Gamma-ray Burst 170728A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 28 Jul 17 06:53:45 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     765008,   Seg_Num: 0
GRB_RA:           58.898d {+03h 55m 35s} (J2000),
                  59.141d {+03h 56m 34s} (current),
                  58.206d {+03h 52m 50s} (1950)
GRB_DEC:         +12.153d {+12d 09' 11"} (J2000),
                 +12.203d {+12d 12' 12"} (current),
                 +12.008d {+12d 00' 28"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4407 [cnts]    Image_Peak=209 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   137     E_range: 15-50 keV
BKG_INTEN:       27713 [cnts]
BKG_TIME:        24796.56 SOD {06:53:16.56} UT
BKG_DUR:         8 [sec]
GRB_DATE:        17962 TJD;   209 DOY;   17/07/28
GRB_TIME:        24808.78 SOD {06:53:28.78} UT
GRB_PHI:          97.80 [deg]
GRB_THETA:        18.88 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     13.60 [sigma]
IMAGE_SIGNIF:    8.37 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +1  -1  +0  +0 -39  +0 
SUN_POSTN:       127.77d {+08h 31m 04s}  +18.92d {+18d 54' 58"}
SUN_DIST:         66.08 [deg]   Sun_angle= 4.6 [hr] (West of Sun)
MOON_POSTN:      189.17d {+12h 36m 40s}   +0.02d {+00d 01' 07"}
MOON_DIST:       128.94 [deg]
MOON_ILLUM:      27 [%]
GAL_COORDS:      177.71,-30.53 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       59.34, -8.04 [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 = 59.34,-20.30 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 28 Jul 17 06:54:46 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     765008,   Seg_Num: 0
POINT_RA:         58.916d {+03h 55m 40s} (J2000)
POINT_DEC:       +12.158d {+12d 09' 30"} (J2000)
IMG_START_DATE:  17962 TJD;   209 DOY;   17/07/28
IMG_START_TIME:  24879.44 SOD {06:54:39.44} UT,   70.7 [sec] since BAT Trigger Time
COUNTS:          30    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        4    Max_iter_allowed= 4
ERROR_CODE:      2
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        Algorithm did not converge; too many iterations.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 28 Jul 17 06:57:14 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     765008,   Seg_Num: 0
GRB_RA:           58.898d {+03h 55m 35s} (J2000),
                  59.141d {+03h 56m 34s} (current),
                  58.206d {+03h 52m 50s} (1950)
GRB_DEC:         +12.153d {+12d 09' 11"} (J2000),
                 +12.203d {+12d 12' 12"} (current),
                 +12.008d {+12d 00' 28"} (1950)
GRB_DATE:        17962 TJD;   209 DOY;   17/07/28
GRB_TIME:        24808.78 SOD {06:53:28.78} UT
TRIGGER_INDEX:   137
GRB_PHI:          97.80 [deg]
GRB_THETA:        18.88 [deg]
DELTA_TIME:      57.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     13.60 [sigma]
IMAGE_SIGNIF:    8.37 [sigma]
LC_URL:          sw00765008000msb.lc
SUN_POSTN:       127.77d {+08h 31m 04s}  +18.92d {+18d 54' 56"}
SUN_DIST:         66.08 [deg]   Sun_angle= 4.6 [hr] (West of Sun)
MOON_POSTN:      189.20d {+12h 36m 47s}   +0.01d {+00d 00' 30"}
MOON_DIST:       128.97 [deg]
MOON_ILLUM:      27 [%]
GAL_COORDS:      177.71,-30.53 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       59.34, -8.04 [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 = 59.34,-20.30 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 28 Jul 17 06:58:47 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     765008,   Seg_Num: 0
GRB_RA:           58.8884d {+03h 55m 33.21s} (J2000),
                  59.1317d {+03h 56m 31.60s} (current),
