Gamma-ray Burst 241218A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Dec 24 00:13:11 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1275005,   Seg_Num: 0
GRB_RA:          185.682d {+12h 22m 44s} (J2000),
                 185.994d {+12h 23m 59s} (current),
                 185.057d {+12h 20m 14s} (1950)
GRB_DEC:         +29.991d {+29d 59' 27"} (J2000),
                 +29.853d {+29d 51' 09"} (current),
                 +30.268d {+30d 16' 05"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       25742 [cnts]    Image_Peak=489 [image_cnts]
TRIGGER_DUR:     12.160 [sec] 
TRIGGER_INDEX:   478     E_range: 25-100 keV
BKG_INTEN:       125398 [cnts]
BKG_TIME:        437.26 SOD {00:07:17.26} UT
BKG_DUR:         64 [sec]
GRB_DATE:        20662 TJD;   353 DOY;   24/12/18
GRB_TIME:        531.15 SOD {00:08:51.15} UT
GRB_PHI:         -141.99 [deg]
GRB_THETA:        35.03 [deg]
SOLN_STATUS:     0x1010D
RATE_SIGNIF:     9.43 [sigma]
IMAGE_SIGNIF:    8.41 [sigma]
MERIT_PARAMS:     +0  +0 +125  +4  +2  -1  +0  +0  +6  +0 
SUN_POSTN:       266.26d {+17h 45m 01s}  -23.39d {-23d 23' 25"}
SUN_DIST:         93.61 [deg]   Sun_angle= 5.4 [hr] (West of Sun)
MOON_POSTN:      123.52d {+08h 14m 06s}  +24.39d {+24d 23' 11"}
MOON_DIST:        55.21 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      186.82, 83.08 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      172.06, 29.52 [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 position matches one of the nearby galaxy sources in the on-board catalog!  
COMMENTS:        This matches a source in the on-board catalog: Num=12081=NGC4308,   delta=0.186 [deg].  
COMMENTS:        This matches a source in the ground catalog: NGC4314, delta=0.106 [deg].  
COMMENTS:        This is a GRB in nearby galaxy or it is noise.  
COMMENTS:        This trigger occurred at longitude,latitude = 78.70,-16.19 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Dec 24 00:14:18 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1275005,   Seg_Num: 0
GRB_RA:          185.6737d {+12h 22m 41.68s} (J2000),
                 185.9854d {+12h 23m 56.50s} (current),
                 185.0483d {+12h 20m 11.58s} (1950)
GRB_DEC:         +29.9793d {+29d 58' 45.4"} (J2000),
                 +29.8410d {+29d 50' 27.7"} (current),
                 +30.2565d {+30d 15' 23.3"} (1950)
GRB_ERROR:       4.8 [arcsec radius, statistical plus systematic, 90%
+containment]
GRB_INTEN:       5.16e-09 [erg/cm2/sec]
GRB_SIGNIF:      11.22 [sigma]
IMG_START_DATE:  20662 TJD;   353 DOY;   24/12/18
IMG_START_TIME:  675.67 SOD {00:11:15.67} UT,   144.5 [sec] since BAT Trigger Time
TAM[0-3]:        327.63 237.13 261.62 243.81
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       266.26d {+17h 45m 01s}  -23.39d {-23d 23' 26"}
SUN_DIST:         93.61 [deg]   Sun_angle= 5.4 [hr] (West of Sun)
MOON_POSTN:      123.53d {+08h 14m 08s}  +24.38d {+24d 23' 02"}
MOON_DIST:        55.19 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      186.93, 83.08 [deg] galactic lon,lat of the burst
ECL_COORDS:      172.06, 29.51 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.
COMMENTS:        This matches a source in the BAT ground catalog: NGC4314, delta=0.092 [deg].  
COMMENTS:        The XRT position is 0.82 arcmin from the BAT position.  
COMMENTS:        The object found at this position is either a very bright burst or a cosmic ray hit.  
COMMENTS:        Examine the XRT Image to differentiate (CRs are much more compact); see examples at:  
COMMENTS:        http://www.swift.psu.edu/xrt/XRT_Postage_Stamp_Image_Photo_Gallery.htm .

