Gamma-ray Burst 240101B

(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:     Mon 01 Jan 24 20:26:54 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1205744,   Seg_Num: 0
GRB_RA:          352.052d {+23h 28m 12s} (J2000),
                 352.336d {+23h 29m 21s} (current),
                 351.461d {+23h 25m 51s} (1950)
GRB_DEC:         +51.645d {+51d 38' 43"} (J2000),
                 +51.778d {+51d 46' 39"} (current),
                 +51.370d {+51d 22' 11"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       38011 [cnts]    Image_Peak=634 [image_cnts]
TRIGGER_DUR:     16.384 [sec] 
TRIGGER_INDEX:   458     E_range: 15-50 keV
BKG_INTEN:       137787 [cnts]
BKG_TIME:        73439.34 SOD {20:23:59.34} UT
BKG_DUR:         64 [sec]
GRB_DATE:        20310 TJD;     1 DOY;   24/01/01
GRB_TIME:        73539.37 SOD {20:25:39.37} UT
GRB_PHI:         -73.74 [deg]
GRB_THETA:         2.92 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     12.00 [sigma]
IMAGE_SIGNIF:    7.41 [sigma]
MERIT_PARAMS:     +1  +0  +0  +4  +1  -2  +0  +1 +11  +0 
SUN_POSTN:       281.87d {+18h 47m 28s}  -22.99d {-22d 59' 13"}
SUN_DIST:         96.68 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      168.30d {+11h 13m 12s}   +8.12d {+08d 07' 27"}
MOON_DIST:       120.00 [deg]
MOON_ILLUM:      71 [%]
GAL_COORDS:      110.03, -9.13 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       20.78, 48.90 [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 = 287.32,13.51 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 01 Jan 24 20:28:19 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     1205744,   Seg_Num: 0
GRB_RA:          352.0966d {+23h 28m 23.1s} (J2000),
                 352.3813d {+23h 29m 31.5s} (current),
                 351.5060d {+23h 26m 01.4s} (1950)
GRB_DEC:         +51.6379d {+51d 38' 16.4"} (J2000),
                 +51.7703d {+51d 46' 13.0"} (current),
                 +51.3623d {+51d 21' 44.4"} (1950)
GRB_ERROR:       5.0 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       79 [cnts]
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  73663.23 SOD {20:27:43.23} UT,   123.9 [sec] since BAT Trigger Time
CENTROID_X:      336.11,  raw= 336  [pixels]
CENTROID_Y:      315.76,  raw= 316  [pixels]
ROLL:            240.66 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   41.65
GRB_POS_XRT_Z:   67.69
IMAGE_URL:       sw01205744000msxps_rw.img
SUN_POSTN:       281.87d {+18h 47m 28s}  -22.99d {-22d 59' 13"}
SUN_DIST:         96.70 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      168.31d {+11h 13m 14s}   +8.12d {+08d 07' 08"}
MOON_DIST:       120.01 [deg]
MOON_ILLUM:      71 [%]
GAL_COORDS:      110.06, -9.15 [deg] galactic lon,lat of the burst
ECL_COORDS:       20.81, 48.88 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 01 Jan 24 20:28:17 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     1205744,   Seg_Num: 0
GRB_RA:          352.0966d {+23h 28m 23.1s} (J2000),
                 352.3813d {+23h 29m 31.5s} (current),
                 351.5060d {+23h 26m 01.4s} (1950)
GRB_DEC:         +51.6379d {+51d 38' 16.4"} (J2000),
                 +51.7703d {+51d 46' 13.0"} (current),
                 +51.3623d {+51d 21' 44.4"} (1950)
GRB_ERROR:       5.0 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       79 [cnts]
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  73663.23 SOD {20:27:43.23} UT,   123.9 [sec] since BAT Trigger Time
CENTROID_X:      336.11,  raw= 336  [pixels]
CENTROID_Y:      315.76,  raw= 316  [pixels]
ROLL:            240.66 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   41.65
GRB_POS_XRT_Z:   67.69
IMAGE_URL:       sw01205744000msxps_rw.img
