Gamma-ray Burst 250312A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 12 Mar 25 13:24:49 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1294765,   Seg_Num: 0
GRB_RA:           29.510d {+01h 58m 02s} (J2000),
                  29.769d {+01h 59m 05s} (current),
                  28.994d {+01h 55m 59s} (1950)
GRB_DEC:         -42.404d {-42d 24' 15"} (J2000),
                 -42.282d {-42d 16' 56"} (current),
                 -42.647d {-42d 38' 49"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       8729 [cnts]    Image_Peak=254 [image_cnts]
TRIGGER_DUR:     2.048 [sec] 
TRIGGER_INDEX:   271     E_range: 50-350 keV
BKG_INTEN:       96843 [cnts]
BKG_TIME:        48220.76 SOD {13:23:40.76} UT
BKG_DUR:         24 [sec]
GRB_DATE:        20746 TJD;    71 DOY;   25/03/12
GRB_TIME:        48257.63 SOD {13:24:17.63} UT
GRB_PHI:         -14.50 [deg]
GRB_THETA:        37.94 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     14.49 [sigma]
IMAGE_SIGNIF:    7.99 [sigma]
MERIT_PARAMS:     +1  +0  +0  +1  +3  -2  +0  +0 -62  +0 
SUN_POSTN:       352.86d {+23h 31m 26s}   -3.08d {-03d 05' 04"}
SUN_DIST:         51.18 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:      155.44d {+10h 21m 45s}  +12.51d {+12d 30' 54"}
MOON_DIST:       124.54 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      265.62,-69.57 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:        5.82,-49.76 [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 = 341.72,-15.54 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 12 Mar 25 13:27:08 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     1294765,   Seg_Num: 0
GRB_RA:           29.5190d {+01h 58m 04.5s} (J2000),
                  29.7786d {+01h 59m 06.8s} (current),
                  29.0033d {+01h 56m 00.7s} (1950)
GRB_DEC:         -42.3957d {-42d 23' 44.5"} (J2000),
                 -42.2738d {-42d 16' 25.6"} (current),
                 -42.6386d {-42d 38' 18.8"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       164 [cnts]
IMG_START_DATE:  20746 TJD;    71 DOY;   25/03/12
IMG_START_TIME:  48393.05 SOD {13:26:33.05} UT,   135.4 [sec] since BAT Trigger Time
CENTROID_X:      302.37,  raw= 302  [pixels]
CENTROID_Y:      276.30,  raw= 276  [pixels]
ROLL:            309.99 [deg]
GAIN:            2
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -52.79
GRB_POS_XRT_Z:   -21.73
IMAGE_URL:       sw01294765000msxps_rw.img
SUN_POSTN:       352.86d {+23h 31m 26s}   -3.08d {-03d 05' 02"}
SUN_DIST:         51.18 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:      155.45d {+10h 21m 49s}  +12.51d {+12d 30' 22"}
MOON_DIST:       124.54 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      265.59,-69.57 [deg] galactic lon,lat of the burst
ECL_COORDS:        5.83,-49.76 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.  
COMMENTS:        The object found at this position is either a very bright burst or a cosmic ray hit.  
COMMENTS:        Examine the XRT Image to differentiate (CRs are much more compact); see examples at:  
COMMENTS:        http://www.swift.psu.edu/xrt/XRT_Postage_Stamp_Image_Photo_Gallery.htm .

