Gamma-ray Burst 180721A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

 
TITLE:           GCN/SWIFT NOTICE 
NOTICE_DATE:     Sat 21 Jul 18 11:07:10 UT 
NOTICE_TYPE:     Swift-BAT GRB Position 
TRIGGER_NUM:     849018,   Seg_Num: 0 
GRB_RA:          347.695d {+23h 10m 47s} (J2000), 
                 347.931d {+23h 11m 43s} (current), 
                 347.059d {+23h 08m 14s} (1950) 
GRB_DEC:          +4.880d {+04d 52' 47"} (J2000), 
                  +4.981d {+04d 58' 50"} (current), 
                  +4.608d {+04d 36' 29"} (1950) 
GRB_ERROR:       3.00 [arcmin radius, statistical only] 
GRB_INTEN:       3334 [cnts]    Image_Peak=174 [image_cnts] 
TRIGGER_DUR:     1.024 [sec]  
TRIGGER_INDEX:   146     E_range: 25-100 keV 
BKG_INTEN:       20057 [cnts] 
BKG_TIME:        39994.70 SOD {11:06:34.70} UT 
BKG_DUR:         8 [sec] 
GRB_DATE:        18320 TJD;   202 DOY;   18/07/21 
GRB_TIME:        40008.39 SOD {11:06:48.39} UT 
GRB_PHI:         -177.97 [deg] 
GRB_THETA:         5.16 [deg] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     14.28 [sigma] 
IMAGE_SIGNIF:    7.61 [sigma] 
MERIT_PARAMS:     +1  +0  +0  +0  +2  -2  +0  +0 +61  +0  
SUN_POSTN:       120.78d {+08h 03m 07s}  +20.43d {+20d 25' 37"} 
SUN_DIST:        127.20 [deg]   Sun_angle= 8.9 [hr] (West of Sun) 
MOON_POSTN:      227.21d {+15h 08m 52s}  -12.22d {-12d 13' 21"} 
MOON_DIST:       121.04 [deg] 
MOON_ILLUM:      67 [%] 
GAL_COORDS:       81.90,-49.80 [deg] galactic lon,lat of the burst (or transient) 
ECL_COORDS:      350.61,  9.35 [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 = 195.88,20.16 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 21 Jul 18 11:08:27 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     849018,   Seg_Num: 0
GRB_RA:          347.7102d {+23h 10m 50.4s} (J2000),
                 347.9460d {+23h 11m 47.0s} (current),
                 347.0747d {+23h 08m 17.9s} (1950)
GRB_DEC:          +4.8540d {+04d 51' 14.4"} (J2000),
                  +4.9550d {+04d 57' 17.8"} (current),
                  +4.5823d {+04d 34' 56.3"} (1950)
GRB_ERROR:       5.8 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       28 [cnts]
IMG_START_DATE:  18320 TJD;   202 DOY;   18/07/21
IMG_START_TIME:  40065.30 SOD {11:07:45.30} UT,   56.9 [sec] since BAT Trigger Time
CENTROID_X:      313.34,  raw= 313  [pixels]
CENTROID_Y:      248.65,  raw= 249  [pixels]
ROLL:            59.58 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -117.25
GRB_POS_XRT_Z:   16.36
IMAGE_URL:       sw00849018000msxps_rw.img
SUN_POSTN:       120.78d {+08h 03m 07s}  +20.43d {+20d 25' 37"}
SUN_DIST:        127.20 [deg]   Sun_angle= 8.9 [hr] (West of Sun)
MOON_POSTN:      227.23d {+15h 08m 54s}  -12.23d {-12d 13' 32"}
MOON_DIST:       121.04 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:       81.90,-49.83 [deg] galactic lon,lat of the burst
ECL_COORDS:      350.61,  9.32 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 21 Jul 18 11:08:28 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     849018,   Seg_Num: 0
GRB_RA:          347.7102d {+23h 10m 50.4s} (J2000),
                 347.9460d {+23h 11m 47.0s} (current),
                 347.0747d {+23h 08m 17.9s} (1950)
GRB_DEC:          +4.8540d {+04d 51' 14.4"} (J2000),
                  +4.9550d {+04d 57' 17.8"} (current),
                  +4.5823d {+04d 34' 56.3"} (1950)
GRB_ERROR:       5.8 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       28 [cnts]
IMG_START_DATE:  18320 TJD;   202 DOY;   18/07/21
IMG_START_TIME:  40065.30 SOD {11:07:45.30} UT,   56.9 [sec] since BAT Trigger Time
CENTROID_X:      313.34,  raw= 313  [pixels]
CENTROID_Y:      248.65,  raw= 249  [pixels]
ROLL:            59.58 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -117.25
GRB_POS_XRT_Z:   16.36
IMAGE_URL:       sw00849018000msxps_rw.img
SUN_POSTN:       120.78d {+08h 03m 07s}  +20.43d {+20d 25' 37"}
SUN_DIST:        127.20 [deg]   Sun_angle= 8.9 [hr] (West of Sun)
