Gamma-ray Burst 211221A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 21 Dec 21 20:51:15 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1090472,   Seg_Num: 0
GRB_RA:           78.938d {+05h 15m 45s} (J2000),
                  79.221d {+05h 16m 53s} (current),
                  78.293d {+05h 13m 10s} (1950)
GRB_DEC:          +0.940d {+00d 56' 25"} (J2000),
                  +0.964d {+00d 57' 49"} (current),
                  +0.885d {+00d 53' 08"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       3368 [cnts]    Image_Peak=159 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   146     E_range: 25-100 keV
BKG_INTEN:       20404 [cnts]
BKG_TIME:        74907.70 SOD {20:48:27.70} UT
BKG_DUR:         8 [sec]
GRB_DATE:        19569 TJD;   355 DOY;   21/12/21
GRB_TIME:        74920.82 SOD {20:48:40.82} UT
GRB_PHI:          73.23 [deg]
GRB_THETA:         7.19 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     13.89 [sigma]
IMAGE_SIGNIF:    7.09 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  -3  +0  +0 +90  +0 
SUN_POSTN:       270.24d {+18h 00m 56s}  -23.44d {-23d 26' 07"}
SUN_DIST:        155.12 [deg]   Sun_angle= -11.3 [hr] (East of Sun)
MOON_POSTN:      122.73d {+08h 10m 55s}  +24.57d {+24d 34' 21"}
MOON_DIST:        48.20 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      200.62,-20.69 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       78.05,-22.04 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This Notice was delayed by more than 60 sec past the end of the trigger integration interval;  
COMMENTS:        probably due to it occurring during a Malindi downlink session.  
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 = 14.83,-18.27 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 21 Dec 21 20:51:51 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1090472,   Seg_Num: 0
GRB_RA:           78.8975d {+05h 15m 35.39s} (J2000),
                  79.1810d {+05h 16m 43.43s} (current),
                  78.2528d {+05h 13m 00.66s} (1950)
GRB_DEC:          +0.9141d {+00d 54' 50.7"} (J2000),
                  +0.9374d {+00d 56' 14.4"} (current),
                  +0.8590d {+00d 51' 32.2"} (1950)
GRB_ERROR:       6.0 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       6.82e-10 [erg/cm2/sec]
GRB_SIGNIF:      5.29 [sigma]
IMG_START_DATE:  19569 TJD;   355 DOY;   21/12/21
IMG_START_TIME:  74974.94 SOD {20:49:34.94} UT,   54.1 [sec] since BAT Trigger Time
TAM[0-3]:        327.65 237.21 261.68 243.60
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       270.24d {+18h 00m 57s}  -23.44d {-23d 26' 07"}
SUN_DIST:        155.08 [deg]   Sun_angle= -11.3 [hr] (East of Sun)
MOON_POSTN:      122.74d {+08h 10m 57s}  +24.57d {+24d 34' 18"}
MOON_DIST:        48.26 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      200.62,-20.74 [deg] galactic lon,lat of the burst
ECL_COORDS:       78.01,-22.06 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 2.87 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 21 Dec 21 20:52:02 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     1090472,   Seg_Num: 0
GRB_RA:           78.8975d {+05h 15m 35.3s} (J2000),
                  79.1810d {+05h 16m 43.4s} (current),
                  78.2528d {+05h 13m 00.6s} (1950)
GRB_DEC:          +0.9141d {+00d 54' 50.7"} (J2000),
                  +0.9374d {+00d 56' 14.4"} (current),
                  +0.8590d {+00d 51' 32.2"} (1950)
GRB_ERROR:       5.8 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       28 [cnts]
IMG_START_DATE:  19569 TJD;   355 DOY;   21/12/21
IMG_START_TIME:  74974.94 SOD {20:49:34.94} UT,   54.1 [sec] since BAT Trigger Time
CENTROID_X:      271.08,  raw= 271  [pixels]
CENTROID_Y:      255.00,  raw= 255  [pixels]
ROLL:            205.15 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -101.58
GRB_POS_XRT_Z:   -85.61
IMAGE_URL:       sw01090472000msxps_rw.img
SUN_POSTN:       270.24d {+18h 00m 57s}  -23.44d {-23d 26' 07"}
SUN_DIST:        155.08 [deg]   Sun_angle= -11.3 [hr] (East of Sun)