SUN_POSTN:       281.87d {+18h 47m 28s}  -22.99d {-22d 59' 13"}
SUN_DIST:         96.70 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      168.31d {+11h 13m 14s}   +8.12d {+08d 07' 08"}
MOON_DIST:       120.01 [deg]
MOON_ILLUM:      71 [%]
GAL_COORDS:      110.06, -9.15 [deg] galactic lon,lat of the burst
ECL_COORDS:       20.81, 48.88 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 01 Jan 24 20:28:07 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1205744,   Seg_Num: 0
GRB_RA:          352.0966d {+23h 28m 23.18s} (J2000),
                 352.3813d {+23h 29m 31.50s} (current),
                 351.5060d {+23h 26m 01.43s} (1950)
GRB_DEC:         +51.6379d {+51d 38' 16.4"} (J2000),
                 +51.7703d {+51d 46' 13.0"} (current),
                 +51.3623d {+51d 21' 44.4"} (1950)
GRB_ERROR:       5.1 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       2.19e-09 [erg/cm2/sec]
GRB_SIGNIF:      8.88 [sigma]
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  73663.23 SOD {20:27:43.23} UT,   123.9 [sec] since BAT Trigger Time
TAM[0-3]:        327.68 237.16 261.56 243.77
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       281.87d {+18h 47m 28s}  -22.99d {-22d 59' 13"}
SUN_DIST:         96.70 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      168.31d {+11h 13m 14s}   +8.12d {+08d 07' 10"}
MOON_DIST:       120.01 [deg]
MOON_ILLUM:      71 [%]
GAL_COORDS:      110.06, -9.15 [deg] galactic lon,lat of the burst
ECL_COORDS:       20.81, 48.88 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 1.73 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 01 Jan 24 20:30:03 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1205744,   Seg_Num: 0
GRB_RA:          352.052d {+23h 28m 12s} (J2000),
                 352.336d {+23h 29m 21s} (current),
                 351.461d {+23h 25m 51s} (1950)
GRB_DEC:         +51.645d {+51d 38' 43"} (J2000),
                 +51.778d {+51d 46' 39"} (current),
                 +51.370d {+51d 22' 11"} (1950)
GRB_DATE:        20310 TJD;     1 DOY;   24/01/01
GRB_TIME:        73539.37 SOD {20:25:39.37} UT
TRIGGER_INDEX:   458
GRB_PHI:         -73.74 [deg]
GRB_THETA:         2.92 [deg]
DELTA_TIME:      76.00 [sec]
TRIGGER_DUR:     16.384 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     12.00 [sigma]
IMAGE_SIGNIF:    7.41 [sigma]
LC_URL:          sw01205744000msb.lc
SUN_POSTN:       281.87d {+18h 47m 28s}  -22.99d {-22d 59' 12"}
SUN_DIST:         96.68 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      168.32d {+11h 13m 17s}   +8.11d {+08d 06' 44"}
MOON_DIST:       120.01 [deg]
MOON_ILLUM:      71 [%]
GAL_COORDS:      110.03, -9.13 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       20.78, 48.90 [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 = 287.32,13.51 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 01 Jan 24 20:30:44 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1205744,   Seg_Num: 0
POINT_RA:        352.060d {+23h 28m 14s} (J2000)
POINT_DEC:       +51.638d {+51d 38' 17"} (J2000)
POINT_ROLL:      240.654d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  73673.83 SOD {20:27:53.83} UT,   134.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.776
N_STARS:         190
X_OFFSET:        314 [pixels]
Y_OFFSET:        545 [pixels]
X_MAX:           1273 [pixels]
Y_MAX:           1504 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    7
SL_URL:          sw01205744000msufc0134.fits
SUN_POSTN:       281.87d {+18h 47m 28s}  -22.99d {-22d 59' 12"}
SUN_DIST:         96.68 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      168.33d {+11h 13m 18s}   +8.11d {+08d 06' 35"}
MOON_DIST:       120.02 [deg]
