Gamma-ray Burst 161004A

(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 04 Oct 16 12:58:50 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     715084,   Seg_Num: 0
GRB_RA:          263.171d {+17h 32m 41s} (J2000),
                 263.387d {+17h 33m 33s} (current),
                 262.526d {+17h 30m 06s} (1950)
GRB_DEC:          -0.928d {-00d 55' 41"} (J2000),
                  -0.939d {-00d 56' 20"} (current),
                  -0.894d {-00d 53' 36"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       3405 [cnts]    Image_Peak=195 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   146     E_range: 25-100 keV
BKG_INTEN:       20821 [cnts]
BKG_TIME:        46695.04 SOD {12:58:15.04} UT
BKG_DUR:         8 [sec]
GRB_DATE:        17665 TJD;   278 DOY;   16/10/04
GRB_TIME:        46708.67 SOD {12:58:28.67} UT
GRB_PHI:          -6.71 [deg]
GRB_THETA:        26.46 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     13.49 [sigma]
IMAGE_SIGNIF:    8.19 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  -1  +0  +0 -30  +0 
SUN_POSTN:       190.79d {+12h 43m 10s}   -4.64d {-04d 38' 20"}
SUN_DIST:         72.58 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      229.39d {+15h 17m 35s}  -13.21d {-13d 12' 44"}
MOON_DIST:        35.83 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:       22.81, 17.00 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      262.61, 22.34 [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 = 77.64,5.63 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 04 Oct 16 12:59:56 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     715084,   Seg_Num: 0
POINT_RA:        263.180d {+17h 32m 43s} (J2000)
POINT_DEC:        -0.932d {-00d 55' 53"} (J2000)
IMG_START_DATE:  17665 TJD;   278 DOY;   16/10/04
IMG_START_TIME:  46789.35 SOD {12:59:49.35} UT,   80.7 [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 04 Oct 16 13:02:21 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     715084,   Seg_Num: 0
GRB_RA:          263.171d {+17h 32m 41s} (J2000),
                 263.387d {+17h 33m 33s} (current),
                 262.526d {+17h 30m 06s} (1950)
GRB_DEC:          -0.928d {-00d 55' 41"} (J2000),
                  -0.939d {-00d 56' 20"} (current),
                  -0.894d {-00d 53' 36"} (1950)
GRB_DATE:        17665 TJD;   278 DOY;   16/10/04
GRB_TIME:        46708.67 SOD {12:58:28.67} UT
TRIGGER_INDEX:   146
GRB_PHI:          -6.71 [deg]
GRB_THETA:        26.46 [deg]
DELTA_TIME:      77.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     13.49 [sigma]
IMAGE_SIGNIF:    8.19 [sigma]
LC_URL:          sw00715084000msb.lc
SUN_POSTN:       190.79d {+12h 43m 10s}   -4.64d {-04d 38' 23"}
SUN_DIST:         72.58 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      229.42d {+15h 17m 41s}  -13.22d {-13d 13' 07"}
MOON_DIST:        35.80 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:       22.81, 17.00 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      262.61, 22.34 [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 = 77.64,5.63 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 04 Oct 16 13:03:03 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     715084,   Seg_Num: 0
POINT_RA:        263.180d {+17h 32m 43s} (J2000)
POINT_DEC:        -0.932d {-00d 55' 53"} (J2000)
POINT_ROLL:      265.435d
IMG_START_DATE:  17665 TJD;   278 DOY;   16/10/04
IMG_START_TIME:  46794.05 SOD {12:59:54.05} UT,   85.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.120
N_STARS:         190
X_OFFSET:        558 [pixels]
Y_OFFSET:        563 [pixels]
X_MAX:           1517 [pixels]
Y_MAX:           1522 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw00715084000msufc0085.fits
SUN_POSTN:       190.79d {+12h 43m 10s}   -4.64d {-04d 38' 24"}
SUN_DIST:         72.59 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      229.43d {+15h 17m 43s}  -13.22d {-13d 13' 12"}
MOON_DIST:        35.80 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:       22.81, 16.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      262.63, 22.33 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 04 Oct 16 13:03:40 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     715084,   Seg_Num: 0
