Gamma-ray Burst 240218A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Feb 24 02:00:14 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1215912,   Seg_Num: 0
GRB_RA:          161.781d {+10h 47m 07s} (J2000),
                 162.091d {+10h 48m 22s} (current),
                 161.138d {+10h 44m 33s} (1950)
GRB_DEC:          +1.304d {+01d 18' 14"} (J2000),
                  +1.176d {+01d 10' 35"} (current),
                  +1.568d {+01d 34' 05"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       2469 [cnts]    Image_Peak=100 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   147     E_range: 25-100 keV
BKG_INTEN:       15841 [cnts]
BKG_TIME:        7183.06 SOD {01:59:43.06} UT
BKG_DUR:         8 [sec]
GRB_DATE:        20358 TJD;    49 DOY;   24/02/18
GRB_TIME:        7200.66 SOD {02:00:00.66} UT
GRB_PHI:         131.03 [deg]
GRB_THETA:        35.07 [deg]
SOLN_STATUS:     0x83
RATE_SIGNIF:     11.35 [sigma]
IMAGE_SIGNIF:    6.54 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  -4  +0  +0 +96  +0 
SUN_POSTN:       331.04d {+22h 04m 09s}  -11.85d {-11d 51' 15"}
SUN_DIST:        164.69 [deg]   Sun_angle= 11.3 [hr] (West of Sun)
MOON_POSTN:       74.82d {+04h 59m 16s}  +27.16d {+27d 09' 39"}
MOON_DIST:        87.04 [deg]
MOON_ILLUM:      65 [%]
GAL_COORDS:      248.58, 50.57 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      162.70, -5.94 [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:        Since the IMAGE_SIGNIF is less than 7 sigma, this is a questionable detection.  
COMMENTS:        This trigger occurred at longitude,latitude = 299.21,7.97 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 18 Feb 24 02:00:51 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      44
TRIGGER_NUM:     729914426
GRB_RA:          144.033d {+09h 36m 08s} (J2000),
                 144.342d {+09h 37m 22s} (current),
                 143.394d {+09h 33m 34s} (1950)
GRB_DEC:          -0.367d {-00d 22' 00"} (J2000),
                  -0.476d {-00d 28' 31"} (current),
                  -0.142d {-00d 08' 31"} (1950)
GRB_ERROR:       23.87 [deg radius, statistical plus systematic]
GRB_INTEN:       172 [cnts/sec]
DATA_SIGNIF:     5.00 [sigma]
INTEG_TIME:      0.512 [sec]
GRB_DATE:        20358 TJD;    49 DOY;   24/02/18
GRB_TIME:        7221.72 SOD {02:00:21.72} UT
GRB_PHI:         170.00 [deg]
GRB_THETA:        90.00 [deg]
DATA_TIME_SCALE: 0.5120 [sec]
HARD_RATIO:      0.22
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      82%  GRB
2nd_MOST_LIKELY:  15%  Distant Particles
DETECTORS:       0,0,0, 0,0,0, 0,1,1, 0,0,0, 0,0,
SUN_POSTN:       331.04d {+22h 04m 09s}  -11.85d {-11d 51' 15"}
SUN_DIST:        165.99 [deg]   Sun_angle= -11.6 [hr] (East of Sun)
MOON_POSTN:       74.82d {+04h 59m 18s}  +27.16d {+27d 09' 42"}
MOON_DIST:        72.09 [deg]
MOON_ILLUM:      65 [%]
GAL_COORDS:      235.05, 35.66 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      146.47,-13.86 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240218084/quicklook/glg_lc_medres34_bn240218084.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 230.42,25.38 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(21.0<100sec) coincident with the SWIFT_BAT event (trignum=1215912).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 18 Feb 24 02:01:11 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      57
TRIGGER_NUM:     729914426
GRB_RA:          157.870d {+10h 31m 29s} (J2000),
                 158.181d {+10h 32m 43s} (current),
                 157.225d {+10h 28m 54s} (1950)
GRB_DEC:          +2.110d {+02d 06' 36"} (J2000),
                  +1.985d {+01d 59' 08"} (current),
                  +2.367d {+02d 22' 02"} (1950)
GRB_ERROR:       5.85 [deg radius, statistical only]
DATA_SIGNIF:     14.90 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        20358 TJD;    49 DOY;   24/02/18
GRB_TIME:        7221.72 SOD {02:00:21.72} UT
GRB_PHI:         184.00 [deg]
GRB_THETA:        91.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:       331.04d {+22h 04m 09s}  -11.85d {-11d 51' 15"}
SUN_DIST:        167.85 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:       74.83d {+04h 59m 19s}  +27.16d {+27d 09' 43"}
MOON_DIST:        83.18 [deg]
MOON_ILLUM:      65 [%]
GAL_COORDS:      243.65, 48.20 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      158.75, -6.66 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240218084/quicklook/glg_lc_medres34_bn240218084.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_729914426.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(21.0<100sec) coincident with the SWIFT_BAT event (trignum=1215912).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 18 Feb 24 02:01:03 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      58
TRIGGER_NUM:     729914426
GRB_RA:          158.583d {+10h 34m 20s} (J2000),
                 158.895d {+10h 35m 35s} (current),
                 157.937d {+10h 31m 45s} (1950)
GRB_DEC:          +3.317d {+03d 19' 00"} (J2000),
                  +3.192d {+03d 11' 29"} (current),
                  +3.575d {+03d 34' 31"} (1950)
GRB_ERROR:       9.30 [deg radius, statistical plus systematic]
GRB_INTEN:       141 [cnts/sec]
DATA_SIGNIF:     10.10 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        20358 TJD;    49 DOY;   24/02/18
