Gamma-ray Burst 250807A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 07 Aug 25 10:46:21 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1340514,   Seg_Num: 0
GRB_RA:           51.420d {+03h 25m 41s} (J2000),
                  51.625d {+03h 26m 30s} (current),
                  51.020d {+03h 24m 05s} (1950)
GRB_DEC:         -47.877d {-47d 52' 38"} (J2000),
                 -47.789d {-47d 47' 18"} (current),
                 -48.052d {-48d 03' 05"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       7829 [cnts]    Image_Peak=934 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   155     E_range: 50-350 keV
BKG_INTEN:       13390 [cnts]
BKG_TIME:        38755.89 SOD {10:45:55.89} UT
BKG_DUR:         8 [sec]
GRB_DATE:        20894 TJD;   219 DOY;   25/08/07
GRB_TIME:        38768.44 SOD {10:46:08.44} UT
GRB_PHI:         -174.94 [deg]
GRB_THETA:        34.65 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     139.04 [sigma]
IMAGE_SIGNIF:    19.67 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +3  +6  +0  +0 +16  +0 
SUN_POSTN:       137.66d {+09h 10m 38s}  +16.28d {+16d 16' 37"}
SUN_DIST:         99.38 [deg]   Sun_angle= 5.7 [hr] (West of Sun)
MOON_POSTN:      294.64d {+19h 38m 33s}  -25.94d {-25d 56' 36"}
MOON_DIST:        87.14 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      258.13,-53.61 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       23.98,-62.76 [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 = 213.03,-18.43 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 07 Aug 25 10:48:23 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     1340514,   Seg_Num: 0
GRB_RA:           51.4478d {+03h 25m 47.4s} (J2000),
                  51.6525d {+03h 26m 36.6s} (current),
                  51.0482d {+03h 24m 11.5s} (1950)
GRB_DEC:         -47.8880d {-47d 53' 16.7"} (J2000),
                 -47.7994d {-47d 47' 57.7"} (current),
                 -48.0623d {-48d 03' 44.1"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       198 [cnts]
IMG_START_DATE:  20894 TJD;   219 DOY;   25/08/07
IMG_START_TIME:  38869.55 SOD {10:47:49.55} UT,   101.1 [sec] since BAT Trigger Time
CENTROID_X:      304.42,  raw= 304  [pixels]
CENTROID_Y:      272.65,  raw= 273  [pixels]
ROLL:            76.20 [deg]
GAIN:            4
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -61.39
GRB_POS_XRT_Z:   -16.91
IMAGE_URL:       sw01340514000msxps_rw.img
SUN_POSTN:       137.66d {+09h 10m 38s}  +16.28d {+16d 16' 36"}
SUN_DIST:         99.36 [deg]   Sun_angle= 5.7 [hr] (West of Sun)
MOON_POSTN:      294.66d {+19h 38m 38s}  -25.94d {-25d 56' 22"}
MOON_DIST:        87.14 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      258.13,-53.59 [deg] galactic lon,lat of the burst
ECL_COORDS:       24.00,-62.78 [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:     Thu 07 Aug 25 10:48:26 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     1340514,   Seg_Num: 0
GRB_RA:           51.4478d {+03h 25m 47.4s} (J2000),
                  51.6525d {+03h 26m 36.6s} (current),
                  51.0482d {+03h 24m 11.5s} (1950)
GRB_DEC:         -47.8880d {-47d 53' 16.7"} (J2000),
                 -47.7994d {-47d 47' 57.7"} (current),
                 -48.0623d {-48d 03' 44.1"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       198 [cnts]
IMG_START_DATE:  20894 TJD;   219 DOY;   25/08/07
IMG_START_TIME:  38869.55 SOD {10:47:49.55} UT,   101.1 [sec] since BAT Trigger Time
CENTROID_X:      304.42,  raw= 304  [pixels]
CENTROID_Y:      272.65,  raw= 273  [pixels]
ROLL:            76.20 [deg]