POINT_RA:        263.180d {+17h 32m 43s} (J2000)
POINT_DEC:        -0.932d {-00d 55' 53"} (J2000)
POINT_ROLL:      265.435d
IMG_START_DATE:  17665 TJD;   278 DOY;   16/10/04
IMG_START_TIME:  46794.05 SOD {12:59:54.05} UT,   85.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.120
N_STARS:         190
X_OFFSET:        558 [pixels]
Y_OFFSET:        563 [pixels]
X_MAX:           1517 [pixels]
Y_MAX:           1522 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw00715084000msufc0085.fits
SUN_POSTN:       190.79d {+12h 43m 10s}   -4.64d {-04d 38' 24"}
SUN_DIST:         72.59 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      229.43d {+15h 17m 44s}  -13.22d {-13d 13' 16"}
MOON_DIST:        35.80 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:       22.81, 16.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      262.63, 22.33 [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 04 Oct 16 13:04:47 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     715084,   Seg_Num: 0
POINT_RA:        263.180d {+17h 32m 43s} (J2000)
POINT_DEC:        -0.932d {-00d 55' 53"} (J2000)
ROLL:            265.435d
IMG_START_DATE:  17665 TJD;   278 DOY;   16/10/04
IMG_START_TIME:  46794.05 SOD {12:59:54.05} UT,   85.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     497278811
X_OFFSET:        877 [pixels]
Y_OFFSET:        882 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1037
Y_GRB_POS:       1042
BINNING_INDEX:   1
IM_URL:          sw00715084000msuni0102.fits
SUN_POSTN:       190.79d {+12h 43m 10s}   -4.64d {-04d 38' 25"}
SUN_DIST:         72.58 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      229.44d {+15h 17m 46s}  -13.22d {-13d 13' 24"}
MOON_DIST:        35.79 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:       22.81, 16.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      262.63, 22.33 [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 04 Oct 16 13:05:07 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     715084,   Seg_Num: 0
POINT_RA:        263.180d {+17h 32m 43s} (J2000)
POINT_DEC:        -0.932d {-00d 55' 53"} (J2000)
ROLL:            265.435d
IMG_START_DATE:  17665 TJD;   278 DOY;   16/10/04
IMG_START_TIME:  46794.05 SOD {12:59:54.05} UT,   85.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     497278811
X_OFFSET:        877 [pixels]
Y_OFFSET:        882 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1037
Y_GRB_POS:       1042
BINNING_INDEX:   1
IM_URL:          sw00715084000msuni0102.fits
SUN_POSTN:       190.79d {+12h 43m 11s}   -4.64d {-04d 38' 26"}
SUN_DIST:         72.58 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      229.45d {+15h 17m 47s}  -13.22d {-13d 13' 26"}
MOON_DIST:        35.79 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:       22.81, 16.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      262.63, 22.33 [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 04 Oct 16 13:04:52 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     715084,   Seg_Num: 0
GRB_RA:          263.1528d {+17h 32m 36.67s} (J2000),
                 263.3691d {+17h 33m 28.57s} (current),
                 262.5078d {+17h 30m 01.86s} (1950)
GRB_DEC:          -0.9487d {-00d 56' 55.3"} (J2000),
                  -0.9596d {-00d 57' 34.7"} (current),
                  -0.9140d {-00d 54' 50.2"} (1950)
GRB_ERROR:       3.7 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  17665 TJD;   278 DOY;   16/10/04
IMG_START_TIME:  46799.00 SOD {12:59:59.00} UT,   90.3 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       190.79d {+12h 43m 10s}   -4.64d {-04d 38' 25"}
SUN_DIST:         72.56 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      229.44d {+15h 17m 46s}  -13.22d {-13d 13' 24"}
MOON_DIST:        35.76 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:       22.78, 17.01 [deg] galactic lon,lat of the burst
