Gamma-ray Burst 160927A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Sep 16 18:05:13 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     713782,   Seg_Num: 0
GRB_RA:          256.264d {+17h 05m 03s} (J2000),
                 256.450d {+17h 05m 48s} (current),
                 255.708d {+17h 02m 50s} (1950)
GRB_DEC:         +17.311d {+17d 18' 38"} (J2000),
                 +17.289d {+17d 17' 19"} (current),
                 +17.378d {+17d 22' 41"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       2023 [cnts]    Image_Peak=117 [image_cnts]
TRIGGER_DUR:     0.512 [sec] 
TRIGGER_INDEX:   483     E_range: 50-350 keV
BKG_INTEN:       14571 [cnts]
BKG_TIME:        65079.07 SOD {18:04:39.07} UT
BKG_DUR:         8 [sec]
GRB_DATE:        17658 TJD;   271 DOY;   16/09/27
GRB_TIME:        65089.89 SOD {18:04:49.89} UT
GRB_PHI:          68.55 [deg]
GRB_THETA:        26.76 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     35.44 [sigma]
IMAGE_SIGNIF:    7.56 [sigma]
MERIT_PARAMS:     +1  +0  +0  -1  +3  -2  +0  +0 -28  +0 
SUN_POSTN:       184.64d {+12h 18m 35s}   -2.01d {-02d 00' 35"}
SUN_DIST:         73.29 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      149.79d {+09h 59m 11s}  +10.91d {+10d 54' 21"}
MOON_DIST:       102.27 [deg]
MOON_ILLUM:      10 [%]
GAL_COORDS:       37.61, 31.07 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      252.80, 39.93 [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 = 313.90,18.56 [deg].

red DSS finding chart ps-file

GCN NOTICE

 
TITLE:           GCN/CALET NOTICE
NOTICE_DATE:     Tue 27 Sep 16 18:08:31 UT
NOTICE_TYPE:     CALET GBM Flight Lightcurve
POINT_RA:         33.29d {+02h 13m 09s} (J2000),
POINT_DEC:       +45.10d {+45d 06' 07"} (J2000),
TRIGGER_NUM:     1159034831
TRIGGER_DATE:    17658 TJD;   271 DOY;   16/09/27
TRIGGER_TIME:    65275.75 SOD {18:07:55.75} UT
TRIGGER_DET:     0 0 1 (HXM1 HXM2 SGM)
SIGNIFICANCE:    23.39 [sigma]
FOREGND_DUR:     4.00 [sec]
BACKGND_DUR1:    16.00 [sec]
ENERGY_BAND:     40-230 [keV]
SC_LON_LAT:      114.58,45.18 [deg]
LC_URL:          http://cgbm.calet.jp/cgbm_trigger/flight//1159034831/index.html
COMMENTS:        CALET-GBM Flight Lightcurve.
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Sep 16 18:06:16 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     713782,   Seg_Num: 0
POINT_RA:        256.240d {+17h 04m 58s} (J2000)
POINT_DEC:       +17.303d {+17d 18' 10"} (J2000)
IMG_START_DATE:  17658 TJD;   271 DOY;   16/09/27
IMG_START_TIME:  65169.39 SOD {18:06:09.39} UT,   79.5 [sec] since BAT Trigger Time
COUNTS:          1    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        0    Max_iter_allowed= 4
ERROR_CODE:      1
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        No source found in the image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Sep 16 18:08:44 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     713782,   Seg_Num: 0
GRB_RA:          256.264d {+17h 05m 03s} (J2000),
                 256.450d {+17h 05m 48s} (current),
                 255.708d {+17h 02m 50s} (1950)
GRB_DEC:         +17.311d {+17d 18' 38"} (J2000),
                 +17.289d {+17d 17' 19"} (current),
                 +17.378d {+17d 22' 41"} (1950)
GRB_DATE:        17658 TJD;   271 DOY;   16/09/27
GRB_TIME:        65089.89 SOD {18:04:49.89} UT
TRIGGER_INDEX:   483
GRB_PHI:          68.55 [deg]
GRB_THETA:        26.76 [deg]
DELTA_TIME:      39.00 [sec]
TRIGGER_DUR:     0.512 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     35.44 [sigma]
IMAGE_SIGNIF:    7.56 [sigma]
LC_URL:          sw00713782000msb.lc
SUN_POSTN:       184.65d {+12h 18m 35s}   -2.01d {-02d 00' 38"}
SUN_DIST:         73.29 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      149.82d {+09h 59m 18s}  +10.90d {+10d 53' 52"}
MOON_DIST:       102.24 [deg]
MOON_ILLUM:      10 [%]
GAL_COORDS:       37.61, 31.07 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      252.80, 39.93 [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 = 313.90,18.56 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Sep 16 18:09:13 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     713782,   Seg_Num: 0
