Gamma-ray Burst 230204A

(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:     Sat 04 Feb 23 02:58:11 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1152509,   Seg_Num: 0
GRB_RA:          238.164d {+15h 52m 39s} (J2000),
                 238.595d {+15h 54m 23s} (current),
                 237.236d {+15h 48m 57s} (1950)
GRB_DEC:         -50.858d {-50d 51' 27"} (J2000),
                 -50.925d {-50d 55' 30"} (current),
                 -50.709d {-50d 42' 32"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       0 [cnts]    Image_Peak=921 [image_cnts]
TRIGGER_DUR:     64.000 [sec] 
TRIGGER_INDEX:   20000     E_range: 15-50 keV
BKG_INTEN:       0 [cnts]
BKG_TIME:        0.00 SOD {00:00:00.00} UT
BKG_DUR:         0 [sec]
GRB_DATE:        19979 TJD;    35 DOY;   23/02/04
GRB_TIME:        10617.30 SOD {02:56:57.30} UT
GRB_PHI:         -67.78 [deg]
GRB_THETA:        26.12 [deg]
SOLN_STATUS:     0x13
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    7.78 [sigma]
MERIT_PARAMS:     +1  +0  +0  +6  +1  -2  +0  +1 -32  +0 
SUN_POSTN:       317.49d {+21h 09m 56s}  -16.33d {-16d 19' 38"}
SUN_DIST:         70.44 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      120.14d {+08h 00m 33s}  +25.53d {+25d 31' 43"}
MOON_DIST:       127.27 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:      329.62,  2.38 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      247.42,-29.89 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is an image trigger.  (The RATE_SIGNIF & BKG_{INTEN, TIME, DUR} are undefined.)  
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 = 60.12,18.54 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 04 Feb 23 03:00:01 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     1152509,   Seg_Num: 0
GRB_RA:          238.1950d {+15h 52m 46.7s} (J2000),
                 238.6259d {+15h 54m 30.2s} (current),
                 237.2654d {+15h 49m 03.6s} (1950)
GRB_DEC:         -50.9167d {-50d 55' 00.1"} (J2000),
                 -50.9840d {-50d 59' 02.5"} (current),
                 -50.7681d {-50d 46' 04.9"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       78 [cnts]
IMG_START_DATE:  19979 TJD;    35 DOY;   23/02/04
IMG_START_TIME:  10764.15 SOD {02:59:24.15} UT,   146.9 [sec] since BAT Trigger Time
CENTROID_X:      308.14,  raw= 308  [pixels]
CENTROID_Y:      190.43,  raw= 190  [pixels]
ROLL:            92.35 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -253.80
GRB_POS_XRT_Z:   1.74
IMAGE_URL:       sw01152509000msxps_rw.img
SUN_POSTN:       317.49d {+21h 09m 57s}  -16.33d {-16d 19' 37"}
SUN_DIST:         70.42 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      120.16d {+08h 00m 37s}  +25.53d {+25d 31' 33"}
MOON_DIST:       127.27 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:      329.60,  2.32 [deg] galactic lon,lat of the burst
ECL_COORDS:      247.45,-29.94 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 04 Feb 23 02:59:59 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     1152509,   Seg_Num: 0
GRB_RA:          238.1950d {+15h 52m 46.7s} (J2000),
                 238.6259d {+15h 54m 30.2s} (current),
                 237.2654d {+15h 49m 03.6s} (1950)
GRB_DEC:         -50.9167d {-50d 55' 00.1"} (J2000),
                 -50.9840d {-50d 59' 02.5"} (current),
                 -50.7681d {-50d 46' 04.9"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       78 [cnts]
IMG_START_DATE:  19979 TJD;    35 DOY;   23/02/04
IMG_START_TIME:  10764.15 SOD {02:59:24.15} UT,   146.9 [sec] since BAT Trigger Time
CENTROID_X:      308.14,  raw= 308  [pixels]
CENTROID_Y:      190.43,  raw= 190  [pixels]
ROLL:            92.35 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -253.80
GRB_POS_XRT_Z:   1.74
IMAGE_URL:       sw01152509000msxps_rw.img
SUN_POSTN:       317.49d {+21h 09m 57s}  -16.33d {-16d 19' 37"}
SUN_DIST:         70.42 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      120.16d {+08h 00m 37s}  +25.53d {+25d 31' 33"}
MOON_DIST:       127.27 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:      329.60,  2.32 [deg] galactic lon,lat of the burst
ECL_COORDS:      247.45,-29.94 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.  