ECL_COORDS:      262.60, 22.31 [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 04 Oct 16 13:07:18 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     715084,   Seg_Num: 0
GRB_RA:          263.1524d {+17h 32m 36.57s} (J2000),
                 263.3687d {+17h 33m 28.48s} (current),
                 262.5074d {+17h 30m 01.77s} (1950)
GRB_DEC:          -0.9506d {-00d 57' 02.1"} (J2000),
                  -0.9615d {-00d 57' 41.5"} (current),
                  -0.9159d {-00d 54' 57.0"} (1950)
GRB_ERROR:       1.1 [arcsec radius, statistical only]
GRB_MAG:         19.03 +/- 0.40 [mag]
FILTER:          10, White
IMG_START_DATE:  17665 TJD;   278 DOY;   16/10/04
IMG_START_TIME:  46792.00 SOD {12:59:52.00} UT,   83.3 [sec] since BAT Trigger Time
SUN_POSTN:       190.80d {+12h 43m 11s}   -4.64d {-04d 38' 28"}
SUN_DIST:         72.55 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      229.46d {+15h 17m 51s}  -13.23d {-13d 13' 40"}
MOON_DIST:        35.74 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:       22.78, 17.01 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      262.60, 22.31 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT UVOT Position Notice.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        Result based on srclist data.  
COMMENTS:        Notice generated automatically.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 04 Oct 16 13:10:55 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     715084,   Seg_Num: 0
POINT_RA:        263.181d {+17h 32m 43s} (J2000)
POINT_DEC:        -0.934d {-00d 56' 01"} (J2000)
POINT_ROLL:      265.433d
IMG_START_DATE:  17665 TJD;   278 DOY;   16/10/04
IMG_START_TIME:  47005.87 SOD {13:03:25.87} UT,   297.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.880
N_STARS:         190
X_OFFSET:        318 [pixels]
Y_OFFSET:        323 [pixels]
X_MAX:           1757 [pixels]
Y_MAX:           1762 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    4
SL_URL:          sw00715084000msufc0297.fits
SUN_POSTN:       190.80d {+12h 43m 11s}   -4.64d {-04d 38' 31"}
SUN_DIST:         72.58 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      229.49d {+15h 17m 58s}  -13.23d {-13d 14' 05"}
MOON_DIST:        35.75 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:       22.81, 16.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      262.63, 22.33 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 04 Oct 16 13:11:25 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     715084,   Seg_Num: 0
POINT_RA:        263.181d {+17h 32m 43s} (J2000)
POINT_DEC:        -0.934d {-00d 56' 01"} (J2000)
POINT_ROLL:      265.433d
IMG_START_DATE:  17665 TJD;   278 DOY;   16/10/04
IMG_START_TIME:  47005.87 SOD {13:03:25.87} UT,   297.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.880
N_STARS:         190
X_OFFSET:        318 [pixels]
Y_OFFSET:        323 [pixels]
X_MAX:           1757 [pixels]
Y_MAX:           1762 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    4
SL_URL:          sw00715084000msufc0297.fits
SUN_POSTN:       190.80d {+12h 43m 11s}   -4.64d {-04d 38' 32"}
SUN_DIST:         72.58 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      229.50d {+15h 17m 59s}  -13.24d {-13d 14' 08"}
MOON_DIST:        35.74 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:       22.81, 16.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      262.63, 22.33 [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 04 Oct 16 13:11:54 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     715084,   Seg_Num: 0
GRB_RA:          263.1521d {+17h 32m 36.50s} (J2000),
                 263.3684d {+17h 33m 28.40s} (current),
                 262.5071d {+17h 30m 01.70s} (1950)
GRB_DEC:          -0.9499d {-00d 56' 59.6"} (J2000),
                  -0.9608d {-00d 57' 39.0"} (current),
                  -0.9151d {-00d 54' 54.5"} (1950)
GRB_ERROR:       2.3 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  17665 TJD;   278 DOY;   16/10/04
IMG_START_TIME:  46799.00 SOD {12:59:59.00} UT,   90.3 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       190.80d {+12h 43m 12s}   -4.64d {-04d 38' 32"}