MOON_POSTN:      122.74d {+08h 10m 57s}  +24.57d {+24d 34' 17"}
MOON_DIST:        48.26 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      200.62,-20.74 [deg] galactic lon,lat of the burst
ECL_COORDS:       78.01,-22.06 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 21 Dec 21 20:52:01 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     1090472,   Seg_Num: 0
GRB_RA:           78.8975d {+05h 15m 35.3s} (J2000),
                  79.1810d {+05h 16m 43.4s} (current),
                  78.2528d {+05h 13m 00.6s} (1950)
GRB_DEC:          +0.9141d {+00d 54' 50.7"} (J2000),
                  +0.9374d {+00d 56' 14.4"} (current),
                  +0.8590d {+00d 51' 32.2"} (1950)
GRB_ERROR:       5.8 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       28 [cnts]
IMG_START_DATE:  19569 TJD;   355 DOY;   21/12/21
IMG_START_TIME:  74974.94 SOD {20:49:34.94} UT,   54.1 [sec] since BAT Trigger Time
CENTROID_X:      271.08,  raw= 271  [pixels]
CENTROID_Y:      255.00,  raw= 255  [pixels]
ROLL:            205.15 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -101.58
GRB_POS_XRT_Z:   -85.61
IMAGE_URL:       sw01090472000msxps_rw.img
SUN_POSTN:       270.24d {+18h 00m 57s}  -23.44d {-23d 26' 07"}
SUN_DIST:        155.08 [deg]   Sun_angle= -11.3 [hr] (East of Sun)
MOON_POSTN:      122.74d {+08h 10m 57s}  +24.57d {+24d 34' 17"}
MOON_DIST:        48.26 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      200.62,-20.74 [deg] galactic lon,lat of the burst
ECL_COORDS:       78.01,-22.06 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 21 Dec 21 20:53:37 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1090472,   Seg_Num: 0
POINT_RA:         78.934d {+05h 15m 44s} (J2000)
POINT_DEC:        +0.924d {+00d 55' 25"} (J2000)
POINT_ROLL:      205.154d
IMG_START_DATE:  19569 TJD;   355 DOY;   21/12/21
IMG_START_TIME:  74984.15 SOD {20:49:44.15} UT,   63.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.488
N_STARS:         107
X_OFFSET:        376 [pixels]
Y_OFFSET:        640 [pixels]
X_MAX:           1335 [pixels]
Y_MAX:           1599 [pixels]
DET_THRESH:      13
PHOTO_THRESH:    7
SL_URL:          sw01090472000msufc0063.fits
SUN_POSTN:       270.24d {+18h 00m 57s}  -23.44d {-23d 26' 07"}
SUN_DIST:        155.10 [deg]   Sun_angle= -11.3 [hr] (East of Sun)
MOON_POSTN:      122.75d {+08h 11m 01s}  +24.57d {+24d 34' 09"}
MOON_DIST:        48.23 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      200.63,-20.70 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       78.05,-22.06 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 21 Dec 21 20:53:55 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1090472,   Seg_Num: 0
POINT_RA:         78.934d {+05h 15m 44s} (J2000)
POINT_DEC:        +0.924d {+00d 55' 25"} (J2000)
POINT_ROLL:      205.154d
IMG_START_DATE:  19569 TJD;   355 DOY;   21/12/21
IMG_START_TIME:  74984.15 SOD {20:49:44.15} UT,   63.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.488
N_STARS:         107
X_OFFSET:        376 [pixels]
Y_OFFSET:        640 [pixels]
X_MAX:           1335 [pixels]
Y_MAX:           1599 [pixels]
DET_THRESH:      13
PHOTO_THRESH:    7
SL_URL:          sw01090472000msufc0063.fits
SUN_POSTN:       270.24d {+18h 00m 57s}  -23.44d {-23d 26' 07"}
SUN_DIST:        155.10 [deg]   Sun_angle= -11.3 [hr] (East of Sun)
MOON_POSTN:      122.76d {+08h 11m 01s}  +24.57d {+24d 34' 08"}
MOON_DIST:        48.24 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      200.63,-20.70 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       78.05,-22.06 [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 21 Dec 21 20:55:02 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1090472,   Seg_Num: 0
POINT_RA:         78.934d {+05h 15m 44s} (J2000)
POINT_DEC:        +0.924d {+00d 55' 25"} (J2000)
ROLL:            205.154d
IMG_START_DATE:  19569 TJD;   355 DOY;   21/12/21
IMG_START_TIME:  74984.15 SOD {20:49:44.15} UT,   63.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     661812612
X_OFFSET:        1034 [pixels]
