Gamma-ray Burst 180425A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 25 Apr 18 06:46:36 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     828672,   Seg_Num: 0
GRB_RA:           64.469d {+04h 17m 53s} (J2000),
                  64.644d {+04h 18m 35s} (current),
                  63.992d {+04h 15m 58s} (1950)
GRB_DEC:         -32.956d {-32d 57' 20"} (J2000),
                 -32.912d {-32d 54' 42"} (current),
                 -33.077d {-33d 04' 36"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       3223 [cnts]    Image_Peak=122 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   148     E_range: 25-100 keV
BKG_INTEN:       20789 [cnts]
BKG_TIME:        24363.15 SOD {06:46:03.15} UT
BKG_DUR:         8 [sec]
GRB_DATE:        18233 TJD;   115 DOY;   18/04/25
GRB_TIME:        24381.78 SOD {06:46:21.78} UT
GRB_PHI:         -62.23 [deg]
GRB_THETA:        36.54 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     11.91 [sigma]
IMAGE_SIGNIF:    7.04 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  -3  +0  +0 -56  +0 
SUN_POSTN:        32.74d {+02h 10m 59s}  +13.20d {+13d 11' 46"}
SUN_DIST:         55.26 [deg]   Sun_angle= -2.1 [hr] (East of Sun)
MOON_POSTN:      158.40d {+10h 33m 35s}  +11.38d {+11d 22' 39"}
MOON_DIST:        99.27 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      233.48,-45.38 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       52.91,-53.16 [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 = 106.51,-16.23 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 25 Apr 18 06:48:17 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     828672,   Seg_Num: 0
GRB_RA:           64.4528d {+04h 17m 48.6s} (J2000),
                  64.6278d {+04h 18m 30.6s} (current),
                  63.9752d {+04h 15m 54.0s} (1950)
GRB_DEC:         -32.9538d {-32d 57' 13.6"} (J2000),
                 -32.9100d {-32d 54' 35.9"} (current),
                 -33.0749d {-33d 04' 29.6"} (1950)
GRB_ERROR:       6.1 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       25 [cnts]
IMG_START_DATE:  18233 TJD;   115 DOY;   18/04/25
IMG_START_TIME:  24460.01 SOD {06:47:40.01} UT,   78.2 [sec] since BAT Trigger Time
CENTROID_X:      257.49,  raw= 257  [pixels]
CENTROID_Y:      313.76,  raw= 314  [pixels]
ROLL:            321.43 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   36.22
GRB_POS_XRT_Z:   -115.27
IMAGE_URL:       sw00828672000msxps_rw.img
SUN_POSTN:        32.75d {+02h 10m 59s}  +13.20d {+13d 11' 47"}
SUN_DIST:         55.25 [deg]   Sun_angle= -2.1 [hr] (East of Sun)
MOON_POSTN:      158.41d {+10h 33m 39s}  +11.37d {+11d 22' 22"}
MOON_DIST:        99.29 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      233.48,-45.40 [deg] galactic lon,lat of the burst
ECL_COORDS:       52.89,-53.15 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 25 Apr 18 06:48:16 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     828672,   Seg_Num: 0
GRB_RA:           64.4528d {+04h 17m 48.6s} (J2000),
                  64.6278d {+04h 18m 30.6s} (current),
                  63.9752d {+04h 15m 54.0s} (1950)
GRB_DEC:         -32.9538d {-32d 57' 13.6"} (J2000),
                 -32.9100d {-32d 54' 35.9"} (current),
                 -33.0749d {-33d 04' 29.6"} (1950)
GRB_ERROR:       6.1 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       25 [cnts]
IMG_START_DATE:  18233 TJD;   115 DOY;   18/04/25
IMG_START_TIME:  24460.01 SOD {06:47:40.01} UT,   78.2 [sec] since BAT Trigger Time
CENTROID_X:      257.49,  raw= 257  [pixels]
CENTROID_Y:      313.76,  raw= 314  [pixels]
ROLL:            321.43 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   36.22
GRB_POS_XRT_Z:   -115.27
IMAGE_URL:       sw00828672000msxps_rw.img
SUN_POSTN:        32.75d {+02h 10m 59s}  +13.20d {+13d 11' 47"}
SUN_DIST:         55.25 [deg]   Sun_angle= -2.1 [hr] (East of Sun)
MOON_POSTN:      158.41d {+10h 33m 39s}  +11.37d {+11d 22' 22"}
MOON_DIST:        99.29 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      233.48,-45.40 [deg] galactic lon,lat of the burst
ECL_COORDS:       52.89,-53.15 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 25 Apr 18 06:48:04 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     828672,   Seg_Num: 0
GRB_RA:           64.4528d {+04h 17m 48.67s} (J2000),