MOON_ILLUM:      71 [%]
GAL_COORDS:      110.03, -9.14 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       20.78, 48.89 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 01 Jan 24 20:30:54 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1205744,   Seg_Num: 0
POINT_RA:        352.060d {+23h 28m 14s} (J2000)
POINT_DEC:       +51.638d {+51d 38' 17"} (J2000)
POINT_ROLL:      240.654d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  73673.83 SOD {20:27:53.83} UT,   134.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.776
N_STARS:         190
X_OFFSET:        314 [pixels]
Y_OFFSET:        545 [pixels]
X_MAX:           1273 [pixels]
Y_MAX:           1504 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    7
SL_URL:          sw01205744000msufc0134.fits
SUN_POSTN:       281.87d {+18h 47m 28s}  -22.99d {-22d 59' 12"}
SUN_DIST:         96.68 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      168.33d {+11h 13m 19s}   +8.11d {+08d 06' 33"}
MOON_DIST:       120.02 [deg]
MOON_ILLUM:      71 [%]
GAL_COORDS:      110.03, -9.14 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       20.78, 48.89 [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:     Mon 01 Jan 24 20:32:22 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1205744,   Seg_Num: 0
POINT_RA:        352.060d {+23h 28m 14s} (J2000)
POINT_DEC:       +51.638d {+51d 38' 17"} (J2000)
ROLL:            240.654d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  73673.83 SOD {20:27:53.83} UT,   134.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     725833706
X_OFFSET:        634 [pixels]
Y_OFFSET:        865 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       794
Y_GRB_POS:       1025
BINNING_INDEX:   1
IM_URL:          sw01205744000msuni0167.fits
SUN_POSTN:       281.87d {+18h 47m 29s}  -22.99d {-22d 59' 12"}
SUN_DIST:         96.68 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      168.34d {+11h 13m 21s}   +8.10d {+08d 06' 13"}
MOON_DIST:       120.03 [deg]
MOON_ILLUM:      71 [%]
GAL_COORDS:      110.03, -9.14 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       20.78, 48.89 [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:     Mon 01 Jan 24 20:32:32 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1205744,   Seg_Num: 0
POINT_RA:        352.060d {+23h 28m 14s} (J2000)
POINT_DEC:       +51.638d {+51d 38' 17"} (J2000)
ROLL:            240.654d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  73673.83 SOD {20:27:53.83} UT,   134.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     725833706
X_OFFSET:        634 [pixels]
Y_OFFSET:        865 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       794
Y_GRB_POS:       1025
BINNING_INDEX:   1
IM_URL:          sw01205744000msuni0167.fits
SUN_POSTN:       281.87d {+18h 47m 29s}  -22.99d {-22d 59' 12"}
SUN_DIST:         96.68 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      168.34d {+11h 13m 22s}   +8.10d {+08d 06' 11"}
MOON_DIST:       120.03 [deg]
MOON_ILLUM:      71 [%]
GAL_COORDS:      110.03, -9.14 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       20.78, 48.89 [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:     Mon 01 Jan 24 20:37:05 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1205744,   Seg_Num: 0
POINT_RA:        352.060d {+23h 28m 14s} (J2000)
POINT_DEC:       +51.639d {+51d 38' 19"} (J2000)
POINT_ROLL:      240.657d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  73832.82 SOD {20:30:32.82} UT,   293.5 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.777
N_STARS:         190
X_OFFSET:        314 [pixels]
Y_OFFSET:        545 [pixels]
X_MAX:           1273 [pixels]