GRB_TIME:        7221.72 SOD {02:00:21.72} UT
GRB_PHI:         185.00 [deg]
GRB_THETA:        90.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.65
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      55%  GRB
2nd_MOST_LIKELY:  42%  Distant Particles
DETECTORS:       0,0,0, 0,0,0, 0,1,1, 0,0,0, 0,0,
SUN_POSTN:       331.04d {+22h 04m 09s}  -11.85d {-11d 51' 15"}
SUN_DIST:        168.36 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:       74.83d {+04h 59m 18s}  +27.16d {+27d 09' 43"}
MOON_DIST:        83.27 [deg]
MOON_ILLUM:      65 [%]
GAL_COORDS:      242.94, 49.52 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      158.96, -5.27 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240218084/quicklook/glg_lc_medres34_bn240218084.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 230.42,25.38 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(21.0<100sec) coincident with the SWIFT_BAT event (trignum=1215912).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 18 Feb 24 02:09:48 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     729914426
GRB_RA:          162.950d {+10h 51m 48s} (J2000),
                 163.264d {+10h 53m 03s} (current),
                 162.300d {+10h 49m 12s} (1950)
GRB_DEC:          +6.540d {+06d 32' 24"} (J2000),
                  +6.411d {+06d 24' 41"} (current),
                  +6.806d {+06d 48' 21"} (1950)
GRB_ERROR:       3.89 [deg radius, statistical only]
GRB_DATE:        20358 TJD;    49 DOY;   24/02/18
GRB_TIME:        7221.72 SOD {02:00:21.72} UT
GRB_PHI:         190.00 [deg]
GRB_THETA:        88.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       331.04d {+22h 04m 11s}  -11.85d {-11d 51' 07"}
SUN_DIST:        166.77 [deg]   Sun_angle= 11.2 [hr] (West of Sun)
MOON_POSTN:       74.91d {+04h 59m 39s}  +27.17d {+27d 10' 25"}
MOON_DIST:        85.62 [deg]
MOON_ILLUM:      65 [%]
GAL_COORDS:      243.39, 54.92 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      161.78, -0.65 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240218084/quicklook/glg_lc_medres34_bn240218084.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240218084/quicklook/glg_locplot_all_bn240218084.png
COMMENTS:        Fermi-GBM Final Position.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file should be available by the time this FINAL notice is produced.  
COMMENTS:        This notice was generated completely by automated pipeline processing.  
COMMENTS:        This is likely a Long GRB.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(21.0<100sec) coincident with the SWIFT_BAT event (trignum=1215912).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Feb 24 02:03:06 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     1215912,   Seg_Num: 0
GRB_RA:          161.7953d {+10h 47m 10.8s} (J2000),
                 162.1054d {+10h 48m 25.2s} (current),
                 161.1526d {+10h 44m 36.6s} (1950)
GRB_DEC:          +1.2782d {+01d 16' 41.5"} (J2000),
                  +1.1505d {+01d 09' 01.6"} (current),
                  +1.5422d {+01d 32' 31.8"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       110 [cnts]
IMG_START_DATE:  20358 TJD;    49 DOY;   24/02/18
IMG_START_TIME:  7350.11 SOD {02:02:30.11} UT,   149.4 [sec] since BAT Trigger Time
CENTROID_X:      285.32,  raw= 285  [pixels]
CENTROID_Y:      362.93,  raw= 363  [pixels]
ROLL:            135.18 [deg]
GAIN:            2
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   152.84
GRB_POS_XRT_Z:   -52.03
IMAGE_URL:       sw01215912000msxps_rw.img
SUN_POSTN:       331.04d {+22h 04m 09s}  -11.85d {-11d 51' 13"}
SUN_DIST:        164.67 [deg]   Sun_angle= 11.3 [hr] (West of Sun)
MOON_POSTN:       74.85d {+04h 59m 23s}  +27.16d {+27d 09' 53"}
MOON_DIST:        87.04 [deg]
MOON_ILLUM:      65 [%]
GAL_COORDS:      248.63, 50.56 [deg] galactic lon,lat of the burst
ECL_COORDS:      162.72, -5.96 [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:     Sun 18 Feb 24 02:03:04 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     1215912,   Seg_Num: 0
GRB_RA:          161.7953d {+10h 47m 10.8s} (J2000),
                 162.1054d {+10h 48m 25.2s} (current),
                 161.1526d {+10h 44m 36.6s} (1950)
GRB_DEC:          +1.2782d {+01d 16' 41.5"} (J2000),
                  +1.1505d {+01d 09' 01.6"} (current),
                  +1.5422d {+01d 32' 31.8"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       110 [cnts]
IMG_START_DATE:  20358 TJD;    49 DOY;   24/02/18
IMG_START_TIME:  7350.11 SOD {02:02:30.11} UT,   149.4 [sec] since BAT Trigger Time
CENTROID_X:      285.32,  raw= 285  [pixels]
CENTROID_Y:      362.93,  raw= 363  [pixels]
ROLL:            135.18 [deg]
GAIN:            2
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   152.84
GRB_POS_XRT_Z:   -52.03
IMAGE_URL:       sw01215912000msxps_rw.img
SUN_POSTN:       331.04d {+22h 04m 09s}  -11.85d {-11d 51' 13"}
SUN_DIST:        164.67 [deg]   Sun_angle= 11.3 [hr] (West of Sun)
MOON_POSTN:       74.85d {+04h 59m 23s}  +27.16d {+27d 09' 53"}
MOON_DIST:        87.04 [deg]
MOON_ILLUM:      65 [%]
GAL_COORDS:      248.63, 50.56 [deg] galactic lon,lat of the burst
ECL_COORDS:      162.72, -5.96 [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:     Sun 18 Feb 24 02:02:54 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1215912,   Seg_Num: 0
