Gamma-ray Burst 230325A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 25 Mar 23 03:15:56 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1161390,   Seg_Num: 0
GRB_RA:          296.820d {+19h 47m 17s} (J2000),
                 297.237d {+19h 48m 57s} (current),
                 295.920d {+19h 43m 41s} (1950)
GRB_DEC:         -46.094d {-46d 05' 38"} (J2000),
                 -46.035d {-46d 02' 06"} (current),
                 -46.218d {-46d 13' 03"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       2519 [cnts]    Image_Peak=219 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   147     E_range: 25-100 keV
BKG_INTEN:       11860 [cnts]
BKG_TIME:        11721.01 SOD {03:15:21.01} UT
BKG_DUR:         8 [sec]
GRB_DATE:        20028 TJD;    84 DOY;   23/03/25
GRB_TIME:        11735.86 SOD {03:15:35.86} UT
GRB_PHI:         108.61 [deg]
GRB_THETA:        30.24 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     29.08 [sigma]
IMAGE_SIGNIF:    11.62 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  +1  +0  +0 -24  +0 
SUN_POSTN:         3.87d {+00h 15m 30s}   +1.68d {+01d 40' 39"}
SUN_DIST:         75.28 [deg]   Sun_angle= 4.4 [hr] (West of Sun)
MOON_POSTN:       45.62d {+03h 02m 29s}  +18.55d {+18d 33' 05"}
MOON_DIST:       115.89 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      352.92,-28.52 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      290.11,-24.51 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 133.78,-15.87 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 25 Mar 23 03:17:35 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1161390,   Seg_Num: 0
GRB_RA:          296.8468d {+19h 47m 23.23s} (J2000),
                 297.2639d {+19h 49m 03.32s} (current),
                 295.9468d {+19h 43m 47.23s} (1950)
GRB_DEC:         -46.0754d {-46d 04' 31.4"} (J2000),
                 -46.0166d {-46d 00' 59.6"} (current),
                 -46.1992d {-46d 11' 57.0"} (1950)
GRB_ERROR:       5.1 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       2.06e-09 [erg/cm2/sec]
GRB_SIGNIF:      8.42 [sigma]
IMG_START_DATE:  20028 TJD;    84 DOY;   23/03/25
IMG_START_TIME:  11829.91 SOD {03:17:09.91} UT,   94.0 [sec] since BAT Trigger Time
TAM[0-3]:        327.66 237.17 261.82 243.45
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:         3.88d {+00h 15m 30s}   +1.68d {+01d 40' 41"}
SUN_DIST:         75.26 [deg]   Sun_angle= 4.4 [hr] (West of Sun)
MOON_POSTN:       45.64d {+03h 02m 33s}  +18.56d {+18d 33' 25"}
MOON_DIST:       115.88 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      352.95,-28.53 [deg] galactic lon,lat of the burst
ECL_COORDS:      290.14,-24.50 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 1.57 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 25 Mar 23 03:17:45 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     1161390,   Seg_Num: 0
GRB_RA:          296.8468d {+19h 47m 23.2s} (J2000),
                 297.2639d {+19h 49m 03.3s} (current),
                 295.9468d {+19h 43m 47.2s} (1950)
GRB_DEC:         -46.0754d {-46d 04' 31.4"} (J2000),
                 -46.0166d {-46d 00' 59.6"} (current),
                 -46.1992d {-46d 11' 57.0"} (1950)
GRB_ERROR:       5.0 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       71 [cnts]
