Gamma-ray Burst 171020A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 20 Oct 17 23:08:09 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     780845,   Seg_Num: 0
GRB_RA:           39.262d {+02h 37m 03s} (J2000),
                  39.508d {+02h 38m 02s} (current),
                  38.575d {+02h 34m 18s} (1950)
GRB_DEC:         +15.186d {+15d 11' 10"} (J2000),
                 +15.263d {+15d 15' 45"} (current),
                 +14.969d {+14d 58' 10"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       32032 [cnts]    Image_Peak=475 [image_cnts]
TRIGGER_DUR:     8.192 [sec] 
TRIGGER_INDEX:   477     E_range: 25-100 keV
BKG_INTEN:       224131 [cnts]
BKG_TIME:        83140.12 SOD {23:05:40.12} UT
BKG_DUR:         64 [sec]
GRB_DATE:        18046 TJD;   293 DOY;   17/10/20
GRB_TIME:        83230.75 SOD {23:07:10.75} UT
GRB_PHI:          74.60 [deg]
GRB_THETA:        28.27 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     17.46 [sigma]
IMAGE_SIGNIF:    8.64 [sigma]
MERIT_PARAMS:     +1  +0  +0  +3  +2  -1  +0  +0 +97  +0 
SUN_POSTN:       205.77d {+13h 43m 04s}  -10.67d {-10d 40' 17"}
SUN_DIST:        165.85 [deg]   Sun_angle= 11.1 [hr] (West of Sun)
MOON_POSTN:      220.29d {+14h 41m 09s}  -10.47d {-10d 28' 23"}
MOON_DIST:       175.15 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      157.31,-40.53 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       41.65, -0.15 [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 = 348.59,10.53 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 20 Oct 17 23:09:54 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     780845,   Seg_Num: 0
POINT_RA:         39.237d {+02h 36m 57s} (J2000)
POINT_DEC:       +15.171d {+15d 10' 17"} (J2000)
IMG_START_DATE:  18046 TJD;   293 DOY;   17/10/20
IMG_START_TIME:  83375.25 SOD {23:09:35.25} UT,   144.5 [sec] since BAT Trigger Time
COUNTS:          15    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        1    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:     Fri 20 Oct 17 23:11:17 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     780845,   Seg_Num: 0
GRB_RA:           39.262d {+02h 37m 03s} (J2000),
                  39.508d {+02h 38m 02s} (current),
                  38.575d {+02h 34m 18s} (1950)
GRB_DEC:         +15.186d {+15d 11' 10"} (J2000),
                 +15.263d {+15d 15' 45"} (current),
                 +14.969d {+14d 58' 10"} (1950)
GRB_DATE:        18046 TJD;   293 DOY;   17/10/20
GRB_TIME:        83230.75 SOD {23:07:10.75} UT
TRIGGER_INDEX:   477
GRB_PHI:          74.60 [deg]
GRB_THETA:        28.27 [deg]
DELTA_TIME:      58.00 [sec]
TRIGGER_DUR:     8.192 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     17.46 [sigma]
IMAGE_SIGNIF:    8.64 [sigma]
LC_URL:          sw00780845000msb.lc
SUN_POSTN:       205.77d {+13h 43m 04s}  -10.67d {-10d 40' 20"}
SUN_DIST:        165.85 [deg]   Sun_angle= 11.1 [hr] (West of Sun)
MOON_POSTN:      220.31d {+14h 41m 16s}  -10.48d {-10d 28' 52"}
MOON_DIST:       175.15 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      157.31,-40.53 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       41.65, -0.15 [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 = 348.59,10.53 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 20 Oct 17 23:12:37 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     780845,   Seg_Num: 0
POINT_RA:         39.237d {+02h 36m 57s} (J2000)
POINT_DEC:       +15.171d {+15d 10' 17"} (J2000)
POINT_ROLL:      72.670d
IMG_START_DATE:  18046 TJD;   293 DOY;   17/10/20
IMG_START_TIME:  83377.77 SOD {23:09:37.77} UT,   147.0 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.848
N_STARS:         36
X_OFFSET:        627 [pixels]
Y_OFFSET:        430 [pixels]
X_MAX:           1586 [pixels]
Y_MAX:           1389 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    7
SL_URL:          sw00780845000msufc0147.fits
SUN_POSTN:       205.77d {+13h 43m 05s}  -10.67d {-10d 40' 21"}
SUN_DIST:        165.88 [deg]   Sun_angle= 11.1 [hr] (West of Sun)
MOON_POSTN:      220.33d {+14h 41m 18s}  -10.48d {-10d 29' 04"}
