Gamma-ray Burst 161220A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Dec 16 08:34:07 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     727610,   Seg_Num: 0
GRB_RA:          350.817d {+23h 23m 16s} (J2000),
                 351.050d {+23h 24m 12s} (current),
                 350.125d {+23h 20m 30s} (1950)
GRB_DEC:         -47.502d {-47d 30' 07"} (J2000),
                 -47.409d {-47d 24' 31"} (current),
                 -47.777d {-47d 46' 35"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       5839 [cnts]    Image_Peak=198 [image_cnts]
TRIGGER_DUR:     2.048 [sec] 
TRIGGER_INDEX:   443     E_range: 15-50 keV
BKG_INTEN:       58685 [cnts]
BKG_TIME:        30774.66 SOD {08:32:54.66} UT
BKG_DUR:         24 [sec]
GRB_DATE:        17742 TJD;   355 DOY;   16/12/20
GRB_TIME:        30810.24 SOD {08:33:30.24} UT
GRB_PHI:         -179.32 [deg]
GRB_THETA:         3.35 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     11.04 [sigma]
IMAGE_SIGNIF:    7.00 [sigma]
MERIT_PARAMS:     +1  +0  +0  +1  +1  -3  +0  +0 -37  +0 
SUN_POSTN:       268.79d {+17h 55m 11s}  -23.43d {-23d 25' 54"}
SUN_DIST:         67.89 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      171.93d {+11h 27m 43s}   +4.84d {+04d 50' 18"}
MOON_DIST:       137.42 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      337.30,-63.32 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      329.54,-39.31 [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 = 99.03,4.49 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Dec 16 08:35:16 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     727610,   Seg_Num: 0
GRB_RA:          350.8486d {+23h 23m 23.66s} (J2000),
                 351.0822d {+23h 24m 19.72s} (current),
                 350.1577d {+23h 20m 37.85s} (1950)
GRB_DEC:         -47.4978d {-47d 29' 52.0"} (J2000),
                 -47.4045d {-47d 24' 16.2"} (current),
                 -47.7724d {-47d 46' 20.6"} (1950)
GRB_ERROR:       5.2 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.94e-09 [erg/cm2/sec]
GRB_SIGNIF:      9.05 [sigma]
IMG_START_DATE:  17742 TJD;   355 DOY;   16/12/20
IMG_START_TIME:  30879.27 SOD {08:34:39.27} UT,   69.0 [sec] since BAT Trigger Time
TAM[0-3]:        327.64 237.20 261.59 243.45
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       268.80d {+17h 55m 11s}  -23.43d {-23d 25' 54"}
SUN_DIST:         67.91 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      171.94d {+11h 27m 46s}   +4.84d {+04d 50' 07"}
MOON_DIST:       137.42 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      337.28,-63.33 [deg] galactic lon,lat of the burst
ECL_COORDS:      329.57,-39.32 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 1.33 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Dec 16 08:35:25 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     727610,   Seg_Num: 0
GRB_RA:          350.8486d {+23h 23m 23.6s} (J2000),
                 351.0822d {+23h 24m 19.7s} (current),
                 350.1577d {+23h 20m 37.8s} (1950)
GRB_DEC:         -47.4978d {-47d 29' 52.0"} (J2000),
                 -47.4045d {-47d 24' 16.2"} (current),
                 -47.7724d {-47d 46' 20.6"} (1950)
GRB_ERROR:       5.0 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       82 [cnts]
IMG_START_DATE:  17742 TJD;   355 DOY;   16/12/20
IMG_START_TIME:  30879.27 SOD {08:34:39.27} UT,   69.0 [sec] since BAT Trigger Time
CENTROID_X:      340.95,  raw= 341  [pixels]
CENTROID_Y:      293.94,  raw= 294  [pixels]
ROLL:            259.12 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -9.08
GRB_POS_XRT_Z:   84.05
IMAGE_URL:       sw00727610000msxps_rw.img
SUN_POSTN:       268.80d {+17h 55m 11s}  -23.43d {-23d 25' 54"}
SUN_DIST:         67.91 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      171.94d {+11h 27m 46s}   +4.83d {+04d 50' 06"}
MOON_DIST:       137.42 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      337.28,-63.33 [deg] galactic lon,lat of the burst
ECL_COORDS:      329.57,-39.32 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Dec 16 08:35:32 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     727610,   Seg_Num: 0
GRB_RA:          350.8486d {+23h 23m 23.6s} (J2000),
                 351.0822d {+23h 24m 19.7s} (current),
