Gamma-ray Burst 170827A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 27 Aug 17 05:13:51 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     769567,   Seg_Num: 0
GRB_RA:          276.180d {+18h 24m 43s} (J2000),
                 276.489d {+18h 25m 57s} (current),
                 275.306d {+18h 21m 13s} (1950)
GRB_DEC:         -40.220d {-40d 13' 11"} (J2000),
                 -40.209d {-40d 12' 32"} (current),
                 -40.248d {-40d 14' 51"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       0 [cnts]    Image_Peak=1409 [image_cnts]
TRIGGER_DUR:     64.000 [sec] 
TRIGGER_INDEX:   20000     E_range: 15-50 keV
BKG_INTEN:       0 [cnts]
BKG_TIME:        0.00 SOD {00:00:00.00} UT
BKG_DUR:         0 [sec]
GRB_DATE:        17992 TJD;   239 DOY;   17/08/27
GRB_TIME:        18748.40 SOD {05:12:28.40} UT
GRB_PHI:         172.13 [deg]
GRB_THETA:        18.39 [deg]
SOLN_STATUS:     0x13
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    7.28 [sigma]
MERIT_PARAMS:     +1  +0  +0  +6  +1  -3  +0  +1 +48  +0 
SUN_POSTN:       156.02d {+10h 24m 05s}   +9.99d {+09d 59' 27"}
SUN_DIST:        119.56 [deg]   Sun_angle= -8.0 [hr] (East of Sun)
MOON_POSTN:      219.87d {+14h 39m 28s}  -10.13d {-10d 08' 04"}
MOON_DIST:        58.18 [deg]
MOON_ILLUM:      30 [%]
GAL_COORDS:      353.88,-12.44 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      274.93,-16.89 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is an image trigger.  (The RATE_SIGNIF & BKG_{INTEN, TIME, DUR} are undefined.)  
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 = 258.03,-15.13 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 27 Aug 17 05:14:58 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     769567,   Seg_Num: 0
GRB_RA:          276.1508d {+18h 24m 36.19s} (J2000),
                 276.4595d {+18h 25m 50.28s} (current),
                 275.2761d {+18h 21m 06.25s} (1950)
GRB_DEC:         -40.2016d {-40d 12' 05.7"} (J2000),
                 -40.1908d {-40d 11' 26.9"} (current),
                 -40.2293d {-40d 13' 45.5"} (1950)
GRB_ERROR:       4.9 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       4.23e-09 [erg/cm2/sec]
GRB_SIGNIF:      11.57 [sigma]
IMG_START_DATE:  17992 TJD;   239 DOY;   17/08/27
IMG_START_TIME:  18872.50 SOD {05:14:32.50} UT,   124.1 [sec] since BAT Trigger Time
TAM[0-3]:        327.68 237.23 261.72 243.73
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       156.02d {+10h 24m 05s}   +9.99d {+09d 59' 26"}
SUN_DIST:        119.54 [deg]   Sun_angle= -8.0 [hr] (East of Sun)
MOON_POSTN:      219.88d {+14h 39m 30s}  -10.14d {-10d 08' 14"}
MOON_DIST:        58.15 [deg]
MOON_ILLUM:      30 [%]
GAL_COORDS:      353.89,-12.41 [deg] galactic lon,lat of the burst
ECL_COORDS:      274.91,-16.87 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 1.74 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:     Sun 27 Aug 17 05:15:10 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     769567,   Seg_Num: 0
GRB_RA:          276.1508d {+18h 24m 36.1s} (J2000),
                 276.4595d {+18h 25m 50.2s} (current),
                 275.2761d {+18h 21m 06.2s} (1950)
GRB_DEC:         -40.2016d {-40d 12' 05.7"} (J2000),
                 -40.1908d {-40d 11' 26.9"} (current),
                 -40.2293d {-40d 13' 45.5"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       134 [cnts]
IMG_START_DATE:  17992 TJD;   239 DOY;   17/08/27
IMG_START_TIME:  18872.50 SOD {05:14:32.50} UT,   124.1 [sec] since BAT Trigger Time
CENTROID_X:      282.12,  raw= 282  [pixels]
CENTROID_Y:      270.69,  raw= 271  [pixels]
ROLL:            257.61 [deg]
GAIN:            2
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -65.31
GRB_POS_XRT_Z:   -57.22
IMAGE_URL:       sw00769567000msxps_rw.img
SUN_POSTN:       156.02d {+10h 24m 05s}   +9.99d {+09d 59' 26"}
SUN_DIST:        119.54 [deg]   Sun_angle= -8.0 [hr] (East of Sun)