                  64.6278d {+04h 18m 30.67s} (current),
                  63.9752d {+04h 15m 54.03s} (1950)
GRB_DEC:         -32.9538d {-32d 57' 13.6"} (J2000),
                 -32.9100d {-32d 54' 35.9"} (current),
                 -33.0749d {-33d 04' 29.6"} (1950)
GRB_ERROR:       6.3 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       5.37e-10 [erg/cm2/sec]
GRB_SIGNIF:      5.00 [sigma]
IMG_START_DATE:  18233 TJD;   115 DOY;   18/04/25
IMG_START_TIME:  24460.01 SOD {06:47:40.01} UT,   78.2 [sec] since BAT Trigger Time
TAM[0-3]:        327.65 237.21 261.49 243.41
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:        32.75d {+02h 10m 59s}  +13.20d {+13d 11' 47"}
SUN_DIST:         55.25 [deg]   Sun_angle= -2.1 [hr] (East of Sun)
MOON_POSTN:      158.41d {+10h 33m 38s}  +11.37d {+11d 22' 24"}
MOON_DIST:        99.29 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      233.48,-45.40 [deg] galactic lon,lat of the burst
ECL_COORDS:       52.89,-53.15 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 0.84 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 25 Apr 18 06:50:06 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     828672,   Seg_Num: 0
GRB_RA:           64.469d {+04h 17m 53s} (J2000),
                  64.644d {+04h 18m 35s} (current),
                  63.992d {+04h 15m 58s} (1950)
GRB_DEC:         -32.956d {-32d 57' 20"} (J2000),
                 -32.912d {-32d 54' 42"} (current),
                 -33.077d {-33d 04' 36"} (1950)
GRB_DATE:        18233 TJD;   115 DOY;   18/04/25
GRB_TIME:        24381.78 SOD {06:46:21.78} UT
TRIGGER_INDEX:   148
GRB_PHI:         -62.23 [deg]
GRB_THETA:        36.54 [deg]
DELTA_TIME:      58.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     11.91 [sigma]
IMAGE_SIGNIF:    7.04 [sigma]
LC_URL:          sw00828672000msb.lc
SUN_POSTN:        32.75d {+02h 10m 59s}  +13.20d {+13d 11' 49"}
SUN_DIST:         55.26 [deg]   Sun_angle= -2.1 [hr] (East of Sun)
MOON_POSTN:      158.43d {+10h 33m 43s}  +11.37d {+11d 22' 03"}
MOON_DIST:        99.29 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      233.48,-45.38 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       52.91,-53.16 [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 = 106.51,-16.23 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 25 Apr 18 06:50:51 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     828672,   Seg_Num: 0
POINT_RA:         64.486d {+04h 17m 57s} (J2000)
POINT_DEC:       -32.972d {-32d 58' 17"} (J2000)
POINT_ROLL:      321.426d
IMG_START_DATE:  18233 TJD;   115 DOY;   18/04/25
IMG_START_TIME:  24469.75 SOD {06:47:49.75} UT,   88.0 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.040
N_STARS:         37
X_OFFSET:        632 [pixels]
Y_OFFSET:        472 [pixels]
X_MAX:           1591 [pixels]
Y_MAX:           1431 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00828672000msufc0087.fits
SUN_POSTN:        32.75d {+02h 10m 59s}  +13.20d {+13d 11' 50"}
SUN_DIST:         55.28 [deg]   Sun_angle= -2.1 [hr] (East of Sun)
MOON_POSTN:      158.44d {+10h 33m 44s}  +11.37d {+11d 21' 55"}
MOON_DIST:        99.28 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      233.51,-45.37 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       52.92,-53.18 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 25 Apr 18 06:51:07 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     828672,   Seg_Num: 0
POINT_RA:         64.486d {+04h 17m 57s} (J2000)
POINT_DEC:       -32.972d {-32d 58' 17"} (J2000)
POINT_ROLL:      321.426d
IMG_START_DATE:  18233 TJD;   115 DOY;   18/04/25
IMG_START_TIME:  24469.75 SOD {06:47:49.75} UT,   88.0 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.040
N_STARS:         37
X_OFFSET:        632 [pixels]
Y_OFFSET:        472 [pixels]
X_MAX:           1591 [pixels]
Y_MAX:           1431 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00828672000msufc0087.fits
SUN_POSTN:        32.75d {+02h 10m 59s}  +13.20d {+13d 11' 50"}
SUN_DIST:         55.28 [deg]   Sun_angle= -2.1 [hr] (East of Sun)
MOON_POSTN:      158.44d {+10h 33m 45s}  +11.36d {+11d 21' 53"}
MOON_DIST:        99.28 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      233.51,-45.37 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       52.92,-53.18 [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 25 Apr 18 06:52:13 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     828672,   Seg_Num: 0