                 350.1577d {+23h 20m 37.8s} (1950)
GRB_DEC:         -47.4978d {-47d 29' 52.0"} (J2000),
                 -47.4045d {-47d 24' 16.2"} (current),
                 -47.7724d {-47d 46' 20.6"} (1950)
GRB_ERROR:       5.0 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       82 [cnts]
IMG_START_DATE:  17742 TJD;   355 DOY;   16/12/20
IMG_START_TIME:  30879.27 SOD {08:34:39.27} UT,   69.0 [sec] since BAT Trigger Time
CENTROID_X:      340.95,  raw= 341  [pixels]
CENTROID_Y:      293.94,  raw= 294  [pixels]
ROLL:            259.12 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -9.08
GRB_POS_XRT_Z:   84.05
IMAGE_URL:       sw00727610000msxps_rw.img
SUN_POSTN:       268.80d {+17h 55m 11s}  -23.43d {-23d 25' 54"}
SUN_DIST:         67.91 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      171.94d {+11h 27m 46s}   +4.83d {+04d 50' 04"}
MOON_DIST:       137.42 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      337.28,-63.33 [deg] galactic lon,lat of the burst
ECL_COORDS:      329.57,-39.32 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Dec 16 08:37:06 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     727610,   Seg_Num: 0
GRB_RA:          350.817d {+23h 23m 16s} (J2000),
                 351.050d {+23h 24m 12s} (current),
                 350.125d {+23h 20m 30s} (1950)
GRB_DEC:         -47.502d {-47d 30' 07"} (J2000),
                 -47.409d {-47d 24' 31"} (current),
                 -47.777d {-47d 46' 35"} (1950)
GRB_DATE:        17742 TJD;   355 DOY;   16/12/20
GRB_TIME:        30810.24 SOD {08:33:30.24} UT
TRIGGER_INDEX:   443
GRB_PHI:         -179.32 [deg]
GRB_THETA:         3.35 [deg]
DELTA_TIME:      -37.00 [sec]
TRIGGER_DUR:     2.048 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     11.04 [sigma]
IMAGE_SIGNIF:    7.00 [sigma]
LC_URL:          sw00727610000msb.lc
SUN_POSTN:       268.80d {+17h 55m 11s}  -23.43d {-23d 25' 54"}
SUN_DIST:         67.89 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      171.96d {+11h 27m 49s}   +4.83d {+04d 49' 49"}
MOON_DIST:       137.41 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      337.30,-63.32 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      329.54,-39.31 [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 = 99.03,4.49 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Dec 16 08:38:33 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     727610,   Seg_Num: 0
POINT_RA:        350.815d {+23h 23m 16s} (J2000)
POINT_DEC:       -47.505d {-47d 30' 17"} (J2000)
POINT_ROLL:      259.123d
IMG_START_DATE:  17742 TJD;   355 DOY;   16/12/20
IMG_START_TIME:  30888.57 SOD {08:34:48.57} UT,   78.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.838
N_STARS:         15
X_OFFSET:        464 [pixels]
Y_OFFSET:        576 [pixels]
X_MAX:           1423 [pixels]
Y_MAX:           1535 [pixels]
DET_THRESH:      18
PHOTO_THRESH:    11
SL_URL:          sw00727610000msufc0078.fits
SUN_POSTN:       268.80d {+17h 55m 12s}  -23.43d {-23d 25' 54"}
SUN_DIST:         67.88 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      171.97d {+11h 27m 52s}   +4.83d {+04d 49' 35"}
MOON_DIST:       137.41 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      337.30,-63.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.54,-39.32 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Dec 16 08:39:03 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     727610,   Seg_Num: 0
POINT_RA:        350.815d {+23h 23m 16s} (J2000)
POINT_DEC:       -47.505d {-47d 30' 17"} (J2000)
POINT_ROLL:      259.123d
IMG_START_DATE:  17742 TJD;   355 DOY;   16/12/20
IMG_START_TIME:  30888.57 SOD {08:34:48.57} UT,   78.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.838
N_STARS:         15
X_OFFSET:        464 [pixels]
Y_OFFSET:        576 [pixels]
X_MAX:           1423 [pixels]
Y_MAX:           1535 [pixels]
DET_THRESH:      18
PHOTO_THRESH:    11
SL_URL:          sw00727610000msufc0078.fits
SUN_POSTN:       268.80d {+17h 55m 12s}  -23.43d {-23d 25' 54"}
SUN_DIST:         67.88 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      171.97d {+11h 27m 53s}   +4.82d {+04d 49' 30"}