MOON_POSTN:      219.88d {+14h 39m 31s}  -10.14d {-10d 08' 16"}
MOON_DIST:        58.15 [deg]
MOON_ILLUM:      30 [%]
GAL_COORDS:      353.89,-12.41 [deg] galactic lon,lat of the burst
ECL_COORDS:      274.91,-16.87 [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:     Sun 27 Aug 17 05:15:07 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     769567,   Seg_Num: 0
GRB_RA:          276.1508d {+18h 24m 36.1s} (J2000),
                 276.4595d {+18h 25m 50.2s} (current),
                 275.2761d {+18h 21m 06.2s} (1950)
GRB_DEC:         -40.2016d {-40d 12' 05.7"} (J2000),
                 -40.1908d {-40d 11' 26.9"} (current),
                 -40.2293d {-40d 13' 45.5"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       134 [cnts]
IMG_START_DATE:  17992 TJD;   239 DOY;   17/08/27
IMG_START_TIME:  18872.50 SOD {05:14:32.50} UT,   124.1 [sec] since BAT Trigger Time
CENTROID_X:      282.12,  raw= 282  [pixels]
CENTROID_Y:      270.69,  raw= 271  [pixels]
ROLL:            257.61 [deg]
GAIN:            2
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -65.31
GRB_POS_XRT_Z:   -57.22
IMAGE_URL:       sw00769567000msxps_rw.img
SUN_POSTN:       156.02d {+10h 24m 05s}   +9.99d {+09d 59' 26"}
SUN_DIST:        119.54 [deg]   Sun_angle= -8.0 [hr] (East of Sun)
MOON_POSTN:      219.88d {+14h 39m 31s}  -10.14d {-10d 08' 15"}
MOON_DIST:        58.15 [deg]
MOON_ILLUM:      30 [%]
GAL_COORDS:      353.89,-12.41 [deg] galactic lon,lat of the burst
ECL_COORDS:      274.91,-16.87 [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:     Sun 27 Aug 17 05:16:21 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     769567,   Seg_Num: 0
GRB_RA:          276.180d {+18h 24m 43s} (J2000),
                 276.489d {+18h 25m 57s} (current),
                 275.306d {+18h 21m 13s} (1950)
GRB_DEC:         -40.220d {-40d 13' 11"} (J2000),
                 -40.209d {-40d 12' 32"} (current),
                 -40.248d {-40d 14' 51"} (1950)
GRB_DATE:        17992 TJD;   239 DOY;   17/08/27
GRB_TIME:        18748.40 SOD {05:12:28.40} UT
TRIGGER_INDEX:   20000
GRB_PHI:         172.13 [deg]
GRB_THETA:        18.39 [deg]
DELTA_TIME:      0.00 [sec]
TRIGGER_DUR:     64.000 [sec] 
SOLN_STATUS:     0x13
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    7.28 [sigma]
LC_URL:          sw00769567000msb.lc
SUN_POSTN:       156.02d {+10h 24m 06s}   +9.99d {+09d 59' 25"}
SUN_DIST:        119.56 [deg]   Sun_angle= -8.0 [hr] (East of Sun)
MOON_POSTN:      219.89d {+14h 39m 33s}  -10.14d {-10d 08' 26"}
MOON_DIST:        58.16 [deg]
MOON_ILLUM:      30 [%]
GAL_COORDS:      353.88,-12.44 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      274.93,-16.89 [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 an image 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 = 258.03,-15.13 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 27 Aug 17 05:18:04 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     769567,   Seg_Num: 0
POINT_RA:        276.177d {+18h 24m 42s} (J2000)
POINT_DEC:       -40.216d {-40d 12' 58"} (J2000)
POINT_ROLL:      257.607d
IMG_START_DATE:  17992 TJD;   239 DOY;   17/08/27
IMG_START_TIME:  18882.25 SOD {05:14:42.25} UT,   133.8 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.385
N_STARS:         190
X_OFFSET:        440 [pixels]
Y_OFFSET:        520 [pixels]
X_MAX:           1399 [pixels]
Y_MAX:           1479 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw00769567000msufc0133.fits
SUN_POSTN:       156.02d {+10h 24m 06s}   +9.99d {+09d 59' 23"}
SUN_DIST:        119.56 [deg]   Sun_angle= -8.0 [hr] (East of Sun)
MOON_POSTN:      219.90d {+14h 39m 37s}  -10.15d {-10d 08' 41"}
MOON_DIST:        58.15 [deg]
MOON_ILLUM:      30 [%]
GAL_COORDS:      353.89,-12.43 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      274.93,-16.88 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 27 Aug 17 05:18:20 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     769567,   Seg_Num: 0
