 UT and 2025-12-30 06:16:08 UT. Each observation consisted of 4x45 s exposures in the GOTO L-band (400-700 nm). Images were processed using the GOTO pipeline.
We do not detect the optical counterpart (Lanava et al., GCN 43252; Li et al., GCN 43255; Busmann et al., GCN 43258; Masi et al., GCN 43260; Ghosh et al., GCN 43262; Ma et al., GCN 43265) down to 3-sigma limiting magnitudes of L >20.8 (AB) and L >20.6 (AB) at 4.7 hours and 4.9 hours post-trigger, respectively.
Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction.
GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester, the University of Birmingham and the Instituto de Astrofisica de Canarias (IAC).
GCN Circular #43269
L. He (NAOC), L. Izzo (INAF/OACN and DARK/NBI), A. Martin-Carrillo (UCD), A. Saccardi (CEA/Irfu), J. An (NAOC), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), A. Kadela (NOT & NBI) report on behalf of a larger collaboration:
We observed the optical counterpart (Lanava et al., GCN 43252; Li et al., GCN 43255; Busmann et al., GCN 43258; Masi, GCN 43260; Ghosh et al., GCN 43262; Ma et al., GCN 43265) of GRB 251230A / EP251230a (Lanava et al., GCN 43252; Wang et al., GCN 43259; Osborne et al., GCN 43263), using the Nordic Optical Telescope (NOT), equipped with the ALFOSC camera and spectrograph.
We obtained three exposures of 300 s in the r-band starting on 2025 Dec 30 at 06:30:20 UT (5.144 hr after the Swift trigger). The afterglow is clearly detected with an AB magnitude of r = 20.75 +/- 0.02 mag, calibrated against nearby stars from the Pan-STARRS catalogue and not corrected for Galactic extinction. Compared to previous measurements, our photometry suggests rapid optical decay with power-law index ~1.95.
A sequence of 4 spectra of 1200 s each was acquired, covering the wavelength range 3700-9600 AA. In a preliminary reduction of the spectra, we detect a continuum over the entire covered wavelength range. From detection in the blue down to ~3900 AA, and the lack of hydrogen absorption, we set a redshift upper limit z < 2.2. We do not identify clear metal absorption features.
Further analysis is ongoing.

GCN Circular #43270
Donggeun Tak (SNU ARC/SNU), Myungshin Im (SNU ARC/SNU), YoungPyo Hong (SNU ARC/SNU), Hyeonho Choi (SNU ARC/SNU), Donghwan Hyun (SNU ARC/SNU), Gregory S.H. Paek (IfA, SNU ARC/SNU), Seo-Won Chang (SNU ARC/SNU), and Ji Hoon Kim (SNU ARC/SNU) report on behalf of the 7 Dimensional Telescope (7DT) team:
We report optical follow-up observations of GRB251230A (GCN 43252; GCN 43263), conducted with the 7-Dimensional Telescope (7DT), located in Chile.
The 7DT follow-up began at 06:52:54 UTC on 2025-12-30, corresponding to T0 + 5.5 hours, pointing to a region covering the target localization provided by Swift (GCN 43252) at RA, DEC = 179.89760 deg, 11.43870 deg.
Initial observations were made with 12 units in 20 medium-band filters as well as g-, r-, and i-band filters (23 filters in total).