GRB_RA:          161.7953d {+10h 47m 10.87s} (J2000),
                 162.1054d {+10h 48m 25.28s} (current),
                 161.1526d {+10h 44m 36.62s} (1950)
GRB_DEC:          +1.2782d {+01d 16' 41.5"} (J2000),
                  +1.1505d {+01d 09' 01.6"} (current),
                  +1.5422d {+01d 32' 31.8"} (1950)
GRB_ERROR:       4.9 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       3.27e-09 [erg/cm2/sec]
GRB_SIGNIF:      10.48 [sigma]
IMG_START_DATE:  20358 TJD;    49 DOY;   24/02/18
IMG_START_TIME:  7350.11 SOD {02:02:30.11} UT,   149.4 [sec] since BAT Trigger Time
TAM[0-3]:        327.64 237.12 261.53 243.85
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       331.04d {+22h 04m 09s}  -11.85d {-11d 51' 13"}
SUN_DIST:        164.67 [deg]   Sun_angle= 11.3 [hr] (West of Sun)
MOON_POSTN:       74.84d {+04h 59m 23s}  +27.16d {+27d 09' 52"}
MOON_DIST:        87.04 [deg]
MOON_ILLUM:      65 [%]
GAL_COORDS:      248.63, 50.56 [deg] galactic lon,lat of the burst
ECL_COORDS:      162.72, -5.96 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 1.77 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:     Sun 18 Feb 24 02:03:55 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1215912,   Seg_Num: 0
GRB_RA:          161.781d {+10h 47m 07s} (J2000),
                 162.091d {+10h 48m 22s} (current),
                 161.138d {+10h 44m 33s} (1950)
GRB_DEC:          +1.304d {+01d 18' 14"} (J2000),
                  +1.176d {+01d 10' 35"} (current),
                  +1.568d {+01d 34' 05"} (1950)
GRB_DATE:        20358 TJD;    49 DOY;   24/02/18
GRB_TIME:        7200.66 SOD {02:00:00.66} UT
TRIGGER_INDEX:   147
GRB_PHI:         131.03 [deg]
GRB_THETA:        35.07 [deg]
DELTA_TIME:      0.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x83
RATE_SIGNIF:     11.35 [sigma]
IMAGE_SIGNIF:    6.54 [sigma]
LC_URL:          sw01215912000msb.lc
SUN_POSTN:       331.04d {+22h 04m 10s}  -11.85d {-11d 51' 12"}
SUN_DIST:        164.70 [deg]   Sun_angle= 11.3 [hr] (West of Sun)
MOON_POSTN:       74.85d {+04h 59m 25s}  +27.17d {+27d 09' 57"}
MOON_DIST:        87.00 [deg]
MOON_ILLUM:      65 [%]
GAL_COORDS:      248.58, 50.57 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      162.70, -5.94 [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:        Since the IMAGE_SIGNIF is less than 7 sigma, this is a questionable detection.  
COMMENTS:        This trigger occurred at longitude,latitude = 299.21,7.97 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Feb 24 02:05:02 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1215912,   Seg_Num: 0
POINT_RA:        161.755d {+10h 47m 01s} (J2000)
POINT_DEC:        +1.259d {+01d 15' 31"} (J2000)
POINT_ROLL:      135.181d
IMG_START_DATE:  20358 TJD;    49 DOY;   24/02/18
IMG_START_TIME:  7358.97 SOD {02:02:38.97} UT,   158.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.818
N_STARS:         18
X_OFFSET:        216 [pixels]
Y_OFFSET:        280 [pixels]
X_MAX:           1175 [pixels]
Y_MAX:           1239 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    6
SL_URL:          sw01215912000msufc0158.fits
SUN_POSTN:       331.04d {+22h 04m 10s}  -11.85d {-11d 51' 11"}
SUN_DIST:        164.68 [deg]   Sun_angle= 11.3 [hr] (West of Sun)
MOON_POSTN:       74.87d {+04h 59m 28s}  +27.17d {+27d 10' 02"}
MOON_DIST:        86.99 [deg]
MOON_ILLUM:      65 [%]
GAL_COORDS:      248.61, 50.52 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      162.69, -5.99 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Feb 24 02:05:19 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1215912,   Seg_Num: 0
POINT_RA:        161.755d {+10h 47m 01s} (J2000)
POINT_DEC:        +1.259d {+01d 15' 31"} (J2000)
POINT_ROLL:      135.181d
IMG_START_DATE:  20358 TJD;    49 DOY;   24/02/18
IMG_START_TIME:  7358.97 SOD {02:02:38.97} UT,   158.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.818
N_STARS:         18
X_OFFSET:        216 [pixels]
Y_OFFSET:        280 [pixels]
X_MAX:           1175 [pixels]
Y_MAX:           1239 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    6
SL_URL:          sw01215912000msufc0158.fits
SUN_POSTN:       331.04d {+22h 04m 10s}  -11.85d {-11d 51' 11"}
SUN_DIST:        164.68 [deg]   Sun_angle= 11.3 [hr] (West of Sun)
MOON_POSTN:       74.87d {+04h 59m 28s}  +27.17d {+27d 10' 04"}
MOON_DIST:        86.99 [deg]
MOON_ILLUM:      65 [%]
GAL_COORDS:      248.61, 50.52 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      162.69, -5.99 [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:     Sun 18 Feb 24 02:06:20 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1215912,   Seg_Num: 0
POINT_RA:        161.755d {+10h 47m 01s} (J2000)
POINT_DEC:        +1.259d {+01d 15' 31"} (J2000)
ROLL:            135.181d
IMG_START_DATE:  20358 TJD;    49 DOY;   24/02/18
IMG_START_TIME:  7358.97 SOD {02:02:38.97} UT,   158.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     729914591
X_OFFSET:        739 [pixels]
Y_OFFSET:        551 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       899
Y_GRB_POS:       711
BINNING_INDEX:   1
IM_URL:          sw01215912000msuni0191.fits
SUN_POSTN:       331.04d {+22h 04m 10s}  -11.85d {-11d 51' 10"}