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Dec 24 00:14:29 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     1275005,   Seg_Num: 0
GRB_RA:          185.6737d {+12h 22m 41.6s} (J2000),
                 185.9854d {+12h 23m 56.5s} (current),
                 185.0483d {+12h 20m 11.5s} (1950)
GRB_DEC:         +29.9793d {+29d 58' 45.4"} (J2000),
                 +29.8410d {+29d 50' 27.7"} (current),
                 +30.2565d {+30d 15' 23.3"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       126 [cnts]
IMG_START_DATE:  20662 TJD;   353 DOY;   24/12/18
IMG_START_TIME:  675.67 SOD {00:11:15.67} UT,   144.5 [sec] since BAT Trigger Time
CENTROID_X:      329.31,  raw= 329  [pixels]
CENTROID_Y:      262.70,  raw= 263  [pixels]
ROLL:            114.83 [deg]
GAIN:            2
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -84.85
GRB_POS_XRT_Z:   41.75
IMAGE_URL:       sw01275005000msxps_rw.img
SUN_POSTN:       266.26d {+17h 45m 01s}  -23.39d {-23d 23' 26"}
SUN_DIST:         93.61 [deg]   Sun_angle= 5.4 [hr] (West of Sun)
MOON_POSTN:      123.54d {+08h 14m 09s}  +24.38d {+24d 23' 00"}
MOON_DIST:        55.19 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      186.93, 83.08 [deg] galactic lon,lat of the burst
ECL_COORDS:      172.06, 29.51 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.  
COMMENTS:        The object found at this position is either a very bright burst or a cosmic ray hit.  
COMMENTS:        Examine the XRT Image to differentiate (CRs are much more compact); see examples at:  
COMMENTS:        http://www.swift.psu.edu/xrt/XRT_Postage_Stamp_Image_Photo_Gallery.htm .

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Dec 24 00:14:32 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     1275005,   Seg_Num: 0
GRB_RA:          185.6737d {+12h 22m 41.6s} (J2000),
                 185.9854d {+12h 23m 56.5s} (current),
                 185.0483d {+12h 20m 11.5s} (1950)
GRB_DEC:         +29.9793d {+29d 58' 45.4"} (J2000),
                 +29.8410d {+29d 50' 27.7"} (current),
                 +30.2565d {+30d 15' 23.3"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       126 [cnts]
IMG_START_DATE:  20662 TJD;   353 DOY;   24/12/18
IMG_START_TIME:  675.67 SOD {00:11:15.67} UT,   144.5 [sec] since BAT Trigger Time
CENTROID_X:      329.31,  raw= 329  [pixels]
CENTROID_Y:      262.70,  raw= 263  [pixels]
ROLL:            114.83 [deg]
GAIN:            2
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -84.85
GRB_POS_XRT_Z:   41.75
IMAGE_URL:       sw01275005000msxps_rw.img
SUN_POSTN:       266.26d {+17h 45m 01s}  -23.39d {-23d 23' 26"}
SUN_DIST:         93.61 [deg]   Sun_angle= 5.4 [hr] (West of Sun)
MOON_POSTN:      123.54d {+08h 14m 09s}  +24.38d {+24d 22' 60"}
MOON_DIST:        55.19 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      186.93, 83.08 [deg] galactic lon,lat of the burst
ECL_COORDS:      172.06, 29.51 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.  
COMMENTS:        The object found at this position is either a very bright burst or a cosmic ray hit.  
COMMENTS:        Examine the XRT Image to differentiate (CRs are much more compact); see examples at:  
COMMENTS:        http://www.swift.psu.edu/xrt/XRT_Postage_Stamp_Image_Photo_Gallery.htm .