POINT_RA:        276.177d {+18h 24m 42s} (J2000)
POINT_DEC:       -40.216d {-40d 12' 58"} (J2000)
ROLL:            257.607d
IMG_START_DATE:  17992 TJD;   239 DOY;   17/08/27
IMG_START_TIME:  18882.25 SOD {05:14:42.25} UT,   133.8 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     525503701
X_OFFSET:        954 [pixels]
Y_OFFSET:        920 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1114
Y_GRB_POS:       1080
BINNING_INDEX:   1
IM_URL:          sw00769567000msuni0153.fits
SUN_POSTN:       156.02d {+10h 24m 06s}   +9.99d {+09d 59' 23"}
SUN_DIST:        119.56 [deg]   Sun_angle= -8.0 [hr] (East of Sun)
MOON_POSTN:      219.90d {+14h 39m 37s}  -10.15d {-10d 08' 43"}
MOON_DIST:        58.15 [deg]
MOON_ILLUM:      30 [%]
GAL_COORDS:      353.89,-12.43 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      274.93,-16.88 [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:     Sun 27 Aug 17 05:18:33 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     769567,   Seg_Num: 0
POINT_RA:        276.177d {+18h 24m 42s} (J2000)
POINT_DEC:       -40.216d {-40d 12' 58"} (J2000)
ROLL:            257.607d
IMG_START_DATE:  17992 TJD;   239 DOY;   17/08/27
IMG_START_TIME:  18882.25 SOD {05:14:42.25} UT,   133.8 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     525503701
X_OFFSET:        954 [pixels]
Y_OFFSET:        920 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1114
Y_GRB_POS:       1080
BINNING_INDEX:   1
IM_URL:          sw00769567000msuni0153.fits
SUN_POSTN:       156.02d {+10h 24m 06s}   +9.99d {+09d 59' 23"}
SUN_DIST:        119.56 [deg]   Sun_angle= -8.0 [hr] (East of Sun)
MOON_POSTN:      219.91d {+14h 39m 37s}  -10.15d {-10d 08' 45"}
MOON_DIST:        58.14 [deg]
MOON_ILLUM:      30 [%]
GAL_COORDS:      353.89,-12.43 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      274.93,-16.88 [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:     Sun 27 Aug 17 05:18:27 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     769567,   Seg_Num: 0
POINT_RA:        276.177d {+18h 24m 42s} (J2000)
POINT_DEC:       -40.216d {-40d 12' 58"} (J2000)
POINT_ROLL:      257.607d
IMG_START_DATE:  17992 TJD;   239 DOY;   17/08/27
IMG_START_TIME:  18882.25 SOD {05:14:42.25} UT,   133.8 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.385
N_STARS:         190
X_OFFSET:        440 [pixels]
Y_OFFSET:        520 [pixels]
X_MAX:           1399 [pixels]
Y_MAX:           1479 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw00769567000msufc0133.fits
SUN_POSTN:       156.02d {+10h 24m 06s}   +9.99d {+09d 59' 23"}
SUN_DIST:        119.56 [deg]   Sun_angle= -8.0 [hr] (East of Sun)
MOON_POSTN:      219.91d {+14h 39m 37s}  -10.15d {-10d 08' 44"}
MOON_DIST:        58.14 [deg]
MOON_ILLUM:      30 [%]
GAL_COORDS:      353.89,-12.43 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      274.93,-16.88 [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:     Sun 27 Aug 17 05:19:56 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     769567,   Seg_Num: 0
POINT_RA:        276.177d {+18h 24m 42s} (J2000)
POINT_DEC:       -40.216d {-40d 12' 58"} (J2000)
POINT_ROLL:      257.607d
IMG_START_DATE:  17992 TJD;   239 DOY;   17/08/27
IMG_START_TIME:  19040.22 SOD {05:17:20.22} UT,   291.8 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.036
N_STARS:         74
X_OFFSET:        634 [pixels]
Y_OFFSET:        600 [pixels]
X_MAX:           1593 [pixels]
Y_MAX:           1559 [pixels]
DET_THRESH:      3
PHOTO_THRESH:    2
SL_URL:          sw00769567000msufc0291.fits
SUN_POSTN:       156.03d {+10h 24m 06s}   +9.99d {+09d 59' 22"}
SUN_DIST:        119.56 [deg]   Sun_angle= -8.0 [hr] (East of Sun)
MOON_POSTN:      219.92d {+14h 39m 40s}  -10.15d {-10d 08' 57"}
MOON_DIST:        58.13 [deg]
MOON_ILLUM:      30 [%]
