Gamma-ray Burst 111020A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 20 Oct 11 06:34:10 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     505926,   Seg_Num: 0
GRB_RA:          287.027d {+19h 08m 06s} (J2000),
                 287.227d {+19h 08m 54s} (current),
                 286.177d {+19h 04m 43s} (1950)
GRB_DEC:         -37.985d {-37d 59' 05"} (J2000),
                 -37.966d {-37d 57' 55"} (current),
                 -38.064d {-38d 03' 51"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       1529 [cnts]    Image_Peak=125 [image_cnts]
TRIGGER_DUR:     0.256 [sec] 
TRIGGER_INDEX:   123     E_range: 25-100 keV
BKG_INTEN:       29460 [cnts]
BKG_TIME:        23616.51 SOD {06:33:36.51} UT
BKG_DUR:         8 [sec]
GRB_DATE:        15854 TJD;   293 DOY;   11/10/20
GRB_TIME:        23629.05 SOD {06:33:49.05} UT
GRB_PHI:          68.46 [deg]
GRB_THETA:        18.44 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     18.73 [sigma]
IMAGE_SIGNIF:    8.92 [sigma]
MERIT_PARAMS:     +1  +0  +0  -2  +2  -1  +0  +1 -20  +0 
SUN_POSTN:       204.60d {+13h 38m 24s}  -10.23d {-10d 13' 46"}
SUN_DIST:         77.95 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      119.35d {+07h 57m 25s}  +17.04d {+17d 02' 10"}
MOON_DIST:       156.52 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      359.36,-19.37 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      283.85,-15.36 [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 = 167.50,-11.04 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 20 Oct 11 06:35:14 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     505926,   Seg_Num: 0
POINT_RA:        287.010d {+19h 08m 02s} (J2000)
POINT_DEC:       -37.991d {-37d 59' 25"} (J2000)
IMG_START_DATE:  15854 TJD;   293 DOY;   11/10/20
IMG_START_TIME:  23701.83 SOD {06:35:01.83} UT,   72.8 [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:     Thu 20 Oct 11 06:37:44 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     505926,   Seg_Num: 0
GRB_RA:          287.027d {+19h 08m 06s} (J2000),
                 287.227d {+19h 08m 54s} (current),
                 286.177d {+19h 04m 43s} (1950)
GRB_DEC:         -37.985d {-37d 59' 05"} (J2000),
                 -37.966d {-37d 57' 55"} (current),
                 -38.064d {-38d 03' 51"} (1950)
GRB_DATE:        15854 TJD;   293 DOY;   11/10/20
GRB_TIME:        23629.05 SOD {06:33:49.05} UT
TRIGGER_INDEX:   123
GRB_PHI:          68.46 [deg]
GRB_THETA:        18.44 [deg]
DELTA_TIME:      25.00 [sec]
TRIGGER_DUR:     0.256 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     18.73 [sigma]
IMAGE_SIGNIF:    8.92 [sigma]
LC_URL:          sw00505926000msb.lc
SUN_POSTN:       204.60d {+13h 38m 25s}  -10.23d {-10d 13' 49"}
SUN_DIST:         77.94 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      119.39d {+07h 57m 33s}  +17.03d {+17d 01' 39"}
MOON_DIST:       156.50 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      359.36,-19.37 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      283.85,-15.36 [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 = 167.50,-11.04 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 20 Oct 11 06:38:45 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     505926,   Seg_Num: 0
POINT_RA:        287.009d {+19h 08m 02s} (J2000)
POINT_DEC:       -37.991d {-37d 59' 25"} (J2000)
POINT_ROLL:      266.498d
IMG_START_DATE:  15854 TJD;   293 DOY;   11/10/20
IMG_START_TIME:  23708.81 SOD {06:35:08.81} UT,   79.8 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.766
N_STARS:         138
X_OFFSET:        398 [pixels]
Y_OFFSET:        651 [pixels]
X_MAX:           1357 [pixels]
Y_MAX:           1610 [pixels]
DET_THRESH:      18
PHOTO_THRESH:    10
SL_URL:          sw00505926000msufc0079.fits
SUN_POSTN:       204.60d {+13h 38m 25s}  -10.23d {-10d 13' 50"}
SUN_DIST:         77.93 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      119.40d {+07h 57m 35s}  +17.03d {+17d 01' 31"}