GAIN:            4
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -61.39
GRB_POS_XRT_Z:   -16.91
IMAGE_URL:       sw01340514000msxps_rw.img
SUN_POSTN:       137.66d {+09h 10m 38s}  +16.28d {+16d 16' 35"}
SUN_DIST:         99.36 [deg]   Sun_angle= 5.7 [hr] (West of Sun)
MOON_POSTN:      294.66d {+19h 38m 38s}  -25.94d {-25d 56' 22"}
MOON_DIST:        87.14 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      258.13,-53.59 [deg] galactic lon,lat of the burst
ECL_COORDS:       24.00,-62.78 [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:     Thu 07 Aug 25 10:48:13 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1340514,   Seg_Num: 0
GRB_RA:           51.4478d {+03h 25m 47.47s} (J2000),
                  51.6525d {+03h 26m 36.60s} (current),
                  51.0482d {+03h 24m 11.56s} (1950)
GRB_DEC:         -47.8880d {-47d 53' 16.7"} (J2000),
                 -47.7994d {-47d 47' 57.7"} (current),
                 -48.0623d {-48d 03' 44.1"} (1950)
GRB_ERROR:       4.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       7.13e-09 [erg/cm2/sec]
GRB_SIGNIF:      14.07 [sigma]
IMG_START_DATE:  20894 TJD;   219 DOY;   25/08/07
IMG_START_TIME:  38869.55 SOD {10:47:49.55} UT,   101.1 [sec] since BAT Trigger Time
TAM[0-3]:        327.66 237.17 261.60 243.80
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       137.66d {+09h 10m 38s}  +16.28d {+16d 16' 36"}
SUN_DIST:         99.36 [deg]   Sun_angle= 5.7 [hr] (West of Sun)
MOON_POSTN:      294.66d {+19h 38m 38s}  -25.94d {-25d 56' 23"}
MOON_DIST:        87.14 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      258.13,-53.59 [deg] galactic lon,lat of the burst
ECL_COORDS:       24.00,-62.78 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 1.28 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:     Thu 07 Aug 25 10:50:43 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1340514,   Seg_Num: 0
POINT_RA:         51.434d {+03h 25m 44s} (J2000)
POINT_DEC:       -47.872d {-47d 52' 19"} (J2000)
POINT_ROLL:      76.204d
IMG_START_DATE:  20894 TJD;   219 DOY;   25/08/07
IMG_START_TIME:  38879.59 SOD {10:47:59.59} UT,   111.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.289
N_STARS:         22
X_OFFSET:        564 [pixels]
Y_OFFSET:        638 [pixels]
X_MAX:           1523 [pixels]
Y_MAX:           1597 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw01340514000msufc0111.fits
SUN_POSTN:       137.66d {+09h 10m 38s}  +16.28d {+16d 16' 34"}
SUN_DIST:         99.37 [deg]   Sun_angle= 5.7 [hr] (West of Sun)
MOON_POSTN:      294.68d {+19h 38m 44s}  -25.94d {-25d 56' 06"}
MOON_DIST:        87.13 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      258.11,-53.60 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       24.00,-62.76 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 07 Aug 25 10:51:02 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1340514,   Seg_Num: 0
POINT_RA:         51.434d {+03h 25m 44s} (J2000)
POINT_DEC:       -47.872d {-47d 52' 19"} (J2000)
POINT_ROLL:      76.204d
IMG_START_DATE:  20894 TJD;   219 DOY;   25/08/07
IMG_START_TIME:  38879.59 SOD {10:47:59.59} UT,   111.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.289
N_STARS:         22
X_OFFSET:        564 [pixels]
Y_OFFSET:        638 [pixels]
X_MAX:           1523 [pixels]
Y_MAX:           1597 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw01340514000msufc0111.fits
SUN_POSTN:       137.66d {+09h 10m 38s}  +16.28d {+16d 16' 34"}
SUN_DIST:         99.37 [deg]   Sun_angle= 5.7 [hr] (West of Sun)