MOON_DIST:       175.17 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      157.29,-40.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       41.62, -0.16 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 20 Oct 17 23:12:52 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     780845,   Seg_Num: 0
POINT_RA:         39.237d {+02h 36m 57s} (J2000)
POINT_DEC:       +15.171d {+15d 10' 17"} (J2000)
POINT_ROLL:      72.670d
IMG_START_DATE:  18046 TJD;   293 DOY;   17/10/20
IMG_START_TIME:  83377.77 SOD {23:09:37.77} UT,   147.0 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.848
N_STARS:         36
X_OFFSET:        627 [pixels]
Y_OFFSET:        430 [pixels]
X_MAX:           1586 [pixels]
Y_MAX:           1389 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    7
SL_URL:          sw00780845000msufc0147.fits
SUN_POSTN:       205.77d {+13h 43m 05s}  -10.67d {-10d 40' 21"}
SUN_DIST:        165.88 [deg]   Sun_angle= 11.1 [hr] (West of Sun)
MOON_POSTN:      220.33d {+14h 41m 19s}  -10.49d {-10d 29' 06"}
MOON_DIST:       175.17 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      157.29,-40.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       41.62, -0.16 [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:     Fri 20 Oct 17 23:13:33 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     780845,   Seg_Num: 0
GRB_RA:           39.2483d {+02h 37m 00.40s} (J2000),
                  39.4935d {+02h 37m 58.44s} (current),
                  38.5606d {+02h 34m 14.54s} (1950)
GRB_DEC:         +15.2036d {+15d 12' 12.9"} (J2000),
                 +15.2802d {+15d 16' 48.7"} (current),
                 +14.9869d {+14d 59' 13.0"} (1950)
GRB_ERROR:       3.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  18046 TJD;   293 DOY;   17/10/20
IMG_START_TIME:  83397.00 SOD {23:09:57.00} UT,   166.2 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       205.77d {+13h 43m 05s}  -10.67d {-10d 40' 22"}
SUN_DIST:        165.86 [deg]   Sun_angle= 11.1 [hr] (West of Sun)
MOON_POSTN:      220.33d {+14h 41m 20s}  -10.49d {-10d 29' 12"}
MOON_DIST:       175.14 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      157.28,-40.52 [deg] galactic lon,lat of the burst
ECL_COORDS:       41.64, -0.13 [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:     Fri 20 Oct 17 23:14:04 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     780845,   Seg_Num: 0
POINT_RA:         39.237d {+02h 36m 57s} (J2000)
POINT_DEC:       +15.171d {+15d 10' 17"} (J2000)
ROLL:            72.670d
IMG_START_DATE:  18046 TJD;   293 DOY;   17/10/20
IMG_START_TIME:  83377.77 SOD {23:09:37.77} UT,   147.0 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     530233797
X_OFFSET:        946 [pixels]
Y_OFFSET:        749 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1106
Y_GRB_POS:       909
BINNING_INDEX:   1
IM_URL:          sw00780845000msuni0167.fits
SUN_POSTN:       205.77d {+13h 43m 05s}  -10.67d {-10d 40' 22"}
SUN_DIST:        165.88 [deg]   Sun_angle= 11.1 [hr] (West of Sun)
MOON_POSTN:      220.34d {+14h 41m 21s}  -10.49d {-10d 29' 17"}
MOON_DIST:       175.17 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      157.29,-40.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       41.62, -0.16 [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:     Fri 20 Oct 17 23:14:11 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     780845,   Seg_Num: 0
POINT_RA:         39.237d {+02h 36m 57s} (J2000)
POINT_DEC:       +15.171d {+15d 10' 17"} (J2000)
ROLL:            72.670d
IMG_START_DATE:  18046 TJD;   293 DOY;   17/10/20
IMG_START_TIME:  83377.77 SOD {23:09:37.77} UT,   147.0 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     530233797
X_OFFSET:        946 [pixels]
Y_OFFSET:        749 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1106
Y_GRB_POS:       909
BINNING_INDEX:   1
IM_URL:          sw00780845000msuni0167.fits
SUN_POSTN:       205.77d {+13h 43m 05s}  -10.67d {-10d 40' 22"}
SUN_DIST:        165.88 [deg]   Sun_angle= 11.1 [hr] (West of Sun)