                  58.1969d {+03h 52m 47.26s} (1950)
GRB_DEC:         +12.1830d {+12d 10' 58.7"} (J2000),
                 +12.2334d {+12d 14' 00.1"} (current),
                 +12.0377d {+12d 02' 15.7"} (1950)
GRB_ERROR:       3.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  17962 TJD;   209 DOY;   17/07/28
IMG_START_TIME:  24893.00 SOD {06:54:53.00} UT,   84.2 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       127.77d {+08h 31m 04s}  +18.92d {+18d 54' 55"}
SUN_DIST:         66.08 [deg]   Sun_angle= 4.6 [hr] (West of Sun)
MOON_POSTN:      189.21d {+12h 36m 51s}   +0.00d {+00d 00' 14"}
MOON_DIST:       128.99 [deg]
MOON_ILLUM:      27 [%]
GAL_COORDS:      177.68,-30.52 [deg] galactic lon,lat of the burst
ECL_COORDS:       59.33, -8.01 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 28 Jul 17 07:00:07 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     765008,   Seg_Num: 0
POINT_RA:         58.916d {+03h 55m 40s} (J2000)
POINT_DEC:       +12.158d {+12d 09' 30"} (J2000)
POINT_ROLL:      74.524d
IMG_START_DATE:  17962 TJD;   209 DOY;   17/07/28
IMG_START_TIME:  24882.67 SOD {06:54:42.67} UT,   73.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        7.600
N_STARS:         18
X_OFFSET:        346 [pixels]
Y_OFFSET:        633 [pixels]
X_MAX:           1305 [pixels]
Y_MAX:           1592 [pixels]
DET_THRESH:      24
PHOTO_THRESH:    15
SL_URL:          sw00765008000msufc0073.fits
SUN_POSTN:       127.77d {+08h 31m 05s}  +18.92d {+18d 54' 55"}
SUN_DIST:         66.06 [deg]   Sun_angle= 4.6 [hr] (West of Sun)
MOON_POSTN:      189.22d {+12h 36m 53s}   -0.00d {-00d 00' 00"}
MOON_DIST:       128.98 [deg]
MOON_ILLUM:      27 [%]
GAL_COORDS:      177.72,-30.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       59.36, -8.04 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 28 Jul 17 07:00:19 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     765008,   Seg_Num: 0
POINT_RA:         58.916d {+03h 55m 40s} (J2000)
POINT_DEC:       +12.158d {+12d 09' 30"} (J2000)
POINT_ROLL:      74.524d
IMG_START_DATE:  17962 TJD;   209 DOY;   17/07/28
IMG_START_TIME:  24882.67 SOD {06:54:42.67} UT,   73.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        7.600
N_STARS:         18
X_OFFSET:        346 [pixels]
Y_OFFSET:        633 [pixels]
X_MAX:           1305 [pixels]
Y_MAX:           1592 [pixels]
DET_THRESH:      24
PHOTO_THRESH:    15
SL_URL:          sw00765008000msufc0073.fits
SUN_POSTN:       127.77d {+08h 31m 05s}  +18.92d {+18d 54' 55"}
SUN_DIST:         66.06 [deg]   Sun_angle= 4.6 [hr] (West of Sun)
MOON_POSTN:      189.22d {+12h 36m 54s}   -0.00d {-00d 00' 02"}
MOON_DIST:       128.98 [deg]
MOON_ILLUM:      27 [%]
GAL_COORDS:      177.72,-30.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       59.36, -8.04 [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:     Fri 28 Jul 17 07:01:42 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     765008,   Seg_Num: 0
POINT_RA:         58.916d {+03h 55m 40s} (J2000)
POINT_DEC:       +12.158d {+12d 09' 30"} (J2000)
ROLL:            74.524d
IMG_START_DATE:  17962 TJD;   209 DOY;   17/07/28
IMG_START_TIME:  24882.67 SOD {06:54:42.67} UT,   73.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     522917702
X_OFFSET:        665 [pixels]
Y_OFFSET:        952 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       825
Y_GRB_POS:       1112
BINNING_INDEX:   1
IM_URL:          sw00765008000msuni0093.fits
SUN_POSTN:       127.77d {+08h 31m 05s}  +18.91d {+18d 54' 54"}
SUN_DIST:         66.06 [deg]   Sun_angle= 4.6 [hr] (West of Sun)