The following table summarizes the derived 5-sigma upper limits:
Filter       Mag          Mag_err      Exposure        Date Time                    
----------------------------------------------------------------------------------------------------
g            >20.04       N/A          300s            2025-12-30T06:49:06.000      
r            >19.42       N/A          300s            2025-12-30T06:54:28.333      
i            >18.34       N/A          300s            2025-12-30T06:49:04.000      
m400         >18.32       N/A          300s            2025-12-30T06:54:34.667      
m425         >18.89       N/A          300s            2025-12-30T06:54:20.000      
m450         >18.95       N/A          300s            2025-12-30T06:49:02.667      
m475         >19.00       N/A          300s            2025-12-30T06:54:26.000      
m500         >19.04       N/A          300s            2025-12-30T06:49:10.667      
m525         >18.93       N/A          300s            2025-12-30T06:54:29.000      
m550         >18.60       N/A          300s            2025-12-30T06:54:34.000      
m575         >18.79       N/A          300s            2025-12-30T06:49:09.667      
m600         >18.60       N/A          300s            2025-12-30T06:49:08.667      
m625         >18.21       N/A          300s            2025-12-30T06:54:42.667      
m650         >18.25       N/A          300s            2025-12-30T06:49:03.000      
m675         >18.28       N/A          300s            2025-12-30T06:54:38.333      
m700         >18.16       N/A          300s            2025-12-30T06:49:07.000      
m725         >17.72       N/A          300s            2025-12-30T06:54:36.333      
m750         >17.56       N/A          600s            2025-12-30T06:51:49.833      
m775         >17.04       N/A          300s            2025-12-30T06:54:24.667      
m800         >16.81       N/A          300s            2025-12-30T06:49:05.667      
m825         >16.65       N/A          300s            2025-12-30T06:54:29.667      
m850         >16.44       N/A          300s            2025-12-30T06:48:59.000      
m875         >15.91       N/A          300s            2025-12-30T06:49:08.000      
----------------------------------------------------------------------------------------------------

No significant transient event was identified in the preliminary result. Preliminary analysis yields 5σ limiting magnitudes in the range of 15.91–20.04 mag depending on sky brightness and airmass.
Photometric flux calibration was performed using synthetic photometry based on the Gaia DR3 XP catalog (Gaia Collaboration et al. 2022) within the AB magnitude system. Note that no extinction correction has been applied.
The 7-Dimensional Telescope (7DT), located in Chile and comprising 20 wide-field telescopes equipped with 40 medium-bandwidth (~25nm) filters, aims to detect optical counterparts of GW sources and conduct the 7-Dimensional Sky Survey (7DS) of the Southern Hemisphere. Further information about the 7DT is available at https://7ds.snu.ac.kr/ and http://gwuniverse.snu.ac.kr/.

GCN Circular #43271
A.A. Breeveld (UCL-MSSL), N.P.M. Kuin (UCL-MSSL), S. Lanava (PSU) and M. De Pasquale (U. Messina) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 251230A 76s after the BAT trigger (Lanava et al., GCN Circ. 43252). A bright, fading source consistent with the enhanced XRT position (Osborne et al., GCN Circ. 43263) and optical detections (Lanava et al., GCN 43252; Li et al., GCN 43255; Busmann et al., GCN 43258; Masi et al., GCN 43260; Ghosh et al., GCN 43262; Ma et al., GCN 43265, He et al., GCN 43269) is detected in the initial UVOT exposures in the white, v, b, u and uvw1 filters.
The burst is also detected in the UV grism and, while there is some contamination from other zeroth orders, we obtain a tentative redshift of z=1.73.
The preliminary UVOT position is:
```
    RA  (J2000) =  11:59:35.41 = 179.89756 (deg.)
    Dec (J2000) = +11:26:19.2  =  11.43867 (deg.)
```
with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence).
Preliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the finding chart (FC) and other early settled exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white_FC            76          226          147         13.61 ± 0.03
white              868         1017          286         15.63 ± 0.02
v                  619          638           19         14.69 ± 0.07
b                  545          564           20         14.78 ± 0.05
u_FC               288          538          246         13.77 ± 0.02
uvw1               668          687           19         15.2  ± 0.1
uvm2               643         1775          136         >18.8
uvw2               594          614           19         >17.7
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.024 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #43272
B.T. Wang (YNAO, CAS), J.P. Chen (SYSU), D. Zhu, K.J. Zhang (YNU), and Z.X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team:
The fast X-ray transient EP251230a triggered the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Wang et al., GCN 43259) and Swift/BAT as GRB 251230A (Lanava et al., GCN 43252, Osborne et al., GCN 43263), and was followed by several optical telescopes (Li et al., GCN 43255, Lipunov et al., GCN 43256, Busmann et al., GCN 43258, Masi et al., GCN 43260; Ghosh et al., GCN 43262; Ma et al., GCN 43265, Starling et al., GCN 43267, He et al., GCN 43269, Tak et al., GCN 43270, Breeveld et al., GCN 43271). The refined analysis of the WXT data shows that the event started at T0=2025-12-30T01:21:31 (UTC) and lasted for 72 s with a single pulse. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 1.21(-0.48/+0.59) x 10^22 cm^-2 and a photon index of 2.16 (-0.82/+0.89). The derived average unabsorbed 0.5-4 keV flux is 6.56 (-2.40, +2.80) x 10^(-9) erg/s/cm^2.