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 12 Mar 25 13:27:11 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     1294765,   Seg_Num: 0
GRB_RA:           29.5190d {+01h 58m 04.5s} (J2000),
                  29.7786d {+01h 59m 06.8s} (current),
                  29.0033d {+01h 56m 00.7s} (1950)
GRB_DEC:         -42.3957d {-42d 23' 44.5"} (J2000),
                 -42.2738d {-42d 16' 25.6"} (current),
                 -42.6386d {-42d 38' 18.8"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       164 [cnts]
IMG_START_DATE:  20746 TJD;    71 DOY;   25/03/12
IMG_START_TIME:  48393.05 SOD {13:26:33.05} UT,   135.4 [sec] since BAT Trigger Time
CENTROID_X:      302.37,  raw= 302  [pixels]
CENTROID_Y:      276.30,  raw= 276  [pixels]
ROLL:            309.99 [deg]
GAIN:            2
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -52.79
GRB_POS_XRT_Z:   -21.73
IMAGE_URL:       sw01294765000msxps_rw.img
SUN_POSTN:       352.86d {+23h 31m 26s}   -3.08d {-03d 05' 02"}
SUN_DIST:         51.18 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:      155.45d {+10h 21m 49s}  +12.51d {+12d 30' 21"}
MOON_DIST:       124.54 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      265.59,-69.57 [deg] galactic lon,lat of the burst
ECL_COORDS:        5.83,-49.76 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.  
COMMENTS:        The object found at this position is either a very bright burst or a cosmic ray hit.  
COMMENTS:        Examine the XRT Image to differentiate (CRs are much more compact); see examples at:  
COMMENTS:        http://www.swift.psu.edu/xrt/XRT_Postage_Stamp_Image_Photo_Gallery.htm .

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 12 Mar 25 13:26:59 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1294765,   Seg_Num: 0
GRB_RA:           29.5190d {+01h 58m 04.55s} (J2000),
                  29.7786d {+01h 59m 06.86s} (current),
                  29.0033d {+01h 56m 00.78s} (1950)
GRB_DEC:         -42.3957d {-42d 23' 44.5"} (J2000),
                 -42.2738d {-42d 16' 25.6"} (current),
                 -42.6386d {-42d 38' 18.8"} (1950)
GRB_ERROR:       4.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       7.29e-09 [erg/cm2/sec]
GRB_SIGNIF:      12.80 [sigma]
IMG_START_DATE:  20746 TJD;    71 DOY;   25/03/12
IMG_START_TIME:  48393.05 SOD {13:26:33.05} UT,   135.4 [sec] since BAT Trigger Time
TAM[0-3]:        327.64 237.13 261.65 243.41
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       352.86d {+23h 31m 26s}   -3.08d {-03d 05' 02"}
SUN_DIST:         51.18 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:      155.45d {+10h 21m 49s}  +12.51d {+12d 30' 24"}
MOON_DIST:       124.54 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      265.59,-69.57 [deg] galactic lon,lat of the burst
ECL_COORDS:        5.83,-49.76 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 0.66 arcmin from the BAT position.  
COMMENTS:        The object found at this position is either a very bright burst or a cosmic ray hit.  
COMMENTS:        Examine the XRT Image to differentiate (CRs are much more compact); see examples at:  
COMMENTS:        http://www.swift.psu.edu/xrt/XRT_Postage_Stamp_Image_Photo_Gallery.htm .

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 12 Mar 25 13:34:15 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1294765,   Seg_Num: 0
POINT_RA:         29.512d {+01h 58m 03s} (J2000)
POINT_DEC:       -42.411d {-42d 24' 40"} (J2000)
POINT_ROLL:      309.995d
IMG_START_DATE:  20746 TJD;    71 DOY;   25/03/12
IMG_START_TIME:  48685.09 SOD {13:31:25.09} UT,   427.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.354
N_STARS:         51
X_OFFSET:        527 [pixels]
Y_OFFSET:        563 [pixels]
X_MAX:           1486 [pixels]
Y_MAX:           1522 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw01294765000msufc0427.fits
SUN_POSTN:       352.86d {+23h 31m 27s}   -3.08d {-03d 04' 55"}
SUN_DIST:         51.18 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:      155.51d {+10h 22m 03s}  +12.48d {+12d 28' 45"}
MOON_DIST:       124.56 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      265.63,-69.57 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        5.81,-49.77 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 12 Mar 25 13:34:31 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1294765,   Seg_Num: 0
POINT_RA:         29.512d {+01h 58m 03s} (J2000)
POINT_DEC:       -42.411d {-42d 24' 40"} (J2000)
POINT_ROLL:      309.995d
IMG_START_DATE:  20746 TJD;    71 DOY;   25/03/12
IMG_START_TIME:  48685.09 SOD {13:31:25.09} UT,   427.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.354
N_STARS:         51
X_OFFSET:        527 [pixels]
Y_OFFSET:        563 [pixels]
X_MAX:           1486 [pixels]