IMG_START_DATE:  20028 TJD;    84 DOY;   23/03/25
IMG_START_TIME:  11829.91 SOD {03:17:09.91} UT,   94.0 [sec] since BAT Trigger Time
CENTROID_X:      261.76,  raw= 262  [pixels]
CENTROID_Y:      314.07,  raw= 314  [pixels]
ROLL:            71.88 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   37.64
GRB_POS_XRT_Z:   -107.57
IMAGE_URL:       sw01161390000msxps_rw.img
SUN_POSTN:         3.88d {+00h 15m 30s}   +1.68d {+01d 40' 41"}
SUN_DIST:         75.26 [deg]   Sun_angle= 4.4 [hr] (West of Sun)
MOON_POSTN:       45.64d {+03h 02m 33s}  +18.56d {+18d 33' 27"}
MOON_DIST:       115.88 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      352.95,-28.53 [deg] galactic lon,lat of the burst
ECL_COORDS:      290.14,-24.50 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 25 Mar 23 03:17:48 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     1161390,   Seg_Num: 0
GRB_RA:          296.8468d {+19h 47m 23.2s} (J2000),
                 297.2639d {+19h 49m 03.3s} (current),
                 295.9468d {+19h 43m 47.2s} (1950)
GRB_DEC:         -46.0754d {-46d 04' 31.4"} (J2000),
                 -46.0166d {-46d 00' 59.6"} (current),
                 -46.1992d {-46d 11' 57.0"} (1950)
GRB_ERROR:       5.0 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       71 [cnts]
IMG_START_DATE:  20028 TJD;    84 DOY;   23/03/25
IMG_START_TIME:  11829.91 SOD {03:17:09.91} UT,   94.0 [sec] since BAT Trigger Time
CENTROID_X:      261.76,  raw= 262  [pixels]
CENTROID_Y:      314.07,  raw= 314  [pixels]
ROLL:            71.88 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   37.64
GRB_POS_XRT_Z:   -107.57
IMAGE_URL:       sw01161390000msxps_rw.img
SUN_POSTN:         3.88d {+00h 15m 30s}   +1.68d {+01d 40' 41"}
SUN_DIST:         75.26 [deg]   Sun_angle= 4.4 [hr] (West of Sun)
MOON_POSTN:       45.64d {+03h 02m 33s}  +18.56d {+18d 33' 28"}
MOON_DIST:       115.88 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      352.95,-28.53 [deg] galactic lon,lat of the burst
ECL_COORDS:      290.14,-24.50 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 25 Mar 23 03:19:45 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1161390,   Seg_Num: 0
GRB_RA:          296.820d {+19h 47m 17s} (J2000),
                 297.237d {+19h 48m 57s} (current),
                 295.920d {+19h 43m 41s} (1950)
GRB_DEC:         -46.094d {-46d 05' 38"} (J2000),
                 -46.035d {-46d 02' 06"} (current),
                 -46.218d {-46d 13' 03"} (1950)
GRB_DATE:        20028 TJD;    84 DOY;   23/03/25
GRB_TIME:        11735.86 SOD {03:15:35.86} UT
TRIGGER_INDEX:   147
GRB_PHI:         108.61 [deg]
GRB_THETA:        30.24 [deg]
DELTA_TIME:      -43.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     29.08 [sigma]
IMAGE_SIGNIF:    11.62 [sigma]
LC_URL:          sw01161390000msb.lc
SUN_POSTN:         3.88d {+00h 15m 31s}   +1.68d {+01d 40' 43"}
SUN_DIST:         75.28 [deg]   Sun_angle= 4.4 [hr] (West of Sun)
MOON_POSTN:       45.66d {+03h 02m 38s}  +18.56d {+18d 33' 51"}
MOON_DIST:       115.92 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      352.92,-28.52 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      290.11,-24.51 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Lightcurve.  