POINT_RA:        256.240d {+17h 04m 58s} (J2000)
POINT_DEC:       +17.303d {+17d 18' 10"} (J2000)
POINT_ROLL:      262.361d
IMG_START_DATE:  17658 TJD;   271 DOY;   16/09/27
IMG_START_TIME:  65173.94 SOD {18:06:13.94} UT,   84.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.047
N_STARS:         95
X_OFFSET:        335 [pixels]
Y_OFFSET:        682 [pixels]
X_MAX:           1294 [pixels]
Y_MAX:           1641 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00713782000msufc0084.fits
SUN_POSTN:       184.65d {+12h 18m 35s}   -2.01d {-02d 00' 39"}
SUN_DIST:         73.26 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      149.83d {+09h 59m 19s}  +10.90d {+10d 53' 49"}
MOON_DIST:       102.22 [deg]
MOON_ILLUM:      10 [%]
GAL_COORDS:       37.60, 31.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      252.78, 39.92 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Sep 16 18:09:48 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     713782,   Seg_Num: 0
POINT_RA:        256.240d {+17h 04m 58s} (J2000)
POINT_DEC:       +17.303d {+17d 18' 10"} (J2000)
POINT_ROLL:      262.361d
IMG_START_DATE:  17658 TJD;   271 DOY;   16/09/27
IMG_START_TIME:  65173.94 SOD {18:06:13.94} UT,   84.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.047
N_STARS:         95
X_OFFSET:        335 [pixels]
Y_OFFSET:        682 [pixels]
X_MAX:           1294 [pixels]
Y_MAX:           1641 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00713782000msufc0084.fits
SUN_POSTN:       184.65d {+12h 18m 35s}   -2.01d {-02d 00' 39"}
SUN_DIST:         73.26 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      149.83d {+09h 59m 20s}  +10.90d {+10d 53' 44"}
MOON_DIST:       102.22 [deg]
MOON_ILLUM:      10 [%]
GAL_COORDS:       37.60, 31.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      252.78, 39.92 [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:     Tue 27 Sep 16 18:10:38 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     713782,   Seg_Num: 0
POINT_RA:        256.240d {+17h 04m 58s} (J2000)
POINT_DEC:       +17.303d {+17d 18' 10"} (J2000)
ROLL:            262.361d
IMG_START_DATE:  17658 TJD;   271 DOY;   16/09/27
IMG_START_TIME:  65173.94 SOD {18:06:13.94} UT,   84.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     496692390
X_OFFSET:        654 [pixels]
Y_OFFSET:        1001 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       814
Y_GRB_POS:       1161
BINNING_INDEX:   1
IM_URL:          sw00713782000msuni0101.fits
SUN_POSTN:       184.65d {+12h 18m 35s}   -2.01d {-02d 00' 40"}
SUN_DIST:         73.26 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      149.84d {+09h 59m 22s}  +10.89d {+10d 53' 37"}
MOON_DIST:       102.21 [deg]
MOON_ILLUM:      10 [%]
GAL_COORDS:       37.60, 31.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      252.78, 39.92 [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:     Tue 27 Sep 16 18:10:56 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     713782,   Seg_Num: 0
GRB_RA:          256.2426d {+17h 04m 58.22s} (J2000),
                 256.4288d {+17h 05m 42.92s} (current),
                 255.6865d {+17h 02m 44.77s} (1950)
GRB_DEC:         +17.3317d {+17d 19' 54.1"} (J2000),
                 +17.3097d {+17d 18' 34.8"} (current),
                 +17.3992d {+17d 23' 57.1"} (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:  17658 TJD;   271 DOY;   16/09/27
IMG_START_TIME:  65178.00 SOD {18:06:18.00} UT,   88.1 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       184.65d {+12h 18m 35s}   -2.01d {-02d 00' 40"}
SUN_DIST:         73.27 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      149.84d {+09h 59m 22s}  +10.89d {+10d 53' 35"}
MOON_DIST:       102.20 [deg]
MOON_ILLUM:      10 [%]
GAL_COORDS:       37.63, 31.10 [deg] galactic lon,lat of the burst
ECL_COORDS:      252.77, 39.95 [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:     Tue 27 Sep 16 18:10:54 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     713782,   Seg_Num: 0