The autonomous observation by the Follow-up X-ray Telescope (FXT) on board EP was performed at 2025-12-30T01:24:36 (UTC), about 3 minutes after T0. The exposure time of this observation is 1859 s. The on-ground analysis shows that an uncatalogued source was detected at R.A., Dec. = 179.8974, 11.4382 deg (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic). The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic equivalent hydrogen column density of 2.0 x 10^20 cm^-2 and a photon index of 1.83 (-0.04/+0.04). The derived average unabsorbed 0.5-10 keV flux is 4.02 (-0.13/+0.13) x 10^(-11) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters.
Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).
GCN Circular #43275
T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), D.N. Burrows (PSU), S. Lanava (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 5.6 ks of XRT data for GRB 251230A, from 92 s to 50.9 ks after the trigger. The data comprise 329 s in Windowed Timing (WT) mode (the first 6 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode.
The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=7.1 (+/-0.5). At T+129 s the decay flattens to an alpha of 0.2 (+0.3, -1.1) before breaking again at T+194 s to a final decay with index alpha=1.51 (+/-0.05).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.80 (+/-0.06). The best-fitting absorption column is 4.4 (+1.3, -1.2) x 10^20 cm^-2, in excess of the Galactic value of 1.9 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.82 (+/-0.14) and a best-fitting absorption column of 5.7 (+3.6, -3.2) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.6 x 10^-11 (4.1 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     5.7 (+3.6, -3.2) x 10^20 cm^-2
Galactic foreground: 1.9 x 10^20 cm^-2
Excess significance: 2.0 sigma
Photon index:	     1.82 (+/-0.14)
```
If the light curve continues to decay with a power-law decay index of 1.51, the count rate at T+24 hours will be 2.3 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.4 x 10^-14 (9.4 x 10^-14) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01429020.
This circular is an official product of the Swift-XRT team.
GCN Circular #43277
Anshika Gupta, Kuntal Misra, Pankaj Pawar, Dhruv Jain, Debalina Kar (ARIES) report:
We observed the field of GRB 251230A detected by Swift (Lanava et al. 2025, GCN 43252) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations began on 2025-12-30 at 21:36:37 UT, ~ 20.24 hours after the Swift trigger. We have taken multiple frames with an exposure time of 300s in the R filter. We stacked the images after the alignment. We could not detect the optical emission in our stacked image within the error box of Swift/UVOT (Breeveld et al. 2025, GCN 43271). We obtain the following 3-sigma upper limit in the stacked image:
```
Date Start_UT T_start-T0 (hour) Filter  Exp time (s)  Magnitude
===============================================================
2025-12-30  21:36:37    ~20.24     R     300s*6    >22.3
```
The non-detection of the burst is consistent with Li et al. 2025, (GCN 43255); Lipunov et al. 2025, (GCN 43256); Busmann et al. 2025, (GCN 43258); Masi et al. 2025, (GCN 43260); Ghosh et al. 2025, (GCN 43262); Ma et al. 2025, (GCN 43265); Starling et al. 2025, (GCN 43267); He et al. 2025, (GCN 43269); Breeveld et al. 2025, (GCN 43271).
The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalogue.