SUN_DIST:        164.68 [deg]   Sun_angle= 11.3 [hr] (West of Sun)
MOON_POSTN:       74.88d {+04h 59m 31s}  +27.17d {+27d 10' 09"}
MOON_DIST:        86.98 [deg]
MOON_ILLUM:      65 [%]
GAL_COORDS:      248.61, 50.52 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      162.69, -5.99 [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:     Sun 18 Feb 24 02:06:36 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1215912,   Seg_Num: 0
POINT_RA:        161.755d {+10h 47m 01s} (J2000)
POINT_DEC:        +1.259d {+01d 15' 31"} (J2000)
ROLL:            135.181d
IMG_START_DATE:  20358 TJD;    49 DOY;   24/02/18
IMG_START_TIME:  7358.97 SOD {02:02:38.97} UT,   158.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     729914591
X_OFFSET:        739 [pixels]
Y_OFFSET:        551 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       899
Y_GRB_POS:       711
BINNING_INDEX:   1
IM_URL:          sw01215912000msuni0191.fits
SUN_POSTN:       331.04d {+22h 04m 10s}  -11.85d {-11d 51' 10"}
SUN_DIST:        164.69 [deg]   Sun_angle= 11.3 [hr] (West of Sun)
MOON_POSTN:       74.88d {+04h 59m 31s}  +27.17d {+27d 10' 10"}
MOON_DIST:        86.98 [deg]
MOON_ILLUM:      65 [%]
GAL_COORDS:      248.61, 50.52 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      162.69, -5.99 [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 #35741
V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik, D. Vlasenko, G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij (Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias),
D. Buckley (South African Astronomical Observatory),
O.A. Gress, N.M. Budnev, O.Ershova (Irkutsk State University, API),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich (Blagoveschensk Educational State University)
MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB240218.08 (trigger No 1215912,10h 47m 07.44s , +01d 18m 14.4s, R=0.05) errorbox 31 sec after notice time and 55 sec after trigger time at 2024-02-18 02:00:55 UT, with upper limit up to 17.5 mag. The observations began at zenith distance = 47 deg. The sun altitude is -27.1 deg.
The galactic latitude b = 51 deg., longitude l = 250 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2380863
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

      60 |         MASTER-SAAO |  P/ |    10 | 17.5 |        
```
The observation and reduction will continue. The message may be cited.
View this GCN Circular online at https://gcn.nasa.gov/circulars/35741.
GCN Circular #35742
K. L. Page (U Leicester), T. M. Parsotan (GSFC) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 02:00:00 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 240218A (trigger=1215912). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 161.781, +1.304 which is
```
   RA(J2000) = 10h 47m 07s
   Dec(J2000) = +01d 18' 14"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a broad single peak structure after a period of noise with a duration of about 15 sec. The peak count rate was ~1400 counts/sec (15-350 keV), at ~22 sec after the trigger.
The XRT began observing the field at 02:02:30.1 UT, 149.4 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 161.7953, 1.2782 which is equivalent to:
```
   RA(J2000)  = 10h 47m 10.87s
   Dec(J2000) = +01d 16' 41.5"
```
with an uncertainty of 4.9 arcseconds (radius, 90% containment). This location is 106 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy.
UVOT took a finding chart exposure of 119 seconds with the White filter starting 158 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 0.045.
Burst Advocate for this burst is K. L. Page (klp5 AT leicester.ac.uk). 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:     Sun 18 Feb 24 02:46:37 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     1215912,   Seg_Num: 0
GRB_RA:          161.7973d {+10h 47m 11.35s} (J2000),
                 162.1074d {+10h 48m 25.76s} (current),
                 161.1546d {+10h 44m 37.10s} (1950)
GRB_DEC:          +1.2793d {+01d 16' 45.4"} (J2000),
                  +1.1516d {+01d 09' 05.6"} (current),
                  +1.5433d {+01d 32' 35.8"} (1950)
GRB_ERROR:       3.7 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  20358 TJD;    49 DOY;   24/02/18
IMG_START_TIME:  8692.00 SOD {02:24:52.00} UT,   1491.3 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       331.07d {+22h 04m 16s}  -11.84d {-11d 50' 35"}
SUN_DIST:        164.70 [deg]   Sun_angle= 11.3 [hr] (West of Sun)
MOON_POSTN:       75.28d {+05h 01m 07s}  +27.22d {+27d 13' 23"}
MOON_DIST:        86.65 [deg]
MOON_ILLUM:      66 [%]
GAL_COORDS:      248.63, 50.57 [deg] galactic lon,lat of the burst
ECL_COORDS:      162.72, -5.95 [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 #35743
D. B Malesani (DAWN/NBI and Radboud Univ.) and E. Le Floch (CEA) report on behalf of the Stargate collaboration:
We observed the field of GRB 240218A (Page et al., GCN 35742) using the ESO VLT UT3 with the X-shooter acquisition camera. A short sequence of imaging was secured in the r, g, and z bands. No afterglow is detected consistent with the position reported by XRT (https://www.swift.ac.uk/xrt_positions/), with the following upper limits:
```
r band: r > 23.0 (AB) on Feb 18.124 UT (1.00 hr after the GRB);
z band: z > 21.5 (AB) on Feb 18.127 UT (1.07 hr after the GRB).