MOON_POSTN:      294.68d {+19h 38m 44s}  -25.93d {-25d 56' 04"}
MOON_DIST:        87.13 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      258.11,-53.60 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       24.00,-62.76 [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:     Thu 07 Aug 25 10:51:56 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1340514,   Seg_Num: 0
POINT_RA:         51.434d {+03h 25m 44s} (J2000)
POINT_DEC:       -47.872d {-47d 52' 19"} (J2000)
ROLL:            76.204d
IMG_START_DATE:  20894 TJD;   219 DOY;   25/08/07
IMG_START_TIME:  38879.59 SOD {10:47:59.59} UT,   111.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     776256515
X_OFFSET:        884 [pixels]
Y_OFFSET:        958 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1044
Y_GRB_POS:       1118
BINNING_INDEX:   1
IM_URL:          sw01340514000msuni0148.fits
SUN_POSTN:       137.66d {+09h 10m 38s}  +16.28d {+16d 16' 33"}
SUN_DIST:         99.37 [deg]   Sun_angle= 5.7 [hr] (West of Sun)
MOON_POSTN:      294.69d {+19h 38m 46s}  -25.93d {-25d 55' 57"}
MOON_DIST:        87.13 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      258.11,-53.60 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       24.00,-62.76 [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:     Thu 07 Aug 25 10:52:08 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1340514,   Seg_Num: 0
POINT_RA:         51.434d {+03h 25m 44s} (J2000)
POINT_DEC:       -47.872d {-47d 52' 19"} (J2000)
ROLL:            76.204d
IMG_START_DATE:  20894 TJD;   219 DOY;   25/08/07
IMG_START_TIME:  38879.59 SOD {10:47:59.59} UT,   111.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     776256515
X_OFFSET:        884 [pixels]
Y_OFFSET:        958 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1044
Y_GRB_POS:       1118
BINNING_INDEX:   1
IM_URL:          sw01340514000msuni0148.fits
SUN_POSTN:       137.66d {+09h 10m 38s}  +16.28d {+16d 16' 33"}
SUN_DIST:         99.37 [deg]   Sun_angle= 5.7 [hr] (West of Sun)
MOON_POSTN:      294.70d {+19h 38m 47s}  -25.93d {-25d 55' 56"}
MOON_DIST:        87.13 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      258.11,-53.60 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       24.00,-62.76 [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:     Thu 07 Aug 25 10:53:24 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     1340514,   Seg_Num: 0
GRB_RA:           51.4482d {+03h 25m 47.56s} (J2000),
                  51.6529d {+03h 26m 36.70s} (current),
                  51.0486d {+03h 24m 11.66s} (1950)
GRB_DEC:         -47.8878d {-47d 53' 16.0"} (J2000),
                 -47.7992d {-47d 47' 57.0"} (current),
                 -48.0621d {-48d 03' 43.4"} (1950)
GRB_ERROR:       0.8 [arcsec radius, statistical only]
GRB_MAG:         17.97 +/- 0.14 [mag]
FILTER:          10, White
IMG_START_DATE:  20894 TJD;   219 DOY;   25/08/07
IMG_START_TIME:  38876.00 SOD {10:47:56.00} UT,   107.6 [sec] since BAT Trigger Time
SUN_POSTN:       137.66d {+09h 10m 39s}  +16.28d {+16d 16' 32"}
SUN_DIST:         99.37 [deg]   Sun_angle= 5.7 [hr] (West of Sun)
MOON_POSTN:      294.71d {+19h 38m 50s}  -25.93d {-25d 55' 47"}
MOON_DIST:        87.12 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      258.13,-53.59 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       24.00,-62.78 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT UVOT Position Notice.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The UVOT position is 1.1 arcsec from the XRT position.  
COMMENTS:        Result based on Genie data.  