MOON_POSTN:      189.24d {+12h 36m 56s}   -0.00d {-00d 00' 17"}
MOON_DIST:       129.00 [deg]
MOON_ILLUM:      28 [%]
GAL_COORDS:      177.72,-30.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       59.36, -8.04 [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:     Fri 28 Jul 17 07:01:49 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     765008,   Seg_Num: 0
POINT_RA:         58.916d {+03h 55m 40s} (J2000)
POINT_DEC:       +12.158d {+12d 09' 30"} (J2000)
ROLL:            74.524d
IMG_START_DATE:  17962 TJD;   209 DOY;   17/07/28
IMG_START_TIME:  24882.67 SOD {06:54:42.67} UT,   73.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     522917702
X_OFFSET:        665 [pixels]
Y_OFFSET:        952 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       825
Y_GRB_POS:       1112
BINNING_INDEX:   1
IM_URL:          sw00765008000msuni0093.fits
SUN_POSTN:       127.77d {+08h 31m 05s}  +18.91d {+18d 54' 54"}
SUN_DIST:         66.06 [deg]   Sun_angle= 4.6 [hr] (West of Sun)
MOON_POSTN:      189.24d {+12h 36m 57s}   -0.01d {-00d 00' 18"}
MOON_DIST:       129.00 [deg]
MOON_ILLUM:      28 [%]
GAL_COORDS:      177.72,-30.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       59.36, -8.04 [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 #21367
J. K. Cannizzo (NASA/UMBC), A. P. Beardmore (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the Swift Team:
At 06:53:28 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 170728A (trigger=765008). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 58.898, +12.153 which is
```
   RA(J2000) = 03h 55m 35s
   Dec(J2000) = +12d 09' 11"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak structure with a duration of about 3 sec. The peak count rate was ~2400 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 06:54:39.4 UT, 70.6 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source located at RA, Dec 58.88846, 12.18313 which is equivalent to:
```
   RA(J2000)  = 03h 55m 33.23s
   Dec(J2000) = +12d 10' 59.3"
```
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 113 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 consistent with the Galactic value of 2.27 x 10^21 cm^-2 (Willingale et al. 2013).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 73 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 none of the XRT error circle. 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 0.24.
Burst Advocate for this burst is J. K. Cannizzo (cannizzo 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:     Fri 28 Jul 17 07:07:23 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     765008,   Seg_Num: 0
POINT_RA:         58.916d {+03h 55m 40s} (J2000)
POINT_DEC:       +12.158d {+12d 09' 30"} (J2000)
POINT_ROLL:      74.524d
IMG_START_DATE:  17962 TJD;   209 DOY;   17/07/28
IMG_START_TIME:  25095.49 SOD {06:58:15.49} UT,   286.7 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        2.433
N_STARS:         22
X_OFFSET:        106 [pixels]
Y_OFFSET:        393 [pixels]
X_MAX:           1545 [pixels]
Y_MAX:           1832 [pixels]
DET_THRESH:      13
PHOTO_THRESH:    7
SL_URL:          sw00765008000msufc0286.fits
SUN_POSTN:       127.77d {+08h 31m 06s}  +18.91d {+18d 54' 50"}
SUN_DIST:         66.07 [deg]   Sun_angle= 4.6 [hr] (West of Sun)
MOON_POSTN:      189.28d {+12h 37m 08s}   -0.02d {-00d 01' 17"}
MOON_DIST:       129.05 [deg]
MOON_ILLUM:      28 [%]
GAL_COORDS:      177.72,-30.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       59.36, -8.04 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.  