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Dec 24 00:15:16 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1275005,   Seg_Num: 0
GRB_RA:          185.682d {+12h 22m 44s} (J2000),
                 185.994d {+12h 23m 59s} (current),
                 185.057d {+12h 20m 14s} (1950)
GRB_DEC:         +29.991d {+29d 59' 27"} (J2000),
                 +29.853d {+29d 51' 09"} (current),
                 +30.268d {+30d 16' 05"} (1950)
GRB_DATE:        20662 TJD;   353 DOY;   24/12/18
GRB_TIME:        531.15 SOD {00:08:51.15} UT
TRIGGER_INDEX:   478
GRB_PHI:         -141.99 [deg]
GRB_THETA:        35.03 [deg]
DELTA_TIME:      52.00 [sec]
TRIGGER_DUR:     12.160 [sec] 
SOLN_STATUS:     0x10D
RATE_SIGNIF:     9.43 [sigma]
IMAGE_SIGNIF:    8.41 [sigma]
LC_URL:          sw01275005000msb.lc
SUN_POSTN:       266.26d {+17h 45m 02s}  -23.39d {-23d 23' 26"}
SUN_DIST:         93.61 [deg]   Sun_angle= 5.4 [hr] (West of Sun)
MOON_POSTN:      123.54d {+08h 14m 10s}  +24.38d {+24d 22' 53"}
MOON_DIST:        55.19 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      186.82, 83.08 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      172.06, 29.52 [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 matches a source in the on-board catalog.  
COMMENTS:        This matches a source in the ground catalog: NGC4314, delta=0.106 [deg].  
COMMENTS:        This is not a GRB.  
COMMENTS:        This is an interesting source.  
COMMENTS:        This trigger occurred at longitude,latitude = 78.70,-16.19 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Dec 24 00:15:57 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1275005,   Seg_Num: 0
POINT_RA:        185.697d {+12h 22m 47s} (J2000)
POINT_DEC:       +29.996d {+29d 59' 45"} (J2000)
POINT_ROLL:      114.829d
IMG_START_DATE:  20662 TJD;   353 DOY;   24/12/18
IMG_START_TIME:  682.63 SOD {00:11:22.63} UT,   151.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.646
N_STARS:         15
X_OFFSET:        456 [pixels]
Y_OFFSET:        648 [pixels]
X_MAX:           1415 [pixels]
Y_MAX:           1607 [pixels]
DET_THRESH:      13
PHOTO_THRESH:    7
SL_URL:          sw01275005000msufc0151.fits
SUN_POSTN:       266.26d {+17h 45m 02s}  -23.39d {-23d 23' 26"}
SUN_DIST:         93.60 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      123.55d {+08h 14m 12s}  +24.38d {+24d 22' 48"}
MOON_DIST:        55.20 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      186.74, 83.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      172.07, 29.53 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Dec 24 00:16:11 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1275005,   Seg_Num: 0
POINT_RA:        185.697d {+12h 22m 47s} (J2000)
POINT_DEC:       +29.996d {+29d 59' 45"} (J2000)
POINT_ROLL:      114.829d
IMG_START_DATE:  20662 TJD;   353 DOY;   24/12/18
IMG_START_TIME:  682.63 SOD {00:11:22.63} UT,   151.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.646
N_STARS:         15
X_OFFSET:        456 [pixels]
Y_OFFSET:        648 [pixels]
X_MAX:           1415 [pixels]
Y_MAX:           1607 [pixels]
DET_THRESH:      13
PHOTO_THRESH:    7
SL_URL:          sw01275005000msufc0151.fits
SUN_POSTN:       266.26d {+17h 45m 02s}  -23.39d {-23d 23' 26"}
SUN_DIST:         93.60 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      123.55d {+08h 14m 13s}  +24.38d {+24d 22' 46"}
MOON_DIST:        55.20 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      186.74, 83.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      172.07, 29.53 [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:     Wed 18 Dec 24 00:17:25 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1275005,   Seg_Num: 0
POINT_RA:        185.697d {+12h 22m 47s} (J2000)
POINT_DEC:       +29.996d {+29d 59' 45"} (J2000)
ROLL:            114.829d
IMG_START_DATE:  20662 TJD;   353 DOY;   24/12/18
IMG_START_TIME:  682.63 SOD {00:11:22.63} UT,   151.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     756173517
X_OFFSET:        808 [pixels]
Y_OFFSET:        1055 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       968
Y_GRB_POS:       1215
BINNING_INDEX:   1
IM_URL:          sw01275005000msuni0186.fits
SUN_POSTN:       266.26d {+17h 45m 02s}  -23.39d {-23d 23' 26"}
SUN_DIST:         93.60 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      123.56d {+08h 14m 16s}  +24.38d {+24d 22' 35"}