```
We acknowledge excellent support from the VLT staff in Paranal, in particular Jonathan Smoker, Thomas Szeifert, and Rodrigo Romero.
GCN Circular #35744
FROM: Emeric Le Floc'h at CEA-Saclay
C. Adami (LAM) and E. Le Floc'h (CEA-Saclay) report on behalf of the MISTRA= L GRB collaboration:
We observed the field of GRB 240218A (Page et al., GCN 35742) using the MIS= TRAL spectro-imager mounted on the T193 telescope at Observatoire de Haute-= Provence (France). We obtained a sequence of 5 images (5min, 10min, 3x15min= ) for an observation mid-time corresponding to 67min after the GRB) and a t= otal observing time of 1h. Similar to the non detection reported earlier by= Malesani et al. (GCN 35743), we did not detect any afterglow candidate con= sistent with the XRT position, down to the following upper limit :
r > 23 (AB)
The photometry was calibrated against the PanStarrs catalog within a circle= of 2=E2=80=99 (radius) around the GRB position.
We acknowledge excellent support from Observatoire de Haute Provence, in p= articular Yoann Degot Longhi.
GCN Circular #35747
P. D=E2=80=99Avanzo, M. Ferro, R. Brivio, Y.-D. Hu, D. Fugazza, S. Covino (= INAF-OAB) on behalf of the REM team, report:
We observed the field of GRB 240218A (Page et al., GCN 35742) with the REM = 60cm robotic telescope located at the ESO Observatory of La Silla (Chile).= =20 The observations were carried out in the g, r, i, z, H bands, starting on 2= 024 Feb 18 at 02:01:08 UT (i.e. 68 seconds after the burst T0) and lasted f= or about 3 hours.
An uncatalogued, fading source is detected in the initial H REM images. The= source is not detected in the optical filters.=20 From preliminary astrometry we obtain the following position:
```
RA (J2000) = 10:47:11.50
Dec (J2000) = +01:16:38.0
(+/- 0.5=E2=80=9D).
```
This position is located at the South-East edge of the 3.8=E2=80=9D radius = XRT error circle (https://www.swift.ac.uk/xrt_unenh_positions/01215912/
)
From preliminary analysis we derive:
```
H = 14.7 +/- 0.2 mag, at a mid time of t-t0 ~ 103 s after the GRB T0.
H = 15.8 +/ -0.2 mag, at a mid time of t-t0 ~ 511 s after the GRB T0.
```
Magnitudes are in the Vega system and calibrated against the 2MASS catalogue.
The optical magnitude limits reported by Malesani et al. (GCN Circ. 35743), although obtained about 1 hour after the REM detection, may imply a significant red color for the afterglow (r - H > 4 mag, assuming the same decay from ~ 100 s to 3600 s after the GRB T0). In light of the low Galactic extinction along the GRB line of sight and of the absence of evidence for intrinsic N(H) excess in the X-ray afterglow spectrum obtained by Swift/XRT (https://www.swift.ac.uk/xrt_spectra/0= 1215912/ <https://www.swift.ac.uk/xrt_spectra/01215912/>),=20 we suggest that GRB 240218 can be a high-redshift event. Further follow-up, especially in the NIR bands, is encouraged.
GCN Circular #35748
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
Using 75 s of XRT Photon Counting mode data and 1 UVOT images for GRB 240218A, 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 = 161.79682, +1.27634 which is equivalent to:
```
RA (J2000): 10h 47m 11.24s
Dec (J2000): +01d 16' 34.8"
```
with an uncertainty of 4.2 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 #35749
We observed the near-infrared counterpart of GRB 240218A (Page et al., GCN 35742; D'Avanzo et al., GCN 35747) using the ESO VLT UT1 (Kueyen) equipped with the FORS2 imager. Observations were carried out in the Gunn z filter.
The GRB counterpart discovered by REM (D'Avanzo et al., GCN 35747) is well detected in the coaddition of our images (1080 s exposure time), at a mean epoch Feb 18.205 UT (2.925 hr after the GRB). Calibrated against nearby stars from the Pan-STARRS catalog, we preliminarily measure a magnitude z = 23.8 +- 0.15 (AB).
We acknowledge expert support from the VLT observing staff in Paranal, in particular Thomas Szeifert, Jonathan Smoker, Martina Baratella, and Juan Carlos Olivares.
GCN Circular #35755
P. Veres and C. Meegan (both UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 02:00:21.72 UT on 18 February 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240218A (trigger 729914426/240218084), which was also detected by Swift/BAT (Page et al. 2024, GCN 35742). The Fermi GBM on-ground localization is consistent with the Swift BAT position.
The angle from the Fermi LAT boresight is 93 degrees.
The GBM light curve consists of a single pulse followed by weaker emission with a duration (T90) of about 38 s (50-300 keV). The time-averaged spectrum from T0-2.6 to T0+30.2 s is best fit by a Band function with Epeak = 100 +/- 20 keV, alpha = -0.3 +/- 0.3, and beta = -1.9 +/- 0.1.