Y_OFFSET:        976 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1194
Y_GRB_POS:       1136
BINNING_INDEX:   1
IM_URL:          sw01090472000msuni0092.fits
SUN_POSTN:       270.24d {+18h 00m 57s}  -23.44d {-23d 26' 07"}
SUN_DIST:        155.10 [deg]   Sun_angle= -11.3 [hr] (East of Sun)
MOON_POSTN:      122.77d {+08h 11m 04s}  +24.57d {+24d 34' 02"}
MOON_DIST:        48.24 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      200.63,-20.70 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       78.05,-22.06 [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 21 Dec 21 20:55:11 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1090472,   Seg_Num: 0
GRB_RA:           78.938d {+05h 15m 45s} (J2000),
                  79.221d {+05h 16m 53s} (current),
                  78.293d {+05h 13m 10s} (1950)
GRB_DEC:          +0.940d {+00d 56' 25"} (J2000),
                  +0.964d {+00d 57' 49"} (current),
                  +0.885d {+00d 53' 08"} (1950)
GRB_DATE:        19569 TJD;   355 DOY;   21/12/21
GRB_TIME:        74920.82 SOD {20:48:40.82} UT
TRIGGER_INDEX:   146
GRB_PHI:          73.23 [deg]
GRB_THETA:         7.19 [deg]
DELTA_TIME:      -31.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     13.89 [sigma]
IMAGE_SIGNIF:    7.09 [sigma]
LC_URL:          sw01090472000msb.lc
SUN_POSTN:       270.24d {+18h 00m 57s}  -23.44d {-23d 26' 07"}
SUN_DIST:        155.12 [deg]   Sun_angle= -11.3 [hr] (East of Sun)
MOON_POSTN:      122.77d {+08h 11m 04s}  +24.57d {+24d 34' 01"}
MOON_DIST:        48.23 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      200.62,-20.69 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       78.05,-22.04 [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 = 14.83,-18.27 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 21 Dec 21 20:55:17 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1090472,   Seg_Num: 0
POINT_RA:         78.934d {+05h 15m 44s} (J2000)
POINT_DEC:        +0.924d {+00d 55' 25"} (J2000)
ROLL:            205.154d
IMG_START_DATE:  19569 TJD;   355 DOY;   21/12/21
IMG_START_TIME:  74984.15 SOD {20:49:44.15} UT,   63.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     661812612
X_OFFSET:        1034 [pixels]
Y_OFFSET:        976 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1194
Y_GRB_POS:       1136
BINNING_INDEX:   1
IM_URL:          sw01090472000msuni0092.fits
SUN_POSTN:       270.24d {+18h 00m 57s}  -23.44d {-23d 26' 07"}
SUN_DIST:        155.10 [deg]   Sun_angle= -11.3 [hr] (East of Sun)
MOON_POSTN:      122.77d {+08h 11m 04s}  +24.57d {+24d 34' 01"}
MOON_DIST:        48.25 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      200.63,-20.70 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       78.05,-22.06 [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 21 Dec 21 21:01:45 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1090472,   Seg_Num: 0
POINT_RA:         78.933d {+05h 15m 44s} (J2000)
POINT_DEC:        +0.922d {+00d 55' 19"} (J2000)
POINT_ROLL:      205.155d
IMG_START_DATE:  19569 TJD;   355 DOY;   21/12/21
IMG_START_TIME:  75196.16 SOD {20:53:16.16} UT,   275.3 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.719
N_STARS:         141
X_OFFSET:        714 [pixels]
Y_OFFSET:        656 [pixels]
X_MAX:           1673 [pixels]
Y_MAX:           1615 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw01090472000msufc0275.fits
SUN_POSTN:       270.24d {+18h 00m 58s}  -23.44d {-23d 26' 07"}
SUN_DIST:        155.09 [deg]   Sun_angle= -11.3 [hr] (East of Sun)
MOON_POSTN:      122.83d {+08h 11m 18s}  +24.56d {+24d 33' 28"}
MOON_DIST:        48.29 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      200.63,-20.71 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       78.05,-22.06 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 21 Dec 21 21:02:04 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1090472,   Seg_Num: 0
POINT_RA:         78.933d {+05h 15m 44s} (J2000)
POINT_DEC:        +0.922d {+00d 55' 19"} (J2000)
POINT_ROLL:      205.155d
IMG_START_DATE:  19569 TJD;   355 DOY;   21/12/21