SUN_DIST:         72.55 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      229.50d {+15h 18m 00s}  -13.24d {-13d 14' 11"}
MOON_DIST:        35.71 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:       22.78, 17.01 [deg] galactic lon,lat of the burst
ECL_COORDS:      262.60, 22.31 [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 04 Oct 16 13:12:20 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     715084,   Seg_Num: 0
POINT_RA:        263.181d {+17h 32m 43s} (J2000)
POINT_DEC:        -0.934d {-00d 56' 01"} (J2000)
ROLL:            265.433d
IMG_START_DATE:  17665 TJD;   278 DOY;   16/10/04
IMG_START_TIME:  47005.87 SOD {13:03:25.87} UT,   297.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     497279022
X_OFFSET:        877 [pixels]
Y_OFFSET:        882 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1037
Y_GRB_POS:       1042
BINNING_INDEX:   1
IM_URL:          sw00715084000msuni0314.fits
SUN_POSTN:       190.80d {+12h 43m 12s}   -4.64d {-04d 38' 32"}
SUN_DIST:         72.58 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      229.50d {+15h 18m 01s}  -13.24d {-13d 14' 14"}
MOON_DIST:        35.74 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:       22.81, 16.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      262.63, 22.33 [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 04 Oct 16 13:12:35 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     715084,   Seg_Num: 0
POINT_RA:        263.181d {+17h 32m 43s} (J2000)
POINT_DEC:        -0.934d {-00d 56' 01"} (J2000)
ROLL:            265.433d
IMG_START_DATE:  17665 TJD;   278 DOY;   16/10/04
IMG_START_TIME:  47005.87 SOD {13:03:25.87} UT,   297.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     497279022
X_OFFSET:        877 [pixels]
Y_OFFSET:        882 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1037
Y_GRB_POS:       1042
BINNING_INDEX:   1
IM_URL:          sw00715084000msuni0314.fits
SUN_POSTN:       190.80d {+12h 43m 12s}   -4.64d {-04d 38' 33"}
SUN_DIST:         72.58 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      229.51d {+15h 18m 02s}  -13.24d {-13d 14' 16"}
MOON_DIST:        35.74 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:       22.81, 16.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      262.63, 22.33 [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 #19979
P.A. Evans (U Leicester), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), A. A. Breeveld (UCL-MSSL), D. N. Burrows (PSU), A. D'Ai (INAF-IASFPA), V. D'Elia (ASDC), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), B. Mingo (U Leicester), K. L. Page (U Leicester), P. Romano (INAF-IASFPA), T. Sakamoto (AGU), B. Sbarufatti (INAF-OAB/PSU) and E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift Team:
At 12:58:28 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 161004A (trigger=715084). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 263.171, -0.928, which is
```
   RA(J2000)  =  17h 32m 41s
   Dec(J2000) = -00d 55' 41"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a couple of peaks with a total duration of about 5 sec. The peak count rate was ~1800 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 12:59:49.3 UT, 80.7 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 263.15298, -0.94831 which is equivalent to:
```
   RA(J2000)  = 17h 32m 36.72s
   Dec(J2000) = -00d 56' 53.9"
```
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 97 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 in excess of the Galactic value (1.88 x 10^21 cm^-2, Willingale et al. 2013), with an excess column of 4.1 (+3.92/-2.99) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 85 seconds after the BAT trigger. There is a candidate afterglow in the list of sources generated on-board at
```
  RA(J2000)  =	17:32:36.59 = 263.15244
  DEC(J2000) = -00:57:02.2  =  -0.95061
```
with a 90%-confidence error radius of about 1.10 arc sec. This position is 6.6 arc sec. from the center of the XRT error circle. The estimated magnitude is 19.03. No correction has been made for the expected extinction corresponding to E(B-V) of 0.25.