The event fluence (10-1000 keV) in this time interval is (5.2 +/- 0.4)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1.5 s in the 10-1000 keV band is 3.1 +/- 0.2 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular #35756
A. Saccardi (GEPI/Obs. de Paris), D. B. Malesani (DAWN/NBI & Radboud Univ.)= , J. T. Palmerio (GEPI/Obs. de Paris & IAP), S. D. Vergani (GEPI/Obs. de Pa= ris & IAP & INAF/OABr), E. Le Floc=E2=80=99h (CEA), L. Izzo (INAF/OACn & DA= RK/NBI), A. J. Levan (Radboud Univ. & Warwick Univ.), J. P. U. Fynbo (DAWN/= NBI), P. D=E2=80=99Avanzo (INAF/OABr), A. Rossi (INAF/OAS), A. de Ugarte Po= stigo (OCA), report on behalf of the Stargate collaboration:
We observed the field of the Swift and Fermi GRB 240218A (Page et al., GCN = 35742; D=E2=80=99Avanzo et al., GCN 35747; Malesani et al., GCN 35749; Vere= s et al., GCN 35755) using the ESO/VLT UT3 (Melipal) equipped with the X-sh= ooter spectrograph. Our spectra cover the wavelength range 3000-21000 AA, and consist of 4 expo= sures of 1200 s each. The observation starting-time was 2024 Feb 19.179 UT = (~26 hr after the trigger). We detect a clear continuum across the whole NI= R arm. From the detection of multiple absorption features, which we interpr= et as due to SiII, FeII, AlII, CrII, ZnII, MgI, SiII*, FeII*, CIV and SiIV,= we infer a redshift of z =3D 6.782.
We note that this is the highest GRB redshift measured accurately from meta= l absorption lines in a good S/N spectrum. We encourage follow-up at all wavelengths.
We acknowledge the excellent support from the ESO staff in Paranal, in part= icular Jonathan Smoker, Rodrigo Romero and Pascale Hibon.
GCN Circular #35757
K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), A. D'Ai (INAF-IASFPA), J. D. Gropp (PSU), S. Dichiara (PSU), J.A. Kennea (PSU) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 5.7 ks of XRT data for GRB 240218A, from 137 s to 149.4 ks after the BAT trigger. The data comprise 118 s in Windowed Timing (WT) mode (the first 10 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode.
The light curve can be modelled with an initial power-law decay with an index of alpha=2.12 (+0.11, -0.05), followed by a break at T+1538 s to an alpha of 0.70 (+0.06, -0.05).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.39 (+/-0.04). The best-fitting absorption column is 1.39 (+0.29, -0.27) x 10^23 cm^-2, at a redshift of 6.782, in addition to the Galactic value of 4.2 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 4.8 x 10^-11 (5.3 x 10^-11) erg cm^-2 count^-1.
A summary of the WT-mode spectrum is thus:
```
Galactic foreground: 4.2 x 10^20 cm^-2
Intrinsic column:    1.39 (+0.29, -0.27) x 10^23 cm^-2 at z=6.782
Photon index:	     1.39 (+/-0.04)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01215912.
This circular is an official product of the Swift-XRT team.
GCN Circular #35758
D. Svinkin, D. Frederiks, A.Lysenko, A. Ridnaia, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report:
The long-duration GRB 240218A (Swift-BAT detection: Page et al., GCN 35742; Fermi-GBM detection: Veres and Meegan, GCN 35755) was detected by Konus-Wind (KW) in the waiting mode.
A Bayesian block analysis of the KW waiting mode data in the 20-400 keV band reveals a >10 sigma count rate increase in the interval from T0-12.646 s to T0+25.626 s, where T0 = T0(BAT) = 02:00:00 UT. The burst light curve shows a multi-peaked structure with the brightest peak around ~T0(BAT)+20 s.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB240218_T07200/
As observed by Konus-Wind, the burst had a total fluence of 7.62(-2.22,+1.72)x10^-6 erg/cm^2 and a 2.944-s peak energy flux, measured from T0+19.738 s, of 5.29(-1.49,+2.21)x10^-7 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
Modelling the 3-channel time-integrated spectrum of the burst (measured from T0-12.646 s to T0+25.626 s) by a power law with exponential cutoff (CPL) model dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) yields alpha > -0.56 and Ep = 180(-74,+77) keV.
Modelling the 3-channel spectrum near the peak count rate (measured from T0+19.738 to T0+25.626 s) by the CPL model yields alpha = -1.33(-0.29,+0.53) and Ep = 293(-120,+207) keV.
Assuming the redshift z=6.782 (Saccardi et al., GCN 35756) and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014),we estimate the burst isotropic energy release E_iso to 5.4(-1.6,+1.2)x10^53 erg, the isotropic peak luminosity L_iso to 2.9(-0.8,+1.2)x10^53 erg/s, the rest-frame peak energy of the time-integrated spectrum Ep,i,z to 1401(-576,+599) keV, and the rest-frame peak energy at the peak of the emission Ep,p,z to 2280(-934,+1611) keV.
With the obtained estimates, GRB 240218A is inside 68% prediction band for both 'Amati' and 'Yonetoku' relations derived for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021), see http://www.ioffe.ru/LEA/GRBs/GRB240218_T07200/GRB240218A_rest_frame.pdf
All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary.
GCN Circular #35761
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), T. Sakamoto (AGU), (i.e. the Swift-BAT team):
Using the data set from T-240 to T+200 sec from the recent telemetry downlink, we report further analysis of BAT GRB 240218A (trigger #1215912) (Page, et al., GCN Circ. 35742). The BAT ground-calculated position is RA, Dec = 161.810, 1.295 deg which is
```
   RA(J2000)  =  10h 47m 14.4s
   Dec(J2000) = +01d 17' 40.2"
```
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 36%.
The mask weighted light curve shows two major pulses, one that is broad and the other which is narrow.
T90 (15-350 keV) is 66.93 +- 11.28 sec (estimated error including systematics).