IMG_START_TIME:  75196.16 SOD {20:53:16.16} UT,   275.3 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.719
N_STARS:         141
X_OFFSET:        714 [pixels]
Y_OFFSET:        656 [pixels]
X_MAX:           1673 [pixels]
Y_MAX:           1615 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw01090472000msufc0275.fits
SUN_POSTN:       270.24d {+18h 00m 58s}  -23.44d {-23d 26' 07"}
SUN_DIST:        155.09 [deg]   Sun_angle= -11.3 [hr] (East of Sun)
MOON_POSTN:      122.83d {+08h 11m 19s}  +24.56d {+24d 33' 27"}
MOON_DIST:        48.30 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      200.63,-20.71 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       78.05,-22.06 [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 21 Dec 21 21:03:08 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1090472,   Seg_Num: 0
POINT_RA:         78.933d {+05h 15m 44s} (J2000)
POINT_DEC:        +0.922d {+00d 55' 19"} (J2000)
ROLL:            205.155d
IMG_START_DATE:  19569 TJD;   355 DOY;   21/12/21
IMG_START_TIME:  75196.16 SOD {20:53:16.16} UT,   275.3 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     661812824
X_OFFSET:        1034 [pixels]
Y_OFFSET:        976 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1194
Y_GRB_POS:       1136
BINNING_INDEX:   1
IM_URL:          sw01090472000msuni0304.fits
SUN_POSTN:       270.24d {+18h 00m 59s}  -23.44d {-23d 26' 07"}
SUN_DIST:        155.09 [deg]   Sun_angle= -11.3 [hr] (East of Sun)
MOON_POSTN:      122.84d {+08h 11m 21s}  +24.56d {+24d 33' 21"}
MOON_DIST:        48.30 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      200.63,-20.71 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       78.05,-22.06 [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 21 Dec 21 21:03:21 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1090472,   Seg_Num: 0
POINT_RA:         78.933d {+05h 15m 44s} (J2000)
POINT_DEC:        +0.922d {+00d 55' 19"} (J2000)
ROLL:            205.155d
IMG_START_DATE:  19569 TJD;   355 DOY;   21/12/21
IMG_START_TIME:  75196.16 SOD {20:53:16.16} UT,   275.3 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     661812824
X_OFFSET:        1034 [pixels]
Y_OFFSET:        976 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1194
Y_GRB_POS:       1136
BINNING_INDEX:   1
IM_URL:          sw01090472000msuni0304.fits
SUN_POSTN:       270.24d {+18h 00m 59s}  -23.44d {-23d 26' 07"}
SUN_DIST:        155.09 [deg]   Sun_angle= -11.3 [hr] (East of Sun)
MOON_POSTN:      122.84d {+08h 11m 22s}  +24.56d {+24d 33' 20"}
MOON_DIST:        48.30 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      200.63,-20.71 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       78.05,-22.06 [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 Circular #31273
K. L. Page (U Leicester), S. D. Barthelmy (GSFC), S. B. Cenko (GSFC), J.D. Gropp (PSU), J. A. Kennea (PSU), N. J. Klingler (GSFC/UMBC/CRESSTII), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL) and B. Sbarufatti (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 20:48:40 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 211221A (trigger=1090472). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 78.938, +0.940 which is
```
   RA(J2000) = 05h 15m 45s
   Dec(J2000) = +00d 56' 25"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex peak structure with a duration of about 20 sec. The peak count rate was ~1700 counts/sec (15-350 keV), at ~3 sec after the trigger.
The XRT began observing the field at 20:49:34.9 UT, 54.1 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 78.89820, 0.91421 which is equivalent to:
```
   RA(J2000)  = 05h 15m 35.57s
   Dec(J2000) = +00d 54' 51.2"
```
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 170 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 (1.37 x 10^21 cm^-2, Willingale et al. 2013), with an excess column of 9 (+4.75/-2.44) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 6.82e-10 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 63 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 0.143.