Y_MAX:           1504 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    3
SL_URL:          sw01205744000msufc0293.fits
SUN_POSTN:       281.87d {+18h 47m 29s}  -22.99d {-22d 59' 11"}
SUN_DIST:         96.68 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      168.37d {+11h 13m 30s}   +8.09d {+08d 05' 10"}
MOON_DIST:       120.05 [deg]
MOON_ILLUM:      71 [%]
GAL_COORDS:      110.03, -9.14 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       20.78, 48.90 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 01 Jan 24 20:37:20 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1205744,   Seg_Num: 0
POINT_RA:        352.060d {+23h 28m 14s} (J2000)
POINT_DEC:       +51.639d {+51d 38' 19"} (J2000)
POINT_ROLL:      240.657d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  73832.82 SOD {20:30:32.82} UT,   293.5 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.777
N_STARS:         190
X_OFFSET:        314 [pixels]
Y_OFFSET:        545 [pixels]
X_MAX:           1273 [pixels]
Y_MAX:           1504 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    3
SL_URL:          sw01205744000msufc0293.fits
SUN_POSTN:       281.87d {+18h 47m 30s}  -22.99d {-22d 59' 11"}
SUN_DIST:         96.68 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      168.38d {+11h 13m 30s}   +8.09d {+08d 05' 07"}
MOON_DIST:       120.05 [deg]
MOON_ILLUM:      71 [%]
GAL_COORDS:      110.03, -9.14 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       20.78, 48.90 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_srclist.fits.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 01 Jan 24 20:38:27 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1205744,   Seg_Num: 0
POINT_RA:        352.060d {+23h 28m 14s} (J2000)
POINT_DEC:       +51.639d {+51d 38' 19"} (J2000)
ROLL:            240.657d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  73832.82 SOD {20:30:32.82} UT,   293.5 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     725833865
X_OFFSET:        634 [pixels]
Y_OFFSET:        865 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       794
Y_GRB_POS:       1025
BINNING_INDEX:   1
IM_URL:          sw01205744000msuni0326.fits
SUN_POSTN:       281.87d {+18h 47m 30s}  -22.99d {-22d 59' 10"}
SUN_DIST:         96.68 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      168.38d {+11h 13m 32s}   +8.08d {+08d 04' 52"}
MOON_DIST:       120.05 [deg]
MOON_ILLUM:      71 [%]
GAL_COORDS:      110.03, -9.14 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       20.78, 48.90 [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 Circular #35449
S. B. Cenko (GSFC), C. Gronwall (PSU), J.D. Gropp (PSU), H. A. Krimm (NSF), A. Y. Lien (U Tampa) and K. L. Page (U Leicester) report on behalf of the Neil Gehrels Swift Observatory Team:
At 20:25:39 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 240101B (trigger=1205744). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 352.052, +51.645 which is
```
   RA(J2000) = 23h 28m 12s
   Dec(J2000) = +51d 38' 43"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 20 sec. The peak count rate was ~600 counts/sec (15-350 keV), at ~7 sec after the trigger.
The XRT began observing the field at 20:27:43.2 UT, 123.9 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 352.0966, 51.6379 which is equivalent to:
```
   RA(J2000)  = 23h 28m 23.18s
   Dec(J2000) = +51d 38' 16.4"
```
with an uncertainty of 5.1 arcseconds (radius, 90% containment). This location is 102 arcseconds from the BAT onboard position, within the BAT error circle.
The initial flux in the 2.5 s image was 2.19e-09 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 134 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.286.