Burst Advocate for this burst is P.A. Evans (pae9 AT star.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 04 Oct 16 13:16:42 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     715084,   Seg_Num: 0
POINT_RA:        263.181d {+17h 32m 43s} (J2000)
POINT_DEC:        -0.934d {-00d 56' 01"} (J2000)
POINT_ROLL:      265.434d
IMG_START_DATE:  17665 TJD;   278 DOY;   16/10/04
IMG_START_TIME:  47583.14 SOD {13:13:03.14} UT,   874.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.086
N_STARS:         190
X_OFFSET:        318 [pixels]
Y_OFFSET:        323 [pixels]
X_MAX:           1757 [pixels]
Y_MAX:           1762 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw00715084000msufc0874.fits
SUN_POSTN:       190.80d {+12h 43m 12s}   -4.64d {-04d 38' 37"}
SUN_DIST:         72.58 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      229.54d {+15h 18m 10s}  -13.25d {-13d 14' 44"}
MOON_DIST:        35.71 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:       22.81, 16.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      262.63, 22.33 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 04 Oct 16 13:17:17 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     715084,   Seg_Num: 0
POINT_RA:        263.181d {+17h 32m 43s} (J2000)
POINT_DEC:        -0.934d {-00d 56' 01"} (J2000)
ROLL:            265.434d
IMG_START_DATE:  17665 TJD;   278 DOY;   16/10/04
IMG_START_TIME:  47583.14 SOD {13:13:03.14} UT,   874.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     497279600
X_OFFSET:        877 [pixels]
Y_OFFSET:        882 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1037
Y_GRB_POS:       1042
BINNING_INDEX:   1
IM_URL:          sw00715084000msuni0891.fits
SUN_POSTN:       190.80d {+12h 43m 12s}   -4.64d {-04d 38' 37"}
SUN_DIST:         72.58 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      229.55d {+15h 18m 11s}  -13.25d {-13d 14' 47"}
MOON_DIST:        35.70 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:       22.81, 16.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      262.63, 22.33 [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 04 Oct 16 13:17:34 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     715084,   Seg_Num: 0
POINT_RA:        263.181d {+17h 32m 43s} (J2000)
POINT_DEC:        -0.934d {-00d 56' 01"} (J2000)
ROLL:            265.434d
IMG_START_DATE:  17665 TJD;   278 DOY;   16/10/04
IMG_START_TIME:  47583.14 SOD {13:13:03.14} UT,   874.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     497279600
X_OFFSET:        877 [pixels]
Y_OFFSET:        882 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1037
Y_GRB_POS:       1042
BINNING_INDEX:   1
IM_URL:          sw00715084000msuni0891.fits
SUN_POSTN:       190.80d {+12h 43m 12s}   -4.64d {-04d 38' 38"}
SUN_DIST:         72.58 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      229.55d {+15h 18m 12s}  -13.25d {-13d 14' 49"}
MOON_DIST:        35.70 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:       22.81, 16.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      262.63, 22.33 [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.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 04 Oct 16 13:17:09 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     715084,   Seg_Num: 0
POINT_RA:        263.181d {+17h 32m 43s} (J2000)
POINT_DEC:        -0.934d {-00d 56' 01"} (J2000)
POINT_ROLL:      265.434d
IMG_START_DATE:  17665 TJD;   278 DOY;   16/10/04
IMG_START_TIME:  47583.14 SOD {13:13:03.14} UT,   874.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.086
N_STARS:         190
X_OFFSET:        318 [pixels]
Y_OFFSET:        323 [pixels]
X_MAX:           1757 [pixels]
Y_MAX:           1762 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw00715084000msufc0874.fits
SUN_POSTN:       190.80d {+12h 43m 12s}   -4.64d {-04d 38' 37"}
SUN_DIST:         72.58 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      229.54d {+15h 18m 11s}  -13.25d {-13d 14' 47"}