Burst Advocate for this burst is K. L. Page (kimlpage1978 AT gmail.com). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 21 Dec 21 21:09:17 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1090472,   Seg_Num: 0
POINT_RA:         78.933d {+05h 15m 44s} (J2000)
POINT_DEC:        +0.922d {+00d 55' 21"} (J2000)
POINT_ROLL:      205.155d
IMG_START_DATE:  19569 TJD;   355 DOY;   21/12/21
IMG_START_TIME:  75798.55 SOD {21:03:18.55} UT,   877.7 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.179
N_STARS:         190
X_OFFSET:        474 [pixels]
Y_OFFSET:        416 [pixels]
X_MAX:           1913 [pixels]
Y_MAX:           1855 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw01090472000msufc0877.fits
SUN_POSTN:       270.25d {+18h 01m 00s}  -23.44d {-23d 26' 07"}
SUN_DIST:        155.09 [deg]   Sun_angle= -11.3 [hr] (East of Sun)
MOON_POSTN:      122.89d {+08h 11m 35s}  +24.55d {+24d 32' 50"}
MOON_DIST:        48.35 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      200.63,-20.71 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       78.05,-22.06 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 21 Dec 21 21:10:41 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1090472,   Seg_Num: 0
POINT_RA:         78.933d {+05h 15m 44s} (J2000)
POINT_DEC:        +0.922d {+00d 55' 21"} (J2000)
ROLL:            205.155d
IMG_START_DATE:  19569 TJD;   355 DOY;   21/12/21
IMG_START_TIME:  75798.55 SOD {21:03:18.55} UT,   877.7 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     661813426
X_OFFSET:        1033 [pixels]
Y_OFFSET:        975 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1193
Y_GRB_POS:       1135
BINNING_INDEX:   1
IM_URL:          sw01090472000msuni0906.fits
SUN_POSTN:       270.25d {+18h 01m 00s}  -23.44d {-23d 26' 07"}
SUN_DIST:        155.09 [deg]   Sun_angle= -11.3 [hr] (East of Sun)
MOON_POSTN:      122.91d {+08h 11m 38s}  +24.55d {+24d 32' 43"}
MOON_DIST:        48.36 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      200.63,-20.71 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       78.05,-22.06 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 21 Dec 21 21:09:27 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1090472,   Seg_Num: 0
POINT_RA:         78.933d {+05h 15m 44s} (J2000)
POINT_DEC:        +0.922d {+00d 55' 21"} (J2000)
POINT_ROLL:      205.155d
IMG_START_DATE:  19569 TJD;   355 DOY;   21/12/21
IMG_START_TIME:  75798.55 SOD {21:03:18.55} UT,   877.7 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.179
N_STARS:         190
X_OFFSET:        474 [pixels]
Y_OFFSET:        416 [pixels]
X_MAX:           1913 [pixels]
Y_MAX:           1855 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw01090472000msufc0877.fits
SUN_POSTN:       270.25d {+18h 01m 00s}  -23.44d {-23d 26' 07"}
SUN_DIST:        155.09 [deg]   Sun_angle= -11.3 [hr] (East of Sun)
MOON_POSTN:      122.90d {+08h 11m 35s}  +24.55d {+24d 32' 49"}
MOON_DIST:        48.35 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      200.63,-20.71 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       78.05,-22.06 [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 21 Dec 21 21:10:56 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1090472,   Seg_Num: 0
POINT_RA:         78.933d {+05h 15m 44s} (J2000)
POINT_DEC:        +0.922d {+00d 55' 21"} (J2000)
ROLL:            205.155d
IMG_START_DATE:  19569 TJD;   355 DOY;   21/12/21
IMG_START_TIME:  75798.55 SOD {21:03:18.55} UT,   877.7 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     661813426
X_OFFSET:        1033 [pixels]
Y_OFFSET:        975 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1193
Y_GRB_POS:       1135
BINNING_INDEX:   1
IM_URL:          sw01090472000msuni0906.fits
SUN_POSTN:       270.25d {+18h 01m 00s}  -23.44d {-23d 26' 07"}
SUN_DIST:        155.09 [deg]   Sun_angle= -11.3 [hr] (East of Sun)
MOON_POSTN:      122.91d {+08h 11m 38s}  +24.54d {+24d 32' 42"}
MOON_DIST:        48.36 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      200.63,-20.71 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       78.05,-22.06 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 21 Dec 21 21:21:11 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     1090472,   Seg_Num: 0
GRB_RA:           78.8983d {+05h 15m 35.59s} (J2000),
                  79.1818d {+05h 16m 43.62s} (current),