GCN Circular #43279
A. Sankar.K, A. Aryan, T.-W. Chen, C.-S. Lin (all NCU), A. K. H. Kong (NTHU), J. H. Gillanders, S. J. Smartt (both Oxford), Y. J. Yang (NYUAD), Y.-H. Lee, M.-H. Lee, Y.-C. Pan, C.-C. Ngeow, C.-H. Lai, W.-J. Hou, H.-Y. Hsiao, H.-C. Lin, J.-K. Guo (all NCU), S. Yang, Z. N. Wang, L. L. Fan, G. H. Sun (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report:
We observed the field of the fast X-ray transient GRB 251230A/EP251230a (Lanava et al., GCN#43252; Wang et al., GCN#43259; Osborne et al., GCN#43263; Wang et al., GCN#43272; Sbarrato et al., GCN#43275) using the 40cm SLT at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al., 2025, ApJ, 983, 86, doi:10.3847/1538-4357/adb428). The first SLT epoch of observations started at 18:17 UTC on the 30th of December 2025 (MJD 61039.762), 16.91 hr after the Swift/BAT trigger.
We utilized the astroalign (Beroiz et al., 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al., 2022, ApJ, 935, 167) packages to align and stack the individual frames. In the stacked frame, we did not detect the proposed optical counterpart candidate (Li et al., GCN#43255; Busmann et al., GCN#43258; Masi et al., GCN#43260; Ghosh et al., GCN#43262; Ma et al., GCN#43265; Breeveld et al., GCN#43271), which has a tentative redshift upper limit of z < 2.2 (He et al., GCN#43269).
Moreover, we utilized AutoPhOT to perform the PSF photometry. The details of the observations and the measured 3-sigma upper limit (in the AB system) are as follows:
```
Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass
SLT       | r      | 61039.762   | 16.91     | 300 * 24     | >22.5     | 2".10       | 1.17
```
Utilizing the rigorous Lulin Observatory optical follow-up of the Einstein-Probe-discovered FXTs within the first year of the mission's operation, we investigated the possible connection between FXTs and GRBs, as reported in Aryan et al. (2025), ApJS, 281, 20. Our upper limits are the deepest and latest among those reported (Starling et al., GCN#43267; Tak et al., GCN#43270).
The presented upper limit is calibrated using the field stars from the PanSTARRs DR2 and is not corrected for the expected Galactic foreground extinction of A_r = 0.05 mag in the direction of the transient (Schlafly & Finkbeiner, 2011). The methodology, details on the Lulin observatory telescopes, and a compilation of our optical follow-up campaign for FXTs discovered within the first year of operation of the Einstein-Probe mission are presented in Aryan et al., 2025, ApJS, 281, 20, doi:10.3847/1538-4365/adfc69.
GCN Circular #43280
L. He (NAOC), L. Izzo (INAF/OACN and DARK/NBI), A. Martin-Carrillo (UCD), A. Saccardi (CEA/Irfu), K. Valeckas (NOT & NBI) report on behalf of a larger collaboration:
We observed the optical counterpart (Lanava et al., GCN 43252; Li et al., GCN 43255; Busmann et al., GCN 43258; Masi, GCN 43260; Ghosh et al., GCN 43262; Ma et al., GCN 43265; Starling et al., GCN 43267; He et al., GCN 43269; Breeveld et al., GCN 43271; Sankar et al., GCN 43279) of GRB 251230A / EP251230a (Lanava et al., GCN 43252; Wang et al., GCN 43259; Osborne et al., GCN 43263), using the Nordic Optical Telescope (NOT), equipped with the ALFOSC camera. A series of 10 x 150s exposures was taken in the i band starting on 2025 Dec 31 at 04:46:27 (1.14 days after the Swift trigger).
The afterglow is detected in the final stacked images with an AB magnitude of i = 22.93 +/- 0.09 mag, at a mid-time of 1.15 days after the trigger. Our photometry was calibrated using nearby stars from the Pan-STARRS catalog and is not corrected for Galactic extinction.
This new epoch suggests that the fading of the optical afterglow has slowed down considerably from the decay index reported by He et al. GCN 43269. We note that, based on the colour measured in our earlier epoch, the r-band upper limit reported by Sankar et al. GCN 43279 suggests a possible rebrightening.
Happy New Year to everyone!!!