MOON_DIST:        55.19 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      186.74, 83.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      172.07, 29.53 [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:     Wed 18 Dec 24 00:17:38 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1275005,   Seg_Num: 0
POINT_RA:        185.697d {+12h 22m 47s} (J2000)
POINT_DEC:       +29.996d {+29d 59' 45"} (J2000)
ROLL:            114.829d
IMG_START_DATE:  20662 TJD;   353 DOY;   24/12/18
IMG_START_TIME:  682.63 SOD {00:11:22.63} UT,   151.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     756173517
X_OFFSET:        808 [pixels]
Y_OFFSET:        1055 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       968
Y_GRB_POS:       1215
BINNING_INDEX:   1
IM_URL:          sw01275005000msuni0186.fits
SUN_POSTN:       266.26d {+17h 45m 02s}  -23.39d {-23d 23' 26"}
SUN_DIST:         93.60 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      123.57d {+08h 14m 16s}  +24.38d {+24d 22' 33"}
MOON_DIST:        55.18 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      186.74, 83.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      172.07, 29.53 [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:     Wed 18 Dec 24 00:22:11 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1275005,   Seg_Num: 0
POINT_RA:        185.696d {+12h 22m 47s} (J2000)
POINT_DEC:       +29.995d {+29d 59' 43"} (J2000)
POINT_ROLL:      114.828d
IMG_START_DATE:  20662 TJD;   353 DOY;   24/12/18
IMG_START_TIME:  840.68 SOD {00:14:00.68} UT,   309.5 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        1.196
N_STARS:         14
X_OFFSET:        488 [pixels]
Y_OFFSET:        735 [pixels]
X_MAX:           1447 [pixels]
Y_MAX:           1694 [pixels]
DET_THRESH:      9
PHOTO_THRESH:    4
SL_URL:          sw01275005000msufc0309.fits
SUN_POSTN:       266.26d {+17h 45m 03s}  -23.39d {-23d 23' 26"}
SUN_DIST:         93.61 [deg]   Sun_angle= 5.4 [hr] (West of Sun)
MOON_POSTN:      123.61d {+08h 14m 27s}  +24.36d {+24d 21' 54"}
MOON_DIST:        55.15 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      186.75, 83.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      172.07, 29.53 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Dec 24 00:22:25 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1275005,   Seg_Num: 0
POINT_RA:        185.696d {+12h 22m 47s} (J2000)
POINT_DEC:       +29.995d {+29d 59' 43"} (J2000)
POINT_ROLL:      114.828d
IMG_START_DATE:  20662 TJD;   353 DOY;   24/12/18
IMG_START_TIME:  840.68 SOD {00:14:00.68} UT,   309.5 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        1.196
N_STARS:         14
X_OFFSET:        488 [pixels]
Y_OFFSET:        735 [pixels]
X_MAX:           1447 [pixels]
Y_MAX:           1694 [pixels]
DET_THRESH:      9
PHOTO_THRESH:    4
SL_URL:          sw01275005000msufc0309.fits
SUN_POSTN:       266.26d {+17h 45m 03s}  -23.39d {-23d 23' 26"}
SUN_DIST:         93.61 [deg]   Sun_angle= 5.4 [hr] (West of Sun)
MOON_POSTN:      123.61d {+08h 14m 27s}  +24.36d {+24d 21' 52"}
MOON_DIST:        55.15 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      186.75, 83.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      172.07, 29.53 [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:     Wed 18 Dec 24 00:27:35 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1275005,   Seg_Num: 0
POINT_RA:        185.696d {+12h 22m 47s} (J2000)
POINT_DEC:       +29.996d {+29d 59' 44"} (J2000)
POINT_ROLL:      114.828d
IMG_START_DATE:  20662 TJD;   353 DOY;   24/12/18
IMG_START_TIME:  1395.67 SOD {00:23:15.67} UT,   864.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        7.011
N_STARS:         57
X_OFFSET:        248 [pixels]
Y_OFFSET:        495 [pixels]
X_MAX:           1687 [pixels]
Y_MAX:           1934 [pixels]
DET_THRESH:      23
PHOTO_THRESH:    14
SL_URL:          sw01275005000msufc0864.fits
SUN_POSTN:       266.27d {+17h 45m 04s}  -23.39d {-23d 23' 26"}
SUN_DIST:         93.61 [deg]   Sun_angle= 5.4 [hr] (West of Sun)
MOON_POSTN:      123.66d {+08h 14m 39s}  +24.35d {+24d 21' 07"}
MOON_DIST:        55.11 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      186.75, 83.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      172.07, 29.53 [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:     Wed 18 Dec 24 00:29:45 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1275005,   Seg_Num: 0