GAL_COORDS:      353.89,-12.43 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      274.93,-16.88 [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:     Sun 27 Aug 17 05:20:12 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     769567,   Seg_Num: 0
POINT_RA:        276.177d {+18h 24m 42s} (J2000)
POINT_DEC:       -40.216d {-40d 12' 58"} (J2000)
POINT_ROLL:      257.607d
IMG_START_DATE:  17992 TJD;   239 DOY;   17/08/27
IMG_START_TIME:  19040.22 SOD {05:17:20.22} UT,   291.8 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.036
N_STARS:         74
X_OFFSET:        634 [pixels]
Y_OFFSET:        600 [pixels]
X_MAX:           1593 [pixels]
Y_MAX:           1559 [pixels]
DET_THRESH:      3
PHOTO_THRESH:    2
SL_URL:          sw00769567000msufc0291.fits
SUN_POSTN:       156.03d {+10h 24m 06s}   +9.99d {+09d 59' 21"}
SUN_DIST:        119.56 [deg]   Sun_angle= -8.0 [hr] (East of Sun)
MOON_POSTN:      219.92d {+14h 39m 41s}  -10.15d {-10d 09' 00"}
MOON_DIST:        58.13 [deg]
MOON_ILLUM:      30 [%]
GAL_COORDS:      353.89,-12.43 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      274.93,-16.88 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_srclist.fits.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 27 Aug 17 05:21:17 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     769567,   Seg_Num: 0
POINT_RA:        276.177d {+18h 24m 42s} (J2000)
POINT_DEC:       -40.216d {-40d 12' 58"} (J2000)
ROLL:            257.607d
IMG_START_DATE:  17992 TJD;   239 DOY;   17/08/27
IMG_START_TIME:  19040.22 SOD {05:17:20.22} UT,   291.8 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     525503859
X_OFFSET:        954 [pixels]
Y_OFFSET:        920 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1114
Y_GRB_POS:       1080
BINNING_INDEX:   1
IM_URL:          sw00769567000msuni0311.fits
SUN_POSTN:       156.03d {+10h 24m 06s}   +9.99d {+09d 59' 20"}
SUN_DIST:        119.55 [deg]   Sun_angle= -8.0 [hr] (East of Sun)
MOON_POSTN:      219.93d {+14h 39m 43s}  -10.15d {-10d 09' 09"}
MOON_DIST:        58.12 [deg]
MOON_ILLUM:      30 [%]
GAL_COORDS:      353.89,-12.43 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      274.93,-16.88 [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 XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 27 Aug 17 05:21:31 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     769567,   Seg_Num: 0
POINT_RA:        276.177d {+18h 24m 42s} (J2000)
POINT_DEC:       -40.216d {-40d 12' 58"} (J2000)
ROLL:            257.607d
IMG_START_DATE:  17992 TJD;   239 DOY;   17/08/27
IMG_START_TIME:  19040.22 SOD {05:17:20.22} UT,   291.8 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     525503859
X_OFFSET:        954 [pixels]
Y_OFFSET:        920 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1114
Y_GRB_POS:       1080
BINNING_INDEX:   1
IM_URL:          sw00769567000msuni0311.fits
SUN_POSTN:       156.03d {+10h 24m 06s}   +9.99d {+09d 59' 20"}
SUN_DIST:        119.55 [deg]   Sun_angle= -8.0 [hr] (East of Sun)
MOON_POSTN:      219.93d {+14h 39m 43s}  -10.15d {-10d 09' 11"}
MOON_DIST:        58.12 [deg]
MOON_ILLUM:      30 [%]
GAL_COORDS:      353.89,-12.43 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      274.93,-16.88 [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:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.

GCN Circular #21718
F. E. Marshall (NASA/GSFC), A. D'Ai (INAF-IASFPA), K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the Swift Team:
At 05:12:28 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 170827A (trigger=769567). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 276.180, -40.220 which is
```
   RA(J2000) = 18h 24m 43s
   Dec(J2000) = -40d 13' 11"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). As is typical for an image trigger, the immediately-available BAT lightcurve shows no obvious variation.