COMMENTS:        Notice generated automatically.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 07 Aug 25 10:57:29 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1340514,   Seg_Num: 0
POINT_RA:         51.435d {+03h 25m 44s} (J2000)
POINT_DEC:       -47.874d {-47d 52' 24"} (J2000)
POINT_ROLL:      76.204d
IMG_START_DATE:  20894 TJD;   219 DOY;   25/08/07
IMG_START_TIME:  39091.66 SOD {10:51:31.66} UT,   323.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.324
N_STARS:         20
X_OFFSET:        564 [pixels]
Y_OFFSET:        638 [pixels]
X_MAX:           1523 [pixels]
Y_MAX:           1597 [pixels]
DET_THRESH:      6
PHOTO_THRESH:    2
SL_URL:          sw01340514000msufc0323.fits
SUN_POSTN:       137.66d {+09h 10m 39s}  +16.27d {+16d 16' 29"}
SUN_DIST:         99.37 [deg]   Sun_angle= 5.7 [hr] (West of Sun)
MOON_POSTN:      294.75d {+19h 38m 59s}  -25.92d {-25d 55' 19"}
MOON_DIST:        87.11 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      258.12,-53.60 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       24.00,-62.76 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 07 Aug 25 10:57:38 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1340514,   Seg_Num: 0
POINT_RA:         51.435d {+03h 25m 44s} (J2000)
POINT_DEC:       -47.874d {-47d 52' 24"} (J2000)
POINT_ROLL:      76.204d
IMG_START_DATE:  20894 TJD;   219 DOY;   25/08/07
IMG_START_TIME:  39091.66 SOD {10:51:31.66} UT,   323.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.324
N_STARS:         20
X_OFFSET:        564 [pixels]
Y_OFFSET:        638 [pixels]
X_MAX:           1523 [pixels]
Y_MAX:           1597 [pixels]
DET_THRESH:      6
PHOTO_THRESH:    2
SL_URL:          sw01340514000msufc0323.fits
SUN_POSTN:       137.66d {+09h 10m 39s}  +16.27d {+16d 16' 29"}
SUN_DIST:         99.37 [deg]   Sun_angle= 5.7 [hr] (West of Sun)
MOON_POSTN:      294.75d {+19h 39m 00s}  -25.92d {-25d 55' 18"}
MOON_DIST:        87.11 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      258.12,-53.60 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       24.00,-62.76 [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:     Thu 07 Aug 25 11:03:35 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1340514,   Seg_Num: 0
POINT_RA:         51.435d {+03h 25m 44s} (J2000)
POINT_DEC:       -47.874d {-47d 52' 24"} (J2000)
POINT_ROLL:      76.204d
IMG_START_DATE:  20894 TJD;   219 DOY;   25/08/07
IMG_START_TIME:  39644.60 SOD {11:00:44.60} UT,   876.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.634
N_STARS:         45
X_OFFSET:        324 [pixels]
Y_OFFSET:        398 [pixels]
X_MAX:           1763 [pixels]
Y_MAX:           1837 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw01340514000msufc0876.fits
SUN_POSTN:       137.67d {+09h 10m 40s}  +16.27d {+16d 16' 25"}
SUN_DIST:         99.37 [deg]   Sun_angle= 5.7 [hr] (West of Sun)
MOON_POSTN:      294.81d {+19h 39m 14s}  -25.91d {-25d 54' 36"}
MOON_DIST:        87.09 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      258.12,-53.60 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       24.00,-62.76 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN Circular #41262
N. J. Klingler (GSFC/UMBC/CRESSTII), R. Brivio (INAF-OAB), J. J. DeLaunay (PSU), R. Gupta (NASA GSFC), J. A. Kennea (PSU), K. L. Page (U Leicester) and C. Salvaggio (INAF-OAB) report on behalf of the Neil Gehrels Swift Observatory Team:
At 10:46:08.44 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250807A (trigger=1340514). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 51.420, -47.877 which is
```
   RA(J2000) = 03h 25m 41s
   Dec(J2000) = -47d 52' 38"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 80 sec. The peak count rate was ~19000 counts/sec (15-350 keV), at ~35 sec after the trigger.
The XRT began observing the field at 10:47:49.5 UT, 101.1 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 51.4478, -47.8880 which is equivalent to:
```
   RA(J2000)  = 03h 25m 47.47s
   Dec(J2000) = -47d 53' 16.8"
```
with an uncertainty of 4.8 arcseconds (radius, 90% containment). This location is 77 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 150 seconds with the White filter starting 111 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at
```
  RA(J2000)  =	03:25:47.59 =  51.44829
  DEC(J2000) = -47:53:16.2  = -47.88782
```
with a 90%-confidence error radius of about 0.75 arc sec. This position is 1.3 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.98 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.011.