POINT_RA:        185.696d {+12h 22m 47s} (J2000)
POINT_DEC:       +29.996d {+29d 59' 44"} (J2000)
ROLL:            114.828d
IMG_START_DATE:  20662 TJD;   353 DOY;   24/12/18
IMG_START_TIME:  1395.67 SOD {00:23:15.67} UT,   864.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     756174230
X_OFFSET:        807 [pixels]
Y_OFFSET:        1054 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       967
Y_GRB_POS:       1214
BINNING_INDEX:   1
IM_URL:          sw01275005000msuni0899.fits
SUN_POSTN:       266.27d {+17h 45m 04s}  -23.39d {-23d 23' 27"}
SUN_DIST:         93.61 [deg]   Sun_angle= 5.4 [hr] (West of Sun)
MOON_POSTN:      123.69d {+08h 14m 45s}  +24.35d {+24d 20' 48"}
MOON_DIST:        55.09 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      186.75, 83.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      172.07, 29.53 [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:     Wed 18 Dec 24 00:29:58 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1275005,   Seg_Num: 0
POINT_RA:        185.696d {+12h 22m 47s} (J2000)
POINT_DEC:       +29.996d {+29d 59' 44"} (J2000)
ROLL:            114.828d
IMG_START_DATE:  20662 TJD;   353 DOY;   24/12/18
IMG_START_TIME:  1395.67 SOD {00:23:15.67} UT,   864.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     756174230
X_OFFSET:        807 [pixels]
Y_OFFSET:        1054 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       967
Y_GRB_POS:       1214
BINNING_INDEX:   1
IM_URL:          sw01275005000msuni0899.fits
SUN_POSTN:       266.27d {+17h 45m 04s}  -23.39d {-23d 23' 27"}
SUN_DIST:         93.61 [deg]   Sun_angle= 5.4 [hr] (West of Sun)
MOON_POSTN:      123.69d {+08h 14m 45s}  +24.35d {+24d 20' 46"}
MOON_DIST:        55.09 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      186.75, 83.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      172.07, 29.53 [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:     Wed 18 Dec 24 00:38:37 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     1275005,   Seg_Num: 0
GRB_RA:          185.6815d {+12h 22m 43.55s} (J2000),
                 185.9932d {+12h 23m 58.37s} (current),
                 185.0561d {+12h 20m 13.46s} (1950)
GRB_DEC:         +29.9728d {+29d 58' 22.0"} (J2000),
                 +29.8345d {+29d 50' 04.3"} (current),
                 +30.2500d {+30d 14' 59.9"} (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:  20662 TJD;   353 DOY;   24/12/18
IMG_START_TIME:  702.00 SOD {00:11:42.00} UT,   170.9 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       266.27d {+17h 45m 06s}  -23.39d {-23d 23' 27"}
SUN_DIST:         93.62 [deg]   Sun_angle= 5.4 [hr] (West of Sun)
MOON_POSTN:      123.77d {+08h 15m 05s}  +24.33d {+24d 19' 31"}
MOON_DIST:        55.02 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      186.96, 83.09 [deg] galactic lon,lat of the burst
ECL_COORDS:      172.07, 29.50 [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:        This position was enhanced using UVOT field astrometry.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 1.1% < P(seren) < 2.8%.

GCN Circular #38601
M. A. Williams (PSU), R. Gupta (NASA GSFC), N. P. M. Kuin (UCL-MSSL), B. Sbarufatti (INAF-OAB) and A. Tohuvavohu (Caltech) report on behalf of the Neil Gehrels Swift Observatory Team:
At 00:08:51 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 241218A (trigger=1275005). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 185.682, +29.991 which is
```
   RA(J2000) = 12h 22m 44s
   Dec(J2000) = +29d 59' 27"
```
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 25 sec. The peak count rate was ~896 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 00:11:15.6 UT, 144.5 seconds after the BAT trigger. The position determined from promptly downlinked data differs significantly from the on-board position, suggesting that the XRT may have centroided on a cosmic ray; the initial XRT position notice should be treated with caution. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 185.68146, 29.97303 which is equivalent to:
```
   RA(J2000)  = 12h 22m 43.55s
   Dec(J2000) = +29d 58' 22.9"
```
with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 64 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 consistent with the Galactic value of 2.23 x 10^20 cm^-2 (Willingale et al. 2013).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 151 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 0.023.