The XRT began observing the field at 05:14:32.5 UT, 124.1 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 276.1508, -40.2016 which is equivalent to:
```
   RA(J2000)  = +18h 24m 36.19s
   Dec(J2000) = -40d 12' 05.8"
```
with an uncertainty of 4.9 arcseconds (radius, 90% containment). This location is 104 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy.
The initial flux in the 2.5 s image was 4.23e-09 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 133 seconds after the BAT trigger. Only partial images are available and neither the 2.7'x2.7' sub-image nor the 8'x8' region for the list of sources generated on-board covers the XRT error circle. Analysis of any potential afterglow will have to await further data.
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 Circular #21721
P. D'Avanzo, D. Fugazza, S. Covino (INAF/OAB) report on behalf of the REM team:
We observed the field of the short GRB 170827A (Marshall et al., GCN 21718) with the 60-cm robotic telescope REM located at the La Silla Observatory (Chile). The observations started at 05:14:24 UT, 116 seconds after the burst, and were carried out simultaneously in the g, r, i, z and H bands.
A preliminary photometry of the first co-added images indicates that no obvious afterglow candidate is detected within the Swift/XRT error circle (Marshall et al., GCN 21718) down to the following 3sigma limiting AB magnitudes:
```
r > 19.5 at T-T0 = 720s
H > 17.5 at T-T0 = 585s
```
Magnitudes are in the AB system and have been calibrated with respect to the 2MASS (H-band) and APASS (r-band) catalogues.
GCN Circular #21722
F. E. Marshall (NASA/GSFC) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 170827A 134 s after the BAT trigger (Marshall et al., GCN Circ. 21718). No optical afterglow consistent with the XRT position (Marshall et al. GCN Circ. 21718) 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 a subsequent short exposure are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           134          284          147         >19.8
u                  292          298            6         >17.8
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.11 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #21724
T. N. Ukwatta (LANL), 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), T. Sakamoto (AGU), M. Stamatikos (OSU), (i.e. the Swift-BAT team):
Using the data set from T-239 to T+509 sec from the recent telemetry downlink, we report further analysis of BAT GRB 170827A (trigger #769567) (Marshall et al. GCN Circ. 21718). The BAT ground-calculated position is RA, Dec = 276.189, -40.202 deg which is
```
  RA(J2000)  =  18h 24m 45.3s
  Dec(J2000) = -40d 12' 07.9"
```
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 98%.
The mask-weighted light curve shows a weak pulse that starts at ~T+20 s and ends at ~T+140 s. T90 (15-350 keV) is 94.0 +- 12.5 sec (estimated error including systematics).
The time-averaged spectrum from T+19.1 to T+138.9 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.29 +- 0.18. The fluence in the 15-150 keV band is 1.4 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+67.13 sec in the 15-150 keV band is 0.4 +- 0.2 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/769567/BA/
GCN Circular #21728
J. Lyman (Univ. of Warwick), D. Homan (Univ of Edinburgh), P. D'Avanzo (INAF-OAB), Patricia Schady (MPE Garching), K. E. Heintz (DARK/NBI), E. Palazzi (INAF-IASFBo), L. Galbany (Univ. de Chile), J. Anderson (ESO), C. Inserra (Southampton), E. Kankare (QUB), K. Maguire (QUB), S. Smartt (QUB), K. W. Smith (QUB), O. Yaron (Weizmann), D. Young (QUB), I. Manulis (Weizmann) report:
We observed the field of GRB 170827A (Marshall et al., GCN 21718) under the extended Public ESO Spectroscopic Survey for Transient Objects (ePESSTO; see Smartt et al. 2015, A&A, 579, 40 http://www.pessto.org ). The observations were performed on the ESO New Technology Telescope at La Silla with the SofI and EFOSC2 instrument in imaging mode starting from 2017-08-28 at 00:47:05 UT (i.e. 19.58 hours from the burst). Observations were carried out with the Z, J, R and I filters.
Within the XRT error circle (Marshall et al., GCN 21718) we detect an object at the following coordinates:
RA(J2000), Dec(J2000) = 18:24:36.14, -40:12:06.3
(+/- 0.5"). The object has a magnitude R~21.5 (based on preliminary photometry calibrated against the USNOB1 catalogue) at T-T0 = 20.08 hours. We cannot make any statement about variability at this time.We also notice the presence of a fainter object about 2.4" West.
GCN Circular #21729
P. Schady (MPE Garching) reports
I observed the field of GRB 170827A (Swift trigger 769567; Marshall et al., GCN #21718) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile).
Observations started at 00:44 UT on 28-08-2017, 19.5 hours after the GRB trigger. They were performed at an average seeing of 1.5" and at an average airmass of 1.0.