POINT_RA:         64.486d {+04h 17m 57s} (J2000)
POINT_DEC:       -32.972d {-32d 58' 17"} (J2000)
ROLL:            321.426d
IMG_START_DATE:  18233 TJD;   115 DOY;   18/04/25
IMG_START_TIME:  24469.75 SOD {06:47:49.75} UT,   88.0 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     546331690
X_OFFSET:        983 [pixels]
Y_OFFSET:        698 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1143
Y_GRB_POS:       858
BINNING_INDEX:   1
IM_URL:          sw00828672000msuni0108.fits
SUN_POSTN:        32.75d {+02h 11m 00s}  +13.20d {+13d 11' 51"}
SUN_DIST:         55.28 [deg]   Sun_angle= -2.1 [hr] (East of Sun)
MOON_POSTN:      158.45d {+10h 33m 47s}  +11.36d {+11d 21' 42"}
MOON_DIST:        99.29 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      233.51,-45.37 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       52.92,-53.18 [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:     Wed 25 Apr 18 06:52:27 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     828672,   Seg_Num: 0
POINT_RA:         64.486d {+04h 17m 57s} (J2000)
POINT_DEC:       -32.972d {-32d 58' 17"} (J2000)
ROLL:            321.426d
IMG_START_DATE:  18233 TJD;   115 DOY;   18/04/25
IMG_START_TIME:  24469.75 SOD {06:47:49.75} UT,   88.0 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     546331690
X_OFFSET:        983 [pixels]
Y_OFFSET:        698 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1143
Y_GRB_POS:       858
BINNING_INDEX:   1
IM_URL:          sw00828672000msuni0108.fits
SUN_POSTN:        32.75d {+02h 11m 00s}  +13.20d {+13d 11' 51"}
SUN_DIST:         55.28 [deg]   Sun_angle= -2.1 [hr] (East of Sun)
MOON_POSTN:      158.45d {+10h 33m 48s}  +11.36d {+11d 21' 39"}
MOON_DIST:        99.29 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      233.51,-45.37 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       52.92,-53.18 [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:     Wed 25 Apr 18 06:59:28 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     828672,   Seg_Num: 0
POINT_RA:         64.487d {+04h 17m 57s} (J2000)
POINT_DEC:       -32.975d {-32d 58' 29"} (J2000)
POINT_ROLL:      321.427d
IMG_START_DATE:  18233 TJD;   115 DOY;   18/04/25
IMG_START_TIME:  24683.43 SOD {06:51:23.43} UT,   301.7 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.672
N_STARS:         32
X_OFFSET:        663 [pixels]
Y_OFFSET:        378 [pixels]
X_MAX:           1622 [pixels]
Y_MAX:           1337 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw00828672000msufc0301.fits
SUN_POSTN:        32.75d {+02h 11m 01s}  +13.20d {+13d 11' 57"}
SUN_DIST:         55.28 [deg]   Sun_angle= -2.1 [hr] (East of Sun)
MOON_POSTN:      158.52d {+10h 34m 04s}  +11.34d {+11d 20' 28"}
MOON_DIST:        99.34 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      233.51,-45.37 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       52.92,-53.18 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 25 Apr 18 06:59:39 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     828672,   Seg_Num: 0
POINT_RA:         64.487d {+04h 17m 57s} (J2000)
POINT_DEC:       -32.975d {-32d 58' 29"} (J2000)
POINT_ROLL:      321.427d
IMG_START_DATE:  18233 TJD;   115 DOY;   18/04/25
IMG_START_TIME:  24683.43 SOD {06:51:23.43} UT,   301.7 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.672
N_STARS:         32
X_OFFSET:        663 [pixels]
Y_OFFSET:        378 [pixels]
X_MAX:           1622 [pixels]
Y_MAX:           1337 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw00828672000msufc0301.fits
SUN_POSTN:        32.75d {+02h 11m 01s}  +13.20d {+13d 11' 57"}
SUN_DIST:         55.28 [deg]   Sun_angle= -2.1 [hr] (East of Sun)
MOON_POSTN:      158.52d {+10h 34m 04s}  +11.34d {+11d 20' 26"}
MOON_DIST:        99.34 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      233.51,-45.37 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       52.92,-53.18 [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 25 Apr 18 07:00:40 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     828672,   Seg_Num: 0
POINT_RA:         64.487d {+04h 17m 57s} (J2000)