COMMENTS:        WARNING: The centroided position is more than 100 rows or columns from the center of the FOV.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 04 Feb 23 02:59:49 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1152509,   Seg_Num: 0
GRB_RA:          238.1950d {+15h 52m 46.79s} (J2000),
                 238.6259d {+15h 54m 30.21s} (current),
                 237.2654d {+15h 49m 03.69s} (1950)
GRB_DEC:         -50.9167d {-50d 55' 00.1"} (J2000),
                 -50.9840d {-50d 59' 02.5"} (current),
                 -50.7681d {-50d 46' 04.9"} (1950)
GRB_ERROR:       5.0 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       2.77e-09 [erg/cm2/sec]
GRB_SIGNIF:      8.83 [sigma]
IMG_START_DATE:  19979 TJD;    35 DOY;   23/02/04
IMG_START_TIME:  10764.15 SOD {02:59:24.15} UT,   146.9 [sec] since BAT Trigger Time
TAM[0-3]:        327.65 237.17 261.61 243.55
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       317.49d {+21h 09m 57s}  -16.33d {-16d 19' 37"}
SUN_DIST:         70.42 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      120.15d {+08h 00m 37s}  +25.53d {+25d 31' 34"}
MOON_DIST:       127.27 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:      329.60,  2.32 [deg] galactic lon,lat of the burst
ECL_COORDS:      247.45,-29.94 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 3.71 arcmin from the BAT position.  
COMMENTS:        WARNING: The centroided position is more than 100 rows or columns from the center of the FOV.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 04 Feb 23 03:19:06 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1152509,   Seg_Num: 0
POINT_RA:        238.201d {+15h 52m 48s} (J2000)
POINT_DEC:       -50.846d {-50d 50' 45"} (J2000)
POINT_ROLL:      92.345d
IMG_START_DATE:  19979 TJD;    35 DOY;   23/02/04
IMG_START_TIME:  10773.36 SOD {02:59:33.36} UT,   156.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.529
N_STARS:         190
X_OFFSET:        392 [pixels]
Y_OFFSET:        712 [pixels]
X_MAX:           1351 [pixels]
Y_MAX:           1671 [pixels]
DET_THRESH:      20
PHOTO_THRESH:    12
SL_URL:          sw01152509000msufc0156.fits
SUN_POSTN:       317.50d {+21h 10m 00s}  -16.32d {-16d 19' 23"}
SUN_DIST:         70.43 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      120.33d {+08h 01m 18s}  +25.50d {+25d 29' 48"}
MOON_DIST:       127.15 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:      329.64,  2.37 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      247.44,-29.87 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 04 Feb 23 03:19:20 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1152509,   Seg_Num: 0
POINT_RA:        238.201d {+15h 52m 48s} (J2000)
POINT_DEC:       -50.846d {-50d 50' 45"} (J2000)
POINT_ROLL:      92.345d
IMG_START_DATE:  19979 TJD;    35 DOY;   23/02/04
IMG_START_TIME:  10773.36 SOD {02:59:33.36} UT,   156.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.529
N_STARS:         190
X_OFFSET:        392 [pixels]
Y_OFFSET:        712 [pixels]
X_MAX:           1351 [pixels]
Y_MAX:           1671 [pixels]
DET_THRESH:      20
PHOTO_THRESH:    12
SL_URL:          sw01152509000msufc0156.fits
SUN_POSTN:       317.50d {+21h 10m 00s}  -16.32d {-16d 19' 23"}
SUN_DIST:         70.43 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      120.33d {+08h 01m 19s}  +25.50d {+25d 29' 47"}
MOON_DIST:       127.15 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:      329.64,  2.37 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      247.44,-29.87 [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:     Sat 04 Feb 23 03:20:18 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1152509,   Seg_Num: 0
POINT_RA:        238.201d {+15h 52m 48s} (J2000)
POINT_DEC:       -50.846d {-50d 50' 45"} (J2000)
ROLL:            92.345d
IMG_START_DATE:  19979 TJD;    35 DOY;   23/02/04
IMG_START_TIME:  10773.36 SOD {02:59:33.36} UT,   156.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     697172404
X_OFFSET:        1045 [pixels]
Y_OFFSET:        1321 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1205