A point source is present within the 4.9" Swift-XRT error circle (Marshall et al., GCN #21718) in the g'r'i'z' GROND images, consistent with the ePESSTO position reported by Lyman et al. (GCN #21728).
Based on a total exposure time of 36 min in g'r'i'z' and 30 min in JHK, the estimated preliminary magnitudes and upper limits (all in AB system) are
```
g' = 22.8 +/- 0.1 mag
r' = 21.9 +/- 0.1 mag
i' = 21.6 +/- 0.1 mag
z' = 21.4 +/- 0.1 mag
J > 21.1 mag
H > 20.6 mag
K > 20.1 mag
```
Given magnitudes are calibrated against GROND zeropoints as well as 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.09 mag in the direction of the burst (Schlafly & Finkbeiner 2011).
A second fainter source is also detected within the XRT error circle at around 2.3" west of the ePESSTO afterglow candidate. No statement can be made at this time on the variability of either source.
I acknowledge the excellent help provided by the support astronomer in La Silla, Markus Rabus, in obtaining these data.
GCN Circular #21730
A. D'Ai (IASF-PA), V. D'Elia (ASDC), F. E. Marshall (NASA/GSFC) reports on behalf of the Swift-XRT team:
We have analysed 1.1 ks of XRT data for GRB 170827A (Marshall et al. GCN Circ. 21718), from 113 s to 17.3 ks after the BAT trigger. The data comprise 165 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode.
The initial light curve from T0+130s to T0+295s can be modelled with a power-law decay with a decay index of alpha=1.19 (+/-0.08). In the following observation at T0+16.1 ks the afterglow is not detected with a 3-sigma upper limit of 1.6 x 10^-2 count^-1 s^-1.
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.23 (+0.06, -0.05). The best-fitting absorption column is 1.46 (+/-0.15) x 10^21 cm^-2, in excess of the Galactic value of 1.2 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 3.0 x 10^-11 (4.2 x 10^-11) erg cm^-2 count^-1.
A summary of the WT-mode spectrum is thus:
```
Total column:	  1.46 (+/-0.15) x 10^21 cm^-2
Galactic foreground: 1.2 x 10^21 cm^-2
Excess significance: 3.0 sigma
Photon index:	  2.23 (+0.06, -0.05)
```
Given the lack of detection in the second observation, no reliable estimate of the X-ray count rate for the following days is possible.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00769567.
This circular is an official product of the Swift-XRT team.
GCN Circular #21743
P. Schady (MPE Garching) reports
I re-observed the field of GRB 170827A (Swift trigger 769567; Marshall et al., GCN #21718) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) on 29-08-2017, 1.8 days after the GRB trigger and 1 day after the first set of GROND observations (Schady, GCN #21729) . Observations were performed at an average seeing of 1.4" and at an average airmass of 1.0.
The two point sources detected within the 4.9" XRT error circle (Marshall et al., GCN #21718) in the first epoch of GROND observations (Schady, GCN #21729) are still seen in the second epoch of GROND observations and they remain at the same magnitude. Neither of these sources are therefore likely to be the optical counterpart of GRB 170827A.
I acknowledge the excellent help provided by the support astronomer in La Silla, Markus Rabus, in obtaining these data.
GCN Circular #21807
A. Cucchiara, D. Morris, J. Staff, and B. Gendre (U. Virgin Islands) report on behalf of a larger collaboration:
"On August 27.71 UT (T_0 +12.0h) we began observing the center of the field of GRB 170827A (Marshall et al. GCN 21718, D'Ai et al. GCN 21730) using the Las Cumbres Observatory 1m telescope located in Sutherland Observatory.
We performed a series of 5x240s observations in SDSS r' and i=E2=80=99 bands for a total of 20 minutes on sky in each filter at average airmass of 1.05.
In the full median stacked images we identified no optical counterpart within the center of the Swift-XRT refined position or at the ePESSTO NTT optical counterpart location (Evans et al. GCN 21413, Lyman et al. GCN 21728) at the following 3-sigma limits:
```
r' > 20.6 mag
i' > 19.6 mag
```
These values are consistent with the limits and detections reported by other observatories (D'Avanzo et al. GCN 21721, Schady et al. GCN 21729, 21743).
These magnitudes are calibrated against nearby USNO-B1 sources, converted in SDSS bands, and not corrected for Galactic extinction."

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Jochen Greiner, last update: 04-Sep-2017 [Disclaimer]