COMMENTS:        The Pointing RA,Dec,Roll values came from the 1st SrcList Notice.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 28 Jul 17 07:07:36 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     765008,   Seg_Num: 0
POINT_RA:         58.916d {+03h 55m 40s} (J2000)
POINT_DEC:       +12.158d {+12d 09' 30"} (J2000)
POINT_ROLL:      74.524d
IMG_START_DATE:  17962 TJD;   209 DOY;   17/07/28
IMG_START_TIME:  25095.49 SOD {06:58:15.49} UT,   286.7 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        2.433
N_STARS:         22
X_OFFSET:        106 [pixels]
Y_OFFSET:        393 [pixels]
X_MAX:           1545 [pixels]
Y_MAX:           1832 [pixels]
DET_THRESH:      13
PHOTO_THRESH:    7
SL_URL:          sw00765008000msufc0286.fits
SUN_POSTN:       127.77d {+08h 31m 06s}  +18.91d {+18d 54' 50"}
SUN_DIST:         66.07 [deg]   Sun_angle= 4.6 [hr] (West of Sun)
MOON_POSTN:      189.29d {+12h 37m 08s}   -0.02d {-00d 01' 20"}
MOON_DIST:       129.05 [deg]
MOON_ILLUM:      28 [%]
GAL_COORDS:      177.72,-30.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       59.36, -8.04 [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:     Fri 28 Jul 17 07:08:46 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     765008,   Seg_Num: 0
POINT_RA:         58.916d {+03h 55m 40s} (J2000)
POINT_DEC:       +12.158d {+12d 09' 30"} (J2000)
ROLL:            74.524d
IMG_START_DATE:  17962 TJD;   209 DOY;   17/07/28
IMG_START_TIME:  25095.49 SOD {06:58:15.49} UT,   286.7 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     522917914
X_OFFSET:        665 [pixels]
Y_OFFSET:        952 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       825
Y_GRB_POS:       1112
BINNING_INDEX:   1
IM_URL:          sw00765008000msuni0306.fits
SUN_POSTN:       127.78d {+08h 31m 06s}  +18.91d {+18d 54' 50"}
SUN_DIST:         66.07 [deg]   Sun_angle= 4.6 [hr] (West of Sun)
MOON_POSTN:      189.29d {+12h 37m 11s}   -0.03d {-00d 01' 32"}
MOON_DIST:       129.06 [deg]
MOON_ILLUM:      28 [%]
GAL_COORDS:      177.72,-30.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       59.36, -8.04 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The Pointing RA,Dec,Roll values came from the 1st Image Notice.  
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:     Fri 28 Jul 17 07:08:53 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     765008,   Seg_Num: 0
POINT_RA:         58.916d {+03h 55m 40s} (J2000)
POINT_DEC:       +12.158d {+12d 09' 30"} (J2000)
ROLL:            74.524d
IMG_START_DATE:  17962 TJD;   209 DOY;   17/07/28
IMG_START_TIME:  25095.49 SOD {06:58:15.49} UT,   286.7 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     522917914
X_OFFSET:        665 [pixels]
Y_OFFSET:        952 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       825
Y_GRB_POS:       1112
BINNING_INDEX:   1
IM_URL:          sw00765008000msuni0306.fits
SUN_POSTN:       127.78d {+08h 31m 06s}  +18.91d {+18d 54' 50"}
SUN_DIST:         66.07 [deg]   Sun_angle= 4.6 [hr] (West of Sun)
MOON_POSTN:      189.30d {+12h 37m 11s}   -0.03d {-00d 01' 33"}
MOON_DIST:       129.06 [deg]
MOON_ILLUM:      28 [%]
GAL_COORDS:      177.72,-30.51 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       59.36, -8.04 [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 #21368
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 1579 s of XRT Photon Counting mode data and 5 UVOT images for GRB 170728A, 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 = 58.88831, +12.18148 which is equivalent to:
```
RA (J2000): 03h 55m 33.19s
Dec (J2000): +12d 10' 53.3"
```
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 #21370
M. Stamatikos (OSU), S. D. Barthelmy (GSFC), J. K. Cannizzo (NASA/UMBC), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 170728A (trigger #765008) (Cannizzo et al., GCN Circ. 21367). The BAT ground-calculated position is RA, Dec = 58.901, 12.169 deg which is
```
  RA(J2000)  =  03h 55m 36.3s
  Dec(J2000) = +12d 10' 07.3"
```
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 73%.
The mask-weighted light curve shows a weak pulse that starts at ~T0 and ends at ~T+1.5. There is no evidence of extended emission. T90 (15-350 keV) is 1.25 +- 0.23 sec (estimated error including systematics).
The time-averaged spectrum from T+0.17 to T+1.56 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index -0.49 +- 1.81, and Epeak of 38.6 +- 7.3 keV (chi squared 51.37 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 7.1 +- 1.4 x 10^-8 erg/cm2 and the 1-sec peak flux measured from T+0.20 sec in the 15-150 keV band is 1.1 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 2.02 +- 0.26 (chi squared 60.76 for 57 d.o.f.). All the quoted errors are at the 90% confidence level.