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:     Mon 01 Jan 24 20:43:33 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1205744,   Seg_Num: 0
POINT_RA:        352.060d {+23h 28m 14s} (J2000)
POINT_DEC:       +51.639d {+51d 38' 21"} (J2000)
ROLL:            240.657d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  74413.28 SOD {20:40:13.28} UT,   873.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     725834445
X_OFFSET:        633 [pixels]
Y_OFFSET:        864 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       793
Y_GRB_POS:       1024
BINNING_INDEX:   1
IM_URL:          sw01205744000msuni0906.fits
SUN_POSTN:       281.88d {+18h 47m 31s}  -22.99d {-22d 59' 09"}
SUN_DIST:         96.68 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      168.42d {+11h 13m 41s}   +8.06d {+08d 03' 43"}
MOON_DIST:       120.07 [deg]
MOON_ILLUM:      71 [%]
GAL_COORDS:      110.03, -9.14 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       20.78, 48.90 [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:     Mon 01 Jan 24 20:43:46 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1205744,   Seg_Num: 0
POINT_RA:        352.060d {+23h 28m 14s} (J2000)
POINT_DEC:       +51.639d {+51d 38' 21"} (J2000)
ROLL:            240.657d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  74413.28 SOD {20:40:13.28} UT,   873.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     725834445
X_OFFSET:        633 [pixels]
Y_OFFSET:        864 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       793
Y_GRB_POS:       1024
BINNING_INDEX:   1
IM_URL:          sw01205744000msuni0906.fits
SUN_POSTN:       281.88d {+18h 47m 31s}  -22.99d {-22d 59' 09"}
SUN_DIST:         96.68 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      168.42d {+11h 13m 41s}   +8.06d {+08d 03' 40"}
MOON_DIST:       120.07 [deg]
MOON_ILLUM:      71 [%]
GAL_COORDS:      110.03, -9.14 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       20.78, 48.90 [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:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 01 Jan 24 20:38:40 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1205744,   Seg_Num: 0
POINT_RA:        352.060d {+23h 28m 14s} (J2000)
POINT_DEC:       +51.639d {+51d 38' 19"} (J2000)
ROLL:            240.657d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  73832.82 SOD {20:30:32.82} UT,   293.5 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     725833865
X_OFFSET:        634 [pixels]
Y_OFFSET:        865 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       794
Y_GRB_POS:       1025
BINNING_INDEX:   1
IM_URL:          sw01205744000msuni0326.fits
SUN_POSTN:       281.87d {+18h 47m 30s}  -22.99d {-22d 59' 10"}
SUN_DIST:         96.68 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      168.39d {+11h 13m 32s}   +8.08d {+08d 04' 49"}
MOON_DIST:       120.05 [deg]
MOON_ILLUM:      71 [%]
GAL_COORDS:      110.03, -9.14 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       20.78, 48.90 [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:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.

GCN Circular #35454
WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on
behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to Swift GRB 240101B (Cenko et al.,
GCN 35449) starting at 7.38 hours after the burst. A total of
31x60s images were obtained in the clear (roughly R) filters.
We do not detect any optical afterglow candidate within the XRT
position error circle (Cenko et al., GCN 35449), neither in single
image, nor in the co-add images. The typical limiting magnitude of
our single clear image is about 18.5 mag calibrated to the PS1 catalog.
GCN Circular #35455
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
Using 1510 s of XRT Photon Counting mode data and 1 UVOT images for GRB 240101B, 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 = 352.09572, +51.63617 which is equivalent to:
```
RA (J2000): 23h 28m 22.97s
Dec (J2000): +51d 38' 10.2"
```
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 http://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 #35458
N. P. M. Kuin (UCL-MSSL) and S. B. Cenko (GSFC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 240101B 110 s after the BAT trigger (Cenko et al., GCN Circ. 35449). No optical afterglow consistent with the XRT position is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           134          284          147         >21.1
u_FC               294          543          246         >20.1
white              134         1718          411         >21.8
v                  110         1595          130         >19.2
b                  549         1693          117         >20.5
u                  294         1669          343         >20.2
w1                 675         1644          117         >19.3
m2                 648         1619           97         >21.0
w2                 599         1741          134         >19.3
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.287 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #35463
Ivo Peretto (MarSEC, Marana Space Explorer Center, Marana Di Crespadoro, VI, Italy)
Member of: UAI/SSV - Unione Astrofili Italiani/Sezione Stelle Variabili, GRB section. AAVSO (American Association Variable Stars Observers)
In collaboration with: Stefano Lora (MarSEC, Marana Space Explorer Center, Marana di Crespadoro, VI, Italy)
report: We imaged the field of GRB 240101B detected by SWIFT(trigger=3D1205744) with the telescope 14=E2=80=9D RC Officine Stellari of MarSEC (Marana Spac= e Explorer Center).