MOON_DIST:       156.48 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      359.35,-19.36 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      283.83,-15.36 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 20 Oct 11 06:38:59 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     505926,   Seg_Num: 0
GRB_RA:          287.0544d {+19h 08m 13.05s} (J2000),
                 287.2546d {+19h 09m 01.11s} (current),
                 286.2051d {+19h 04m 49.21s} (1950)
GRB_DEC:         -38.0114d {-38d 00' 41.0"} (J2000),
                 -37.9920d {-37d 59' 31.2"} (current),
                 -38.0911d {-38d 05' 27.8"} (1950)
GRB_ERROR:       4.4 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  15854 TJD;   293 DOY;   11/10/20
IMG_START_TIME:  23731.00 SOD {06:35:31.00} UT,   102.0 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       204.60d {+13h 38m 25s}  -10.23d {-10d 13' 50"}
SUN_DIST:         77.96 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      119.40d {+07h 57m 36s}  +17.02d {+17d 01' 29"}
MOON_DIST:       156.48 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      359.35,-19.40 [deg] galactic lon,lat of the burst
ECL_COORDS:      283.87,-15.39 [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:     Thu 20 Oct 11 06:39:13 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     505926,   Seg_Num: 0
POINT_RA:        287.009d {+19h 08m 02s} (J2000)
POINT_DEC:       -37.991d {-37d 59' 25"} (J2000)
POINT_ROLL:      266.498d
IMG_START_DATE:  15854 TJD;   293 DOY;   11/10/20
IMG_START_TIME:  23708.81 SOD {06:35:08.81} UT,   79.8 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.766
N_STARS:         138
X_OFFSET:        398 [pixels]
Y_OFFSET:        651 [pixels]
X_MAX:           1357 [pixels]
Y_MAX:           1610 [pixels]
DET_THRESH:      18
PHOTO_THRESH:    10
SL_URL:          sw00505926000msufc0079.fits
SUN_POSTN:       204.60d {+13h 38m 25s}  -10.23d {-10d 13' 50"}
SUN_DIST:         77.93 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      119.40d {+07h 57m 36s}  +17.02d {+17d 01' 27"}
MOON_DIST:       156.48 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      359.35,-19.36 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      283.83,-15.36 [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:     Thu 20 Oct 11 06:40:11 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     505926,   Seg_Num: 0
POINT_RA:        287.009d {+19h 08m 02s} (J2000)
POINT_DEC:       -37.991d {-37d 59' 25"} (J2000)
ROLL:            266.498d
IMG_START_DATE:  15854 TJD;   293 DOY;   11/10/20
IMG_START_TIME:  23708.81 SOD {06:35:08.81} UT,   79.8 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     340785316
X_OFFSET:        717 [pixels]
Y_OFFSET:        970 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       877
Y_GRB_POS:       1130
BINNING_INDEX:   1
IM_URL:          sw00505926000msuni0087.fits
SUN_POSTN:       204.60d {+13h 38m 25s}  -10.23d {-10d 13' 51"}
SUN_DIST:         77.93 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      119.41d {+07h 57m 38s}  +17.02d {+17d 01' 19"}
MOON_DIST:       156.47 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      359.35,-19.36 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      283.83,-15.36 [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:     Thu 20 Oct 11 06:40:27 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     505926,   Seg_Num: 0
POINT_RA:        287.009d {+19h 08m 02s} (J2000)
POINT_DEC:       -37.991d {-37d 59' 25"} (J2000)
ROLL:            266.498d
IMG_START_DATE:  15854 TJD;   293 DOY;   11/10/20
IMG_START_TIME:  23708.81 SOD {06:35:08.81} UT,   79.8 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     340785316
X_OFFSET:        717 [pixels]
Y_OFFSET:        970 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       877
Y_GRB_POS:       1130
BINNING_INDEX:   1
IM_URL:          sw00505926000msuni0087.fits
SUN_POSTN:       204.60d {+13h 38m 25s}  -10.23d {-10d 13' 51"}