The time-averaged spectrum from T-38.93 to T+63.55 sec is best fit by a power law
with an exponential cutoff. This fit gives a photon index 1.00 +- 0.32,
and Epeak of 103.1 +- 45.5 keV (chi squared 62.59 for 56 d.o.f.). For this
model the total fluence in the 15-150 keV band is 5.2 +- 0.3 x 10^-06 erg/cm2
and the 1-sec peak flux measured from T+21.62 sec in the 15-150 keV band is
3.0 +- 0.3 ph/cm2/sec. A fit to a simple power law gives a photon index
of 1.51 +- 0.07 (chi squared 71.30 for 57 d.o.f.). All the quoted errors
are at the 90% confidence level.
The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1215912/
GCN Circular #35762
A. Rossi, E. Maiorano, G. Stratta (INAF-OAS), P. D'Avanzo (INAF-OAB) report on behalf of the CIBO collaboration:
We observed the field of the long GRB 240218A, detected by Swift-BAT (Page et al., GCN 35742), Fermi-GBM (Veres and Meegan, GCN 35755) and Konus-Wind (Svinkin et al., GCN 35758), and with spectroscopic redshift of z=6.782 (Saccardi et al., GCN 35756).
We obtained 40 min of J-, 1 hr of H- and 1.2 hr of Ks-band imaging with the LUCI cameras mounted on LBT (Mt. Graham, AZ, USA) on 2024-02-19 (mid-time 08:20:00 UT), 1.3 days after the burst trigger.
We clearly detect the NIR afterglow (D'Avanzo et al., GCN 35747, Malesani et al., GCN 35749) and measure a preliminary H-band magnitude of H ~ 20.2 AB, calibrated against 2MASS field stars, and not corrected for the foreground Galactic extinction.
We acknowledge the excellent support of A. Cardwell e J. Williams from the LBTO staff and E. Marini from LBT-INAF staff, in obtaining these observations.
GCN Circular #35765
S. de Wet (UCT), P.M. Vreeswijk (Radboud) and P.J. Groot (Radboud/UCT/SAAO) report on behalf of the MeerLICHT consortium:
The 0.6m wide-field MeerLICHT optical telescope located in Sutherland, South Africa, obtained a repeating series of 60s exposures in the q,u,g,r,i,z filters following the detection of GRB 240218A by Swift (Page et al., GCN 35742). Our observations began 96 seconds after the Swift trigger and continued for approximately 1 hour following the filter sequence quqgqrqiqz.
We do not detect an optical source at a position consistent with the high-redshift counterpart detected by REM and the VLT (D'Avanzo et al., GCN 35747; Malesani, GCN 35749; Saccardi et al., GCN 35756) in any individual exposure. Our earliest 3-sigma AB limiting magnitudes in each filter are:
```
u > 19.29 at 3.6 minutes post-trigger
g > 20.58 at 6.5 minutes post-trigger
q > 21.10 at 2.1 minutes post-trigger
r > 20.29 at 9.4 minutes post-trigger
i > 19.81 at 13.4 minutes post-trigger
z > 18.87 at 15.3 minutes post-trigger.
```
We additionally co-added all of the images in each filter and obtain the following 3-sigma AB limiting magnitudes at an average time of 36 minutes post-trigger:
```
u > 20.33 
g > 21.61 
q > 22.67
r > 21.21
i > 20.54
z > 19.54.
```
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 #35794
G. Schroeder (Northwestern), C. Pe=C3=B1a, T. Laskar (Utah), K. D. Alexande= r (Arizona) report:
"We observed GRB 240218A (Page et al., GCN 35742; Veres et al., GCN 35755;= Svinkin et al., GCN 35758) with the Karl G. Jansky Very Large Array (VLA) = under program 24A-299 (PI: Laskar) beginning on 2024 Feb 23 at 09:38:35 UT = (5.32 days post-burst) for 2.5 hours at multiple frequencies.
In preliminary analysis, we clearly detect a radio source at a mean frequen= cy of 9.8 GHz with a flux density of ~280 microJy at the position:
```
RA(J2000) =3D 10:47:11.480
Dec(J2000) =3D +01:16:35.29
```
with an uncertainty of ~0.2" in each coordinate. This position is consisten= t with the X-ray position (Evans et al. GCN 35748) but offset (~2.7") from = the preliminary NIR afterglow position reported by D'Avanzo et al. (GCN 357= 47). Further observations are planned.
We thank the VLA staff for scheduling and executing these observations."
GCN Circular #35818
A. Volnova (IKI), A. Pozanenko (IKI), B. Safonov (SAI MSU), A. Tatarnikov (SAI MSU), N. Pankov (HSE, IKI), S. Belkin (IKI, HSE) report on behalf of IKI-GRB-FuN:
We observed the field of GRB 240218A (Page et al., GCN 35742; Veres et al., GCN 35755; Svinkin et al., GCN 35758) with the Astronomical Near-Infrared Camera-spectrograph (ANC) of the 2.5-meter telescope (SAI-2.5) of the Caucasian Mountain Observatory (CMO SAI) on Feb.23, 2024 starting on 22:16:46 UT, taking 47 frames of 1-minute exposure in the H-band under moderate conditions with seeing of 1.4". We do not detect the NIR counterpart (D'Avanzo et al., GCN 35747; Saccardi et al., 35756; Schroeder et al., GCN 35794; Rossi et al., GCN 35762; de Wet et al., GCN 35765) within the enhanced XRT error box (Evans et al., GCN 35748). Preliminary photometry of the stacked image is following
```
Date       UT start   t-T0     Filter  Exp.    OT     UL(3sigma)
                      (mid, days)  (s)
2024-02-23 22:16:46   5.86743  H       47*59   n/d    20.8   
```
The photometry is based on nearby 2MASS stars:
```
2MASS_ID         RA              Dec           H      errH
10471145+0118146 10:47:11.45808 +01:18:14.6268 15.422 0.098
10471594+0117439 10:47:15.94200 +01:17:43.9836 14.562 0.062
10471583+0116464 10:47:15.83136 +01:16:46.4844 14.243 0.045
```
GCN Circular #35843
A. de Ugarte Postigo (CNRS/OCA & LAM), T. Laskar (Utah), M. Bremer (IRAM),
C. C. Thoene (ASU-CAS), J. F. Agui Fernandez (CAHA), S. Antier (OCA), S. Ba= sa (LAM), M. Michalowski (AOI-AMU), D. A. Perley (LJMU), S. Martin (ESO, AL= MA),
K. D. Alexander (Arizona), E. Berger (Harvard), R. Chornock (Berkeley), W. = Fong (Northwestern), R. Margutti (UC Berkeley), C. Pe=C3=B1a (Utah), P. Sch= ady (Bath), G. Schroeder (Northwestern),
report:
We observed the field of GRB 240218A (Page et al. 35742, Svinkin et al. GCN 35758) at a redshift of z = 6.782 (Saccardi et al. GCN 35756) with NOEMA at 74 and 90 GHz at a mean epoch 10.88 days after the burst.