MOON_DIST:        35.70 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:       22.81, 16.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      262.63, 22.33 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN Circular #19980
E. Mazaeva (IKI), I. Reva (Fesenkov Astrophysical Institute), A. Kusakin (Fesenkov Astrophysical Institute), A. Volnova (IKI), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of GRB 161004A (Evans et al., GCN 19979) with Zeiss-1000 (East) 1-m telescope of Tien Shan Astronomical Observatory. We obtained several images in R filter starting on Oct. 04 (UT) 13:36:52. In the XRT error circle we do not detect any new object. Wa do not detect also candidate afterglow (Evans et al., GCN 19979). Preliminary photometry of a combined image is following
```
Date       UT start   t-T0   Filter   Exp.  OT     Err.  UL
                       (mid, days)     (s)
2016-10-04 13:36:52 0.04321  R       15*180 n/d    n/d   21.9
```
Photometry is based on nearby SDSS-DR9 stars (Lupton transformations):
```
SDSS-DR9_id         R(Lupton)
J173243.09-005731.3 17.04
J173250.91-005842.7 16.77
J173251.94-005803.2 15.75
J173253.88-005801.6 15.62
J173253.02-005938.3 16.02
J173232.00-005640.3 16.34
J173227.11-005646.8 16.41
J173227.04-005816.8 16.51
J173227.48-005856.9 16.62
J173236.27-010018.1 16.96
J173241.54-005823.1 16.26
```
A finding chart can be found at http://grb.rssi.ru/GRB161004A/GRB161004A_TSHAO_161004_XRT_UVOT.png
GCN Circular #19981
U.Quadri, L.Strabla and R.Girelli report:
We imaged the field of GRB 161004A detected by SWIFT(trigger 715084) 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 4.90 hour after the GRB trigger, at the end of twilight, with our Newton telescope D=250 mm F/D=4.8.
Weather conditions were good.
We co-added 3 series of 10 exposures of 60 sec each.
```
Start T0+      End T0+      Vlim
4.9 hour       5.5 hour        18
```
We did not found any optical counterpart in the error box of the XRTcandidate. P.A. Evans (U Leicester), S. D. Barthelmy (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 #19983
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team.
Using 4971 s of XRT Photon Counting mode data and 10 UVOT images for GRB 161004A, 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 = 263.15236, -0.95067 which is equivalent to:
```
RA (J2000): 17h 32m 36.57s
Dec (J2000): -00d 57' 02.4"
```
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 #19984
A. A. Breeveld (UCL-MSSL) and P. A. Evans (U. Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 161004A 85 s after the BAT trigger (Evans et al., GCN Circ. 19979). A source consistent with the enhanced XRT position (Beardmore et al., GCN Circ. 19983) is detected in the initial UVOT exposures in the white and u filters only.
The preliminary UVOT position is:
```
     RA  (J2000) =3D  17:32:36.54 =3D 263.15224 (deg.)
     Dec (J2000) =3D -00:57:02.7  =3D  -0.95075 (deg.)
```
with an estimated uncertainty of 0.56 arc sec. (radius, 90% confidence).
Preliminary detections and 3-sigma upper limits using the UVOT=20 photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white               85          235          147         19.47 =B1 0.16
v                  627         6121          432        >20.1
b                  552        10926         1144        >21.8
u                  297          547          246         19.55 =B1 0.29
w1                 848         6531          413        >20.2
m2                4690         6326          393        >20.3
w2                 602        12506         1063        >20.8
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) =3D 0.25 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #19985
P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), T.G.R. Roegiers (PSU), A.P. Beardmore (U. Leicester), S.L. Gibson (U. Leicester), A. D'Ai (INAF-IASFPA) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 6.1 ks of XRT data for GRB 161004A (Evans et al. GCN Circ. 19979), from 84 s to 18.2 ks after the BAT trigger. The data comprise 112 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN Circ. 19983).