Y_MAX:           1522 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw01294765000msufc0427.fits
SUN_POSTN:       352.86d {+23h 31m 27s}   -3.08d {-03d 04' 55"}
SUN_DIST:         51.18 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:      155.51d {+10h 22m 03s}  +12.48d {+12d 28' 41"}
MOON_DIST:       124.56 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      265.63,-69.57 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        5.81,-49.77 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 12 Mar 25 13:36:14 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1294765,   Seg_Num: 0
POINT_RA:         29.512d {+01h 58m 03s} (J2000)
POINT_DEC:       -42.411d {-42d 24' 40"} (J2000)
ROLL:            309.995d
IMG_START_DATE:  20746 TJD;    71 DOY;   25/03/12
IMG_START_TIME:  48685.09 SOD {13:31:25.09} UT,   427.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     763479120
X_OFFSET:        846 [pixels]
Y_OFFSET:        882 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1006
Y_GRB_POS:       1042
BINNING_INDEX:   1
IM_URL:          sw01294765000msuni0463.fits
SUN_POSTN:       352.86d {+23h 31m 27s}   -3.08d {-03d 04' 53"}
SUN_DIST:         51.18 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:      155.53d {+10h 22m 06s}  +12.47d {+12d 28' 18"}
MOON_DIST:       124.57 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      265.63,-69.57 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        5.81,-49.77 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 12 Mar 25 13:35:24 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     1294765,   Seg_Num: 0
GRB_RA:           29.5192d {+01h 58m 04.60s} (J2000),
                  29.7788d {+01h 59m 06.91s} (current),
                  29.0035d {+01h 56m 00.82s} (1950)
GRB_DEC:         -42.3959d {-42d 23' 45.2"} (J2000),
                 -42.2740d {-42d 16' 26.4"} (current),
                 -42.6388d {-42d 38' 19.6"} (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:  20746 TJD;    71 DOY;   25/03/12
IMG_START_TIME:  48642.00 SOD {13:30:42.00} UT,   384.4 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       352.86d {+23h 31m 27s}   -3.08d {-03d 04' 54"}
SUN_DIST:         51.18 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:      155.52d {+10h 22m 05s}  +12.47d {+12d 28' 29"}
MOON_DIST:       124.56 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      265.59,-69.57 [deg] galactic lon,lat of the burst
ECL_COORDS:        5.83,-49.76 [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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 12 Mar 25 13:36:20 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1294765,   Seg_Num: 0
POINT_RA:         29.512d {+01h 58m 03s} (J2000)
POINT_DEC:       -42.411d {-42d 24' 40"} (J2000)
ROLL:            309.995d
IMG_START_DATE:  20746 TJD;    71 DOY;   25/03/12
IMG_START_TIME:  48685.09 SOD {13:31:25.09} UT,   427.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     763479120
X_OFFSET:        846 [pixels]
Y_OFFSET:        882 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1006
Y_GRB_POS:       1042
BINNING_INDEX:   1
IM_URL:          sw01294765000msuni0463.fits
SUN_POSTN:       352.86d {+23h 31m 27s}   -3.08d {-03d 04' 53"}
SUN_DIST:         51.18 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:      155.53d {+10h 22m 06s}  +12.47d {+12d 28' 16"}
MOON_DIST:       124.57 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      265.63,-69.57 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        5.81,-49.77 [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:     Wed 12 Mar 25 13:45:11 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1294765,   Seg_Num: 0
POINT_RA:         29.512d {+01h 58m 03s} (J2000)
POINT_DEC:       -42.411d {-42d 24' 40"} (J2000)
POINT_ROLL:      309.995d
IMG_START_DATE:  20746 TJD;    71 DOY;   25/03/12
IMG_START_TIME:  49114.13 SOD {13:38:34.13} UT,   856.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.518
N_STARS:         51
X_OFFSET:        287 [pixels]
Y_OFFSET:        323 [pixels]
X_MAX:           1726 [pixels]
Y_MAX:           1762 [pixels]
DET_THRESH:      18
PHOTO_THRESH:    10
SL_URL:          sw01294765000msufc0856.fits
SUN_POSTN:       352.87d {+23h 31m 29s}   -3.08d {-03d 04' 44"}
SUN_DIST:         51.18 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:      155.60d {+10h 22m 23s}  +12.44d {+12d 26' 15"}
MOON_DIST:       124.59 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      265.63,-69.57 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        5.81,-49.77 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN Circular #39686
A. Melandri (INAF-OAR), V. D'Elia (SSDC & INAF-OAR), J. J. DeLaunay (PSU), S. Dichiara (PSU), R. Gupta (NASA GSFC), J. A. Kennea (PSU), M. J. Moss (GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 13:24:17 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250312A (trigger=1294765). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 29.510, -42.404 which is