MOON_POSTN:      220.34d {+14h 41m 21s}  -10.49d {-10d 29' 18"}
MOON_DIST:       175.17 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      157.29,-40.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       41.62, -0.16 [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:     Fri 20 Oct 17 23:17:41 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     780845,   Seg_Num: 0
POINT_RA:         39.238d {+02h 36m 57s} (J2000)
POINT_DEC:       +15.173d {+15d 10' 23"} (J2000)
POINT_ROLL:      72.667d
IMG_START_DATE:  18046 TJD;   293 DOY;   17/10/20
IMG_START_TIME:  83536.92 SOD {23:12:16.92} UT,   306.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.817
N_STARS:         106
X_OFFSET:        387 [pixels]
Y_OFFSET:        190 [pixels]
X_MAX:           1826 [pixels]
Y_MAX:           1629 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    3
SL_URL:          sw00780845000msufc0306.fits
SUN_POSTN:       205.77d {+13h 43m 05s}  -10.67d {-10d 40' 25"}
SUN_DIST:        165.88 [deg]   Sun_angle= 11.1 [hr] (West of Sun)
MOON_POSTN:      220.37d {+14h 41m 28s}  -10.50d {-10d 29' 49"}
MOON_DIST:       175.17 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      157.29,-40.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       41.62, -0.15 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 20 Oct 17 23:17:51 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     780845,   Seg_Num: 0
POINT_RA:         39.238d {+02h 36m 57s} (J2000)
POINT_DEC:       +15.173d {+15d 10' 23"} (J2000)
POINT_ROLL:      72.667d
IMG_START_DATE:  18046 TJD;   293 DOY;   17/10/20
IMG_START_TIME:  83536.92 SOD {23:12:16.92} UT,   306.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.817
N_STARS:         106
X_OFFSET:        387 [pixels]
Y_OFFSET:        190 [pixels]
X_MAX:           1826 [pixels]
Y_MAX:           1629 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    3
SL_URL:          sw00780845000msufc0306.fits
SUN_POSTN:       205.77d {+13h 43m 06s}  -10.67d {-10d 40' 26"}
SUN_DIST:        165.88 [deg]   Sun_angle= 11.1 [hr] (West of Sun)
MOON_POSTN:      220.37d {+14h 41m 29s}  -10.50d {-10d 29' 51"}
MOON_DIST:       175.17 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      157.29,-40.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       41.62, -0.15 [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:     Fri 20 Oct 17 23:18:23 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     780845,   Seg_Num: 0
GRB_RA:           39.2481d {+02h 37m 00.45s} (J2000),
                  39.4933d {+02h 37m 58.40s} (current),
                  38.5604d {+02h 34m 14.50s} (1950)
GRB_DEC:         +15.2037d {+15d 12' 13.3"} (J2000),
                 +15.2803d {+15d 16' 49.1"} (current),
                 +14.9870d {+14d 59' 13.3"} (1950)
GRB_ERROR:       2.2 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  18046 TJD;   293 DOY;   17/10/20
IMG_START_TIME:  83397.00 SOD {23:09:57.00} UT,   166.2 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       205.77d {+13h 43m 06s}  -10.67d {-10d 40' 26"}
SUN_DIST:        165.86 [deg]   Sun_angle= 11.1 [hr] (West of Sun)
MOON_POSTN:      220.37d {+14h 41m 30s}  -10.50d {-10d 29' 56"}
MOON_DIST:       175.14 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      157.28,-40.52 [deg] galactic lon,lat of the burst
ECL_COORDS:       41.64, -0.13 [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:     Fri 20 Oct 17 23:19:02 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     780845,   Seg_Num: 0
POINT_RA:         39.238d {+02h 36m 57s} (J2000)
POINT_DEC:       +15.173d {+15d 10' 23"} (J2000)
ROLL:            72.667d
IMG_START_DATE:  18046 TJD;   293 DOY;   17/10/20
IMG_START_TIME:  83536.92 SOD {23:12:16.92} UT,   306.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     530233956
X_OFFSET:        946 [pixels]
Y_OFFSET:        749 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1106
Y_GRB_POS:       909
BINNING_INDEX:   1
IM_URL:          sw00780845000msuni0326.fits
SUN_POSTN:       205.77d {+13h 43m 06s}  -10.67d {-10d 40' 27"}