                  78.2536d {+05h 13m 00.85s} (1950)
GRB_DEC:          +0.9144d {+00d 54' 51.8"} (J2000),
                  +0.9377d {+00d 56' 15.5"} (current),
                  +0.8593d {+00d 51' 33.3"} (1950)
GRB_ERROR:       3.5 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  19569 TJD;   355 DOY;   21/12/21
IMG_START_TIME:  75034.00 SOD {20:50:34.00} UT,   113.2 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       270.26d {+18h 01m 02s}  -23.44d {-23d 26' 07"}
SUN_DIST:        155.07 [deg]   Sun_angle= -11.3 [hr] (East of Sun)
MOON_POSTN:      123.00d {+08h 12m 01s}  +24.53d {+24d 31' 50"}
MOON_DIST:        48.46 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      200.62,-20.74 [deg] galactic lon,lat of the burst
ECL_COORDS:       78.01,-22.06 [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 http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN Circular #31274
V. Lipunov, V.Kornilov, E.Gorbovskoy, K.Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko, G.Antipov, D.Zimnukhov, V.Senik, T.Pogrosheva, E.Minkina, A.Chasovnikov, V.Topolev, V.Grinshpun, D.Kuvshinov, D. Cheryasov (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),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev (Irkutsk State University, API),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational State University)
MASTER-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 211221A ( K. L. Page et al., GCN 31273) errorbox 3401 sec after notice time and 3560 sec after trigger time at 2021-12-21 21:48:01 UT, with upper limit up to 14.8 mag. The observations began at zenith distance = 46 deg. The sun altitude is -68.8 deg.
MASTER-OAFA robotic telescope located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB 211221A errorbox 13726 sec after notice time and 13885 sec after trigger time at 2021-12-22 00:40:06 UT, with upper limit up to 16.7 mag. Observations started at twilight. The observations began at zenith distance = 54 deg. The sun altitude is -12.1 deg.
The galactic latitude b = -20 deg., longitude l = 201 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1823335
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

    3651 |   MASTER-Kislovodsk |   C |   180 | 12.7 |        
    3651 |   MASTER-Kislovodsk |   C |   180 | 12.2 |        
    3851 |   MASTER-Kislovodsk |   C |   180 | 13.0 |        
    3851 |   MASTER-Kislovodsk |   C |   180 | 13.4 |        
    4052 |   MASTER-Kislovodsk |   C |   180 | 14.2 |        
    4252 |   MASTER-Kislovodsk |   C |   180 | 14.8 |        
    4252 |   MASTER-Kislovodsk |   C |   180 | 14.5 |        
    4453 |   MASTER-Kislovodsk |   C |   180 | 14.4 |        
    4453 |   MASTER-Kislovodsk |   C |   180 | 13.5 |        
   10415 |   MASTER-Kislovodsk |   C |   180 | 14.5 |        
   10896 |   MASTER-Kislovodsk |   C |   180 | 13.8 |        
   10896 |   MASTER-Kislovodsk |   C |   180 | 14.4 |        
   11497 |   MASTER-Kislovodsk |   C |   180 | 13.4 |        
   11497 |   MASTER-Kislovodsk |   C |   180 | 13.1 |        
   11897 |   MASTER-Kislovodsk |   C |   180 | 13.5 |        
   12787 |   MASTER-Kislovodsk |   C |   180 | 14.1 |        
   13976 |         MASTER-OAFA |   C |   180 | 16.7 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #31275
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
Using 892 s of XRT Photon Counting mode data and 2 UVOT images for GRB 211221A, 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 = 78.89745, +0.91449 which is equivalent to:
```
RA (J2000): 05h 15m 35.39s
Dec (J2000): +00d 54' 52.2"
```
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 #31276
D. B. Malesani (Univ. Radboud and DAWN/NBI), Z. Zhu (NAOC/CAS), A. Viitanen (Univ. Helsinki and NOT), E. Biancalani (Leiden Obs. and NOT) report on behalf of a larger collaboration:
We observed the field of the solstice GRB 211221A (Page et al., GCN 31273) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were carried out under good conditions in the r and z bands, with mean times 2021 Dec 22.00 and 22.01 UT, respectively (3.2 and 3.5 hr after the GRB). The exposure times were 3x300 (in r) and 5x200 s (in z).
We detect no new objects inside or close to the UVOT-enhanced XRT error circle (Evans et al., GCN 31275), down to (preliminary) limits:
```
r > 23.5 AB
z > 23.0 AB
```
Calibration of the photometry is relative to nearby stars from the Pan-STARRS catalogue.