Burst Advocate for this burst is N. J. Klingler (noelklin AT umbc.edu). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 07 Aug 25 11:03:52 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1340514,   Seg_Num: 0
POINT_RA:         51.435d {+03h 25m 44s} (J2000)
POINT_DEC:       -47.874d {-47d 52' 24"} (J2000)
POINT_ROLL:      76.204d
IMG_START_DATE:  20894 TJD;   219 DOY;   25/08/07
IMG_START_TIME:  39644.60 SOD {11:00:44.60} UT,   876.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.634
N_STARS:         45
X_OFFSET:        324 [pixels]
Y_OFFSET:        398 [pixels]
X_MAX:           1763 [pixels]
Y_MAX:           1837 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw01340514000msufc0876.fits
SUN_POSTN:       137.67d {+09h 10m 40s}  +16.27d {+16d 16' 25"}
SUN_DIST:         99.37 [deg]   Sun_angle= 5.7 [hr] (West of Sun)
MOON_POSTN:      294.81d {+19h 39m 14s}  -25.91d {-25d 54' 34"}
MOON_DIST:        87.09 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      258.12,-53.60 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       24.00,-62.76 [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:     Thu 07 Aug 25 11:04:51 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1340514,   Seg_Num: 0
POINT_RA:         51.435d {+03h 25m 44s} (J2000)
POINT_DEC:       -47.874d {-47d 52' 24"} (J2000)
ROLL:            76.204d
IMG_START_DATE:  20894 TJD;   219 DOY;   25/08/07
IMG_START_TIME:  39644.60 SOD {11:00:44.60} UT,   876.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     776257280
X_OFFSET:        883 [pixels]
Y_OFFSET:        957 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1043
Y_GRB_POS:       1117
BINNING_INDEX:   1
IM_URL:          sw01340514000msuni0913.fits
SUN_POSTN:       137.67d {+09h 10m 40s}  +16.27d {+16d 16' 24"}
SUN_DIST:         99.37 [deg]   Sun_angle= 5.7 [hr] (West of Sun)
MOON_POSTN:      294.82d {+19h 39m 17s}  -25.91d {-25d 54' 28"}
MOON_DIST:        87.08 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      258.12,-53.60 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       24.00,-62.76 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 07 Aug 25 11:04:58 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1340514,   Seg_Num: 0
POINT_RA:         51.435d {+03h 25m 44s} (J2000)
POINT_DEC:       -47.874d {-47d 52' 24"} (J2000)
ROLL:            76.204d
IMG_START_DATE:  20894 TJD;   219 DOY;   25/08/07
IMG_START_TIME:  39644.60 SOD {11:00:44.60} UT,   876.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     776257280
X_OFFSET:        883 [pixels]
Y_OFFSET:        957 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1043
Y_GRB_POS:       1117
BINNING_INDEX:   1
IM_URL:          sw01340514000msuni0913.fits
SUN_POSTN:       137.67d {+09h 10m 40s}  +16.27d {+16d 16' 24"}
SUN_DIST:         99.37 [deg]   Sun_angle= 5.7 [hr] (West of Sun)
MOON_POSTN:      294.82d {+19h 39m 17s}  -25.91d {-25d 54' 27"}
MOON_DIST:        87.08 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      258.12,-53.60 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       24.00,-62.76 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 07 Aug 25 11:29:27 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     1340514,   Seg_Num: 0
GRB_RA:           51.4469d {+03h 25m 47.25s} (J2000),
                  51.6516d {+03h 26m 36.39s} (current),
                  51.0473d {+03h 24m 11.34s} (1950)
GRB_DEC:         -47.8867d {-47d 53' 12.1"} (J2000),
                 -47.7981d {-47d 47' 53.0"} (current),
                 -48.0610d {-48d 03' 39.4"} (1950)
GRB_ERROR:       3.5 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  20894 TJD;   219 DOY;   25/08/07
IMG_START_TIME:  40084.00 SOD {11:08:04.00} UT,   1315.6 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       137.68d {+09h 10m 44s}  +16.27d {+16d 16' 07"}
SUN_DIST:         99.38 [deg]   Sun_angle= 5.7 [hr] (West of Sun)
MOON_POSTN:      295.06d {+19h 40m 14s}  -25.86d {-25d 51' 36"}