MOON_DIST:       137.41 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      337.30,-63.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.54,-39.32 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_srclist.fits.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Dec 16 08:40:25 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     727610,   Seg_Num: 0
POINT_RA:        350.815d {+23h 23m 16s} (J2000)
POINT_DEC:       -47.505d {-47d 30' 17"} (J2000)
ROLL:            259.123d
IMG_START_DATE:  17742 TJD;   355 DOY;   16/12/20
IMG_START_TIME:  30888.57 SOD {08:34:48.57} UT,   78.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     503915705
X_OFFSET:        651 [pixels]
Y_OFFSET:        968 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       811
Y_GRB_POS:       1128
BINNING_INDEX:   1
IM_URL:          sw00727610000msuni0096.fits
SUN_POSTN:       268.80d {+17h 55m 12s}  -23.43d {-23d 25' 54"}
SUN_DIST:         67.88 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      171.98d {+11h 27m 56s}   +4.82d {+04d 49' 16"}
MOON_DIST:       137.40 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      337.30,-63.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.54,-39.32 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Dec 16 08:40:30 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     727610,   Seg_Num: 0
POINT_RA:        350.815d {+23h 23m 16s} (J2000)
POINT_DEC:       -47.505d {-47d 30' 17"} (J2000)
ROLL:            259.123d
IMG_START_DATE:  17742 TJD;   355 DOY;   16/12/20
IMG_START_TIME:  30888.57 SOD {08:34:48.57} UT,   78.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     503915705
X_OFFSET:        651 [pixels]
Y_OFFSET:        968 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       811
Y_GRB_POS:       1128
BINNING_INDEX:   1
IM_URL:          sw00727610000msuni0096.fits
SUN_POSTN:       268.80d {+17h 55m 12s}  -23.43d {-23d 25' 54"}
SUN_DIST:         67.88 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      171.98d {+11h 27m 56s}   +4.82d {+04d 49' 16"}
MOON_DIST:       137.40 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      337.30,-63.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.54,-39.32 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Dec 16 08:46:10 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     727610,   Seg_Num: 0
POINT_RA:        350.815d {+23h 23m 16s} (J2000)
POINT_DEC:       -47.504d {-47d 30' 13"} (J2000)
POINT_ROLL:      259.121d
IMG_START_DATE:  17742 TJD;   355 DOY;   16/12/20
IMG_START_TIME:  31047.29 SOD {08:37:27.29} UT,   237.0 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        1.165
N_STARS:         29
X_OFFSET:        331 [pixels]
Y_OFFSET:        648 [pixels]
X_MAX:           1290 [pixels]
Y_MAX:           1607 [pixels]
DET_THRESH:      9
PHOTO_THRESH:    4
SL_URL:          sw00727610000msufc0237.fits
SUN_POSTN:       268.80d {+17h 55m 13s}  -23.43d {-23d 25' 54"}
SUN_DIST:         67.88 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      172.03d {+11h 28m 08s}   +4.81d {+04d 48' 20"}
MOON_DIST:       137.39 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      337.30,-63.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.54,-39.32 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Dec 16 08:46:27 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     727610,   Seg_Num: 0
POINT_RA:        350.815d {+23h 23m 16s} (J2000)
POINT_DEC:       -47.504d {-47d 30' 13"} (J2000)
POINT_ROLL:      259.121d
IMG_START_DATE:  17742 TJD;   355 DOY;   16/12/20
IMG_START_TIME:  31047.29 SOD {08:37:27.29} UT,   237.0 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        1.165
N_STARS:         29
X_OFFSET:        331 [pixels]
Y_OFFSET:        648 [pixels]
X_MAX:           1290 [pixels]
Y_MAX:           1607 [pixels]
DET_THRESH:      9
PHOTO_THRESH:    4
SL_URL:          sw00727610000msufc0237.fits
SUN_POSTN:       268.80d {+17h 55m 13s}  -23.43d {-23d 25' 54"}
SUN_DIST:         67.88 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      172.03d {+11h 28m 08s}   +4.80d {+04d 48' 17"}
MOON_DIST:       137.39 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      337.30,-63.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.54,-39.32 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_srclist.fits.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Dec 16 08:47:34 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     727610,   Seg_Num: 0