SUN_DIST:         77.93 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      119.41d {+07h 57m 39s}  +17.02d {+17d 01' 16"}
MOON_DIST:       156.47 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      359.35,-19.36 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      283.83,-15.36 [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:     Thu 20 Oct 11 06:45:35 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     505926,   Seg_Num: 0
POINT_RA:        287.007d {+19h 08m 02s} (J2000)
POINT_DEC:       -37.992d {-37d 59' 31"} (J2000)
POINT_ROLL:      266.499d
IMG_START_DATE:  15854 TJD;   293 DOY;   11/10/20
IMG_START_TIME:  23920.82 SOD {06:38:40.82} UT,   291.8 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        1.235
N_STARS:         137
X_OFFSET:        158 [pixels]
Y_OFFSET:        411 [pixels]
X_MAX:           1597 [pixels]
Y_MAX:           1850 [pixels]
DET_THRESH:      9
PHOTO_THRESH:    4
SL_URL:          sw00505926000msufc0291.fits
SUN_POSTN:       204.61d {+13h 38m 26s}  -10.23d {-10d 13' 56"}
SUN_DIST:         77.92 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      119.46d {+07h 57m 50s}  +17.01d {+17d 00' 32"}
MOON_DIST:       156.44 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      359.35,-19.35 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      283.83,-15.37 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 20 Oct 11 06:45:59 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     505926,   Seg_Num: 0
POINT_RA:        287.007d {+19h 08m 02s} (J2000)
POINT_DEC:       -37.992d {-37d 59' 31"} (J2000)
POINT_ROLL:      266.499d
IMG_START_DATE:  15854 TJD;   293 DOY;   11/10/20
IMG_START_TIME:  23920.82 SOD {06:38:40.82} UT,   291.8 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        1.235
N_STARS:         137
X_OFFSET:        158 [pixels]
Y_OFFSET:        411 [pixels]
X_MAX:           1597 [pixels]
Y_MAX:           1850 [pixels]
DET_THRESH:      9
PHOTO_THRESH:    4
SL_URL:          sw00505926000msufc0291.fits
SUN_POSTN:       204.61d {+13h 38m 26s}  -10.23d {-10d 13' 56"}
SUN_DIST:         77.92 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      119.46d {+07h 57m 51s}  +17.01d {+17d 00' 29"}
MOON_DIST:       156.44 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      359.35,-19.35 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      283.83,-15.37 [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:     Thu 20 Oct 11 06:46:27 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     505926,   Seg_Num: 0
GRB_RA:          287.0518d {+19h 08m 12.43s} (J2000),
                 287.2520d {+19h 09m 00.48s} (current),
                 286.2025d {+19h 04m 48.59s} (1950)
GRB_DEC:         -38.0123d {-38d 00' 44.2"} (J2000),
                 -37.9929d {-37d 59' 34.5"} (current),
                 -38.0920d {-38d 05' 31.0"} (1950)
GRB_ERROR:       2.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  15854 TJD;   293 DOY;   11/10/20
IMG_START_TIME:  23731.00 SOD {06:35:31.00} UT,   102.0 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       204.61d {+13h 38m 26s}  -10.23d {-10d 13' 57"}
SUN_DIST:         77.96 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      119.47d {+07h 57m 52s}  +17.01d {+17d 00' 25"}
MOON_DIST:       156.43 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      359.34,-19.39 [deg] galactic lon,lat of the burst
ECL_COORDS:      283.86,-15.39 [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:     Thu 20 Oct 11 06:47:02 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     505926,   Seg_Num: 0
POINT_RA:        287.007d {+19h 08m 02s} (J2000)
POINT_DEC:       -37.992d {-37d 59' 31"} (J2000)
ROLL:            266.499d
IMG_START_DATE:  15854 TJD;   293 DOY;   11/10/20
IMG_START_TIME:  23920.82 SOD {06:38:40.82} UT,   291.8 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     340785528
X_OFFSET:        717 [pixels]
Y_OFFSET:        970 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       877
Y_GRB_POS:       1130