```
   RA(J2000) = 01h 58m 02s
   Dec(J2000) = -42d 24' 15"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). Only the first 8 seconds of the BAT light curve are immediately available. This limited data shows a complex peak structure that extends beyond the T+8s cut-off. The peak count rate was ~1800 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 13:26:33.0 UT, 135.4 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source with an enhanced position: RA, Dec 29.51911, -42.39599 which is equivalent to:
```
   RA(J2000)  = 01h 58m 04.59s
   Dec(J2000) = -42d 23' 45.6"
```
with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 37 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 (1.79 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 3 (+2.65/-2.31) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 7.29e-09 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 427 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 0.017.
Burst Advocate for this burst is A. Melandri (andrea.melandri 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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 12 Mar 25 13:45:21 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1294765,   Seg_Num: 0
POINT_RA:         29.512d {+01h 58m 03s} (J2000)
POINT_DEC:       -42.411d {-42d 24' 40"} (J2000)
POINT_ROLL:      309.995d
IMG_START_DATE:  20746 TJD;    71 DOY;   25/03/12
IMG_START_TIME:  49114.13 SOD {13:38:34.13} UT,   856.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.518
N_STARS:         51
X_OFFSET:        287 [pixels]
Y_OFFSET:        323 [pixels]
X_MAX:           1726 [pixels]
Y_MAX:           1762 [pixels]
DET_THRESH:      18
PHOTO_THRESH:    10
SL_URL:          sw01294765000msufc0856.fits
SUN_POSTN:       352.87d {+23h 31m 29s}   -3.08d {-03d 04' 44"}
SUN_DIST:         51.18 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:      155.60d {+10h 22m 24s}  +12.44d {+12d 26' 13"}
MOON_DIST:       124.59 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      265.63,-69.57 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        5.81,-49.77 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 12 Mar 25 13:46:38 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1294765,   Seg_Num: 0
POINT_RA:         29.512d {+01h 58m 03s} (J2000)
POINT_DEC:       -42.411d {-42d 24' 40"} (J2000)
ROLL:            309.995d
IMG_START_DATE:  20746 TJD;    71 DOY;   25/03/12
IMG_START_TIME:  49114.13 SOD {13:38:34.13} UT,   856.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     763479549
X_OFFSET:        846 [pixels]
Y_OFFSET:        882 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1006
Y_GRB_POS:       1042
BINNING_INDEX:   1
IM_URL:          sw01294765000msuni0892.fits
SUN_POSTN:       352.87d {+23h 31m 29s}   -3.08d {-03d 04' 43"}
SUN_DIST:         51.18 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:      155.61d {+10h 22m 26s}  +12.43d {+12d 25' 56"}
MOON_DIST:       124.60 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      265.63,-69.57 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        5.81,-49.77 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 12 Mar 25 13:46:51 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1294765,   Seg_Num: 0
POINT_RA:         29.512d {+01h 58m 03s} (J2000)
POINT_DEC:       -42.411d {-42d 24' 40"} (J2000)
ROLL:            309.995d
IMG_START_DATE:  20746 TJD;    71 DOY;   25/03/12
IMG_START_TIME:  49114.13 SOD {13:38:34.13} UT,   856.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     763479549
X_OFFSET:        846 [pixels]
Y_OFFSET:        882 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1006
Y_GRB_POS:       1042
BINNING_INDEX:   1
IM_URL:          sw01294765000msuni0892.fits
SUN_POSTN:       352.87d {+23h 31m 29s}   -3.08d {-03d 04' 42"}
SUN_DIST:         51.18 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:      155.61d {+10h 22m 26s}  +12.43d {+12d 25' 53"}
MOON_DIST:       124.60 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      265.63,-69.57 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        5.81,-49.77 [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 Circular #39689
V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, 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. 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 GRB 250312A ( A. Melandri et al., GCN 39686) errorbox 15966 sec after notice time and 16003 sec after trigger time at 2025-03-12 17:51:00 UT, with upper limit up to 18.2 mag. Observations started at twilight. The observations began at zenith distance = 54 deg. The sun altitude is -11.5 deg.