POINT_RA:        256.240d {+17h 04m 58s} (J2000)
POINT_DEC:       +17.303d {+17d 18' 10"} (J2000)
ROLL:            262.361d
IMG_START_DATE:  17658 TJD;   271 DOY;   16/09/27
IMG_START_TIME:  65173.94 SOD {18:06:13.94} UT,   84.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     496692390
X_OFFSET:        654 [pixels]
Y_OFFSET:        1001 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       814
Y_GRB_POS:       1161
BINNING_INDEX:   1
IM_URL:          sw00713782000msuni0101.fits
SUN_POSTN:       184.65d {+12h 18m 35s}   -2.01d {-02d 00' 40"}
SUN_DIST:         73.26 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      149.84d {+09h 59m 22s}  +10.89d {+10d 53' 35"}
MOON_DIST:       102.21 [deg]
MOON_ILLUM:      10 [%]
GAL_COORDS:       37.60, 31.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      252.78, 39.92 [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 #19952
S. L. Gibson (U Leicester), N. Gehrels (NASA/GSFC), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the Swift Team:
At 18:04:49 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 160927A (trigger=713782). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 256.264, +17.311 which is
```
   RA(J2000) = 17h 05m 03s
   Dec(J2000) = +17d 18' 38"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 0.5 sec. The peak count rate was ~5000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 18:06:09.3 UT, 79.5 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 256.24288, 17.33165 which is equivalent to:
```
   RA(J2000)  = 17h 04m 58.29s
   Dec(J2000) = +17d 19' 53.9"
```
with an uncertainty of 3.7 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. We cannot determine whether the source is fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 7.14 x 10^20 cm^-2 (Willingale et al. 2013).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 84 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 0.08.
Burst Advocate for this burst is S. L. Gibson (slg44 AT le.ac.uk). 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:     Tue 27 Sep 16 18:16:39 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     713782,   Seg_Num: 0
POINT_RA:        256.238d {+17h 04m 57s} (J2000)
POINT_DEC:       +17.301d {+17d 18' 05"} (J2000)
POINT_ROLL:      262.360d
IMG_START_DATE:  17658 TJD;   271 DOY;   16/09/27
IMG_START_TIME:  65386.06 SOD {18:09:46.06} UT,   296.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.585
N_STARS:         128
X_OFFSET:        95 [pixels]
Y_OFFSET:        442 [pixels]
X_MAX:           1534 [pixels]
Y_MAX:           1881 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw00713782000msufc0296.fits
SUN_POSTN:       184.65d {+12h 18m 36s}   -2.01d {-02d 00' 46"}
SUN_DIST:         73.26 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      149.89d {+09h 59m 34s}  +10.88d {+10d 52' 48"}
MOON_DIST:       102.17 [deg]
MOON_ILLUM:      10 [%]
GAL_COORDS:       37.59, 31.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      252.77, 39.92 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Sep 16 18:17:03 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     713782,   Seg_Num: 0
POINT_RA:        256.238d {+17h 04m 57s} (J2000)
POINT_DEC:       +17.301d {+17d 18' 05"} (J2000)
POINT_ROLL:      262.360d
IMG_START_DATE:  17658 TJD;   271 DOY;   16/09/27
IMG_START_TIME:  65386.06 SOD {18:09:46.06} UT,   296.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.585
N_STARS:         128
X_OFFSET:        95 [pixels]
Y_OFFSET:        442 [pixels]
X_MAX:           1534 [pixels]
Y_MAX:           1881 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw00713782000msufc0296.fits
SUN_POSTN:       184.65d {+12h 18m 36s}   -2.01d {-02d 00' 46"}
SUN_DIST:         73.26 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      149.90d {+09h 59m 35s}  +10.88d {+10d 52' 45"}
MOON_DIST:       102.16 [deg]
MOON_ILLUM:      10 [%]
GAL_COORDS:       37.59, 31.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      252.77, 39.92 [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:     Tue 27 Sep 16 18:17:09 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     713782,   Seg_Num: 0