BINNING_INDEX:   1
IM_URL:          sw00505926000msuni0299.fits
SUN_POSTN:       204.61d {+13h 38m 26s}  -10.23d {-10d 13' 57"}
SUN_DIST:         77.92 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      119.47d {+07h 57m 54s}  +17.01d {+17d 00' 20"}
MOON_DIST:       156.43 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      359.35,-19.35 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      283.83,-15.37 [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:     Thu 20 Oct 11 06:47:17 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     505926,   Seg_Num: 0
POINT_RA:        287.007d {+19h 08m 02s} (J2000)
POINT_DEC:       -37.992d {-37d 59' 31"} (J2000)
ROLL:            266.499d
IMG_START_DATE:  15854 TJD;   293 DOY;   11/10/20
IMG_START_TIME:  23920.82 SOD {06:38:40.82} UT,   291.8 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     340785528
X_OFFSET:        717 [pixels]
Y_OFFSET:        970 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       877
Y_GRB_POS:       1130
BINNING_INDEX:   1
IM_URL:          sw00505926000msuni0299.fits
SUN_POSTN:       204.61d {+13h 38m 26s}  -10.23d {-10d 13' 58"}
SUN_DIST:         77.92 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      119.48d {+07h 57m 54s}  +17.00d {+17d 00' 18"}
MOON_DIST:       156.43 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      359.35,-19.35 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      283.83,-15.37 [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 #12460
T. Sakamoto (NASA/UMBC), M. M. Chester (PSU), J. R. Cummings (NASA/UMBC), P. A. Evans (U Leicester), C. Guidorzi (U Ferrara), V. Mangano (INAF-IASFPA), K. L. Page (U Leicester), D. M. Palmer (LANL) and P. Romano (INAF-IASFPA) report on behalf of the Swift Team:
At 06:33:49 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 111020A (trigger=505926). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 287.027, -37.985 which is
```
   RA(J2000) = 19h 08m 06s
   Dec(J2000) = -37d 59' 05"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a short single peak structure with a duration of about 0.5 sec. The peak count rate was ~3000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 06:35:01.8 UT, 72.8 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 287.05305, -38.01178 which is equivalent to:
```
   RA(J2000)  = 19h 08m 12.73s
   Dec(J2000) = -38d 00' 42.4"
```
with an uncertainty of 4.1 arcseconds (radius, 90% containment). This location is 121 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 6.89 x 10^20 cm^-2 (Kalberla et al. 2005).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 79 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 0.43.
Burst Advocate for this burst is T. Sakamoto (Taka.Sakamoto AT 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 #12460
T. Sakamoto (NASA/UMBC), M. M. Chester (PSU), J. R. Cummings (NASA/UMBC), P. A. Evans (U Leicester), C. Guidorzi (U Ferrara), V. Mangano (INAF-IASFPA), K. L. Page (U Leicester), D. M. Palmer (LANL) and P. Romano (INAF-IASFPA) report on behalf of the Swift Team:
At 06:33:49 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 111020A (trigger=505926). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 287.027, -37.985 which is
```
   RA(J2000) = 19h 08m 06s
   Dec(J2000) = -37d 59' 05"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a short single peak structure with a duration of about 0.5 sec. The peak count rate was ~3000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 06:35:01.8 UT, 72.8 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 287.05305, -38.01178 which is equivalent to:
```
   RA(J2000)  = 19h 08m 12.73s
   Dec(J2000) = -38d 00' 42.4"
```
with an uncertainty of 4.1 arcseconds (radius, 90% containment). This location is 121 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 6.89 x 10^20 cm^-2 (Kalberla et al. 2005).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 79 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 0.43.