The galactic latitude b = -69 deg., longitude l = 264 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2809737
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   16093 |         MASTER-SAAO |   C |   180 | 17.1 |        
   16292 |         MASTER-SAAO |   C |   180 | 18.2 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #39693
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
Using 1241 s of XRT Photon Counting mode data and 2 UVOT images for GRB 250312A, 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 = 29.51954, -42.39605 which is equivalent to:
```
RA (J2000): 01h 58m 4.69s
Dec (J2000): -42d 23' 45.8"
```
with an uncertainty of 2.4 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the Swift-XRT team.
GCN Circular #39697
D.N. Burrows (PSU), M. A. Williams (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), S. Dichiara (PSU) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 8.3 ks of XRT data for GRB 250312A, from 385 s to 34.7 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode.
The light curve can be modelled with a power-law decay with a decay index of alpha=0.51 (+/-0.06).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.80 (+0.22, -0.21). The best-fitting absorption column is 1.3 (+0.7, -0.6) x 10^21 cm^-2, in excess of the Galactic value of 1.8 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.9 x 10^-11 (4.7 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     1.3 (+0.7, -0.6) x 10^21 cm^-2
Galactic foreground: 1.8 x 10^20 cm^-2
Excess significance: 3.0 sigma
Photon index:	     1.80 (+0.22, -0.21)
```
If the light curve continues to decay with a power-law decay index of 0.51, the count rate at T+24 hours will be 0.022 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.5 x 10^-13 (1.0 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/01294765.
This circular is an official product of the Swift-XRT team.
GCN Circular #39765
M. H.Siegel (PSU) and A. Melandri (INAF-OAR) on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 250312A 464s after the BAT trigger (Melandri et al., GCN Circ. 39686). No optical afterglow consistent with the enhanced XRT position (Evans et al., GCN Circ. 39693) 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)         464         1563          165            >20.47
white              743         1563          223            >20.50
b                  718         1539           38            >18.84
b                 6529        33943         1081            >20.52
u                 6324        23538          403            >19.80
uvw1             21814        22713          885            >19.99
uvm2             10515        16904         1012            >19.85
uvw2              6939        28312         1082            >20.24
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.015 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #39829
Jia-Cong Liu, Shao-Lin Xiong, Peng Zhang, Yan-Qiu Zhang, Chen-Wei Wang (IHEP) report on behalf of the GECAM team:
GECAM-A detected a long burst, GRB 250312A, at 2025-03-12T13:24:17 UTC (denoted as T0), which was also observed by Swift/BAT (A. Melandri et al. 2025, GCN 39686).
According to the GECAM-A light curves in about 50-200 keV, this burst mainly consists of a pulse with a T90 of about 5.0 ± 0.2 s.
The GECAM light curve can be found here: https://www.bursthub.cn//admin/static/gecamgrb250312A.png
We note that these results are preliminary. Refined analysis will be reported. Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two microsatellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS).

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Jochen Greiner, last update: 22-Mar-2025 [Disclaimer]