GCN Circular #43281
S. Antier (IJCLAB), A. Klotz (IRAP), D. Akl (NYUAD), C. Limonta (OCA), A. Dupin (OCA), Q. André (OCA), M. Coughlin (UNM), R. Strausbaugh (EIU), Z. Maksut (NU), E. Abdikamalov (NU), P. Hello (IJCLAB), S. Karpov (FZU), M. Pillas (IAP), C. Douzet (IJCLAB), Z. Wang (BNU), N. Kochiashvili (AbAO), A. Iskandar (XAO) on behalf of GRANDMA:
We observed the field of the fast X-ray transient GRB 251230A/EP251230a (Lanava et al., GCN 43252; Wang et al., GCN 43259; Osborne et al., GCN 43263; Wang et al., GCN 43272; Sbarrato et al., GCN 43275) using TAROT/TCA with no filter. The observations started at 01:22:07 UTC on the 30th of December 2025, 36s post Swift trigger time, and lasted for 3 hours.
We detected the optical afterglow candidate in the first (earliest) measurement with TAROT/TCA (60s exposure time), and we measured on 2025-12-30 01:23:19, r = 13.1 +/- 0.05 mag, after color correction. The data were reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022), using the PS1 catalogue for reference.
Part of the light curve is public here on Skyportal/ICARE (https://skyportal-icare.ijclab.in2p3.fr) and also accessible in the public-report group of Skyportal: https://skyportal-icare.ijclab.in2p3.fr/public/sources/GRB-251230_012141/version/b0d22ea59d7dca3f28dc30442ec03598
We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023).
The results are consistent with other measurements reported.
GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/).
GCN Circular #43282
Y. N. Ma, L. P. Xin, Y. L. Qiu, C. Wu, H. L. Li, Z. H. Yao, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), J. X. Cao (GXU), W. L. Zhang (PMO) report on behalf of the SVOM/VT team.
SVOM/VT conducted continued observations of GRB 251230A / EP251230a detected by Swift/BAT and EP/WXT (Lanava et al., GCN 43252; Wang et al., GCN 43259; Osborne et al., GCN 43263; Wang et al., GCN 43272; Sbarrato et al., GCN 43275). The magnitudes of the optical afterglow (Li et al., GCN 43255; Lipunov et al., GCN 43256; Busmann et al., GCN 43258; Masi, GCN 43260; Ghosh et al., GCN 43262; Ma et al., GCN 43265; Starling et al., GCN 43267; He et al., GCN 43269; Tak et al., GCN 43270; Breeveld et al., GCN 43271; Gupta et al., GCN 43277; Sankar.K et al., GCN 43279; He et al., GCN 43280; Antier et al., GCN 43281) are:
```
mid time (h) | exposure time (s) | band | mag (AB) 
-------------|-------------------|------|----------
    16.51    |        37*50      | VT_B | 23.0+-0.3 
    29.48    |        41*50      | VT_B |   >23.4    
    16.51    |        37*50      | VT_R | 22.5+-0.2 
    29.46    |        39*50      | VT_R |   >23.1
```
Our photometry was not corrected for Galactic extinction. Further analysis is ongoing.
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Centre for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.
Happy New Year to everyone ! ! !
GCN Circular #43299
Hao-Xuan Guo, Chen-Wei Wang, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng (IHEP) report on behalf of the Insight-HXMT team:
At 2025-12-30T01:22:22.000 (T0), Insight-HXMT/HE detected a burst, GRB 251230A / EP251230a, which is also detected by Swift (Lanava et al., GCN #43252) and EP-WXT (Li et al., GCN #43255 and Wang et al., GCN #43272).
The Insight-HXMT/HE light curve mainly consists of multiple pulses with T90 of 54.4 +11.6/-8.4 s. The 1s peak rate, measured from T0-0.70 s, is 797 cnts/sec. Insight-HXMT/HE detected a total of 10,311 counts from this burst.
The Insight-HXMT /HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb251230A.png
All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the Low-Gain mode with the energy range of about 300-3000 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope.
Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org
GCN Circular #43301
Hao-Xuan Guo, Chen-Wei Wang, Zheng-Hang Yu, Shao-Lin Xiong (IHEP) report on behalf of GECAM team:
GECAM-B was triggered in-flight by GRB 251230A / EP251230a at 2025-12-30T01:21:44.050 UTC (denoted as T0), which is also detected by Swift (Lanava et al., GCN #43252), EP-WXT (Li et al., GCN #43255 and Wang et al., GCN #43272) and Insight-HXMT/HE (Guo et al., GCN #43299).