MOON_DIST:        86.99 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      258.13,-53.59 [deg] galactic lon,lat of the burst
ECL_COORDS:       24.00,-62.77 [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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 07 Aug 25 10:58:38 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1340514,   Seg_Num: 0
POINT_RA:         51.435d {+03h 25m 44s} (J2000)
POINT_DEC:       -47.874d {-47d 52' 24"} (J2000)
ROLL:            76.204d
IMG_START_DATE:  20894 TJD;   219 DOY;   25/08/07
IMG_START_TIME:  39091.66 SOD {10:51:31.66} UT,   323.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     776256727
X_OFFSET:        884 [pixels]
Y_OFFSET:        958 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1044
Y_GRB_POS:       1118
BINNING_INDEX:   1
IM_URL:          sw01340514000msuni0360.fits
SUN_POSTN:       137.66d {+09h 10m 39s}  +16.27d {+16d 16' 28"}
SUN_DIST:         99.37 [deg]   Sun_angle= 5.7 [hr] (West of Sun)
MOON_POSTN:      294.76d {+19h 39m 02s}  -25.92d {-25d 55' 11"}
MOON_DIST:        87.10 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      258.12,-53.60 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       24.00,-62.76 [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:     Thu 07 Aug 25 10:58:56 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1340514,   Seg_Num: 0
POINT_RA:         51.435d {+03h 25m 44s} (J2000)
POINT_DEC:       -47.874d {-47d 52' 24"} (J2000)
ROLL:            76.204d
IMG_START_DATE:  20894 TJD;   219 DOY;   25/08/07
IMG_START_TIME:  39091.66 SOD {10:51:31.66} UT,   323.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     776256727
X_OFFSET:        884 [pixels]
Y_OFFSET:        958 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1044
Y_GRB_POS:       1118
BINNING_INDEX:   1
IM_URL:          sw01340514000msuni0360.fits
SUN_POSTN:       137.66d {+09h 10m 40s}  +16.27d {+16d 16' 28"}
SUN_DIST:         99.37 [deg]   Sun_angle= 5.7 [hr] (West of Sun)
MOON_POSTN:      294.76d {+19h 39m 03s}  -25.92d {-25d 55' 09"}
MOON_DIST:        87.10 [deg]
MOON_ILLUM:      96 [%]
GAL_COORDS:      258.12,-53.60 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       24.00,-62.76 [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 #41270
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
Using 769 s of XRT Photon Counting mode data and 3 UVOT images for GRB 250807A, 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 = 51.44795, -47.88761 which is equivalent to:
```
RA (J2000): 03h 25m 47.51s
Dec (J2000): -47d 53' 15.4"
```
with an uncertainty of 2.0 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 #41271
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
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 GRB250807.65 (trigger No 1340561,01h 02m 20.40s , -59d 05m 38.4s, R=0.05) errorbox 10317 sec after notice time and 10401 sec after trigger time at 2025-08-07 18:36:29 UT, with upper limit up to 17.8 mag. The observations began at zenith distance = 76 deg. The sun altitude is -32.1 deg.
The galactic latitude b = -58 deg., longitude l = 300 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2963168
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   10491 |         MASTER-SAAO |   C |   180 | 17.1 |        
   10491 |         MASTER-SAAO |   C |   180 | 17.8 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #41274
Y. N. Ma, Z. H. Yao, L. P. Xin, Y. L. Qiu, C. Wu, H. L. Li, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team.
SVOM/VT performed a Target of Opportunity observation of GRB 250807A detected by Swift-BAT（Klingler et al., GCN 41262; Evans et al., GCN 41270). The observation began at 2025-08-07T11:21:39.516 UTC, 35.52 minutes after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
The optical afterglow (Evans et al., GCN 41262) is detected in both VT_R and VT_B using VT X-band data at R.A. = 51.448126 , DEC = -47.887663 degrees:
```
RA (J2000) = 3:25:47.55 
Dec (J2000) = -47:53:15.58 
```
with an uncertainty of 0.5 arcsec.