GCN Circular #31277
P.J. Groot (Radboud/UCT/SAAO), S. de Wet (UCT), D. B. Malesani (Radboud/DAWN,NBI), P.M. Vreeswijk (Radboud), report on behalf of the MeerLICHT consortium:
The position of GRB211221A (Page et al., GCN 31273; Evans et al., GCN 31275; Lipunov et al., GCN 31274; Malesani et al., GCN 31276) was observed with the 0.6m wide-field MeerLICHT telescope, located at Sutherland, South Africa, starting at 2021-12-22, 00:24 UT, approximately 3.5 hr after the detection by Swift. A series of 60s observations in the u,g,q,r,i,z bands was started that lasted until 2021-12-22, 01:21 UT. All data was processed automatically using the BlackBOX/ZOGY pipeline (Vreeswijk et al, forthcoming). Cloudy conditions prevented observations earlier in the night.
Co-adding the single exposures in each filter leads to deeper 3-sigma AB-magnitude limits at the Swift-XRT position reported by Evans et al. (GCN 31275) of:
```
u > 19.97 at 00:51:03 UT
g > 20.55 at 01:02:18 UT
q > 21.85 at 00:59:14 UT
r > 20.67 at 00:56:55 UT
i > 20.32 at 00:52:09 UT
z > 19.70 at 00:56:24 UT.
```
These limits are consistent with those reported by Malesani et al. (GCN 31276) taken at the same time.
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
GCN Circular #31279
Y.-D. Hu, T.-R. Sun, A. J. Castro-Tirado, E. Fernandez-Garcia, M. D. Caballero-Garcia, R. Sanchez-Ramirez, M. A. Castro Tirado (IAA-CSIC), C. Perez del Pulgar, A. Castellon, I. Carrasco (Univ. de Malaga), S. Guziy (Univ. of Nikolaev) and D. R. Xiong, Y. F. Fan, J. M. Bai, C. J. Wang, Y. X. Xin, X. H. Zhao (Yunnan Observatories of CAS) on behalf of a larger collaboration, report:
Following the detection of GRB 211221A by Swift (Page et al. GCNC 31273), the 0.6m BOOTES-4/MET robotic telescope at Lijiang Astronomical Observatory (China) automatically responded to this burst starting on Dec. 21 at 20:51:37 UT (~177 sec after trigger). No new source is detected at the position reported by Swift-XRT (Page et al. GCNC 31273) which down to 19.7 mag in the co-added image of first achieved 10 x 20 s exposure frames in the clear filter. This non-detection is consistent with the reports from UVOT (Page et al. GCNC 31273), MASTER (Lipunov et al. GCNC 31274), NOT (Malesani et al. GCNC 31276) and MeerLICHT (Groot et al. GCNC 31277).
We thank the staff at Lijiang observatory for their excellent support.
GCN Circular #31281
M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), J. D. Gropp (PSU), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester) and K.L. Page report on behalf of the Swift-XRT team:
We have analysed 5.9 ks of XRT data for GRB 211221A (Page et al. GCN Circ. 31273), from 44 s to 73.7 ks after the BAT trigger. The data comprise 52 s in Windowed Timing (WT) mode (the first 8 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 31275).
The light curve can be modelled with a power-law decay with a decay index of alpha=1.02 (+0.05, -0.04).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.59 (+0.31, -0.29). The best-fitting absorption column is 1.1 (+0.4, -0.3) x 10^22 cm^-2, in excess of the Galactic value of 1.4 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 6.2 x 10^-11 (9.0 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     1.1 (+0.4, -0.3) x 10^22 cm^-2
Galactic foreground: 1.4 x 10^21 cm^-2
Excess significance: 5.0 sigma
Photon index:	     1.59 (+0.31, -0.29)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01090472.
This circular is an official product of the Swift-XRT team.
GCN Circular #31285
T. Komesh (NU), B. Grossan (UCB, NU), Z. Maksut (NU), M. Krugov (FAI),� E. Linder (UCB, NU), E. Abdikamalov (NU), G. F. Smoot (HKUST, UCB, NU), report on behalf of the Energetic Cosmos Laboratory:
The Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO) observed the field of GRB 211221A 19 s after receipt an automated GCN / BAT position alert, observing in Sloan i' band, with the Burst Simultaneous Three-Channel Imager (BSTI; Grossan, Kumar & Smoot 2019, JHEA, 32, 14).