POINT_DEC:       -32.975d {-32d 58' 29"} (J2000)
ROLL:            321.427d
IMG_START_DATE:  18233 TJD;   115 DOY;   18/04/25
IMG_START_TIME:  24683.43 SOD {06:51:23.43} UT,   301.7 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     546331904
X_OFFSET:        983 [pixels]
Y_OFFSET:        698 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1143
Y_GRB_POS:       858
BINNING_INDEX:   1
IM_URL:          sw00828672000msuni0322.fits
SUN_POSTN:        32.75d {+02h 11m 01s}  +13.20d {+13d 11' 58"}
SUN_DIST:         55.28 [deg]   Sun_angle= -2.1 [hr] (East of Sun)
MOON_POSTN:      158.53d {+10h 34m 06s}  +11.34d {+11d 20' 16"}
MOON_DIST:        99.34 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      233.51,-45.37 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       52.92,-53.18 [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 #22672
F. E. Marshall (NASA/GSFC), P. D'Avanzo (INAF-OAB), P. A. Evans (U Leicester), H. A. Krimm (NSF/USRA), A. Melandri (INAF-OAB), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift Observatory Team:
At 06:46:21 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180425A (trigger=828672). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 64.469, -32.956 which is
```
   RA(J2000) = 04h 17m 53s
   Dec(J2000) = -32d 57' 20"
```
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 15 sec. The peak count rate was ~1800 counts/sec (15-350 keV), at ~2 sec after the trigger.
The XRT began observing the field at 06:47:40.0 UT, 78.2 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source with an enhanced position: RA, Dec 64.4517, -32.9519 which is equivalent to:
```
   RA(J2000)  = 04h 17m 48.41s
   Dec(J2000) = -32d 57' 06.9"
```
with an uncertainty of 2.2 arcseconds (radius, 90% containment). This location is 54 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 http://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 (2.90 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 2 (+2.26/-2.02) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 5.37e-10 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 87 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 0.03.
Burst Advocate for this burst is F. E. Marshall (marshall AT milkyway.gsfc.nasa.gov). 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/too.html.)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 25 Apr 18 07:00:55 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     828672,   Seg_Num: 0
POINT_RA:         64.487d {+04h 17m 57s} (J2000)
POINT_DEC:       -32.975d {-32d 58' 29"} (J2000)
ROLL:            321.427d
IMG_START_DATE:  18233 TJD;   115 DOY;   18/04/25
IMG_START_TIME:  24683.43 SOD {06:51:23.43} UT,   301.7 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     546331904
X_OFFSET:        983 [pixels]
Y_OFFSET:        698 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1143
Y_GRB_POS:       858
BINNING_INDEX:   1
IM_URL:          sw00828672000msuni0322.fits
SUN_POSTN:        32.75d {+02h 11m 01s}  +13.20d {+13d 11' 58"}
SUN_DIST:         55.28 [deg]   Sun_angle= -2.1 [hr] (East of Sun)
MOON_POSTN:      158.53d {+10h 34m 07s}  +11.34d {+11d 20' 13"}
MOON_DIST:        99.34 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      233.51,-45.37 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       52.92,-53.18 [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:     Wed 25 Apr 18 06:59:58 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     828672,   Seg_Num: 0
GRB_RA:           64.4517d {+04h 17m 48.40s} (J2000),
                  64.6267d {+04h 18m 30.41s} (current),
                  63.9741d {+04h 15m 53.77s} (1950)
GRB_DEC:         -32.9519d {-32d 57' 06.8"} (J2000),
                 -32.9081d {-32d 54' 29.0"} (current),
                 -33.0730d {-33d 04' 22.8"} (1950)
GRB_ERROR:       2.2 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  18233 TJD;   115 DOY;   18/04/25
IMG_START_TIME:  24616.00 SOD {06:50:16.00} UT,   234.2 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        32.75d {+02h 11m 01s}  +13.20d {+13d 11' 57"}
SUN_DIST:         55.25 [deg]   Sun_angle= -2.1 [hr] (East of Sun)
MOON_POSTN:      158.52d {+10h 34m 05s}  +11.34d {+11d 20' 23"}
MOON_DIST:        99.36 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      233.47,-45.40 [deg] galactic lon,lat of the burst