Burst Advocate for this burst is M. A. Williams (mjw6837 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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Dec 24 00:27:21 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1275005,   Seg_Num: 0
POINT_RA:        185.696d {+12h 22m 47s} (J2000)
POINT_DEC:       +29.996d {+29d 59' 44"} (J2000)
POINT_ROLL:      114.828d
IMG_START_DATE:  20662 TJD;   353 DOY;   24/12/18
IMG_START_TIME:  1395.67 SOD {00:23:15.67} UT,   864.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        7.011
N_STARS:         57
X_OFFSET:        248 [pixels]
Y_OFFSET:        495 [pixels]
X_MAX:           1687 [pixels]
Y_MAX:           1934 [pixels]
DET_THRESH:      23
PHOTO_THRESH:    14
SL_URL:          sw01275005000msufc0864.fits
SUN_POSTN:       266.27d {+17h 45m 04s}  -23.39d {-23d 23' 26"}
SUN_DIST:         93.61 [deg]   Sun_angle= 5.4 [hr] (West of Sun)
MOON_POSTN:      123.66d {+08h 14m 39s}  +24.35d {+24d 21' 09"}
MOON_DIST:        55.11 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      186.75, 83.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      172.07, 29.53 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Dec 24 00:23:42 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1275005,   Seg_Num: 0
POINT_RA:        185.696d {+12h 22m 47s} (J2000)
POINT_DEC:       +29.995d {+29d 59' 43"} (J2000)
ROLL:            114.828d
IMG_START_DATE:  20662 TJD;   353 DOY;   24/12/18
IMG_START_TIME:  840.68 SOD {00:14:00.68} UT,   309.5 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     756173675
X_OFFSET:        808 [pixels]
Y_OFFSET:        1055 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       968
Y_GRB_POS:       1215
BINNING_INDEX:   1
IM_URL:          sw01275005000msuni0344.fits
SUN_POSTN:       266.26d {+17h 45m 03s}  -23.39d {-23d 23' 26"}
SUN_DIST:         93.61 [deg]   Sun_angle= 5.4 [hr] (West of Sun)
MOON_POSTN:      123.63d {+08h 14m 30s}  +24.36d {+24d 21' 40"}
MOON_DIST:        55.14 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      186.75, 83.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      172.07, 29.53 [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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 18 Dec 24 00:23:33 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1275005,   Seg_Num: 0
POINT_RA:        185.696d {+12h 22m 47s} (J2000)
POINT_DEC:       +29.995d {+29d 59' 43"} (J2000)
ROLL:            114.828d
IMG_START_DATE:  20662 TJD;   353 DOY;   24/12/18
IMG_START_TIME:  840.68 SOD {00:14:00.68} UT,   309.5 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     756173675
X_OFFSET:        808 [pixels]
Y_OFFSET:        1055 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       968
Y_GRB_POS:       1215
BINNING_INDEX:   1
IM_URL:          sw01275005000msuni0344.fits
SUN_POSTN:       266.26d {+17h 45m 03s}  -23.39d {-23d 23' 26"}
SUN_DIST:         93.61 [deg]   Sun_angle= 5.4 [hr] (West of Sun)
MOON_POSTN:      123.62d {+08h 14m 30s}  +24.36d {+24d 21' 42"}
MOON_DIST:        55.14 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      186.75, 83.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      172.07, 29.53 [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 #38604
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team.