Y_GRB_POS:       1481
BINNING_INDEX:   1
IM_URL:          sw01152509000msuni0187.fits
SUN_POSTN:       317.50d {+21h 10m 00s}  -16.32d {-16d 19' 22"}
SUN_DIST:         70.43 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      120.34d {+08h 01m 21s}  +25.49d {+25d 29' 42"}
MOON_DIST:       127.15 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:      329.64,  2.37 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      247.44,-29.87 [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:     Sat 04 Feb 23 03:20:25 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1152509,   Seg_Num: 0
POINT_RA:        238.201d {+15h 52m 48s} (J2000)
POINT_DEC:       -50.846d {-50d 50' 45"} (J2000)
ROLL:            92.345d
IMG_START_DATE:  19979 TJD;    35 DOY;   23/02/04
IMG_START_TIME:  10773.36 SOD {02:59:33.36} UT,   156.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     697172404
X_OFFSET:        1045 [pixels]
Y_OFFSET:        1321 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1205
Y_GRB_POS:       1481
BINNING_INDEX:   1
IM_URL:          sw01152509000msuni0187.fits
SUN_POSTN:       317.50d {+21h 10m 00s}  -16.32d {-16d 19' 22"}
SUN_DIST:         70.43 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      120.34d {+08h 01m 21s}  +25.49d {+25d 29' 41"}
MOON_DIST:       127.15 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:      329.64,  2.37 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      247.44,-29.87 [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:     Sat 04 Feb 23 03:25:54 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1152509,   Seg_Num: 0
POINT_RA:        238.199d {+15h 52m 48s} (J2000)
POINT_DEC:       -50.846d {-50d 50' 46"} (J2000)
POINT_ROLL:      92.347d
IMG_START_DATE:  19979 TJD;    35 DOY;   23/02/04
IMG_START_TIME:  10931.56 SOD {03:02:11.56} UT,   314.3 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        2.290
N_STARS:         167
X_OFFSET:        725 [pixels]
Y_OFFSET:        1001 [pixels]
X_MAX:           1684 [pixels]
Y_MAX:           1960 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw01152509000msufc0314.fits
SUN_POSTN:       317.50d {+21h 10m 01s}  -16.32d {-16d 19' 18"}
SUN_DIST:         70.43 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      120.39d {+08h 01m 33s}  +25.49d {+25d 29' 11"}
MOON_DIST:       127.11 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:      329.64,  2.37 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      247.44,-29.87 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 04 Feb 23 03:26:07 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1152509,   Seg_Num: 0
POINT_RA:        238.199d {+15h 52m 48s} (J2000)
POINT_DEC:       -50.846d {-50d 50' 46"} (J2000)
POINT_ROLL:      92.347d
IMG_START_DATE:  19979 TJD;    35 DOY;   23/02/04
IMG_START_TIME:  10931.56 SOD {03:02:11.56} UT,   314.3 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        2.290
N_STARS:         167
X_OFFSET:        725 [pixels]
Y_OFFSET:        1001 [pixels]
X_MAX:           1684 [pixels]
Y_MAX:           1960 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw01152509000msufc0314.fits
SUN_POSTN:       317.50d {+21h 10m 01s}  -16.32d {-16d 19' 18"}
SUN_DIST:         70.43 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      120.39d {+08h 01m 33s}  +25.49d {+25d 29' 10"}
MOON_DIST:       127.11 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:      329.64,  2.37 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      247.44,-29.87 [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:     Sat 04 Feb 23 03:26:47 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1152509,   Seg_Num: 0
POINT_RA:        238.199d {+15h 52m 48s} (J2000)
POINT_DEC:       -50.846d {-50d 50' 46"} (J2000)
ROLL:            92.347d
IMG_START_DATE:  19979 TJD;    35 DOY;   23/02/04
IMG_START_TIME:  10931.56 SOD {03:02:11.56} UT,   314.3 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     697172562
X_OFFSET:        1045 [pixels]
Y_OFFSET:        1321 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1205
Y_GRB_POS:       1481