GRB_RA:          256.2429d {+17h 04m 58.29s} (J2000),
                 256.4291d {+17h 05m 42.99s} (current),
                 255.6868d {+17h 02m 44.84s} (1950)
GRB_DEC:         +17.3314d {+17d 19' 53.0"} (J2000),
                 +17.3094d {+17d 18' 33.7"} (current),
                 +17.3989d {+17d 23' 56.1"} (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:  17658 TJD;   271 DOY;   16/09/27
IMG_START_TIME:  65178.00 SOD {18:06:18.00} UT,   88.1 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       184.65d {+12h 18m 36s}   -2.01d {-02d 00' 46"}
SUN_DIST:         73.27 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      149.90d {+09h 59m 35s}  +10.88d {+10d 52' 44"}
MOON_DIST:       102.16 [deg]
MOON_ILLUM:      10 [%]
GAL_COORDS:       37.63, 31.10 [deg] galactic lon,lat of the burst
ECL_COORDS:      252.77, 39.95 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        This position was enhanced using UVOT field astrometry.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Sep 16 18:18:00 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     713782,   Seg_Num: 0
POINT_RA:        256.238d {+17h 04m 57s} (J2000)
POINT_DEC:       +17.301d {+17d 18' 05"} (J2000)
ROLL:            262.360d
IMG_START_DATE:  17658 TJD;   271 DOY;   16/09/27
IMG_START_TIME:  65386.06 SOD {18:09:46.06} UT,   296.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     496692602
X_OFFSET:        654 [pixels]
Y_OFFSET:        1001 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       814
Y_GRB_POS:       1161
BINNING_INDEX:   1
IM_URL:          sw00713782000msuni0313.fits
SUN_POSTN:       184.65d {+12h 18m 37s}   -2.01d {-02d 00' 47"}
SUN_DIST:         73.26 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      149.90d {+09h 59m 37s}  +10.88d {+10d 52' 37"}
MOON_DIST:       102.16 [deg]
MOON_ILLUM:      10 [%]
GAL_COORDS:       37.59, 31.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      252.77, 39.92 [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:     Tue 27 Sep 16 18:18:09 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     713782,   Seg_Num: 0
POINT_RA:        256.238d {+17h 04m 57s} (J2000)
POINT_DEC:       +17.301d {+17d 18' 05"} (J2000)
ROLL:            262.360d
IMG_START_DATE:  17658 TJD;   271 DOY;   16/09/27
IMG_START_TIME:  65386.06 SOD {18:09:46.06} UT,   296.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     496692602
X_OFFSET:        654 [pixels]
Y_OFFSET:        1001 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       814
Y_GRB_POS:       1161
BINNING_INDEX:   1
IM_URL:          sw00713782000msuni0313.fits
SUN_POSTN:       184.65d {+12h 18m 37s}   -2.01d {-02d 00' 47"}
SUN_DIST:         73.26 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      149.91d {+09h 59m 37s}  +10.88d {+10d 52' 36"}
MOON_DIST:       102.16 [deg]
MOON_ILLUM:      10 [%]
GAL_COORDS:       37.59, 31.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      252.77, 39.92 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Sep 16 18:22:18 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     713782,   Seg_Num: 0
POINT_RA:        256.238d {+17h 04m 57s} (J2000)
POINT_DEC:       +17.301d {+17d 18' 05"} (J2000)
POINT_ROLL:      262.360d
IMG_START_DATE:  17658 TJD;   271 DOY;   16/09/27
IMG_START_TIME:  65965.98 SOD {18:19:25.98} UT,   876.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.041
N_STARS:         190
X_OFFSET:        95 [pixels]
Y_OFFSET:        442 [pixels]
X_MAX:           1534 [pixels]
Y_MAX:           1881 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00713782000msufc0876.fits
SUN_POSTN:       184.65d {+12h 18m 37s}   -2.01d {-02d 00' 51"}
SUN_DIST:         73.26 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      149.94d {+09h 59m 46s}  +10.87d {+10d 52' 02"}
MOON_DIST:       102.13 [deg]
MOON_ILLUM:      10 [%]
GAL_COORDS:       37.59, 31.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      252.77, 39.92 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Sep 16 18:22:46 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     713782,   Seg_Num: 0