The spectrum is on the very soft end of the BAT-detected short GRB, only a handful of BAT-detected short GRBs have comparable hardness ratio as this burst (Lien & Sakamoto et al. 2016).
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/765008/BA/
GCN Circular #21378
J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB) and J.K. Cannizzo report on behalf of the Swift-XRT team:
We have analysed 4.8 ks of XRT data for GRB 170728A (Cannizzo et al. GCN Circ. 21367), from 84 s to 22.2 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN Circ. 21368).
The light curve can be modelled with a power-law decay with a decay index of alpha=0.89 (+/-0.07).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.22 (+0.32, -0.25). The best-fitting absorption column is 2.7 (+1.1, -0.4) x 10^21 cm^-2, consistent with the Galactic value of 2.3 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.3 x 10^-11 (5.3 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     2.7 (+1.1, -0.4) x 10^21 cm^-2
Galactic foreground: 2.3 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:	     2.22 (+0.32, -0.25)
```
If the light curve continues to decay with a power-law decay index of 0.89, the count rate at T+24 hours will be 2.8 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.1 x 10^-14 (1.5 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/00765008.
This circular is an official product of the Swift-XRT team.
GCN Circular #21382
A. Cucchiara, D. Morris (U. of Virgin Islands), and C. Guidorzi (U. Ferrara), reports on behalf of a larger collaboration:
"On July 28.38 UT (T_0 +2.1h) we began observing the center of the field of GRB 170728A (Cannizzo et al. GCN 21367, Evans et al. GCN 21368) using the Las Cumbres Observatory 1m telescope in Cerro Tololo. We performed a series of 4x240s observations in R and Ic band for a total of 16 minutes on sky in each filter at average airmass of 1.8. Further observations were requested in Sloane i' filter for a total of 360s.
In the full combined R and I+i' stacks we identified no optical counterpart within the center of Swift-XRT refined position (Evans et al. GCN 21368) at the following 3-sigma limits:
```
R > 18.9 mag
I > 18.4 mag
```
These magnitudes are calibrated against nearby USNO-B1 sources, and are not corrected for Galactic extinction."
GCN Circular #21386
GRB 170728A: Swift/UVOT Detection
S. J. Laporte (PSU) and J. K. Cannizzo (NASA/UMBC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 170728A 74 s after the BAT trigger (Cannizzo et al., GCN Circ. 21367). A fading source consistent with the XRT position (Goad et al. GCN Circ. 21368) is detected in the initial UVOT exposures.
The preliminary UVOT position is:
```
    RA  (J2000) =  03:55:33.17 =  58.88819 (deg.)
    Dec (J2000) = +12:10:54.7  =  12.18187 (deg.)
```
with an estimated uncertainty of 0.56 arc sec. (radius, 90% confidence).
Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white             70            219          147         19.20+-0.17   
white             70           4048          342         19.93+-0.18
v                 4264         5808          267        >19.1
b                 3655        11916          345        >19.7
u                  287        22167         1283        >20.0
w1                6020        21852         1105        >20.1
m2                5814        16112         1082        >20.6
w2                4059         4259          197        >19.6
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.24 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #21465
K. P. Mooley (Hintze Fellow, Oxford), T. D. Staley, R. P. Fender (Oxford), G. E. Anderson (Curtin), T. Cantwell (Manchester), D. Titterington, S. H. Carey, J. Hickish, Y. C. Perrott, N. Razavi-Ghods, P. Scott (Cambridge), K. Grainge, A. Scaife (Manchester)
The AMI Large Array robotically triggered on the Swift alert for GRB 170728A (Cannizzo et al., GCN 21367) as part of the 4pisky program, and subsequent follow up observations were obtained up to 10 days post-burst. Our observations at 15 GHz on 2017 Jul 28.32, Jul 30.25, Aug 01.27 and Aug 05.23 (UT) do not reveal any radio source at the XRT location (Goad et al., GCN 21368), with 3sigma upper limits of 141 uJy, 131 uJy, 129 uJy and 133 uJy respectively.
We thank the AMI staff for scheduling these observations. The AMI-GRB database is a log of all GRB follow up observations with the AMI, and is available at http://4pisky.org/ami-grb/.
Redshift z= 1.493 +- 0.009 from host galaxy emission ([OII])
W.-F. Fong et al. 2022, ApJ 940, 56

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