Burst Advocate for this burst is T. Sakamoto (Taka.Sakamoto AT 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:     Thu 20 Oct 11 06:51:19 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     505926,   Seg_Num: 0
POINT_RA:        287.007d {+19h 08m 02s} (J2000)
POINT_DEC:       -37.992d {-37d 59' 31"} (J2000)
POINT_ROLL:      266.499d
IMG_START_DATE:  15854 TJD;   293 DOY;   11/10/20
IMG_START_TIME:  24500.98 SOD {06:48:20.98} UT,   871.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.641
N_STARS:         190
X_OFFSET:        158 [pixels]
Y_OFFSET:        411 [pixels]
X_MAX:           1597 [pixels]
Y_MAX:           1850 [pixels]
DET_THRESH:      18
PHOTO_THRESH:    10
SL_URL:          sw00505926000msufc0871.fits
SUN_POSTN:       204.61d {+13h 38m 27s}  -10.23d {-10d 14' 01"}
SUN_DIST:         77.92 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      119.51d {+07h 58m 03s}  +17.00d {+16d 59' 43"}
MOON_DIST:       156.41 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      359.35,-19.35 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      283.83,-15.37 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 20 Oct 11 06:51:37 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     505926,   Seg_Num: 0
POINT_RA:        287.007d {+19h 08m 02s} (J2000)
POINT_DEC:       -37.992d {-37d 59' 31"} (J2000)
POINT_ROLL:      266.499d
IMG_START_DATE:  15854 TJD;   293 DOY;   11/10/20
IMG_START_TIME:  24500.98 SOD {06:48:20.98} UT,   871.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.641
N_STARS:         190
X_OFFSET:        158 [pixels]
Y_OFFSET:        411 [pixels]
X_MAX:           1597 [pixels]
Y_MAX:           1850 [pixels]
DET_THRESH:      18
PHOTO_THRESH:    10
SL_URL:          sw00505926000msufc0871.fits
SUN_POSTN:       204.61d {+13h 38m 27s}  -10.23d {-10d 14' 02"}
SUN_DIST:         77.92 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      119.52d {+07h 58m 04s}  +16.99d {+16d 59' 41"}
MOON_DIST:       156.40 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      359.35,-19.35 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      283.83,-15.37 [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:     Thu 20 Oct 11 06:53:17 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     505926,   Seg_Num: 0
POINT_RA:        287.007d {+19h 08m 02s} (J2000)
POINT_DEC:       -37.992d {-37d 59' 31"} (J2000)
ROLL:            266.499d
IMG_START_DATE:  15854 TJD;   293 DOY;   11/10/20
IMG_START_TIME:  24500.98 SOD {06:48:20.98} UT,   871.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     340786108
X_OFFSET:        717 [pixels]
Y_OFFSET:        970 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       877
Y_GRB_POS:       1130
BINNING_INDEX:   1
IM_URL:          sw00505926000msuni0879.fits
SUN_POSTN:       204.61d {+13h 38m 27s}  -10.23d {-10d 14' 03"}
SUN_DIST:         77.92 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      119.53d {+07h 58m 07s}  +16.99d {+16d 59' 27"}
MOON_DIST:       156.39 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      359.35,-19.35 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      283.83,-15.37 [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:     Thu 20 Oct 11 06:53:39 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     505926,   Seg_Num: 0
POINT_RA:        287.007d {+19h 08m 02s} (J2000)
POINT_DEC:       -37.992d {-37d 59' 31"} (J2000)
ROLL:            266.499d
IMG_START_DATE:  15854 TJD;   293 DOY;   11/10/20
IMG_START_TIME:  24500.98 SOD {06:48:20.98} UT,   871.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     340786108
X_OFFSET:        717 [pixels]
Y_OFFSET:        970 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       877
Y_GRB_POS:       1130
BINNING_INDEX:   1
IM_URL:          sw00505926000msuni0879.fits
SUN_POSTN:       204.61d {+13h 38m 27s}  -10.23d {-10d 14' 03"}
SUN_DIST:         77.92 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      119.53d {+07h 58m 08s}  +16.99d {+16d 59' 23"}
MOON_DIST:       156.39 [deg]
MOON_ILLUM:      49 [%]
GAL_COORDS:      359.35,-19.35 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      283.83,-15.37 [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 #12461
XMM-Newton will observe GRB 111020A at location (RA=19h 08m 12.73s, DEC=-38d 00' 42.4", J2000), starting at 19:41:49 UT, on October 20, 2011, for an exposure of 30,000 seconds.
GCN Circular #12462
J. C. Tello (IAA-CSIC), A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), A. J. Castro-Tirado, J. Gorosabel (IAA-CSIC), on behalf of a larger collaboration, report:
We have observed the field of the short GRB 111020A, detected by Swift/BAT (Palmer et al., GCNC 12460) with the 0.6m Yock-Allen telescope at the BOOTES-3 station in Blenheim (New Zealand). Unfiltered images were obtained starting 69.72 minutes after the burst (07:43:32 UT), no new source is visible in the co-added image with total exposure 6900 sec (115 images ending in 09:40:53 UT), the limiting magnitude for the combined image is R = 19.5 (calibrated against USNO B1.0).
USNO B1-0519-0893471, a catalogued R=18.7 magnitude source is at the edge of the XRT circle but shows no evident variability.
GCN Circular #12463
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team.