POINT_RA:        256.238d {+17h 04m 57s} (J2000)
POINT_DEC:       +17.301d {+17d 18' 05"} (J2000)
POINT_ROLL:      262.360d
IMG_START_DATE:  17658 TJD;   271 DOY;   16/09/27
IMG_START_TIME:  65965.98 SOD {18:19:25.98} UT,   876.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.041
N_STARS:         190
X_OFFSET:        95 [pixels]
Y_OFFSET:        442 [pixels]
X_MAX:           1534 [pixels]
Y_MAX:           1881 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00713782000msufc0876.fits
SUN_POSTN:       184.66d {+12h 18m 37s}   -2.01d {-02d 00' 52"}
SUN_DIST:         73.26 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      149.95d {+09h 59m 47s}  +10.87d {+10d 51' 58"}
MOON_DIST:       102.12 [deg]
MOON_ILLUM:      10 [%]
GAL_COORDS:       37.59, 31.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      252.77, 39.92 [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:     Tue 27 Sep 16 18:24:04 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     713782,   Seg_Num: 0
POINT_RA:        256.238d {+17h 04m 57s} (J2000)
POINT_DEC:       +17.301d {+17d 18' 05"} (J2000)
ROLL:            262.360d
IMG_START_DATE:  17658 TJD;   271 DOY;   16/09/27
IMG_START_TIME:  65965.98 SOD {18:19:25.98} UT,   876.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     496693182
X_OFFSET:        654 [pixels]
Y_OFFSET:        1001 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       814
Y_GRB_POS:       1161
BINNING_INDEX:   1
IM_URL:          sw00713782000msuni0893.fits
SUN_POSTN:       184.66d {+12h 18m 37s}   -2.01d {-02d 00' 53"}
SUN_DIST:         73.26 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      149.96d {+09h 59m 50s}  +10.86d {+10d 51' 48"}
MOON_DIST:       102.11 [deg]
MOON_ILLUM:      10 [%]
GAL_COORDS:       37.59, 31.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      252.77, 39.92 [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).  
COMMENTS:        This notice was forced out after watchdog timer expiring -- most likely due to missing packet(s);  
COMMENTS:        as a consequence some of the fields may be incoorect (eg TRIGGER_NUM,RA,DEC).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 27 Sep 16 18:24:13 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     713782,   Seg_Num: 0
POINT_RA:        256.238d {+17h 04m 57s} (J2000)
POINT_DEC:       +17.301d {+17d 18' 05"} (J2000)
ROLL:            262.360d
IMG_START_DATE:  17658 TJD;   271 DOY;   16/09/27
IMG_START_TIME:  65965.98 SOD {18:19:25.98} UT,   876.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     496693182
X_OFFSET:        654 [pixels]
Y_OFFSET:        1001 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       814
Y_GRB_POS:       1161
BINNING_INDEX:   1
IM_URL:          sw00713782000msuni0893.fits
SUN_POSTN:       184.66d {+12h 18m 37s}   -2.02d {-02d 00' 53"}
SUN_DIST:         73.25 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      149.96d {+09h 59m 50s}  +10.86d {+10d 51' 47"}
MOON_DIST:       102.11 [deg]
MOON_ILLUM:      10 [%]
GAL_COORDS:       37.59, 31.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      252.77, 39.92 [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:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.  
COMMENTS:        This notice was forced out after watchdog timer expiring -- most likely due to missing packet(s);  
COMMENTS:        as a consequence some of the fields may be incoorect (eg TRIGGER_NUM,RA,DEC).

GCN Circular #19953
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Using promptly downlinked XRT event data for GRB 160927A, we find an enhanced XRT position of the afterglow: RA, Dec: 256.2427, 17.3316 which is equivalent to:
```
   RA (J2000)  = 17 04 58.24
   Dec (J2000) = +17 19 53.7
```
with an uncertainty of 2.1 arcseconds (radius, 90% confidence). Analysis of the promptly available data is online at http://www.swift.ac.uk/sper/713782.
Position enhancement is is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular is an official product of the Swift-XRT team.