MOON_POSTN:      227.23d {+15h 08m 54s}  -12.23d {-12d 13' 32"}
MOON_DIST:       121.04 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:       81.90,-49.83 [deg] galactic lon,lat of the burst
ECL_COORDS:      350.61,  9.32 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 21 Jul 18 11:08:15 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     849018,   Seg_Num: 0
GRB_RA:          347.7102d {+23h 10m 50.44s} (J2000),
                 347.9460d {+23h 11m 47.04s} (current),
                 347.0747d {+23h 08m 17.92s} (1950)
GRB_DEC:          +4.8540d {+04d 51' 14.4"} (J2000),
                  +4.9550d {+04d 57' 17.8"} (current),
                  +4.5823d {+04d 34' 56.3"} (1950)
GRB_ERROR:       5.9 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       7.38e-10 [erg/cm2/sec]
GRB_SIGNIF:      5.29 [sigma]
IMG_START_DATE:  18320 TJD;   202 DOY;   18/07/21
IMG_START_TIME:  40065.30 SOD {11:07:45.30} UT,   56.9 [sec] since BAT Trigger Time
TAM[0-3]:        327.68 237.18 261.66 243.76
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       120.78d {+08h 03m 07s}  +20.43d {+20d 25' 37"}
SUN_DIST:        127.20 [deg]   Sun_angle= 8.9 [hr] (West of Sun)
MOON_POSTN:      227.22d {+15h 08m 54s}  -12.23d {-12d 13' 30"}
MOON_DIST:       121.04 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:       81.90,-49.83 [deg] galactic lon,lat of the burst
ECL_COORDS:      350.61,  9.32 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 1.78 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 21 Jul 18 11:10:26 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     849018,   Seg_Num: 0
GRB_RA:          347.695d {+23h 10m 47s} (J2000),
                 347.931d {+23h 11m 43s} (current),
                 347.059d {+23h 08m 14s} (1950)
GRB_DEC:          +4.880d {+04d 52' 47"} (J2000),
                  +4.981d {+04d 58' 50"} (current),
                  +4.608d {+04d 36' 29"} (1950)
GRB_DATE:        18320 TJD;   202 DOY;   18/07/21
GRB_TIME:        40008.39 SOD {11:06:48.39} UT
TRIGGER_INDEX:   146
GRB_PHI:         -177.97 [deg]
GRB_THETA:         5.16 [deg]
DELTA_TIME:      71.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     14.28 [sigma]
IMAGE_SIGNIF:    7.61 [sigma]
LC_URL:          sw00849018000msb.lc
SUN_POSTN:       120.78d {+08h 03m 07s}  +20.43d {+20d 25' 36"}
SUN_DIST:        127.20 [deg]   Sun_angle= 8.9 [hr] (West of Sun)
MOON_POSTN:      227.24d {+15h 08m 58s}  -12.23d {-12d 13' 50"}
MOON_DIST:       121.02 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:       81.90,-49.80 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      350.61,  9.35 [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 = 195.88,20.16 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 21 Jul 18 11:16:15 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     849018,   Seg_Num: 0
POINT_RA:        347.699d {+23h 10m 48s} (J2000)
POINT_DEC:        +4.882d {+04d 52' 56"} (J2000)
POINT_ROLL:      59.584d
IMG_START_DATE:  18320 TJD;   202 DOY;   18/07/21
IMG_START_TIME:  40128.21 SOD {11:08:48.21} UT,   119.8 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.301
N_STARS:         190
X_OFFSET:        0 [pixels]
Y_OFFSET:        0 [pixels]
X_MAX:           2047 [pixels]
Y_MAX:           2047 [pixels]
DET_THRESH:      5
PHOTO_THRESH:    2
SL_URL:          sw00849018000msufc0119.fits
SUN_POSTN:       120.78d {+08h 03m 08s}  +20.43d {+20d 25' 33"}
SUN_DIST:        127.20 [deg]   Sun_angle= 8.9 [hr] (West of Sun)
MOON_POSTN:      227.29d {+15h 09m 10s}  -12.25d {-12d 14' 43"}
MOON_DIST:       120.97 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:       81.91,-49.80 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      350.61,  9.35 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 21 Jul 18 11:16:28 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     849018,   Seg_Num: 0
POINT_RA:        347.699d {+23h 10m 48s} (J2000)
POINT_DEC:        +4.882d {+04d 52' 56"} (J2000)