Using 2124 s of XRT Photon Counting mode data and 3 UVOT images for GRB 111020A, 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 = 287.05219, -38.01216 which is equivalent to:
```
RA (J2000): 19h 08m 12.53s
Dec (J2000): -38d 00' 43.8"
```
with an uncertainty of 1.6 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 #12464
T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+963 sec from recent telemetry downlinks, we report further analysis of BAT GRB 111020A (trigger #505926) (Sakamoto, et al., GCN Circ. 12460). The BAT ground-calculated position is RA, Dec = 287.029, -38.031 deg, which is
```
   RA(J2000)  =  19h 08m 06.9s 
   Dec(J2000) = -38d 01' 50.3" 
```
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 74%.
The mask-weighted light curve shows a single spike starting at ~T+0.0, peaking at ~T+0.1 sec, and ending at ~T+1.0 sec. There is a hint (at the 2.5-sigma level) of a soft tail out to ~T+10 sec. T90 (15-350 keV) is 0.40 +- 0.09 sec (estimated error including systematics).
The time-averaged spectrum from T-0.04 to T+0.39 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.37 +- 0.26. The fluence in the 15-150 keV band is 6.5 +- 1.0 x 10^-8 erg/cm2. The 1-sec peak photon flux measured from T-0.32 sec in the 15-150 keV band is 0.9 +- 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/505926/BA/
GCN Circular #12465
C. Guidorzi (U. Ferrera), N. R. Tanvir (U. Leicester), C. Mottram, D. Bersier (Liverpool JMU), report:
On 2011 October 20 at 11:02:37 UT the 2-m Faulkes Telescope South began observing short GRB 111020A (Sakamoto et al., GCN Circ. 12460) using the Ri filters, corresponding to approximately 4.5 hours after the burst trigger time.
We detect no uncatalogued sources, either inside or near the enhanced XRT error circle (Osborne et al. GCN Circ. 12463), to the following limiting magnitudes:
```
Mid time from Total Exp Filter Magnitude
trigger (hours) (s)
------------------------------------------------
4.75 6x300 R> 21.0
5.32 6x300 i> 21.7
------------------------------------------------
```
Magnitudes have been calibrated from nearby USNOB-1 stars using their R2 and I nominal values.
GCN Circular #12466
S. R. Oates (MSSL-UCL) and T. Sakamoto (NASA/UMBC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 111020A 80 s after the BAT trigger (Sakamoto et al., GCN Circ. 12460). No optical afterglow consistent with the XRT position (Osborne et al., GCN Circ. 12463) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) for the first finding chart (FC) exposure and subsequent exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC            80          230          147         >20.0
u_FC               292          542          246         >19.6
white               80         7160          766         >20.3
v                  622         6135          275         >18.8
b                  547         6956          471         >19.9
u                  292        18728         1973         >20.3
w1                 670        18066         2242         >21.0
m2                6140        22385         2310         >21.1
w2                1027         5930          216         >20.5
```
This photometry may be complicated by the presence of a catalogued source approximately 3'' away from the centre of the enhanced XRT error circle. The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.43 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #12467
W. Fong (Harvard), E. Berger (Harvard) and D. Fox (PSU) report:
We imaged the location of the short GRB 111020A (GCN 12460) with GMOS on the Gemini-South 8-m telescope on 2011 October 21.01 UT (mid-time of 17.7 hours post-burst). We obtained 9x180s exposures in i-band with 0.8" seeing.
We find no sources within the enhanced XRT error circle (GCN 12463) to a 3-sigma limiting magnitude of i~25 mag.
However, we find two faint objects just outside of the XRT error circle with coordinates (J2000):
```
S1:
RA = 19:08:12.501
Dec = -38:00:41.80

S2:
RA = 19:08:12.698
Dec = -38:00:44.46
```
S1 has a brightness of i~23.7 mag and appears to be point-like. S2 is fainter, at the threshold of detectability with a brightness of i~25 mag.
The nearest galaxy is located at:
```
G1:
RA = 19:08:12.231
Dec = -38:00:48.80
```
with a magnitude of i~23.3 mag, and 6.2" from the center of the XRT error circle.