Using 1225 s of XRT Photon Counting mode data and 2 UVOT images for GRB 241218A, 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 = 185.68168, +29.97318 which is equivalent to:
```
RA (J2000): 12h 22m 43.60s
Dec (J2000): +29d 58' 23.5"
```
with an uncertainty of 2.4 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest position can be viewed at 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 #38605
R. Strausbaugh (Eastern Illinois University), A. Cucchiara (NASA) report on behalf of a larger collaboration:
We observed the Swift GRB 241218A field (Williams et al., GCN 38601) with the LCOGT 1-meter Sinistro instrument at the Teide Tenerife site, on December 18, from 03:45 to 04:17 UT (corresponding to 3.62 to 4.15 hours after the GRB trigger time) with the sdss r and i filters.
We performed a series of 3x300s exposures in i-band and r-band. We do not detect a source within the Swift XRT enhanced error region (Beardmore et al., GCN 38604) in either band.
The following 5-sigma upper limits are calculated using the PanSTARRS catalog as reference:
```
r > 21.2
i > 20.9
```
These magnitudes are not corrected for galactic extinction.
GCN Circular #38611
Z. Maksut (NU), B. Grossan (UCB, NU), T. Komesh (NU), Z. Abdullayev (NU), M. Krugov (FAI) and E. Abdikamalov (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 241218A, 12 seconds after receipt of an automated GCN / BAT position alert, in Sloan g' and r' bands, with the Burst Simultaneous Three-Channel Imager (Grossan, Kumar & Smoot 2019, JHEA, 32, 14).
We started observations of GRB 241218A (Williams et al., GCN 38601; Strausbaugh et al., GCN 38605) at UT 00:13:43 on 2024-12-18, 292 seconds after the BAT trigger. Observations were made in clear conditions. We report the following upper limit results:
```
start time  t_m-t0(s)  end time    UL g'   UL r'   exposure_time (image x s)
-----------------------------------------------------------------------
00:26:30     1191     00:29:30     19.51     19.57    3 x 60
```
The start and end time is in UT. t_m is the middle time, t0 is the BAT trigger time, t_m-t0 is given in seconds. UL gives the 5 sigma upper limit sensitivity in magnitudes, for images co-added to the given exposure time. Calibration was done with 4 Pan-STARRS catalog stars on our images. No color corrections were applied to the values above.
----------------------------------
```
NU = Nazarbayev University, Astana, Kazakhstan
UCB = University of California, Berkeley, USA
FAI = Fesenkov Astrophysical Institute, Kazakhstan
```
GCN Circular #38614
V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (INAF-OAB), C. Salvaggio (INAF-OAB), M. A. Williams (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 6.1 ks of XRT data for GRB 241218A, from 131 s to 23.9 ks after the BAT trigger. The data comprise 19 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode.
The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=2.7 (+0.4, -0.3). At T+539 s the decay flattens to an alpha of -1.5 (+0.0, -0.7) before breaking again at T+972 s to a final decay with index alpha=1.52 (+0.19, -0.15).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.72 (+0.22, -0.12). The best-fitting absorption column is consistent with the Galactic value of 2.2 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.8 x 10^-11 (3.9 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     2.2 (+/-4.5) x 10^20 cm^-2
Galactic foreground: 2.2 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.72 (+0.22, -0.12)
```
If the light curve continues to decay with a power-law decay index of 1.52, the count rate at T+24 hours will be 4.1 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.5 x 10^-14 (1.6 x 10^-14) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01275005.
This circular is an official product of the Swift-XRT team.
GCN Circular #38617
A. Bochenek and D. A. Perley (LJMU) report:
We observed the Gamma-Ray Burst GRB 241218a (Williams et al., GCN 38601) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 3x200s exposures with the SDSS r’ and SDSS i’ filters starting at 2024-12-18 03:33:56 UT, approximately 3.4 hours after the trigger.
We do not detect any new sources at the Swift/XRT enhanced position (Beardmore et al., GCN 38604). The 3-sigma limiting magnitudes on the stacked images are r > 20.9 mag and i > 21.0 mag, calculated using the nearby PanSTARRS secondary standards as reference. The photometry was not corrected for extinction.
GCN Circular #38620
R. Brivio, M. Ferro, P. D’Avanzo (INAF-OAB), D. B. Malesani (DAWN/NBI and Radboud Univ.) S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of GRB 241218A detected by Swift (Williams et al., GCN 38601) with the REM 60cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z bands, starting on 2024 December 18 at 08:05:53 UT (i.e. 8.0 hours after the Swift trigger), and lasting for about 1 hour.