POINT_RA:        350.815d {+23h 23m 16s} (J2000)
POINT_DEC:       -47.504d {-47d 30' 13"} (J2000)
ROLL:            259.121d
IMG_START_DATE:  17742 TJD;   355 DOY;   16/12/20
IMG_START_TIME:  31047.29 SOD {08:37:27.29} UT,   237.0 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     503915864
X_OFFSET:        651 [pixels]
Y_OFFSET:        968 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       811
Y_GRB_POS:       1128
BINNING_INDEX:   1
IM_URL:          sw00727610000msuni0255.fits
SUN_POSTN:       268.80d {+17h 55m 13s}  -23.43d {-23d 25' 54"}
SUN_DIST:         67.88 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      172.04d {+11h 28m 10s}   +4.80d {+04d 48' 06"}
MOON_DIST:       137.38 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      337.30,-63.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.54,-39.32 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Dec 16 08:47:53 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     727610,   Seg_Num: 0
POINT_RA:        350.815d {+23h 23m 16s} (J2000)
POINT_DEC:       -47.504d {-47d 30' 13"} (J2000)
ROLL:            259.121d
IMG_START_DATE:  17742 TJD;   355 DOY;   16/12/20
IMG_START_TIME:  31047.29 SOD {08:37:27.29} UT,   237.0 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     503915864
X_OFFSET:        651 [pixels]
Y_OFFSET:        968 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       811
Y_GRB_POS:       1128
BINNING_INDEX:   1
IM_URL:          sw00727610000msuni0255.fits
SUN_POSTN:       268.81d {+17h 55m 13s}  -23.43d {-23d 25' 54"}
SUN_DIST:         67.88 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      172.05d {+11h 28m 11s}   +4.80d {+04d 48' 03"}
MOON_DIST:       137.38 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      337.30,-63.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.54,-39.32 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Dec 16 08:54:55 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     727610,   Seg_Num: 0
POINT_RA:        350.815d {+23h 23m 16s} (J2000)
POINT_DEC:       -47.504d {-47d 30' 13"} (J2000)
POINT_ROLL:      259.121d
IMG_START_DATE:  17742 TJD;   355 DOY;   16/12/20
IMG_START_TIME:  31672.12 SOD {08:47:52.12} UT,   861.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.313
N_STARS:         84
X_OFFSET:        91 [pixels]
Y_OFFSET:        408 [pixels]
X_MAX:           1530 [pixels]
Y_MAX:           1847 [pixels]
DET_THRESH:      13
PHOTO_THRESH:    6
SL_URL:          sw00727610000msufc0861.fits
SUN_POSTN:       268.81d {+17h 55m 15s}  -23.43d {-23d 25' 54"}
SUN_DIST:         67.87 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      172.10d {+11h 28m 25s}   +4.78d {+04d 46' 54"}
MOON_DIST:       137.36 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      337.30,-63.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.54,-39.32 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Dec 16 08:55:20 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     727610,   Seg_Num: 0
POINT_RA:        350.815d {+23h 23m 16s} (J2000)
POINT_DEC:       -47.504d {-47d 30' 13"} (J2000)
POINT_ROLL:      259.121d
IMG_START_DATE:  17742 TJD;   355 DOY;   16/12/20
IMG_START_TIME:  31672.12 SOD {08:47:52.12} UT,   861.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.313
N_STARS:         84
X_OFFSET:        91 [pixels]
Y_OFFSET:        408 [pixels]
X_MAX:           1530 [pixels]
Y_MAX:           1847 [pixels]
DET_THRESH:      13
PHOTO_THRESH:    6
SL_URL:          sw00727610000msufc0861.fits
SUN_POSTN:       268.81d {+17h 55m 15s}  -23.43d {-23d 25' 54"}
SUN_DIST:         67.87 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      172.11d {+11h 28m 26s}   +4.78d {+04d 46' 50"}
MOON_DIST:       137.36 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      337.30,-63.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.54,-39.32 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_srclist.fits.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Dec 16 08:56:23 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     727610,   Seg_Num: 0
POINT_RA:        350.815d {+23h 23m 16s} (J2000)