ECL_COORDS:       52.88,-53.15 [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 0.11% < P(seren) < 0.58%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 25 Apr 18 07:07:12 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     828672,   Seg_Num: 0
POINT_RA:         64.487d {+04h 17m 57s} (J2000)
POINT_DEC:       -32.975d {-32d 58' 29"} (J2000)
POINT_ROLL:      321.427d
IMG_START_DATE:  18233 TJD;   115 DOY;   18/04/25
IMG_START_TIME:  25260.34 SOD {07:01:00.34} UT,   878.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.120
N_STARS:         78
X_OFFSET:        423 [pixels]
Y_OFFSET:        138 [pixels]
X_MAX:           1862 [pixels]
Y_MAX:           1577 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw00828672000msufc0878.fits
SUN_POSTN:        32.76d {+02h 11m 02s}  +13.20d {+13d 12' 03"}
SUN_DIST:         55.28 [deg]   Sun_angle= -2.1 [hr] (East of Sun)
MOON_POSTN:      158.59d {+10h 34m 21s}  +11.32d {+11d 19' 10"}
MOON_DIST:        99.38 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      233.51,-45.37 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       52.92,-53.18 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 25 Apr 18 07:07:31 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     828672,   Seg_Num: 0
POINT_RA:         64.487d {+04h 17m 57s} (J2000)
POINT_DEC:       -32.975d {-32d 58' 29"} (J2000)
POINT_ROLL:      321.427d
IMG_START_DATE:  18233 TJD;   115 DOY;   18/04/25
IMG_START_TIME:  25260.34 SOD {07:01:00.34} UT,   878.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.120
N_STARS:         78
X_OFFSET:        423 [pixels]
Y_OFFSET:        138 [pixels]
X_MAX:           1862 [pixels]
Y_MAX:           1577 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw00828672000msufc0878.fits
SUN_POSTN:        32.76d {+02h 11m 02s}  +13.20d {+13d 12' 03"}
SUN_DIST:         55.28 [deg]   Sun_angle= -2.1 [hr] (East of Sun)
MOON_POSTN:      158.59d {+10h 34m 22s}  +11.32d {+11d 19' 06"}
MOON_DIST:        99.39 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      233.51,-45.37 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       52.92,-53.18 [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 25 Apr 18 07:08:35 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     828672,   Seg_Num: 0
POINT_RA:         64.487d {+04h 17m 57s} (J2000)
POINT_DEC:       -32.975d {-32d 58' 29"} (J2000)
ROLL:            321.427d
IMG_START_DATE:  18233 TJD;   115 DOY;   18/04/25
IMG_START_TIME:  25260.34 SOD {07:01:00.34} UT,   878.6 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     546332481
X_OFFSET:        982 [pixels]
Y_OFFSET:        697 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1142
Y_GRB_POS:       857
BINNING_INDEX:   1
IM_URL:          sw00828672000msuni0899.fits
SUN_POSTN:        32.76d {+02h 11m 02s}  +13.20d {+13d 12' 04"}
SUN_DIST:         55.28 [deg]   Sun_angle= -2.1 [hr] (East of Sun)
MOON_POSTN:      158.60d {+10h 34m 24s}  +11.32d {+11d 18' 56"}
MOON_DIST:        99.39 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      233.51,-45.37 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       52.92,-53.18 [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 25 Apr 18 07:08:48 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     828672,   Seg_Num: 0
POINT_RA:         64.487d {+04h 17m 57s} (J2000)
POINT_DEC:       -32.975d {-32d 58' 29"} (J2000)
ROLL:            321.427d
IMG_START_DATE:  18233 TJD;   115 DOY;   18/04/25
IMG_START_TIME:  25260.34 SOD {07:01:00.34} UT,   878.6 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     546332481
X_OFFSET:        982 [pixels]
Y_OFFSET:        697 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1142
Y_GRB_POS:       857
BINNING_INDEX:   1
IM_URL:          sw00828672000msuni0899.fits
SUN_POSTN:        32.76d {+02h 11m 02s}  +13.20d {+13d 12' 04"}
SUN_DIST:         55.28 [deg]   Sun_angle= -2.1 [hr] (East of Sun)
MOON_POSTN:      158.60d {+10h 34m 25s}  +11.31d {+11d 18' 53"}
MOON_DIST:        99.39 [deg]
MOON_ILLUM:      76 [%]
GAL_COORDS:      233.51,-45.37 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       52.92,-53.18 [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 #22673
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team.