The late-time light curve (from T0+4.3 ks) can be modelled with a power-law decay with a decay index of alpha=1.3 (+0.5, -0.4).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.94 (+0.11, -0.09). The best-fitting absorption column is consistent with the Galactic value of 1.9 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.59 (+0.18, -0.16) and a best-fitting absorption column of 2.2 (+0.9, -0.4) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.6 x 10^-11 (5.5 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     2.2 (+0.9, -0.4) x 10^21 cm^-2
Galactic foreground: 1.9 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.59 (+0.18, -0.16)
```
If the light curve continues to decay with a power-law decay index of 1.3, the count rate at T+24 hours will be 1.1 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.9 x 10^-14 (5.9 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/00715084.
This circular is an official product of the Swift-XRT team.
GCN Circular #19986
A. Moskvitin (SAO RAS), A. Volnova (IKI), and A. Pozanenko (IKI) report on behalf of the larger GRB follow-up team.
We observed the field of GRB 161004A (Evans et al., GCN 19979) with Zeiss-1000 - the 1-meter telescope of Special Astrophysical Observatory of Russian Academy of Sciences. We obtain several images with filter Rc starting on October, 4 (UT) 15:44:35.
In the refined XRT error circle (Beardmore et al., GCN 19983) we do not detect the optical counterpart (Breeveld and Evans, GCN 19984). Preliminary photometry of a combined image is following
```
Date       UT start   t-T0     Filter   Exp.   OT      UL
                   (mid, days)          (s)
2016-10-04 15:44:35   0.1396    Rc      12*300 n/d    22.4
```
Photometry is based on nearby SDSS-DR9 stars reported by Mazaeva et al. (GCN 19980).
GCN Circular #19993
Eleonora Troja (GSFC), Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jos=EF=BF=BD A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes=EF=BF=BDs Gonz=EF=BF=BDlez (UNAM), Carlos Rom=EF=BF=BDn-Z=EF=BF= =BD=EF=BF=BDiga (UNAM), Neil Gehrels (GSFC), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report:
We observed the field of GRB 161004A (Evans, et al., GCN 19979) with=20 the Reionization and Transients Infrared Camera (RATIR; www.ratir.org)=20 on the 1.5m Harold Johnson Telescope at the Observatorio Astron=EF=BF=BDm= ico=20 Nacional on Sierra San Pedro M=EF=BF=BDrtir from 2016/10 5.10 to 2016/10 = 5.22=20 UTC (13.49 to 16.23 hours after the BAT trigger), obtaining a total=20 of 1.73 hours exposure in the r and i bands and 0.65 hours exposure in=20 the Z, Y, J, and H bands.
For a source within the Swift-UVOT error circle (Breeveld & Evans,=20 GCN 19984), in comparison with the USNO-B1 and 2MASS catalogs, we=20 obtain the following upper limits (3-sigma):
```
  r > 23.3
  i > 23.2
  Z > 22.4
  Y > 21.8
  J > 21.3
  H > 19.4
```
These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB.
We thank the staff of the Observatorio Astron=EF=BF=BDmico Nacional in San Pedro M=EF=BF=BDrtir.
GCN Circular #20001
D. M. Palmer (LANL), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), P. A. Evans (U Leicester), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), J. P. Norris (BSU), 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 161004A (trigger #715084) (Evans, et al., GCN Circ. 19979). The BAT ground-calculated position is RA, Dec = 263.127, -0.947 deg which is
```
    RA(J2000)  =  17h 32m 30.6s
    Dec(J2000) = -00d 56' 50.7"
```
with an uncertainty of 2.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 92%.
The mask-weighted light curve shows a single peak starting at T-0.1 sec, peaking at T+0.5 sec and ending at T+5 sec. T90 (15-350 keV) is 1.08 +- 0.21 sec (estimated error including systematics).