COMMENTS:           
COMMENTS:        The next comments were copied from the BAT_POS Notice:  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 133.78,-15.87 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 25 Mar 23 03:21:36 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1161390,   Seg_Num: 0
POINT_RA:        296.811d {+19h 47m 15s} (J2000)
POINT_DEC:       -46.095d {-46d 05' 40"} (J2000)
POINT_ROLL:      71.884d
IMG_START_DATE:  20028 TJD;    84 DOY;   23/03/25
IMG_START_TIME:  11837.84 SOD {03:17:17.84} UT,   102.0 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.812
N_STARS:         77
X_OFFSET:        520 [pixels]
Y_OFFSET:        544 [pixels]
X_MAX:           1479 [pixels]
Y_MAX:           1503 [pixels]
DET_THRESH:      20
PHOTO_THRESH:    12
SL_URL:          sw01161390000msufc0101.fits
SUN_POSTN:         3.88d {+00h 15m 31s}   +1.68d {+01d 40' 45"}
SUN_DIST:         75.29 [deg]   Sun_angle= 4.4 [hr] (West of Sun)
MOON_POSTN:       45.67d {+03h 02m 42s}  +18.57d {+18d 34' 13"}
MOON_DIST:       115.94 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      352.92,-28.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      290.11,-24.51 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 25 Mar 23 03:21:51 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1161390,   Seg_Num: 0
POINT_RA:        296.811d {+19h 47m 15s} (J2000)
POINT_DEC:       -46.095d {-46d 05' 40"} (J2000)
POINT_ROLL:      71.884d
IMG_START_DATE:  20028 TJD;    84 DOY;   23/03/25
IMG_START_TIME:  11837.84 SOD {03:17:17.84} UT,   102.0 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.812
N_STARS:         77
X_OFFSET:        520 [pixels]
Y_OFFSET:        544 [pixels]
X_MAX:           1479 [pixels]
Y_MAX:           1503 [pixels]
DET_THRESH:      20
PHOTO_THRESH:    12
SL_URL:          sw01161390000msufc0101.fits
SUN_POSTN:         3.88d {+00h 15m 31s}   +1.68d {+01d 40' 45"}
SUN_DIST:         75.29 [deg]   Sun_angle= 4.4 [hr] (West of Sun)
MOON_POSTN:       45.68d {+03h 02m 42s}  +18.57d {+18d 34' 16"}
MOON_DIST:       115.94 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      352.92,-28.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      290.11,-24.51 [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 25 Mar 23 03:23:05 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1161390,   Seg_Num: 0
POINT_RA:        296.811d {+19h 47m 15s} (J2000)
POINT_DEC:       -46.095d {-46d 05' 40"} (J2000)
ROLL:            71.884d
IMG_START_DATE:  20028 TJD;    84 DOY;   23/03/25
IMG_START_TIME:  11837.84 SOD {03:17:17.84} UT,   102.0 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     701407068
X_OFFSET:        941 [pixels]
Y_OFFSET:        707 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1101
Y_GRB_POS:       867
BINNING_INDEX:   1
IM_URL:          sw01161390000msuni0132.fits
SUN_POSTN:         3.88d {+00h 15m 31s}   +1.68d {+01d 40' 46"}
SUN_DIST:         75.29 [deg]   Sun_angle= 4.4 [hr] (West of Sun)
MOON_POSTN:       45.69d {+03h 02m 45s}  +18.58d {+18d 34' 31"}
MOON_DIST:       115.95 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      352.92,-28.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      290.11,-24.51 [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 25 Mar 23 03:23:18 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1161390,   Seg_Num: 0
POINT_RA:        296.811d {+19h 47m 15s} (J2000)
POINT_DEC:       -46.095d {-46d 05' 40"} (J2000)
ROLL:            71.884d
IMG_START_DATE:  20028 TJD;    84 DOY;   23/03/25
IMG_START_TIME:  11837.84 SOD {03:17:17.84} UT,   102.0 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     701407068
X_OFFSET:        941 [pixels]
Y_OFFSET:        707 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1101
Y_GRB_POS:       867
BINNING_INDEX:   1
IM_URL:          sw01161390000msuni0132.fits
SUN_POSTN:         3.88d {+00h 15m 31s}   +1.68d {+01d 40' 47"}
SUN_DIST:         75.29 [deg]   Sun_angle= 4.4 [hr] (West of Sun)
MOON_POSTN:       45.69d {+03h 02m 45s}  +18.58d {+18d 34' 34"}
MOON_DIST:       115.96 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      352.92,-28.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      290.11,-24.51 [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 25 Mar 23 03:28:48 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1161390,   Seg_Num: 0
POINT_RA:        296.812d {+19h 47m 15s} (J2000)
POINT_DEC:       -46.094d {-46d 05' 39"} (J2000)
POINT_ROLL:      71.882d
IMG_START_DATE:  20028 TJD;    84 DOY;   23/03/25