GCN Circular #12468
V. Mangano (INAF IASFPA) and T. Sakamoto (NASA/UMBC) reports on behalf of the Swift-XRT team:
We have analysed 20 ks of XRT data for GRB 111020A (Sakamoto et al. GCN Circ. 12460), from 59 s to 69.8 ks after the BAT trigger. The data comprise 7 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN. Circ 12463).
The light curve can be modelled with a power-law decay with a decay index of alpha=0.72 (+/-0.06).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.14 (+0.19, -0.41). The best-fitting absorption column is 10.0 (+5.4, -1.8) x 10^21 cm^-2, in excess of the Galactic value of 6.9 x 10^20 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 5.3 x 10^-11 (1.2 x 10^-10) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     10.0 (+5.4, -1.8) x 10^21 cm^-2
Galactic foreground: 6.9 x 10^20 cm^-2
Excess significance: 8.9 sigma
Photon index:	     2.14 (+0.19, -0.41)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00505926.
This circular is an official product of the Swift-XRT team.
GCN Circular #12469
W. Fong, A. Zauderer and E. Berger (Harvard) report:
"We observed the position of GRB 111020A (GCN 12460) with the EVLA beginning on 2011 October 20.98 UT (16.9 hours post-burst) at a mean frequency of 5.8 GHz. In 1 hour of observations we do not detect any radio source within the enhanced XRT error circle (GCN 12463) to a 3-sigma limit of ~50 microJy. Further observations are in progress."
GCN Circular #12470
W. Fong and E. Berger (Harvard) report:
"We re-imaged the field of GRB 111020A (GCN 12640) with GMOS on the Gemini-South telescope on 2011 October 22.01 UT (mid-time of 1.7 days post-burst, and 23.1 hours after our initial observations; GCN 12467). We obtained 11x180s exposures in i-band in 0.73" seeing.
We still detect the two faint sources S1 and S2 from our previous GMOS observation (GCN 12467), and neither source shows evidence for fading. Digital image subtraction of the two epochs using the ISIS package reveals no residuals inside or near the XRT error circle. We therefore place a limit on the optical afterglow of i~25 mag at 17.7 hours after the burst."
GCN Circular #12477
T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), J. Norris (BSU), T. N. Ukwatta (MSU)
We report the spectral lag analysis for GRB 111020A (GCN Circ. 12460) based on the BAT data. Using 64 ms binned light curves, the spectral lag for 15-25 keV to 50-100 keV is 124 +36/-38 msec. This significant lag is due to a broader pulse in the 15-25 keV band comparing to that in the 50-100 keV band which indicates the strong pulse evolution from hard to soft. Although the burst duration itself is short (T90 = 40 ms; GCN Circ. 12464), this positive lag argues against a "short" classification.
However, there is a possibility that the broader pulse seen in the 15-25 keV band is composed from two pulses instead of a single pulse. If this is the case, the lag result above could be confused by cross-correlating the 2nd pulse in the 15-25 keV and the 1st pulse in the 50-100 keV band. Due to the limiting signal-to-noise in the light curve data, it is not possible to claim whether the broad pulse in the 15-25 keV has two pulses or just a single pulse.
Give the large non-zero lag and the possible double peak interpretation that could cause a false lag, we think it equally like that this burst is short or long.
GCN Circular #12492
E. Berger, R. Margutti, and W. Fong (Harvard) report:
"We observed the field of the short GRB 111020A (GCN 12640) with the Chandra X-ray Observatory + ACIS-S starting on 2011 October 23.14 UT (2.86 days after the burst) for a total of 19.8 ksec. We clearly detect a source in coincidence with the enhanced XRT error circle (GCN 12463) at the following coordinates (J2000):
```
RA = 19:08:12.502
DEC = -38:00:42.58
```
with an uncertainty of about 0.5". The position includes a minor correction to the Chandra astrometry using two X-ray sources with stellar counterparts in our Gemini i-band images (which were astrometrically matched to the 2MASS catalog; GCNs 12467, 12470). The Chandra position is offset by 1.2" from the centroid of the most recent XRT position (which has a 90% containment uncertainty of 1.6"). Further analysis of the Chandra data is on-going.
We thank Harvey Tananbaum and the CXO scheduling staff for rapidly approving and executing this observation."