GCN Circular #19954
A. Tkachenko, R. Burenin, M. Pavlinsky, R. Sunyaev (IKI), I. Bikmaev, E. Irtuganov, N. Sakhibullin (KFU/AST), I. Khamitov, H. Kirbiyik (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.)
report:
We observed field of Swift short hard GRB 160927A (Gibson et al., GCN 19952) with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK National Observatory, Turkey) using TFOSC. We obtained four 600s exposures in SDSS-r filter at high airmass and very poor seeing (2.5 arcsec) starting at 18:59:24 UT, i.e. approximately 55 min after the burst.
At the edge of improved XRT localization (Evans et al., GCN 19953) we find faint optical source, which is not present in SDSS image, at the position:
RA,Dec: 17:04:58.21 +17:19:55.5 (J2000)
For this source we estimate SDSS-r mag =~ 22.3. The finding chart can be found at:
http://dlc.rsdc.rssi.ru/~rodion/grb/160927a/r.jpg
GCN Circular #19955
Martin Jelinek, Jan Strobl, Rene Hudec, Vojtech Simon and Cyril Polasek (ASU CAS Ondrejov, CZ) report:
The 50cm robotic telescope (D50) of Ondrejov observatory in Czech republic reacted robotically to the alert of GRB160927A (Gibson et al, GCNC 19952), obtaining a series of 10s unfiltered images starting at 18:05:29.9UT, i.e. 40s post trigger.
We do not detect any new source within or near the XRT error circle (Evans, GCNC 19953) in comparison to USNO-B1.0 catalog neither in single images (3-sigma limit R>18.7) nor in a combined 25x10s frame (mean exp time 124s post trigger, 3-sigma limit R>20.5).
GCN Circular #19956
P. D'Avanzo, A. Melandri (INAF-OAB), E. Palazzi (INAF-IASFBo), V. D'Elia (INAF/OAR & ASI/ASDC), L. Di Fabrizio, D. Carosati (INAF-TNG) report on behalf of the CIBO collaboration:
We observed the field of the short GRB 160927A (Gibson et al., GCN 19952) with the 3.6m Telescopio Nazionale Galileo (TNG) equipped with DOLoRes. Observations were carried out in the r-sdss filter. Observations started on Sept 27 at 20:12:49 UT (2.13 hours after the burst) and consist in a series of 5 images, each one lasting 180 seconds.
At the enhanced XRT position (Evans, GCN 19953) in the co-added image we detect an object at the following coordinates (J2000):
RA, Dec = 17:04:58.22, +17:19:54.9
+/- 0.5". The object has a magnitude r = 22.6 +/- 0.1 (calibrated against nearby SDSS stars). This object is the same reported by Tkachenko et al. (GCN 19954). Given the mild evidence for fading, we propose this object as the optical afterglow of GRB 160927A.
GCN Circular #19957
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 3482 s of XRT Photon Counting mode data and 5 UVOT images for GRB 160927A, 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 = 256.24259, +17.33197 which is equivalent to:
```
RA (J2000): 17h 04m 58.22s
Dec (J2000): +17d 19' 55.1"
```
with an uncertainty of 1.7 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 #19958
K.L. Page (U. Leicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), L.M. McCauley (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), B. Mingo (U. Leicester), A.P. Beardmore (U. Leicester) and S.L. Gibson report on behalf of the Swift-XRT team:
We have analysed 6.6 ks of XRT data for GRB 160927A (Gibson et al. GCN Circ. 19952), from 89 s to 13.2 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. 19953).
The light curve can be modelled with a power-law decay with a decay index of alpha=0.99 (+0.08, -0.07).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.72 (+0.29, -0.17). The best-fitting absorption column is 7.6 (+9.0, -0.4) x 10^20 cm^-2, consistent with the Galactic value of 7.1 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.9 x 10^-11 (4.3 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     7.6 (+9.0, -0.4) x 10^20 cm^-2
Galactic foreground: 7.1 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.72 (+0.29, -0.17)
```
If the light curve continues to decay with a power-law decay index of 0.99, the count rate at T+24 hours will be 9.0 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.5 x 10^-14 (3.9 x 10^-14) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00713782.
This circular is an official product of the Swift-XRT team.
GCN Circular #19959
P Wiseman (MPE Garching), J Bolmer (ESO Vitacura), and J Greiner (MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 160927A (Swift trigger 713782; Gibson et al. , GCN #19952) 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 23:26 UT on 27/09/2016, 5h 21m after the GRB trigger, and continued for ~1 hour, mostly during astronomical twilight. They were performed at an average seeing of 1.8" and at an average airmass of 2.