According to the GECAM-B light curve in about 70-6000 keV, this burst mainly consists of multi-pulses with a duration (T90) of 71.2 +4.6/-8.2 s.
The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251230A.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 #43321
Kaushik Chatterjee, Guowang Du, Yu Pan, Yifei Ding, Guangya Zeng, Brajesh Kumar, Yuan Fang, Jinghua Zhang, Xingzhu Zou, Xinlei Chen, Xufeng Zhu, Tao Wang, Xinzhong Er, Yuanpei Yang, Xiangkun Liu, Xiaowei Liu (SWIFAR, YNU) report on behalf of the Mephisto Team:
The EP-WXT trigger 01709250693 (trigger time 2025-12-30T01:22:21), identified as EP251230a/GRB251230A (Lanava et al., GCN 43252; Li et al. GCN 43255; Wang. C. et al., GCN 43259; Osborne et al., GCN 43263) was observed with the following facility of the Yunnan University, located at the Lijiang Observatory: the 1.6m Multi-channel Photometric Survey Telescope (Mephisto). A set of simultaneous multi-band (ugi and vrz) frames were collected starting from 2025-12-30 UTC19:34:28 (~ 16.9 hr after the trigger) and continued till 2025-12-30 UTC20:00:18. The optical counterpart reported previously (Busmann et al., GCN 43258; Masi et al., GCN 43260; Ghosh et al., GCN 43262; Ma et al., GCN 43265) was not detected in our stacked frames and the upper limits (5 sigma) are listed below.
```
---------------------------------------------------
Start_Time(UT)      | Band | Exp(s)  | LimMag (AB)
---------------------------------------------------
2025-12-30T19:34:28 |   u  | 45.0*7  |   >21.08
2025-12-30T19:54:43 |   v  | 45.0*6  |   >20.89
2025-12-30T19:34:30 |   g  | 45.0*6  |   >21.36
2025-12-30T19:54:45 |   r  | 45.0*6  |   >21.38
2025-12-30T19:34:30 |   i  | 45.0*7  |   >21.04
2025-12-30T19:54:44 |   z  | 45.0*6  |   >20.32
---------------------------------------------------
```
Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. The facility is operated by the South-Western Institute for Astronomy Research (SWIFAR), Yunnan University. It provides real-time, high-quality colors of stellar objects. The Mephisto mosaic cameras were installed in October 2025. The first light was achieved in all three channels on 10 October 2025 and presently, these are under the commissioning phase. All the data have been reduced by the Mephisto data processing pipeline. Here, we note that the current data processing pipeline is still at a preliminary stage, with flux calibration precision in each band at the level of about 5% or even higher.
GCN Circular #43353
D. Buckley (South African Astronomical Observatory),
V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik, D. Vlasenko, G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij (Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias),
O.A. Gress, N.M. Budnev, O.Ershova (Irkutsk State University, API),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich (Blagoveschensk Educational State University)
MASTER-SAAO robotic telescope [1] located in South Africa (South African Astronomical Observatory) was pointed to the GRB 251230A ( S. Lanava et al., GCN 43252) 1908 sec after notice time and 1930 sec after trigger time at 2025-12-30 01:53:52 UT. On our first (180s exposure) set we found 1 optical transient within Swift error-box (ra=179.892 dec=11.415 r=0.05) brighter than 19.2.