The observations with a series of 120 sec exposures started at 2024-01-01 2= 1:42:43 UT, 77 min. after the GRB trigger, with a Ritchey-Chretien telescop= e D=3D360 mm f/ 8.
at the following position:
```
RA(J2000) =3D 23h 28m 12s
Dec(J2000) =3D +51d 38' 43"
```
Weather conditions were medium with Moon illuminated 70% at 2=C2=B0 from th= e horizon.
We co-added 30 exposures of 120 sec each.
```
Start T0+      End T0+       V lim.
 77 min          137 min       20.12
```
We did not found any optical counterpart in A.R. 23 28 12, DEC. +51 38 43 p= osition and in the error box of the XRT candidate. ref.: S. B. Cenko (GSFC) et al., GCN Circular 35449
Magnitudes were estimated with the Gaia DR3 and are not corrected for galactic dust extinction.
Reference: https://www.marsec.org/
The message may be cited.
GCN Circular #35470
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), S. Dichiara (PSU), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 6.9 ks of XRT data for GRB 240101B, from 138 s to 126.6 ks after the BAT trigger. The data comprise 189 s in Windowed Timing (WT) mode (the first 12 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode.
The late-time light curve (from T0+5.0 ks) can be modelled with a power-law decay with a decay index of alpha=0.80 (+0.33, -0.29).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.28 (+0.14, -0.13). The best-fitting absorption column is 6.5 (+/-0.8) x 10^21 cm^-2, in excess of the Galactic value of 2.9 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.39 (+0.29, -0.27) and a best-fitting absorption column of 7.9 (+2.0, -1.8) 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 (9.4 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     7.9 (+2.0, -1.8) x 10^21 cm^-2
Galactic foreground: 2.9 x 10^21 cm^-2
Excess significance: 4.7 sigma
Photon index:	     2.39 (+0.29, -0.27)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01205744.
This circular is an official product of the Swift-XRT team.
GCN Circular #35472
C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), S. B. Cenko (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/UMBC), T. Sakamoto (AGU), M. Stamatikos (OSU) (i.e. the Swift-BAT team):
Using the data set from T-60 to T+243 sec from the recent telemetry downlink, we report further analysis of BAT GRB 240101B (trigger #1205744) (Cenko, et al., GCN Circ. 35449). The BAT ground-calculated position is RA, Dec = 352.147, 51.646 deg which is
```
   RA(J2000)  =  23h 28m 35.3s
   Dec(J2000) = +51d 38' 46.9"
```
with an uncertainty of 3.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%.
The mask-weighted light curve shows a single peak from approximately T+0 To T+18 seconds. There is a possible precursor at T-50 sec.
T90 (15-350 keV) is 43.1 +- 12.6 sec (estimated error including systematics). The time-averaged spectrum from T+2.18 to T+48.32 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.70 +- 0.26. The fluence in the 15-150 keV band is 4.6 +- 0.8 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+10.28 sec in the 15-150 keV band is 0.5 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/1205744/BA/
GCN Circular #35483
Amit K. Ror, Rahul Gupta, Amar Aryan, and Shashi B. Pandey (ARIES) report: We observed the field of the GRB 240101B detected by Swift (Cenko et al. 2024, GCN 35449) 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 were started on 2024-01-02 at 12:43:55 UT, i.e., ~ 0.68 days after the BAT trigger. We have taken multiple frames with an exposure time of 300 s in the R filter. We stacked the images after the alignment. We did not detect any optical afterglow in our stacked image within the enhanced Swift-XRT error box (Evans et al., 2024, GCN 35455). We obtain the following preliminary 3-sigma upper limit in the stacked image:
```
Date Start_UT T_start-T0 (days) Filter  Exp time (s)  Limiting magnitude
=========================================================
2024-01-02 12:43:55    ~0.68      R     300*12       > 21.7
```
Our non-detection is consistent with Zheng et al. 2024, GCN 35454; Kuin et al. 2024, GCN 35458; and Peretto 2024, GCN 35463.
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 catalog. This circular may be cited.

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Jochen Greiner, last update: 05-Jan-2024 [Disclaimer]