POINT_ROLL:      59.584d
IMG_START_DATE:  18320 TJD;   202 DOY;   18/07/21
IMG_START_TIME:  40128.21 SOD {11:08:48.21} UT,   119.8 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.301
N_STARS:         190
X_OFFSET:        0 [pixels]
Y_OFFSET:        0 [pixels]
X_MAX:           2047 [pixels]
Y_MAX:           2047 [pixels]
DET_THRESH:      5
PHOTO_THRESH:    2
SL_URL:          sw00849018000msufc0119.fits
SUN_POSTN:       120.78d {+08h 03m 08s}  +20.43d {+20d 25' 33"}
SUN_DIST:        127.20 [deg]   Sun_angle= 8.9 [hr] (West of Sun)
MOON_POSTN:      227.29d {+15h 09m 11s}  -12.25d {-12d 14' 45"}
MOON_DIST:       120.97 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:       81.91,-49.80 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      350.61,  9.35 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 21 Jul 18 11:17:20 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     849018,   Seg_Num: 0
POINT_RA:        347.699d {+23h 10m 48s} (J2000)
POINT_DEC:        +4.882d {+04d 52' 56"} (J2000)
ROLL:            59.584d
IMG_START_DATE:  18320 TJD;   202 DOY;   18/07/21
IMG_START_TIME:  40128.21 SOD {11:08:48.21} UT,   119.8 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     553864149
X_OFFSET:        875 [pixels]
Y_OFFSET:        1082 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1035
Y_GRB_POS:       1242
BINNING_INDEX:   1
IM_URL:          sw00849018000msuni0141.fits
SUN_POSTN:       120.79d {+08h 03m 09s}  +20.43d {+20d 25' 32"}
SUN_DIST:        127.20 [deg]   Sun_angle= 8.9 [hr] (West of Sun)
MOON_POSTN:      227.30d {+15h 09m 12s}  -12.25d {-12d 14' 52"}
MOON_DIST:       120.96 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:       81.91,-49.80 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      350.61,  9.35 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 21 Jul 18 11:17:35 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     849018,   Seg_Num: 0
POINT_RA:        347.699d {+23h 10m 48s} (J2000)
POINT_DEC:        +4.882d {+04d 52' 56"} (J2000)
ROLL:            59.584d
IMG_START_DATE:  18320 TJD;   202 DOY;   18/07/21
IMG_START_TIME:  40128.21 SOD {11:08:48.21} UT,   119.8 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     553864149
X_OFFSET:        875 [pixels]
Y_OFFSET:        1082 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1035
Y_GRB_POS:       1242
BINNING_INDEX:   1
IM_URL:          sw00849018000msuni0141.fits
SUN_POSTN:       120.79d {+08h 03m 09s}  +20.43d {+20d 25' 32"}
SUN_DIST:        127.20 [deg]   Sun_angle= 8.9 [hr] (West of Sun)
MOON_POSTN:      227.30d {+15h 09m 13s}  -12.25d {-12d 14' 55"}
MOON_DIST:       120.96 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:       81.91,-49.80 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      350.61,  9.35 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 21 Jul 18 11:16:49 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     849018,   Seg_Num: 0
GRB_RA:          347.7099d {+23h 10m 50.37s} (J2000),
                 347.9457d {+23h 11m 46.97s} (current),
                 347.0744d {+23h 08m 17.85s} (1950)
GRB_DEC:          +4.8552d {+04d 51' 18.7"} (J2000),
                  +4.9562d {+04d 57' 22.1"} (current),
                  +4.5835d {+04d 35' 00.6"} (1950)
GRB_ERROR:       2.3 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  18320 TJD;   202 DOY;   18/07/21
IMG_START_TIME:  40107.00 SOD {11:08:27.00} UT,   98.6 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       120.79d {+08h 03m 08s}  +20.43d {+20d 25' 33"}
SUN_DIST:        127.20 [deg]   Sun_angle= 8.9 [hr] (West of Sun)
MOON_POSTN:      227.30d {+15h 09m 11s}  -12.25d {-12d 14' 48"}
MOON_DIST:       120.97 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:       81.90,-49.83 [deg] galactic lon,lat of the burst
ECL_COORDS:      350.61,  9.32 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        This position was enhanced using UVOT field astrometry.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN Circular #22994