Our observations show no detection of the afterglow (D=E2=80=99Avanzo et al. GCN 35747, Malesani et al. GCN 35749, Rossi et al. GCN 35762, Schroeder et al. GCN 35794) down to a 3-sigma limit of 65 microJy.
Based on observations carried out under project number W23DI with the IRAM NOEMA Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).
GCN Circular #35866
A.L. Thakur (INAF-IAPS), R. Ricci (INAF-IRA), G. Bruni, L. Piro, G. Gianfag= na (INAF-IAPS), M. Wieringa (ATNF) report:
We observed the high-redshift GRB240218A (Page et al. GCN 35742, Veres and = Meegan et al. GCN 35755, Svinkin et al. GCN 37558, D=E2=80=99Avanzo et al. = GCN 35747, Saccardi et al. GCN 35756) with the Australian Telescope Compact= Array under program C3546 (PI Thakur) on 4 March 2024 at a mean epoch of ~= 15 days post-burst. Observations were performed in the C-band for a total = duration of ~6 hours.
Given the declination of the radio counterpart, the ATCA beam in the curren= t array configuration is highly elongated on the North-South axis. We perfo= rmed a check for potential confusing sources using a VLASS field at 3 GHz, = centred on the position of the radio afterglow as detected by the VLA at RA= =3D10:47:11.480 Dec=3D+01:16:35.29 (Schroeder et al., GCN 35794). No confus= ing sources are visible down to an rms of 130 uJy/beam.
In the preliminary 5.5 GHz ATCA image, we detect a source with a flux of ~ = 0.2 mJy at a position consistent with the VLA detection.
Further monitoring of this counterpart is planned.
We thank CSIRO Space and Astronomy staff, particularly Jamie Stevens, for e= xcellent support in planning and performing these observations. We acknowle= dge the Gomeroi people as the traditional owners of the Observatory site. T= he Australia Telescope Compact Array is part of the Australia Telescope Nat= ional Facility (https://ror.org/05qajvd42), which is funded by the Australi= an Government for operation as a National Facility managed by CSIRO.
GCN Circular #35877
C. Pe=C3=B1a, T. Laskar (Utah), G. Schroeder (Northwestern), and K. D. Alexander (Arizona) report:
We observed GRB 240218A (Page et al., GCN 35742; Veres et al., GCN 35755; S= vinkin et al., GCN 35758) with Chandra/ACIS-S beginning on 2024 Mar 4 at 23= :02:14 UT (16 days post-burst) for a total exposure of 20ks. In preliminary= analysis, we detect a point source with a count rate of 5.5e-4 counts/s (0= .3-8 keV; observer frame) at a position consistent with the VLA and XRT pos= ition (Schroeder et al., GCN 35794; Evans et al. GCN 35748). Using spectral= parameters from the Swift/XRT PC-mode spectrum at a redshift z=3D6.782 (Sa= ccardi et al., GCN 35756), we find a preliminary unabsorbed flux of ~ 1.2e-= 14 erg/(s cm^2) in the 0.3-8 keV band (observer frame).
This measurement confirms a potential break in the Swift/XRT observations a= t ~ 0.8 days after the trigger. The post-break decay rate of ~ -1.9 is cons= istent with a jet break. Further analysis is underway.
We thank Pat Slane, Douglas Swartz, and James Steiner for approving our DDT= request. We thank Jen Lauer along with the rest of the CXC staff for arran= ging and executing the observations.
GCN Circular #35878
T. Laskar, C. Pe=C3=B1a (Utah), G. Schroeder (Northwestern), and K. D. Alexander (Arizona) report on behalf of a larger collaboration:
"We observed GRB 240218A (Page et al., GCN 35742; Veres et al., GCN 35755; Svinkin et al., GCN 35758) with the Atacama Large Millimeter/Submillimeter Array (ALMA) at 97.5 GHz beginning on 2024 March 02 02:46:33 UT (13.0 d after the burst). ALMA observations of this burst were delayed due to ALMA's annual February shutdown.
Preliminary analysis reveals a mm source with flux density of ~ 0.1 mJy at 97.5 GHz and position:
```
RA (J2000) = 10:47:11.5
Dec (J2000) = 1:16:36.0
```
with uncertainty ~ 0.3" in each coordinate, consistent with the X-ray position (Evans et al. GCN 35748) and radio position (Schroeder et al., GCN 35794).
We thank the JAO staff, AoD, P2G, and the entire ALMA team for their help with these observations."

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