BINNING_INDEX:   1
IM_URL:          sw01152509000msuni0345.fits
SUN_POSTN:       317.51d {+21h 10m 01s}  -16.32d {-16d 19' 17"}
SUN_DIST:         70.43 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      120.40d {+08h 01m 35s}  +25.48d {+25d 29' 06"}
MOON_DIST:       127.10 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:      329.64,  2.37 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      247.44,-29.87 [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:     Sat 04 Feb 23 03:27:01 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1152509,   Seg_Num: 0
POINT_RA:        238.199d {+15h 52m 48s} (J2000)
POINT_DEC:       -50.846d {-50d 50' 46"} (J2000)
ROLL:            92.347d
IMG_START_DATE:  19979 TJD;    35 DOY;   23/02/04
IMG_START_TIME:  10931.56 SOD {03:02:11.56} UT,   314.3 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     697172562
X_OFFSET:        1045 [pixels]
Y_OFFSET:        1321 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1205
Y_GRB_POS:       1481
BINNING_INDEX:   1
IM_URL:          sw01152509000msuni0345.fits
SUN_POSTN:       317.51d {+21h 10m 01s}  -16.32d {-16d 19' 17"}
SUN_DIST:         70.43 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      120.40d {+08h 01m 35s}  +25.48d {+25d 29' 05"}
MOON_DIST:       127.10 [deg]
MOON_ILLUM:      98 [%]
GAL_COORDS:      329.64,  2.37 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      247.44,-29.87 [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 #33260
A. D'Ai (INAF-IASFPA), E. Ambrosi (INAF-IASFPA), V. D'Elia (SSDC & INAF-OAR), J. A. Kennea (PSU), A. Y. Lien (U Tampa), A. Melandri (INAF-OAB), D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB), M. H. Siegel (PSU), A. Tohuvavohu (U Toronto) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 02:56:57 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 230204A (trigger=1152509). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 238.164d, -50.858d which is
```
   RA(J2000) = 15h 52m 39s
   Dec(J2000) = -50d 51' 27"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). Due to a telemetry gap, the BAT lightcurve before T+8s is not immediately available, and no obvious variation is visible in the remainder of the lightcurve, as is typical for an image trigger.
The XRT began observing the field at 02:59:24.1 UT, 146.8 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 238.1950, -50.9167 which is equivalent to:
```
   RA(J2000)  = 15h 52m 46.80s
   Dec(J2000) = -50d 55' 00.1"
```
with an uncertainty of 5.0 arcseconds (radius, 90% containment).
The initial flux in the 2.5 s image was 2.77e-09 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 156 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 none of the XRT error circle. 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 large, but uncertain, extinction expected.
We note that this source is near the Galactic plane (lat=2.38 deg) and was detected as a 64 s image trigger, which raises the possibility that this is a Galactic transient. We would name this source Swift J1552.8-5055 if it is not a GRB.
Further analysis of the nature of this source will require the full downlinked dataset.
Burst Advocate for this burst is A. D'Ai (antonino.dai AT inaf.it). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)
GCN Circular #33261
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
Using 1193 s of XRT Photon Counting mode data and 1 UVOT images for GRB 230204A, 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 = 238.19965, -50.91653 which is equivalent to:
```
RA (J2000): 15h 52m 47.91s
Dec (J2000): -50d 54' 59.5"
```
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 #33263
R. Strausbaugh (University of Minnesota), A. Cucchiara (NASA) report on behalf of a larger collaboration:
We observed the GRB 230204A/Swift J1552.8-5055 (D'Ai et al., GCN 33260) field with the LCOGT 1-meter Sinistro instrument at the Cerro Tololo Interamerican Observatory, Chile site, on February 4, from 07:24 to 7:57 UT (corresponding to 4.47 to 5.02 hours after GRB trigger time) with the Bessel R and I filters.