B. Sbarufatti (PSU), F. E. Marshall (NASA/GSFC) and D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift Observatory Team:
At 11:06:48 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180721A (trigger=849018). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 347.695, +4.880 which is
```
   RA(J2000) = 23h 10m 47s
   Dec(J2000) = +04d 52' 47"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 60 sec. The peak count rate was ~1800 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 11:07:45.3 UT, 56.9 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source with an enhanced position: RA, Dec 347.7100, 4.8553 which is equivalent to:
```
   RA(J2000)  = 23h 10m 50.41s
   Dec(J2000) = +04d 51' 19.1"
```
with an uncertainty of 2.3 arcseconds (radius, 90% containment). This location is 103 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 (6.47 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.7 (+3.22/-2.74) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 7.38e-10 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 250 seconds with the U filter starting 119 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 19.2 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 18.0 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.07.
Burst Advocate for this burst is B. Sbarufatti (bxs60 AT psu.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/too.html.)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 21 Jul 18 11:24:11 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     849018,   Seg_Num: 0
POINT_RA:        347.699d {+23h 10m 48s} (J2000)
POINT_DEC:        +4.882d {+04d 52' 56"} (J2000)
POINT_ROLL:      59.583d
IMG_START_DATE:  18320 TJD;   202 DOY;   18/07/21
IMG_START_TIME:  40880.31 SOD {11:21:20.31} UT,   871.9 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.366
N_STARS:         38
X_OFFSET:        315 [pixels]
Y_OFFSET:        522 [pixels]
X_MAX:           1754 [pixels]
Y_MAX:           1961 [pixels]
DET_THRESH:      6
PHOTO_THRESH:    2
SL_URL:          sw00849018000msufc0871.fits
SUN_POSTN:       120.79d {+08h 03m 10s}  +20.42d {+20d 25' 29"}
SUN_DIST:        127.21 [deg]   Sun_angle= 8.9 [hr] (West of Sun)
MOON_POSTN:      227.36d {+15h 09m 26s}  -12.27d {-12d 15' 54"}
MOON_DIST:       120.91 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:       81.91,-49.80 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      350.61,  9.35 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 21 Jul 18 11:24:28 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     849018,   Seg_Num: 0
POINT_RA:        347.699d {+23h 10m 48s} (J2000)
POINT_DEC:        +4.882d {+04d 52' 56"} (J2000)
POINT_ROLL:      59.583d
IMG_START_DATE:  18320 TJD;   202 DOY;   18/07/21
IMG_START_TIME:  40880.31 SOD {11:21:20.31} UT,   871.9 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.366
N_STARS:         38
X_OFFSET:        315 [pixels]
Y_OFFSET:        522 [pixels]
X_MAX:           1754 [pixels]
Y_MAX:           1961 [pixels]
DET_THRESH:      6
PHOTO_THRESH:    2
SL_URL:          sw00849018000msufc0871.fits
SUN_POSTN:       120.79d {+08h 03m 10s}  +20.42d {+20d 25' 29"}
SUN_DIST:        127.21 [deg]   Sun_angle= 8.9 [hr] (West of Sun)
MOON_POSTN:      227.36d {+15h 09m 27s}  -12.27d {-12d 15' 57"}
MOON_DIST:       120.90 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:       81.91,-49.80 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      350.61,  9.35 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 21 Jul 18 11:25:17 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     849018,   Seg_Num: 0
POINT_RA:        347.699d {+23h 10m 48s} (J2000)
POINT_DEC:        +4.882d {+04d 52' 56"} (J2000)
ROLL:            59.583d
IMG_START_DATE:  18320 TJD;   202 DOY;   18/07/21
IMG_START_TIME:  40880.31 SOD {11:21:20.31} UT,   871.9 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     553864901
X_OFFSET:        874 [pixels]