Based on 22.4 min of total exposures around a mid-time of 5.58 hours after the trigger we marginally detect the source reported by Tkachenko et al. (GCN #19954) and D'Avanzo et al. (GCN#19956) in the GROND r'-band with an AB magnitude of:
r' = 23.9 +/- 0.4 mag.
The apparent fading since the RTT150 and TNG observations is convincing evidence for this source being the afterglow, and further suggests a steepening of the afterglow light-curve since the TNG observation.
The given magnitude is calibrated against SDSS zeropoints and is not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.07 mag in the direction of the burst (Schlafly & Finkbeiner, 2011).
GCN Circular #19960
D. Xu (NAOC/CAS), D. Malesani (DARK/NBI and DTU Space), H. Dahle, B. Racine (Oslo U.), T. Pursimo (NOT), J. P. U. Fynbo (DARK/NBI), report on behalf of a larger collaboration:
We observed the field of GRB 160927A (Gibson et al., GCN 19952) using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations started at 21:24:39 UT on 2016-09-27 (i.e., 3.33 hr after the trigger) and 5x300s SDSS r-band frames were obtained.
The previously reported optical afterglow of the burst (Tkachenko et al., GCN 19954; D'Avanzo et al., GCN 19956; Wiseman et al., GCN 19959) is clearly detected in our stacked r-band image. It has m(r)=23.07 +/- 0.10 at a median time of 3.56 hr post-burst, calibrated with nearby SDSS stars.
Combined with the RTT150, TNG, and GROND data points reported in the above GCN Circulars, we confirm the steepening of the afterglow light-curve (Wiseman et al., GCN 19959). A rough estimate gives rise to alpha_1~0.6, a break time of ~3.1 hr post-burst, and alpha_2~1.7 (but poorly constrained).
GCN Circular #19961
A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), S. L. Gibson (U Leicester), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-61 to T+242 sec from the recent telemetry downlink, we report further analysis of BAT GRB 160927A (trigger #713782) (Gibson, et al., GCN Circ. 19952). The BAT ground-calculated position is RA, Dec = 256.268, 17.334 deg which is
```
    RA(J2000)  =  17h 05m 04.2s
    Dec(J2000) = +17d 20' 01.8"
```
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 50%.
The mask-weighted light curve in 16 msec binning shows at least two peaks. The first peak starts at T-0.2 sec, peaks at T+0.2 sec and ends at T+0.3 sec. The second peak starts at T+0.3 sec, peaks at T+0.4 sec and ends at T+0.5 sec. T90 (15-350 keV) is 0.48 +- 0.10 sec (estimated error including systematics).
The time-averaged spectrum from T+0 to T+0.54 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.12 +- 0.26. The fluence in the 15-150 keV band is 1.4 +- 0.2 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.23 sec in the 15-150 keV band is 1.9 +- 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/713782/BA/
GCN Circular #19962
U.Quadri, L.Strabla and R.Girelli report:
We imaged the field of GRB 160927A detected by SWIFT(trigger 713782) with the robotic telescope of (IAU station 565) Bassano Bresciano Observatory, Italy. Member of: AAVSO - American Association of Variable Star Observers. ISSP - Italian Supernovae Search Project. UAI/SSV - Unione Astrofili Italiani/sezione stelle variabili.
The observations started 11.72 min after the GRB trigger, with our Newton telescope D=250 mm F/D=4.8.
Weather conditions were good.
We co-added 52 exposures of 60 sec each.
```
Start T0+      End T0+      CV lim
11.72 min     65.71 min     19.5
```
We did not found any optical counterpart in the error box of the XRTcandidate. S. L. Gibson (U Leicester), N. Gehrels (NASA/GSFC), et al.
Magnitudes were estimated with the UCAC4 cat. and are not corrected for galactic dust extinction.
Reference: http://www.osservatoriobassano.org/GRB.asp
The message may be cited.