From preliminary photometry we do not detect any optical counterpart at the XRT enhanced position (Beardmore et al., GCN 38604) down to the following 3sigma magnitude upper limits:
r > 19.2 (AB; calibrated against the Pan-STARRS catalogue) at a mid-time of t - t0 = 8.4 hr after the trigger.
GCN Circular #38629
R. Gupta (GSFC), S. D. Barthelmy (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU), M. A. Williams (PSU) (i.e. the Swift-BAT team):
Using the data set from T-520 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 241218A (trigger #1275005) (M. A. Williams, et al., GCN Circ. 38601). The BAT ground-calculated position is RA, Dec = 185.687, 29.984 deg which is
```
   RA(J2000)  =  12h 22m 44.8s
   Dec(J2000) = +29d 59' 04.2"
```
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 52%.
The mask-weighted light curve shows a single pulse of emission lasting 40 seconds with a possible second pulse at T+70 seconds. The T90 (15-350 keV) is 23.31 +- 4.19 sec (estimated error including systematics).
The time-averaged spectrum from T-1.82 to T+26.16 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.31 +- 0.26. The fluence in the 15-150 keV band is 5.5 +- 1.0 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+16.64 sec in the 15-150 keV band is 0.6 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1275005
GCN Circular #38630
S.Y. Fu (NAOC), D. B. Malesani (DAWN/NBI and Radboud Univ.), Z.P. Zhu, X. Liu, D. Xu (NAOC), L. Cotter (UCD), A. Amanda Djupvik (NOT) report on behalf of a large collaboration:
We observed the field of GRB 241218A detected by Swift (Williams et al., GCN 38601) using the StanCam instrument mounted on the Nordic Optical Telescope (NOT), 3 x 300 s in the Bessel R band and 5x200 s in the Sloan z band frames were obtained. Observations started at 04:37:19 UT on 2024-12-18, i.e., 4.5 hr after the trigger.
No new source is detected in the stacked frames within the enhanced Swift/XRT error circle (Beardmore et al. GCN 38604), with the limiting magnitudes of R > ~ 21.7 (Vega, converted from r-band, Lupton 2005) and z > ~ 21.0 (AB), calibrated with nearby Pan-STARRS stars and without Galactic extinction correction.
GCN Circular #38634
M. H. Siegel (PSU) and M. Williams (PSU) report on behalf of the Swift/UVOTteam:
The Swift/UVOT began settled observations of the field of GRB 241218A 152 s after the BAT trigger (Williams et al., GCN Circ. 38601). No optical afterglow consistent with the XRT position (D'Elia et al., GCN Circ. 38614) 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           152          301          147         >20.7
u_FC               310          559          246         >19.8
white              152         1014          334         >21.0
v                  640         1411           97         >18.5
b                  565         1337           78         >18.7
u                  310         1312          304         >19.8
w1                 689          709           19         >21.1
```
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 #38639
N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP) report on behalf of IKI-GRB-FuN:
We performed optical observations of the field of GRB 241218A (Williams et. al, GCN 38601; Beardmore et. al, GCN 38604; Strausbaugh et. al, GCN 38605; Maksut et. al, GCN 38611; D'Elia et. al, GCN 38614; Brivio et. al, GCN 38620; Gupta et. al, GCN 38629; Fu et. al, GCN 38630; Siegel et. al, GCN 38634) in the R filter with AZT-33IK of Sayan observatory (Mondy). The observations began on 2024-12-18 20:52 UT, i.e. ~0.88 days since Swift trigger. We do not detect an optical counterpart inside the XRT enhanced localization (Beardmore et. al, GCN 38604) in the stacked image of 58x60 sec. The preliminary photometry is given below:
```
Date       UT start  t-T0         Exp.    Filter  UL(3sigma)
                     (mid, days)  (s)
2024-12-18 20:53:01  0.88415     58*60   R       20.8
```
The magnitudes were calibrated using nearby stars from USNO-B1.0 catalog (R2 magnitudes) and are not corrected for the Galactic extinction. The results are consistent with non-detections reported by other groups.

Back to JG's homepage

Jochen Greiner, last update: 19-Dec-2024 [Disclaimer]