IMG_START_TIME:  12050.08 SOD {03:20:50.08} UT,   314.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        3.027
N_STARS:         41
X_OFFSET:        621 [pixels]
Y_OFFSET:        387 [pixels]
X_MAX:           1580 [pixels]
Y_MAX:           1346 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    8
SL_URL:          sw01161390000msufc0314.fits
SUN_POSTN:         3.88d {+00h 15m 32s}   +1.68d {+01d 40' 52"}
SUN_DIST:         75.29 [deg]   Sun_angle= 4.4 [hr] (West of Sun)
MOON_POSTN:       45.74d {+03h 02m 57s}  +18.59d {+18d 35' 40"}
MOON_DIST:       116.00 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      352.92,-28.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      290.11,-24.51 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN Circular #33516
M. J. Moss (GWU), N. P. M. Kuin (UCL-MSSL), S. Laha (GSFC/UMBC), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL) and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift Observatory Team:
At 03:15:35 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 230325A (trigger=1161390). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 296.820, -46.094 which is
```
   RA(J2000) = 19h 47m 17s
   Dec(J2000) = -46d 05' 38"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure structure with a duration of about 40 sec. The peak count rate was ~2200 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 03:17:09.9 UT, 94.0 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source located at RA, Dec 296.84910, -46.07455 which is equivalent to:
```
   RA(J2000)  = 19h 47m 23.78s
   Dec(J2000) = -46d 04' 28.4"
```
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This location is 100 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (4.88 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.9 (+3.24/-2.71) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 2.06e-09 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 101 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 0.046.
Burst Advocate for this burst is M. J. Moss (mikejmoss3 AT gmail.com). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 25 Mar 23 03:29:04 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1161390,   Seg_Num: 0
POINT_RA:        296.812d {+19h 47m 15s} (J2000)
POINT_DEC:       -46.094d {-46d 05' 39"} (J2000)
POINT_ROLL:      71.882d
IMG_START_DATE:  20028 TJD;    84 DOY;   23/03/25
IMG_START_TIME:  12050.08 SOD {03:20:50.08} UT,   314.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        3.027
N_STARS:         41
X_OFFSET:        621 [pixels]
Y_OFFSET:        387 [pixels]
X_MAX:           1580 [pixels]
Y_MAX:           1346 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    8
SL_URL:          sw01161390000msufc0314.fits
SUN_POSTN:         3.88d {+00h 15m 32s}   +1.68d {+01d 40' 52"}
SUN_DIST:         75.29 [deg]   Sun_angle= 4.4 [hr] (West of Sun)
MOON_POSTN:       45.74d {+03h 02m 58s}  +18.60d {+18d 35' 43"}
MOON_DIST:       116.00 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      352.92,-28.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      290.11,-24.51 [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 25 Mar 23 03:30:10 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1161390,   Seg_Num: 0
POINT_RA:        296.812d {+19h 47m 15s} (J2000)
POINT_DEC:       -46.094d {-46d 05' 39"} (J2000)
ROLL:            71.882d
IMG_START_DATE:  20028 TJD;    84 DOY;   23/03/25
IMG_START_TIME:  12050.08 SOD {03:20:50.08} UT,   314.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     701407281
X_OFFSET:        941 [pixels]
Y_OFFSET:        707 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1101
Y_GRB_POS:       867
BINNING_INDEX:   1
IM_URL:          sw01161390000msuni0345.fits
SUN_POSTN:         3.88d {+00h 15m 32s}   +1.68d {+01d 40' 53"}
SUN_DIST:         75.29 [deg]   Sun_angle= 4.4 [hr] (West of Sun)
MOON_POSTN:       45.75d {+03h 03m 00s}  +18.60d {+18d 35' 56"}
MOON_DIST:       116.01 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      352.92,-28.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      290.11,-24.51 [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 #33517
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Using promptly downlinked XRT event data for GRB 230325A, we find an enhanced XRT position of the afterglow: RA, Dec: 296.84935, -46.07561 which is equivalent to:
```
   RA (J2000)  = 19 47 23.85
   Dec (J2000) = -46 04 32.2
```
with an uncertainty of 1.9 arcseconds (radius, 90% confidence). Analysis of the promptly available data is online at http://www.swift.ac.uk/sper/1161390.