POINT_DEC:       -47.504d {-47d 30' 13"} (J2000)
ROLL:            259.121d
IMG_START_DATE:  17742 TJD;   355 DOY;   16/12/20
IMG_START_TIME:  31672.12 SOD {08:47:52.12} UT,   861.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     503916489
X_OFFSET:        650 [pixels]
Y_OFFSET:        967 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       810
Y_GRB_POS:       1127
BINNING_INDEX:   1
IM_URL:          sw00727610000msuni0879.fits
SUN_POSTN:       268.81d {+17h 55m 15s}  -23.43d {-23d 25' 54"}
SUN_DIST:         67.87 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      172.12d {+11h 28m 28s}   +4.78d {+04d 46' 40"}
MOON_DIST:       137.36 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      337.30,-63.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.54,-39.32 [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 20 Dec 16 08:56:42 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     727610,   Seg_Num: 0
POINT_RA:        350.815d {+23h 23m 16s} (J2000)
POINT_DEC:       -47.504d {-47d 30' 13"} (J2000)
ROLL:            259.121d
IMG_START_DATE:  17742 TJD;   355 DOY;   16/12/20
IMG_START_TIME:  31672.12 SOD {08:47:52.12} UT,   861.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     503916489
X_OFFSET:        650 [pixels]
Y_OFFSET:        967 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       810
Y_GRB_POS:       1127
BINNING_INDEX:   1
IM_URL:          sw00727610000msuni0879.fits
SUN_POSTN:       268.81d {+17h 55m 15s}  -23.43d {-23d 25' 54"}
SUN_DIST:         67.87 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      172.12d {+11h 28m 29s}   +4.78d {+04d 46' 37"}
MOON_DIST:       137.36 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      337.30,-63.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      329.54,-39.32 [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 Circular #20302
V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), T. Sakamoto (AGU), B. Sbarufatti (INAF-OAB/PSU) and T. N. Ukwatta (LANL) report on behalf of the Swift Team:
At 08:33:30 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 161220A (trigger=727610). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 350.817, -47.502 which is
```
   RA(J2000) = 23h 23m 16s
   Dec(J2000) = -47d 30' 07"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a FRED-like structure with a duration of about 12 sec. The peak count rate was ~1285 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 08:34:39.2 UT, 69.1 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source located at RA, Dec 350.84774, -47.49773, which is equivalent to:
```
   RA(J2000)  = 23h 23m 23.46s
   Dec(J2000) = -47d 29' 51.8"
```
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 76 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 1.19 x 10^20 cm^-2 (Willingale et al. 2013).
The initial flux in the 2.5 s image was 1.94e-09 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 78 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 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. Results from the list of sources generated on-board are not available at this time. No correction has been made for the expected extinction corresponding to E(B-V) of 0.01.
Burst Advocate for this burst is V. D'Elia (delia AT asdc.asi.it). 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 #20307
F. E. Marshall (NASA/GSFC) and V. D'Elia (ASDC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 161220A 78 s after the BAT trigger (D'Elia et al., GCN Circ. 20302). No optical afterglow consistent with the XRT position (D'Elia et al. GCN Circ. 20302) 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            78          228          147         >20.5
white               78         1012          295         >21.0
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #20312
P. Wiseman, T. Kruehler, and J. Greiner (all MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 161220A (Swift trigger 727610; D'Elia et al., GCN #20302) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m MPG telescope at the ESO La Silla Observatory (Chile).
Observations started at 00:36 UT on 2016-12-21, 16 hrs after the GRB trigger. They were performed at an average seeing of 0".9, and at an average airmass of 1.2.