The magnitudes are:
```
mid time (sec) | exposure time (s) | band | mag (AB) | mag err 
---------------|-------------------|------|----------|-------- 
     2236      |          70       | VT_B |   20.52  | 0.08  
     14319     |          70       | VT_B |   21.07  | 0.10 
     2236      |          70       | VT_R |   18.98  | 0.03  
     14319     |          70       | VT_R |   19.29  | 0.03 
```
Our photometry was not corrected for Galactic extinction.
During our observations, the light curves exhibit an initial brightening followed by a decay phase.
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Centre for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.
GCN Circular #41281
S.Salunke (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a bright long-duration GRB 250807A which was also detected by Swift/BAT (N. J. Klingler et.al, GCN Circ. 41262), and Konus-Wind (reported through GCN Notices).
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2025-08-07 10:46:42.50 UTC. The measured peak count rate associated with the burst is 535 (+49, -47) counts/s above the background in the combined data of all quadrants, with a total of 6218 (+449, -269) counts. The local mean background count rate was 275 (+1, -4) counts/s. Using cumulative rates, we measure a T90 of 44 (+2, -3) s. In the preliminary analysis, we find 630 Compton events associated with this event.
The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2025-08-07 10:46:42.27 UTC. The measured peak count rate associated with the burst is 3662 (+110, -125) counts/s above the background in the combined data of all quadrants, with a total of 36237 (+1153, -1203) counts. The local mean background count rate was 1239 (+5, -6) counts/s. We measure a T90 of 48 (+1, -3) s from the cumulative Veto light curve.
CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project.
CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb
GCN Circular #41283
SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Sebastien Guillot (IRAP)
Report on behalf of the SVOM team:
SVOM/GRM was triggered in-flight by GRB 250807A (SVOM trigger reference: sb25080702) at 2025-08-07T10:46:06.700 UTC (T0), which is also detected by Swift/BAT (N. J. Klingler et al., GCN #41262), AstroSat (S.Salunke et al., GCN #41281) and Konus-Wind.
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple pulses with a T90 of 71.0 +4.5/-7.0 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250807A.png
In addition, the position of this burst, as determined by Swift/BAT (RA= 51.420, DEC= -47.877, GCN #41064), is located at about 69 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. Nonetheless, the burst is seen (via analysis of X-band data) in the ECLAIRs data above 50 keV at the T0 given by GRM, likely through the ECLAIRs shielding.
With this localization, the time-averaged spectrum from T0-15 to T0+130 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.19 +/-0.03 and the cutoff energy, parameterized as Epeak, is 547 +52/-45 keV. The event fluence (10-1000 keV) in this time interval is (1.00 +/-0.10)E-04 erg/cm^2. Thus GRB 250807A is consistent with Type II GRBs in the 'Amati' relation diagram, as shown at: https://www.bursthub.cn//admin/static/grb250807A_amati.png
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS.
The SVOM point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang@ihep.ac.cn)
GCN Circular #41290
J.P. Osborne (U. Leicester), R. Brivio (INAF-OAB), A. D'Ai (INAF-IASFPA), S. Campana (INAF-OAB), D.N. Burrows (PSU), M.A. Williams (PSU), S. Dichiara (PSU), K.L. Page (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 4.6 ks of XRT data for GRB 250807A, from 93 s to 91.2 ks after the trigger. The data comprise 1.2 ks in Windowed Timing (WT) mode (the first 5 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode.
The late-time light curve (from T0+6.7 ks) can be modelled with a power-law decay with a decay index of alpha=1.75 (+0.11, -0.10).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.96 (+/-0.03). The best-fitting absorption column is 1.90 (+/-0.11) x 10^21 cm^-2, in excess of the Galactic value of 1.4 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.85 (+0.11, -0.10) and a best-fitting absorption column of 1.8 (+0.4, -0.3) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.9 x 10^-11 (4.9 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     1.8 (+0.4, -0.3) x 10^21 cm^-2
Galactic foreground: 1.4 x 10^20 cm^-2
Excess significance: 8.0 sigma
Photon index:	     1.85 (+0.11, -0.10)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01340514.