Position enhancement is is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular is an official product of the Swift-XRT team.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 25 Mar 23 03:30:22 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1161390,   Seg_Num: 0
POINT_RA:        296.812d {+19h 47m 15s} (J2000)
POINT_DEC:       -46.094d {-46d 05' 39"} (J2000)
ROLL:            71.882d
IMG_START_DATE:  20028 TJD;    84 DOY;   23/03/25
IMG_START_TIME:  12050.08 SOD {03:20:50.08} UT,   314.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     701407281
X_OFFSET:        941 [pixels]
Y_OFFSET:        707 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1101
Y_GRB_POS:       867
BINNING_INDEX:   1
IM_URL:          sw01161390000msuni0345.fits
SUN_POSTN:         3.88d {+00h 15m 32s}   +1.68d {+01d 40' 53"}
SUN_DIST:         75.29 [deg]   Sun_angle= 4.4 [hr] (West of Sun)
MOON_POSTN:       45.75d {+03h 03m 01s}  +18.60d {+18d 35' 58"}
MOON_DIST:       116.01 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      352.92,-28.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      290.11,-24.51 [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 25 Mar 23 03:29:13 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     1161390,   Seg_Num: 0
GRB_RA:          296.8493d {+19h 47m 23.83s} (J2000),
                 297.2664d {+19h 49m 03.92s} (current),
                 295.9493d {+19h 43m 47.83s} (1950)
GRB_DEC:         -46.0755d {-46d 04' 31.7"} (J2000),
                 -46.0167d {-46d 01' 00.0"} (current),
                 -46.1993d {-46d 11' 57.4"} (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:  20028 TJD;    84 DOY;   23/03/25
IMG_START_TIME:  11977.00 SOD {03:19:37.00} UT,   241.1 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:         3.88d {+00h 15m 32s}   +1.68d {+01d 40' 52"}
SUN_DIST:         75.26 [deg]   Sun_angle= 4.4 [hr] (West of Sun)
MOON_POSTN:       45.74d {+03h 02m 58s}  +18.60d {+18d 35' 45"}
MOON_DIST:       115.98 [deg]
MOON_ILLUM:      14 [%]
GAL_COORDS:      352.95,-28.53 [deg] galactic lon,lat of the burst
ECL_COORDS:      290.14,-24.50 [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 0.58% < P(seren) < 1.1%.

GCN Circular #33518
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 290 s of XRT Photon Counting mode data and 1 UVOT images for GRB 230325A, 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 = 296.84984, -46.07613 which is equivalent to:
```
RA (J2000): 19h 47m 23.96s
Dec (J2000): -46d 04' 34.1"
```
with an uncertainty of 2.3 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 #33520
K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), S. Dichiara (PSU), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto) and M.J. Moss report on behalf of the Swift-XRT team:
We have analysed 7.1 ks of XRT data for GRB 230325A (Moss et al. GCN Circ. 33516), from 83 s to 45.2 ks after the BAT trigger. The data comprise 139 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 enhanced XRT position for this burst was given by Goad et al. (GCN Circ. 33517).
The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=1.1 (+/-0.5). At T+123 s the decay steepens to an alpha of 3.24 (+0.27, -0.16) before breaking again at T+598 s to a final decay with index alpha=0.42 (+/-0.14).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.16 (+0.11, -0.10). The best-fitting absorption column is 3.2 (+/-0.4) x 10^21 cm^-2, in excess of the Galactic value of 4.9 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.13 (+0.25, -0.23) and a best-fitting absorption column of 2.5 (+0.9, -0.8) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.4 x 10^-11 (5.1 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     2.5 (+0.9, -0.8) x 10^21 cm^-2
Galactic foreground: 4.9 x 10^20 cm^-2
Excess significance: 4.2 sigma
Photon index:	     2.13 (+0.25, -0.23)
```
If the light curve continues to decay with a power-law decay index of 0.42, the count rate at T+24 hours will be 0.028 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.3 x 10^-13 (1.4 x 10^-12) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01161390.
This circular is an official product of the Swift-XRT team.