Similar to Marshall & D'Elia (GCN #20307), we detect no credible optical/NIR afterglow consistent with the XRT position. Based on combined images with 14.5 min of total exposures in g'r'i'z' and 12.0 min in JHK at a mid-time of 00:45 UT on 2016-12-21, we derive the following upper limits (all in AB system).
```
g' > 22.7 mag
r' > 22.7 mag
i' > 21.3 mag
z' > 21.8 mag
J > 20.8 mag
H > 20.4 mag
K > 17.2 mag
```
Given magnitudes are calibrated against USNO as well as 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.005 mag in the direction of the burst (Schlafly & Finkbeiner 2011).
GCN Circular #20315
C. Guidorzi (U. Ferrara), S. Kobayashi, I.A. Steele (LJMU), A. Gomboc (U. Nova Gorica), C.G. Mundell (U. Bath) on behalf of a large collaboration report:
We observed Swift GRB 161220A (D'Elia et al. GCN 20302) on December 20, from 11:02 to 11:13 UT (2.5-2.7 hours since the GRB) with the 2-m LCO Faulkes Telescope South in Siding Springs with the SDSS i filter under poor sky transparency conditions. Within the XRT error circle we do not find any object brighter than i~20 mag (total exposure of 5x120s) as calibrated against nearby USNOB1 stars.
GCN Circular #20316
A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), P. D'Avanzo (INAF-OAB), A. D'Ai (INAF-IASFPA), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), S.L. Gibson (U. Leicester) and V. D'Elia report on behalf of the Swift-XRT team:
We have analysed 3.4 ks of XRT data for GRB 161220A (D'Elia et al. GCN Circ. 20302), from 60 s to 58.3 ks after the BAT trigger. The data comprise 85 s in Windowed Timing (WT) mode (the first 7 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The refined XRT position is RA, Dec = 350.8479, -47.4978 which is equivalent to:
```
RA (J2000): 23 23 23.49
Dec(J2000): -47 29 52.2
```
with an uncertainty of 3.6 arcsec (radius, 90% confidence).
The light curve can be modelled with a series of power-law decays. The light curve initially rises, with an index alpha=-1.5 (+0.0, -2.0). At T+71.0 s it breaks to an alpha of 4.75 (+0.51, -0.29) before breaking again at T+217 s to a final decay with index alpha=0.82 (+0.13, -0.11).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 3.57 (+0.20, -0.19). The best-fitting absorption column is 3.2 (+/-0.4) x 10^21 cm^-2, in excess of the Galactic value of 1.2 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 2.1 x 10^-11 (9.9 x 10^-11) erg cm^-2 count^-1.
A summary of the WT-mode spectrum is thus:
```
Total column:	     3.2 (+/-0.4) x 10^21 cm^-2
Galactic foreground: 1.2 x 10^20 cm^-2
Excess significance: 12.4 sigma
Photon index:	     3.57 (+0.20, -0.19)
```
If the light curve continues to decay with a power-law decay index of 0.82, the count rate at T+24 hours will be 2.7 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.7 x 10^-14 (2.6 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00727610.
This circular is an official product of the Swift-XRT team.
GCN Circular #20325
T. Sakamoto (AGU), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), V. D'Elia (ASDC), N. Gehrels (GSFC), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-61 to T+243 sec from the recent telemetry downlink, we report further analysis of BAT GRB 161220A (trigger #727610) (D'Elia, et al., GCN Circ. 20302). The BAT ground-calculated position is RA, Dec = 350.841, -47.480 deg which is
```
   RA(J2000)  =  23h 23m 21.7s
   Dec(J2000) = -47d 28' 47.3"
```
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%.
The mask-weighted light curve shows a single episode that starts around T-4 sec, peaks around T+3 sec and ends at ~T+4 sec. T90 (15-350 keV) is 6 +- 1 sec (estimated error including systematics).
The time-averaged spectrum from T-2.24 to T+4.66 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.01 +- 0.25. The fluence in the 15-150 keV band is 1.7 +- 0.3 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+2.42 sec in the 15-150 keV band is 0.5 +- 0.1 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/727610/BA/

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Jochen Greiner, last update: 21-Dec-2016 [Disclaimer]