This circular is an official product of the Swift-XRT team.
GCN Circular #41291
S. P. R. Shilling (Lancaster U.) and N. J. Klingler (GSFC/UMBC/CRESSTII) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 250807A 111 s after the BAT trigger (Klingler et al., GCN Circ. 41262). A source consistent with the enhanced XRT position (Evans et al., GCN Circ. 41270) is detected in the initial UVOT exposures.
Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white              111          261          147         18.00 +/- 0.04
v                  653         1769          136        >18.8
b                  579         1695          117        >19.5
u                  323         1840          361         19.88 +/- 0.31
w1                 702         1818          117        >19.0
w2                 801          821           19        >17.7
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.011 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #41295
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 250807A (Swift-BAT detection: Klingler et al., GCN 41262; AstroSat-CZTI detection: Salunke et al., GCN 41281; SVOM-GRM detection: Wang et al., GCN 41283) triggered Konus-Wind at T0=38766.990 s UT (10:46:06.990).
The burst light curve shows a multipeaked structure which starts at ~T0-2.3 s and has a total duration of ~79 s. The emission is seen up to ~2 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250807_T38766/
As observed by Konus-Wind, the burst had the total fluence of 1.03(-0.09,+0.08)x10^-4 erg/cm2, and the 64-ms peak flux, measured from T0+35.904 s, of 1.11(-0.10,+0.10)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst (measured from T0 to T0+79.104 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.04(-0.04,+0.04), the high energy photon index beta = -2.74(-0.66,+0.26), the peak energy Ep = 369(-26,+26) keV (chi2 = 132/97 dof).
The spectrum near the maximum count rate (measured from T0+29.952 to T0+38.144 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.04(-0.05,+0.05) and Ep = 390(-25,+28) keV (chi2 = 105/86 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -3.5 (chi2 = 105/85 dof).
All the quoted errors are at the 68% confidence level. All the quoted values are preliminary.
GCN Circular #41299
Y. N. Ma, Z. H. Yao, L. P. Xin, Y. L. Qiu, C. Wu, H. L. Li, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team.
SVOM/VT conducted continued observations of GRB 250807A detected by Swift/BAT（Klingler et al., GCN 41262), AstroSat-CZTI (Salunke et al., GCN 41281), SVOM/GRM (Wang et al,. GCN 41283) and Konus-Wind (Svinkin et al,. GCN 41295).
The magnitude of the optical afterglow (Klingler et al., GCN 41262; Ma et al., GCN 41274; Shilling et al., GCN 41291) is:
```
  mid time | exposure time (s) | band | mag (AB) | mag err 
-----------|-------------------|------|----------|-------- 
  18.25h   |        31*70      | VT_R |   21.59  | 0.08 
```
Our photometry was not corrected for Galactic extinction.
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Centre for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.
GCN Circular #41318
R. Gupta (GSFC), S. D. Barthelmy (GSFC), N. J. Klingler (GSFC/UMBC/CRESSTII), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+520 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250807A (trigger #1340514) (Klingler, et al., GCN Circ. 41262). The BAT ground-calculated position is RA, Dec = 51.435, -47.882 deg which is
```
   RA(J2000)  =  03h 25m 44.4s
   Dec(J2000) = -47d 52' 54.4"
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 72%.
The mask-weighted light curve displays a complex structure with several pulses. T90 (15-350 keV) is 75.46 +- 2.19 sec (estimated error including systematics).
The time-averaged spectrum from T-20.35 to T+119.49 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.32 +- 0.03. The fluence in the 15-150 keV band is 2.5 +- 0.0 x 10^-05 erg/cm2. The 1-sec peak photon flux measured from T+33.82 sec in the 15-150 keV band is 16.7 +- 0.5 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1340514

Back to JG's homepage

Jochen Greiner, last update: 09-Aug-2025 [Disclaimer]