Y_OFFSET:        1081 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1034
Y_GRB_POS:       1241
BINNING_INDEX:   1
IM_URL:          sw00849018000msuni0893.fits
SUN_POSTN:       120.79d {+08h 03m 10s}  +20.42d {+20d 25' 29"}
SUN_DIST:        127.21 [deg]   Sun_angle= 8.9 [hr] (West of Sun)
MOON_POSTN:      227.37d {+15h 09m 28s}  -12.27d {-12d 16' 04"}
MOON_DIST:       120.90 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:       81.91,-49.80 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      350.61,  9.35 [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:     Sat 21 Jul 18 11:25:23 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     849018,   Seg_Num: 0
POINT_RA:        347.699d {+23h 10m 48s} (J2000)
POINT_DEC:        +4.882d {+04d 52' 56"} (J2000)
ROLL:            59.583d
IMG_START_DATE:  18320 TJD;   202 DOY;   18/07/21
IMG_START_TIME:  40880.31 SOD {11:21:20.31} UT,   871.9 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     553864901
X_OFFSET:        874 [pixels]
Y_OFFSET:        1081 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1034
Y_GRB_POS:       1241
BINNING_INDEX:   1
IM_URL:          sw00849018000msuni0893.fits
SUN_POSTN:       120.79d {+08h 03m 10s}  +20.42d {+20d 25' 29"}
SUN_DIST:        127.21 [deg]   Sun_angle= 8.9 [hr] (West of Sun)
MOON_POSTN:      227.37d {+15h 09m 29s}  -12.27d {-12d 16' 05"}
MOON_DIST:       120.90 [deg]
MOON_ILLUM:      67 [%]
GAL_COORDS:       81.91,-49.80 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      350.61,  9.35 [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 #22995
C. Guidorzi, R. Martone (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell (U. Bath), A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU), A. Cucchiara, D. Morris (U. of Virgin Islands) on behalf of a large collaboration report:
The LCO 2-m unit at Haleakala Observatory (Hawaii) automatically began observing Swift GRB 180721A (Sbarufatti et al. GCN 22994) on July 21, 11:21:40 UT (14.9 minutes after the GRB trigger time) with the SDSS i' filter. Within the Swift-XRT error circle we do not detect any source down to i'>20.2 mag at a mid time of 20.4 minutes post GRB with a 5x120s exposure, as calibrated against nearby SDSS objects.
GCN Circular #22997
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 1486 s of XRT Photon Counting mode data and 3 UVOT images for GRB 180721A, 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 = 347.71167, +4.85678 which is equivalent to:
```
RA (J2000): 23h 10m 50.80s
Dec (J2000): +04d 51' 24.4"
```
with an uncertainty of 2.8 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 #22999
A.P. Beardmore (U. Leicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), S. J. LaPorte (PSU), J.A. Kennea (PSU), P.A. Evans (U. Leicester), S.L. Gibson (U. Leicester) and B. Sbarufatti report on behalf of the Swift-XRT team:
We have analysed 6.6 ks of XRT data for GRB 180721A (Sbarufatti et al. GCN Circ. 22994), from 63 s to 17.7 ks after the BAT trigger. The data comprise 17 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN Circ. 22997).
The light curve can be modelled with an initial power-law decay with an index of alpha=2.9 (+0.8, -0.5), followed by a break at T+203 s to an alpha of 0.84 (+/-0.07).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.14 (+0.24, -0.23). The best-fitting absorption column is 1.4 (+0.7, -0.6) x 10^21 cm^-2, in excess of the Galactic value of 6.5 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 3.2 x 10^-11 (4.3 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     1.4 (+0.7, -0.6) x 10^21 cm^-2
Galactic foreground: 6.5 x 10^20 cm^-2
Excess significance: 2.1 sigma
Photon index:	     2.14 (+0.24, -0.23)
```
If the light curve continues to decay with a power-law decay index of 0.84, the count rate at T+24 hours will be 3.6 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.2 x 10^-13 (1.6 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/00849018.