GCN Circular #33521
Danielle Pieterse (Radboud Univ.), Johan P. U. Fynbo (DAWN/NBI), Luca Izzo (DARK/NBI), Jesse Palmerio (GEPI, Obs. Paris and IAP), Andrea Saccardi (GEPI, Obs. Paris), Nial R. Tanvir (Leicester), Dong Xu (NAO/CAS), Zi-Pei Zhu (NAOC, HUST), Daniele B. Malesani (Radboud univ. and DAWN/NBI) and Pall Jakobsson (Univ. Iceland), report on behalf of the Stargate collabaration:
We observed the field of GRB 230325A (Moss et al., GCN 33516) using the ESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph. Images were also taken with the acquisition camera. An object is visible consistent with the UVOT-enhanced XRT position (Goad et al., GCN 33518), at coordinates (0.5" error):
```
RA = 19:47:23.98� (J2000)
Dec = -46:04:33.3� (J2000)
```
For this object, we measure the following magnitudes (calibrated against nearby objects from the Legacy Survey; Dey et al. 2019, AJ, 157, 168):
```
Filter Mean date������� Time since GRB� Exptime� Magnitude
 ������� (UT)������������ (days)��������� (s)����� (AB)
--------------------------------------------------------------
r����� 2023 Mar 25.371� 0.235���������� 45������ 22.70 +- 0.08
z����� 2023 Mar 25.372� 0.236���������� 60������ 22.35 +- 0.08
g����� 2023 Mar 25.374� 0.237���������� 45������ 22.16 +- 0.23
```
An object is present at a consistent location in the Legacy Survey, but significantly fainter, and it is the likely GRB host galaxy. The consistency with the XRT position and the flux increase compared to the Legacy Survey confirm that the object we see in the X-shooter images is the optical afterglow of GRB 230325A.
Spectroscopy was carried out, covering the wavelength range 3000-21000 AA, and consisting of 2 exposures by 600 s each. The observation mid time was 2023 Mar 25.383 UT (0.247 days after the GRB).
Only a faint continuum is detected from this source, which allows us to set a redshift upper limit z <~ 3. In addition, two emission lines are visible, which are consistent with Halpha and [O III] 5008 at a common redshift z = 1.664, which we suggest to be the GRB redshift.
We acknowledge excellent support from the ESO observing staff in Paranal, in particular Fuyan Bian and Konrad Tristram.
GCN Circular #33522
N Paul Kuin (UCL/MSSL) and M. J. Moss (GWU)report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 230325A 102 s after the BAT trigger (Moss et al., GCN Circ. 33516). No optical afterglow consistent with the XRT position (Goad et al. GCN Circ. 33518) 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           102          252          147         >20.1
u_FC               314          540          222         >19.2
white              102         4222          344         >20.8
v                 4434         4634          197         >18.9
b                 3818         4018          197         >20.0
u                  314         5106          277         >19.3
w1                4845         5045          197         >19.9
m2                4640         4839          197         >19.8
w2                4230         4429          197         >20.2
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.046 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #33523
A. Y. Lien (U Tampa), S. D. Barthelmy (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), C. B. Markwardt (GSFC), M. J. Moss (GWU), D. M. Palmer (LANL), T. Parsotan (GSFC/UMBC), T. Sakamoto (AGU), M. Stamatikos (OSU) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 230325A (trigger #1161390) (Moss, et al., GCN Circ. 33516). The BAT ground-calculated position is RA, Dec = 296.854, -46.067 deg which is
```
   RA(J2000)  =  19h 47m 24.9s
   Dec(J2000) = -46d 03' 59.8"
```
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 48%.
The mask-weighted light curve shows a main pulse with a FRED shape, from approximately T+0 to T+8 seconds. This is preceded by some precursor emission starting around T-10 sec, and some low-level emission out to about T+40 sec. The spacecraft slewed away from the burst location around T+620 seconds. T90 (15-350 keV) is 38.05 +- 11.56 sec (estimated error including systematics).
The time-averaged spectrum from T-8.55 to T+41.70 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.82 +- 0.18. The fluence in the 15-150 keV band is 1.3 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T-0.07 sec in the 15-150 keV band is 3.3 +- 0.4 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/1161390/BA/

Back to JG's homepage

Jochen Greiner, last update: 26-Mar-2023 [Disclaimer]