GCN Circular #19963
Paul Kuin(MSSL-UCL) and S. L. Gibson (U. Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 160927A 85 s after the BAT trigger (Gibson et al., GCN Circ. 19952). No optical afterglow consistent with the optical position (D'Avanzo et al. GCN Circ. 19956) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC            85          235          147         >21.0
u_FC               297          547          246         >20.4
white               85        13184         1426         >21.8
v                  627         6999          510         >19.9
b                  553        12500         1179         >21.5
u                  297        11587         1433         >21.1
w1                 850         7411          491         >20.2
m2                 826         7204          294         >20.5
w2                 602         6794          510         >21.0
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.08 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #19964
W. Fong (Univ. of Arizona), S. Sheppard (Carnegie DTM) and E. Berger (Harvard) report:
We imaged the location of the short-duration GRB 160927A (Gibson et al., GCN 19952) with the Inamori-Magellan Areal Camera and Spectrograph (IMACS) mounted on the Magellan/Baade 6.5-m telescope at a mid-time of 2016 Sep 28.00 UT (5.94 hr post-burst). We obtained 4x200-sec of r-band exposures in 0.75" seeing at an airmass of 1.9. We clearly detect the optical afterglow (Tkachenko et al., GCN 19954; D'Avanzo et al., GCN 19956; Wiseman et al., GCN 19959; Xu et al., GCN 19960). Tied to 10 SDSS stars in the field, we calculate a magnitude of r_AB=23.84 +/- 0.21, not corrected for Galactic extinction in the direction of the burst.
GCN Circular #19978
K. P. Mooley, 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 the short/hard GRB 160927A (Gibson et al., GCN 19952) as part of the 4pisky program, and subsequent follow up observations were obtained up to 3 days post-burst. Our observations at 15 GHz on 2016 Sep 27.79, Sep 28.70, and Sep 29.70 (UT; 1 hour, 23 hours, and 47 hours post-burst respectively) do not reveal any radio source at the XRT location (Page et al., GCN 19958), with 3sigma upper limits of 132 uJy, 119 uJy, and 110 uJy respectively. The 3sigma upper limit from the first two epochs combined is 80 uJy.
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/.
GCN Circular #20002
M. Moriyama, A. Yoshida, T. Sakamoto, Y. Kawakubo, Y. Yamada (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), I. Takahashi (IPMU), Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), W. Ishizaki (ICRR), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena) and the CALET collaboration:
The short-duration GRB 160927A (Gibson et al., GCN Circ. 19952) was detected by the ground analysis of the CALET Gamma-ray Burst Monitor (CGBM) data at 18:04:49.88 on 27 September 2016. The highest signal-to-noise based on the light curve data is 5.3 sigma. The burst signal was seen by the SGM instrument.
The light curve of the SGM shows a single peak starting at T0, peaking at T+0.4 sec and ending at T+0.6 sec. The T90 duration measured by the SGM data is 0.35 +- 0.11 sec (40-1000 keV).
The light curve is available at
http://cgbm.calet.jp/cgbm_trigger/flight/1159034645/
The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.
GCN Circular #20004
A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), L. Izzo (IAA-CSIC), D.A. Kann (TLS Tautenburg), C.C. Thoene (IAA-CSIC), Z. Cano (IAA-CSIC), D. Reverte-Paya (GRANTECAN, IAC, ULL) report on behalf of a larger collaboration:
We observed the afterglow of the short-hard GRB 160927A (Gibson et al., GCN 19952) with OSIRIS on the 10.4m GTC telescope. Observations consisted in 10x190s exposures in r-band, with a mean epoch on 28 September 2016 at 20:26 UT (26.52 hr after the burst). The optical counterpart (Tkachenko et al., GCN 19954; D=E2=80=99Avanzo et al., GCN 19956; Wiseman et al. GCN 1959; Xu et al., GCN 19960; Fong et al., GCN 19964) is detected at a magnitude of r_AB =3D 25.3+/-0.2, as compared to several SDSS field stars.
Combining this observation with the rest of the available GCN data, the light curve indicates an early evolution with a shallow decay, followed by a faster decay (as already mentioned by Wiseman et al. GCN 1959 and Xu et al., GCN 19960), with the break at around the TNG epoch, after which we estimate a decay rate of with alpha =3D -1.03+/-0.08 (where F~t^alpha).This decay is significantly shallower than the one reported by (Xu et al., GCN 19960), indicating that the light curve may be flattening at the time of the GTC observation. This could be due to the contribution of an additional component (either the host galaxy, or more unlikely the contribution of a kilonova) or just due to the uncertainties of the different photometric measurements.

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Jochen Greiner, last update: 06-Oct-2016 [Disclaimer]