We started observations at 20:51:35 UT on 2021-12-21, 175 s after the BAT trigger. Observations were made in clear conditions starting at about 30 deg. target altitude. No source consistent with the XRT (P. Evans et al., GCN Circ. 31275) was detected.� We report the following results:
```
start time��� t-t0(s)� end time������� ULi'������ exposure_time (s)
------------��� --------� ------------��������� ------ --------------------
20:51:35 ��� 175 � 20:52:35 �������� 17.9 ��������� 60
20:52:50 ��� 257 � 22:12:50 �������� 18.4 ������� 150
```
start time is in UT. t-t0(s) gives the time since trigger, in seconds. UL i', gives the 5 sigma upper limit sensitivity in magnitudes, for images co-added to the given exposure time. The first row in the table corresponds to co-adds of an initial short exposure image sequence of 7.5 s. The second row corresponds to co-adds from a continuing series of 15 s exposures.� Calibration was done with the 3 bright Pan-STARRS catalog stars on our images.
We caution the reader that these are preliminary results, without color or other corrections. Please also note that times are approximate.
```
----------------------------------
NU = Nazarbayev University, Nur-Sultan, Kazakhstan
UCB = University of California, Berkeley, USA
HKUST = Hong Kong University of Science and Technology
FAI = Fesenkov Astrophysical Institute, Kazakhstan
```
The NUTTelA-TAO Team acknowledges the support of the staff of the Assy-Turgen Astrophysical Observatory, Almaty, Kazakhstan, and the Fesenkov Astrophysical Institute, Almaty, Kazkhstan.
GCN Circular #31289
S. D. Barthelmy (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (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-239 to T+963 sec sec from the recent telemetry downlink, we report further analysis of BAT GRB 211221A (trigger #1090472) (Page et al., GCN 31273). The BAT ground-calculated position is RA, Dec = 78.906, 0.902 deg which is
```
   RA(J2000)  =  05h 15m 37.4s
   Dec(J2000) = +00d 54' 06.2"
```
with an uncertainty of 2.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 97%.
The BAT light curve showed a complex peak structure with a duration of about 20 sec. There may be hints of precursor activity and low-level post-peak emission from the GRB as seen in the mask weighted light curve. The post-peak emission lasts beyond the available event data (which ends at T+963). T90 (15-350 keV) is 671.67 +- 105.96 sec (estimated error including systematics).
The time-averaged spectrum from T-129.40 to T+688.36 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.48 +- 0.13. The fluence in the 15-150 keV band is 4.0 +- 0.3 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T-0.27 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/1090472/BA/
GCN Circular #31291
C. Fletcher (USRA) reports on behalf of the Fermi-GBM Team:
Swift-BAT detected GRB 211221A at 20:48:40 UT (GCN 31273). There was no Fermi-GBM onboard trigger around the event.
An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM identified no counterparts.
The GBM targeted search [1], the most sensitive, coherent search for GRB-like signals identified a transient most significantly on the 8.192 s timescale, with a location consistent with the Swift-BAT event and a S/N of 21, using the standard search protocol. The GBM targeted search event was found with the highest significance with a "normal" spectrum (Band function with Epeak = 230 keV, alpha = -1.0, beta = -2.3) for a GRB.
[1] Goldstein et al. 2019 arXiv:1903.12597
GCN Circular #31317
M. H. Siegel (PSU) and K. L. Page (U. Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 211221A 63 s after the BAT trigger (Page et al., GCN Circ. 31273). No optical afterglow consistent with the XRT position (Evans et al. GCN Circ. 31275) 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            63          213          147         >20.7
u_FC               275          525          246         >20.1
white               63         1010          317         >21.1
v                  606          799           39         >18.6
b                  531          724           39         >19.4
u                  275          872          285         >20.0
w1                 655          848           39         >18.1
m2                 631          650           19         >17.8
w2                 582          774           39         >19.0
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.143 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #31503
Ahmed M. Fouad, Ali Takey & Yosry Azzam at KAO observatory, Egypt report:
The observation of GRB 211221A started on 2021-12-21 from 22:25:01 UT to 23:10:10 UT, i.e. 1hr_36m_21s to 2hr_21m_30s after the BAT trigger (Evans et al. GCN Circ. 31273).
No detection of the afterglow in the optical Bessel V & R bands consistent with the XRT position, the magnitude limit in the GRB field according to the faintest objects is V = 22.92 & R = 22.15. The instrumental magnitudes were computed using aperture photometry in photutils (python package).

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Jochen Greiner, last update: 20-Jan-2022 [Disclaimer]