```
 T-Tmid      Date      Time       Expt.        Ra                Dec           Mag
---------|---------------------|-------|-----------------|-----------------|-------
    2020   2025-12-30 01:53:52     180   (11h 59m 35.40s , +11d 26m 18.8s)     16.4
```
The 5-sigma upper limit has been about 19.2mag 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 #43378
N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP), A. Volnova (IKI) report on behalf of IKI-GRB-FuN:
We performed optical observations of the field of GRB 251230A (Lanava et al., GCN 43252; Wang et. al, GCN 43259; Osborne et. al, GCN 43263; Wang et. al, GCN 43272; Sbarrato et al., GCN 43275; Guo et. al, GCN 43299; Guo et. al, GCN 43301) in the R filter with the AZT-33IK 1.5-meter telescope of the Sayan Solar Observatory (SSO Mondy). The observations began on 2025-12-30 19:36:42 UT, i.e. ~0.77 days since trigger. The optical counterpart (Li et al., GCN 43255; Busmann et al., GCN 43258; Masi et al., GCN 43260; Ghosh et al., GCN 43262; Ma et al., GCN 43265; He et al., GCN 43269; Breeveld et. al, GCN 43271; He et al., GCN 43280; Antier et. al, GCN 43281; Ma et al., GCN 43282; Chatterjee et. al, GCN 43321) is not detected in the co-add image. The preliminary photometry and observation details are provided below:
```
Date       UT start  t-T0         Exp.    Filter   OT  Err.  UL
                     (mid, days)  (s)                        (3sigma)
2025-12-30 19:36:42  0.77001      15*120  R        n/d n/d   20.4
```
The photometry was calibrated using nearby stars from USNO-B1.0 and is not corrected for the Galactic extinction. The obtained results do not contradict the measurements reported by other teams, including upper limits (Starling et. al, GCN 43267; Tak et al., GCN 43270; Gupta et. al, GCN 43277; Sankar et al., GCN 43279).
GCN Circular #43405
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 251230A / EP251230a (Swift-BAT detection: Lanava et al., GCN 43252; Einstein Probe-WXT detection: Wang et al., GCN 43259; Wang et al., GCN 43272; Insight-HXMT/HE detection: Guo et al., GCN 43299; GECAM-B detection: Guo et al., GCN 43301) triggered Konus-Wind at T0=04927.542 s UT (01:22:07.542).
The burst light curve shows a multipeaked structure which starts at ~T0-25 s and has a total duration of ~73 s. The emission is seen up to ~2 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB251230_T04927/
As observed by Konus-Wind, the burst had the total fluence of 2.03(-0.15,+0.17)x10^-5 erg/cm2, and the 64-ms peak flux, measured from T0-0.224 s, of 2.51(-0.71,+0.80)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst (measured from T0 to T0+49.408 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.04(-0.14,+0.16) and Ep = 354(-47,+64) keV (chi2 = 93/98 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.2 (chi2 = 93/97 dof).
The spectrum near the maximum count rate (measured from T0 to T0+0.256 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.70(-0.51,+0.72) and Ep = 350(-85,+147) keV (chi2 = 19/15 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.8 (chi2 = 18/14 dof).
All the quoted errors are at the 68% confidence level. All the quoted values are preliminary.
GCN Circular #43608
S. de Wet (DTU Space) and P.J. Groot (Radboud/UCT/SAAO) report on behalf of the MeerLICHT consortium:
The 0.6m wide-field MeerLICHT optical telescope located in Sutherland, South Africa, obtained a repeating series of 60s exposures in the q,u,g,r,i,z filters following the detection of GRB 251230A by Swift (Lanava et al., GCN 43252). Our observations began 185 seconds after the Swift trigger and continued for approximately 26 minutes following the filter sequence quqgqrqiqz. A further four exposures were taken after a gap of approximately 30 minutes.
We detect the bright optical afterglow in all of our images, and report the following first detections in each filter:
```
q = 12.99 +/- 0.01 at 01:25:21 UT
u = 13.95 +/- 0.05 at 01:26:41 UT
g = 14.24 +/- 0.02 at 01:29:24 UT
r = 14.43 +/- 0.01 at 01:32:07 UT
i = 14.67 +/- 0.01 at 01:34:51 UT
z = 14.80 +/- 0.03 at 01:37:36 UT
```
We measure a power-law decline rate of -1.54 in the q-band. A light curve is available at the following link: https://raw.githubusercontent.com/simdewet/GRB_lightcurves/main/GRB251230A.pdf
MeerLICHT is built and run by a consortium consisting of Radboud University, University of Cape Town, the South African Astronomical Observatory, the University of Oxford, the University of Manchester and the University of Amsterdam.

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Jochen Greiner, last update: 03-Feb-2026 [Disclaimer]