GCN Circular #12739
S. Campana (INAF-Osservatorio astronomico di Brera) reports:
XMM-Newton observed the short GRB 111020A (Sakamoto et al. 2011, GCN 12460) on Oct 20, 2011 21:50:05 UT (15.3 hr after the burst onset). The ~20 ks observation was affected in the first part by a mild enhanced background event which we filtered out. The resulting pn/MOS1/MOS2 exposure times were 15, 17 and 17 ks, respectively.
A source is well detected at a position consistent with the Swift's (Osborne et al. 2011, GCN 12463) and Chandra's (Berger et al. 2011, GCN 12492) ones. The pn count rate is (2.2+/-0.2)x10^{-2} cts/s. We extracted 422, 166, and 142 source photons from the pn, MOS1, and MOS2, respectively. The spectrum can be fitted with a power law model including a non-negligible absorption component in addition to the Galactic one (6.9x10^{20} cm^{-2}). The best fit power law implies a photon index of Gamma=1.9+/-0.3 (90% c.l. for one parameter of interest) and an additional column density of NH=(6+/-2)x10^{21} cm^{-2} (90% c.l.). This provides a lower limit to the intrinsic column density. The reduced chi^2 of the fit is 0.83 (31 d.o.f.). The unabsorbed 0.5-10 keV is ~2x10^{-13} erg/cm^2/s.
1204.5475 from 26 Apr 12
Wen-fai Fong et al.: A Jet Break in the X-ray Light Curve of Short GRB 111020A: Implications for Energetics and Rates
We present broad-band observations of the afterglow and environment of the short GRB 111020A. An extensive X-ray light curve from Swift/XRT, XMM-Newton and Chandra, spanning ~100 seconds to 10 days after the burst, reveals a significant break at t~2 days with pre- and post-break decline rates of alphaX,1 ~ -0.78 and alphaX,2<-1.7, respectively. Interpreted as a jet break, we infer a collimated outflow with an opening angle of ~3-8 degrees. The resulting beaming-corrected gamma-ray (10-1000 keV band) and blastwave kinetic energies are (2-3)e48 erg and (0.3-2)e49 erg, respectively, with the range depending on the unknown redshift of the burst. We report a radio afterglow limit of <39 microJy (3-sigma) from EVLA observations which, along with our finding that vc24.4 mag at 18 hours after the burst, and reveal a potential host galaxy with i~24.3 mag. The sub-arcsecond localization from Chandra provides a precise offset of 0.80"+/-0.11" (1-sigma) from this galaxy corresponding to an offset of 5-7 kpc for z=0.5-1.5. We find a high excess neutral Hydrogen column density of (7.5+/-2.0)e21 cm^(-2) (z=0). Our observations demonstrate that a growing fraction of short GRBs are collimated which may lead to a true event rate of >100-1000 Gpc^(-3) yr^(-1), in good agreement with the NS-NS merger rate of ~200-3000 Gpc^(-3) yr^(-1). This consistency is promising for coincident short GRB-gravitational wave searches in the forthcoming era of Advanced LIGO/VIRGO.
1402.0766 from 5 Feb 14
R.L.Tunnicliffe et al.: On the nature of the 'hostless' short GRBs
A significant proportion ($\sim30\%$) of the short-duration gamma-ray bursts (SGRBs) localised by Swift have no detected host galaxy coincident with the burst location to deep limits, and also no high-likelihood association with proximate galaxies on the sky. These SGRBs may represent a population at moderately high redshifts ($z\gtrsim1$), for which the hosts are faint, or a population where the progenitor has been kicked far from its host or is sited in an outlying globular cluster. We consider the afterglow and host observations of three 'hostless' bursts (GRBs 090305A, 091109B and 111020A), coupled with a new observational diagnostic to aid the association of SGRBs with putative host galaxies to investigate this issue. Considering the well localised SGRB sample, 7/25 SGRBs can be classified as 'hostless' by our diagnostic. Statistically, however, the proximity of these seven SGRBs to nearby galaxies is higher than is seen for random positions on the sky. This suggests that the majority of 'hostless' SGRBs have likely been kicked from proximate galaxies at moderate redshift. Though this result still suggests only a small proportion of SGRBs will be within the AdLIGO horizon for NS-NS or NS-BH inspiral detection ($z\sim0.1$), in the particular case of GRB 111020A a plausible host candidate is at $z=0.02$.

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Jochen Greiner, last update: 05-Feb-2014 [Disclaimer]