This circular is an official product of the Swift-XRT team.
GCN Circular #23001
H. A. Krimm (NSF/USRA), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), B. Sbarufatti (PSU), 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 180721A (trigger #849018) (Sbarufatti et al., GCN Circ. 22994). The BAT ground-calculated position is RA, Dec = 347.708, 4.871 deg which is
```
  RA(J2000)  =  23h 10m 49.9s
  Dec(J2000) = +04d 52' 16.1"
```
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%.
The mask-weighted light curve shows a single-pulse structure that starts at ~T-1 s, peaks at ~T+2 s, and ends at ~T+10 s. The main pulse is followed by some weak emission that last till ~T+50 s. T90 (15-350 keV) is 47.6 +- 3.0 sec (estimated error including systematics).
The time-averaged spectrum from T-0.39 to T+48.92 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.25 +- 0.22. The fluence in the 15-150 keV band is 5.9 +- 0.9 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+1.82 sec in the 15-150 keV band is 0.9 +- 0.1 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/849018/BA/
GCN Circular #23014
N. P. M. Kuin (UCL-MSSL) and B. Sbarufatti (PSU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 180721A 120 s after the BAT trigger (Sbarufatti et al., GCN Circ. 22994). No optical afterglow consistent with the XRT position (Goad et al, GCN Circ. 22997) 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

u_FC               120          370          246         >20.1
v                  425         1693          156         >19.1
b                  375         1642          175         >19.9
u                  120         1617          529         >20.1
w1                 474         1742          156         >19.6
m2                1697         1717           19         >18.3
w2                 401         1668          156         >20.5
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.07 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #23018
I. Carrasco (Univ. de Malaga), Y. Hu, E. Fernandez-Garcia, J. C. Tello and A. J. Castro-Tirado (IAA-CSIC), D. Hiriart and W. H. Lee (UNAM), S. Jeong and I. H. Park (SKKU), M. D. Caballero-Garcia (ASU-CAS, CZ) and R. Cunniffe (Inst. of Physics, CZ) on behalf of a larger collaboration, report:
The 60cm BOOTES-5/JGT robotic telescope at Observatorio Astronomico Nacional in San Pedro Martir (Mexico) automatically responded in 21s (and 53s after the GRB onset) to the Swift trigger of GRB 180721A (Sbarufatti et al., GCNC 22994). The first image (10s exposure, r-band) was obtained at 11:07:10 UT. At the position of the Swift X-ray afterglow (Goad et al. GCNC 22997), no optical afterglow is detected down 18.1 mag. Furthermore, on the co-add of the images obtained until 11:33:52 UT no afterglow is detected down to 21 mag, consistent with the limit reported by Guidorzi et al. (GCNC 22995).
We thank the staff at Observatorio Astronomico Nacional in San Pedro Martir for its excellent support.
GCN Circular #23022
M. Oeda, R. Itoh, K. L. Murata, Y. Tachibana, S. Harita, K. Morita, K. Shiraishi, K. Iida, R. Adachi, S. Niwano, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration:
We searched for the optical counterpart of GRB 180721A (B. Sbarufatti et al., GCN Circular #22994) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50cm telescope of Akeno Observatory, Yamanashi, Japan.
The observation started on 2018-07-21 13:44:45.05 UT. We did not find any point source at the enhanced position of the XRT error circle (M.R. Goad et al., GCN Circular #22997) in all three bands. We obtained following 5-sigma upper limits for the magnitudes.
```
T0+[min]    MID-UT      T-EXP[sec]    g'       Rc        Ic
-------------------------------------------------------------------------------------------------------
157.95     14:27:28  4,740   >16.9   >17.3   >16.9
-------------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
```
We used UCAC-4 catalog for flux calibration.
GCN Circular #23034
WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, responded to Swift GRB 180721A (Sbarufatti et al., GCN 22994) starting at 11:25:23 UT, ~19 minutes after the burst. Observations were performed with an automatic sequence in the clear (roughly R), V, and I filters, and the exposure time was 20 s per image. We do not detect any optical afterglow candidate within the enhanced XRT position error circle (Goad et al., GCN 22997) neither in single image, nor in the co-add images. The typical limiting magnitude of our single clear image is about 19.5 mag calibrated to the Pan-STARRS1 catalog.

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