We performed a series of 3x300s exposures in both bands. We detect a source consistent with the XRT enhanced error position (Evens et al., GCN 33261) that is not present in USNO, SkyMapper, or 2MASS catalogs. The coordinates for this candidate are: 238.19844d, -50.917039d.
As the field is near the galactic plane, the field is quite crowded. It is possible that this source is present in the catalogs mentioned, but was not able to be resolved due to different plate scales. Future observations are planned to determine if the detected source is fading and other follow-up efforts are encouraged.
The following magnitudes are calculated using the USNO-B1.0 catalog as reference:
```
R = 17.75 +/- 0.02
I = 17.16 +/- 0.01
```
Due to the crowded field, these magnitudes may be contaminated by a nearby bright star. These magnitudes are not corrected for galactic extinction.
GCN Circular #33264
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAB), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), D.N. Burrows (PSU) and A. D'Ai report on behalf of the Swift-XRT team:
We have analysed 6.4 ks of XRT data for GRB 230204A (D'Ai et al. GCN Circ. 33260), from 136 s to 46.9 ks after the BAT trigger. The data comprise 250 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. 33261).
The light curve can be modelled with a power-law decay with a decay index of alpha=2.37 (+0.16, -0.14).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.64 (+/-0.10). The best-fitting absorption column is 2.61 (+0.21, -0.20) x 10^22 cm^-2, in excess of the Galactic value of 1.0 x 10^22 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.5 (+/-0.4) and a best-fitting absorption column of 2.1 (+0.7, -0.6) x 10^22 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 7.6 x 10^-11 (1.2 x 10^-10) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     2.1 (+0.7, -0.6) x 10^22 cm^-2
Galactic foreground: 1.0 x 10^22 cm^-2
Excess significance: 2.8 sigma
Photon index:	     1.5 (+/-0.4)
```
If the light curve continues to decay with a power-law decay index of 2.37, the count rate at T+24 hours will be 1.2 x 10^-5 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.2 x 10^-16 (1.4 x 10^-15) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01152509.
This circular is an official product of the Swift-XRT team.
GCN Circular #33266
S. J. LaPorte (PSU) and A. D'Ai (INAF-IASFPA) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 230204A 156 s after the BAT trigger (D'Ai et al., GCN Circ. 33260). No optical afterglow consistent with the XRT position (Evans et al. GCN Circ. 33261) is detected in the initial UVOT exposures. A known source with no significant signs of fading is detected 2.88 arcsec from the XRT position at:
```
RA (J2000): 15h 52m 47.83s
Dec (J2000): -50d 54' 56.74"
```
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           156            306          147          >17.5
u_FC                  314            564          246         >19.1
white                  156          1372          373         >17.8
v                         645          1596          117         >15.9
b                         570          1521            97         >17.9
u                         314          5553          382         >19.1
w1                      695           5489          274         >19.1
m2                      670          1446            97         >18.8
w2                       621          1571          117         >18.5
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 2.516 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #33279
T. Parsotan (GSFC/UMBC), S. D. Barthelmy (GSFC), A. D'Ai (INAF-IASFPA), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 230204A (trigger #1152509) (D'Ai et al., GCN Circ. 33260). The BAT ground-calculated position is RA, Dec = 238.166, -50.848 deg which is
```
   RA(J2000)  =  15h 52m 39.8s
   Dec(J2000) = -50d 50' 52.8"
```
with an uncertainty of 2.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 48%.
The mask-weighted light curve shows a multi-peaked structure that starts at ~T-10 and ends at ~T+200 s. The most prominent peak occurs at ~T+148 s. T90 (15-350 keV) is 182.05 +- 16.73 sec (estimated error including systematics).
The time-averaged spectrum from T-6.81 to T+195.62 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.72 +- 0.13. The fluence in the 15-150 keV band is 3.7 +- 0.3 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+148.12 sec in the 15-150 keV band is 0.9 +- 0.2 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/1152509/BA/

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Jochen Greiner, last update: 06-Feb-2023 [Disclaimer]