The time-averaged spectrum from T-0.11 to T+1.06 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.26 +- 0.33. The fluence in the 15-150 keV band is 9.5 +- 1.6 x 10^-8 erg/cm2. The 1-sec peak photon flux measured from T+0.06 sec in the 15-150 keV band is 1.0 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
Due to a low signal-to-noise of the data, the lag analysis is not possible. Therefore, it is not clear whether this burst belongs to a short GRB or not.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/715084/BA/
GCN Circular #20011
E. Mazaeva (IKI), I. Reva (Fesenkov Astrophysical Institute), A. Kusakin (Fesenkov Astrophysical Institute), A. Volnova (IKI), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We present a refined analysis of our observations (Mazaeva et al., GCN 19980) of the field of GRB 161004A (Evans et al., GCN 19979) with Zeiss-1000 (East) 1-m telescope of Tien Shan Astronomical Observatory. We obtained several images in R filter starting on Oct. 04 (UT) 13:36:52. In a combined image of the first 30 minutes of our observations we detect the afterglow (Breeveld et al., GCN 19984). Preliminary photometry of a combined image is following
```
Date       UT start   t-T0   Filter   Exp.  OT     Err.  UL
                       (mid, days)     (s)
2016-10-04 13:36:52 0.03632  R       9*180  21.65  0.25  21.7
```
Photometry is based on nearby SDSS-DR9 stars used in GCN 19980.
GCN Circular #20012
E. Mazaeva (IKI), A. Pozanenko (IKI), B. Hafizov (UBAI), A. Volnova (IKI), O. Burhonov (UBAI) report on behalf of larger GRB follow-up collaboration:
We observed the field of GRB 161004A (Evans et al., GCN 19979) with AZT-22 telescope of Maidanak observatory equipped with SNUCAM in R filter starting on Oct. 04 (UT) 14:25:10. We clearly detected optical afterglow (Evans et al., GCN 19979; Breeveld et al., GCN 19984; Mazaeva et al., GRB 20011). Preliminary photometry of the afterglow in a combined image is following
```
Date         UT start   t-T0    Filter   Exp.     OT    Err.   UL
                        (mid, days)        (s)

2016-10-04   14:25:10  0.06981  R        15*120   22.0  0.15   22.7
```
Photometry is based on nearby SDSS-DR9 stars used in GCN 19980.
GCN Circular #20053
S. D. Barthelmy (GSFC), P.A. Evans (U Leicester), N. Gehrels (GSFC), A. Y. Lien (GSFC/UMBC), J. P. Norris (BSU), P. O'Brien (U Leicester), K. L. Page (U Leicester), J. L. Racusin (NASA/GSFC), and H. Ziaeepour report on behalf of the Swift Team:
We performed further analysis of GRB161004A (trigger #715084; Evans et al., GCN Circ. 19979), to explore the possibility to clarify its short/long nature.
Using the full BAT event data set from T-240 to T+962 sec, the updated T90 is 3 +/- 1.4 s (using the 1-s binned light curve). This T90 is longer than the 1.08 +- 0.21 s originally reported (Palmer et al, GCN Circ. 20001). However, we note that due to the weakness of the burst, the standard pipeline finds a T90 that varies from ~ 1.3 s to ~ 3 s when using light curves with different bin sizes.
The image analysis with the BAT data in 15-150 keV finds no significant detections for extended emission within several hundred seconds after the trigger. However, the BAT image from T+250 s to T+350 s, which is the time period around the peak of the XRT flare, does show a slight increase of significance of 3.8 sigma (comparing to ~ 1 to 2 sigma detections for other periods). Therefore, it is possible that the XRT flare might be the second peak of the prompt emission, but was close to the detection limit of the BAT.
The time averaged spectrum is best fit by a simple power-law model, with an index of 1.3 +/- 0.33. This value is consistent with the average value of the short GRB distribution, and slightly on the harder side of the long burst distribution, but still within the majority (Lien & Sakamoto et al. 2016).
The lag analysis is still unavailable due to the weakness of the burst (Palmer et al, GCN Circ. 20001).
The bright flare in the XRT light curve around T+300 s is unusual for short GRBs. However, Swift have detected short GRBs with flares before (e.g., GRB 070724A, GRB 100816A; Margutti et al., 2011, MNRAS, 417, 2144), and thus we cannot rule out the short-burst possibility base on this.
Therefore, we conclude that the burst nature remains ambiguous with current information.

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Jochen Greiner, last update: 16-Oct-2016 [Disclaimer]