Using 1083 s of XRT Photon Counting mode data and 2 UVOT images for GRB 180425A, 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 = 64.45159, -32.95216 which is equivalent to:
```
RA (J2000): 04h 17m 48.38s
Dec (J2000): -32d 57' 07.8"
```
with an uncertainty of 1.8 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 #22674
S.W.K. Emery (UCL-MSSL) and F. E. Marshall (NASA/GSFC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 180425A 88 s after the BAT trigger (Marshall et al., GCN Circ. 22672). No optical afterglow consistent with the XRT position (Osborne et al., GCN Circ. 22673) 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 early exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white               88         1201          353         >21.0
u                  302         1152          285         >20.5
v                  631         1250           78         >18.5
b                  557         1176           58         >19.4
uvw1               680         1299           78         >19.0
uvm2               827         1275           58         >18.5
uvw2               606         1226           58         >19.0
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.03 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #22675
T. Sakamoto (AGU), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (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 180425A (trigger #828672) (Marshall, et al., GCN Circ. 22672). The BAT ground-calculated position is RA, Dec = 64.450, -32.949 deg which is
```
  RA(J2000)  =  04h 17m 48.1s
  Dec(J2000) = -32d 56' 58.1"
```
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 27%.
The mask-weighted light curve shows a single triangular shaped peak beginning at T-2 sec, peaking at T+3 sec and declining to background by T+14 sec. T90 (15-350 keV) is 11.2 +- 2.6 sec (estimated error including systematics).
The time-averaged spectrum from T+0.06 to T+12.73 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.35 +- 0.13. The fluence in the 15-150 keV band is 1.1 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+2.33 sec in the 15-150 keV band is 2.2 +- 0.3 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/828672/BA/
GCN Circular #22676
P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Tohuvavohu (PSU), S. J. LaPorte (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and F.E. Marshall report on behalf of the Swift-XRT team:
We have analysed 6.7 ks of XRT data for GRB 180425A (Marshall et al. GCN Circ. 22672), from 84 s to 23.0 ks after the BAT trigger. The data comprise 132 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN Circ. 22673).
The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=1.20 (+0.11, -0.12). At T+446 s the decay steepens to an alpha of 2.09 (+0.33, -0.28) before breaking again at T+2630 s to a final decay with index alpha=0.34 (+/-0.30).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.02 (+0.15, -0.14). The best-fitting absorption column is 8.0 (+3.8, -3.4) x 10^20 cm^-2, in excess of the Galactic value of 2.9 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.98 (+0.19, -0.18) and a best-fitting absorption column of 1.2 (+/-0.5) 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 (4.2 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     1.2 (+/-0.5) x 10^21 cm^-2
Galactic foreground: 2.9 x 10^20 cm^-2
Excess significance: 3.0 sigma
Photon index:	     1.98 (+0.19, -0.18)
```
If the light curve continues to decay with a power-law decay index of 0.34, the count rate at T+24 hours will be 0.016 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.3 x 10^-13 (6.6 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00828672.
This circular is an official product of the Swift-XRT team.

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Jochen Greiner, last update: 25-Apr-2018 [Disclaimer]