SUN_DIST:        165.88 [deg]   Sun_angle= 11.1 [hr] (West of Sun)
MOON_POSTN:      220.38d {+14h 41m 31s}  -10.50d {-10d 30' 02"}
MOON_DIST:       175.17 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      157.29,-40.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       41.62, -0.15 [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:     Fri 20 Oct 17 23:19:12 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     780845,   Seg_Num: 0
POINT_RA:         39.238d {+02h 36m 57s} (J2000)
POINT_DEC:       +15.173d {+15d 10' 23"} (J2000)
ROLL:            72.667d
IMG_START_DATE:  18046 TJD;   293 DOY;   17/10/20
IMG_START_TIME:  83536.92 SOD {23:12:16.92} UT,   306.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     530233956
X_OFFSET:        946 [pixels]
Y_OFFSET:        749 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1106
Y_GRB_POS:       909
BINNING_INDEX:   1
IM_URL:          sw00780845000msuni0326.fits
SUN_POSTN:       205.77d {+13h 43m 06s}  -10.67d {-10d 40' 27"}
SUN_DIST:        165.88 [deg]   Sun_angle= 11.1 [hr] (West of Sun)
MOON_POSTN:      220.38d {+14h 41m 31s}  -10.50d {-10d 30' 03"}
MOON_DIST:       175.17 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      157.29,-40.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       41.62, -0.15 [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:     Fri 20 Oct 17 23:24:30 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     780845,   Seg_Num: 0
POINT_RA:         39.238d {+02h 36m 57s} (J2000)
POINT_DEC:       +15.173d {+15d 10' 23"} (J2000)
POINT_ROLL:      72.668d
IMG_START_DATE:  18046 TJD;   293 DOY;   17/10/20
IMG_START_TIME:  84091.11 SOD {23:21:31.11} UT,   860.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.985
N_STARS:         148
X_OFFSET:        387 [pixels]
Y_OFFSET:        190 [pixels]
X_MAX:           1826 [pixels]
Y_MAX:           1629 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    8
SL_URL:          sw00780845000msufc0860.fits
SUN_POSTN:       205.78d {+13h 43m 07s}  -10.68d {-10d 40' 31"}
SUN_DIST:        165.89 [deg]   Sun_angle= 11.1 [hr] (West of Sun)
MOON_POSTN:      220.43d {+14h 41m 42s}  -10.51d {-10d 30' 51"}
MOON_DIST:       175.18 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      157.29,-40.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       41.62, -0.15 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 20 Oct 17 23:24:44 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     780845,   Seg_Num: 0
POINT_RA:         39.238d {+02h 36m 57s} (J2000)
POINT_DEC:       +15.173d {+15d 10' 23"} (J2000)
POINT_ROLL:      72.668d
IMG_START_DATE:  18046 TJD;   293 DOY;   17/10/20
IMG_START_TIME:  84091.11 SOD {23:21:31.11} UT,   860.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.985
N_STARS:         148
X_OFFSET:        387 [pixels]
Y_OFFSET:        190 [pixels]
X_MAX:           1826 [pixels]
Y_MAX:           1629 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    8
SL_URL:          sw00780845000msufc0860.fits
SUN_POSTN:       205.78d {+13h 43m 07s}  -10.68d {-10d 40' 32"}
SUN_DIST:        165.89 [deg]   Sun_angle= 11.1 [hr] (West of Sun)
MOON_POSTN:      220.43d {+14h 41m 43s}  -10.52d {-10d 30' 53"}
MOON_DIST:       175.18 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      157.29,-40.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       41.62, -0.15 [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:     Fri 20 Oct 17 23:26:08 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     780845,   Seg_Num: 0
POINT_RA:         39.238d {+02h 36m 57s} (J2000)
POINT_DEC:       +15.173d {+15d 10' 23"} (J2000)
ROLL:            72.668d
IMG_START_DATE:  18046 TJD;   293 DOY;   17/10/20
IMG_START_TIME:  84091.11 SOD {23:21:31.11} UT,   860.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     530234510
X_OFFSET:        946 [pixels]
Y_OFFSET:        749 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1106
Y_GRB_POS:       909
BINNING_INDEX:   1
IM_URL:          sw00780845000msuni0880.fits
SUN_POSTN:       205.78d {+13h 43m 07s}  -10.68d {-10d 40' 33"}
SUN_DIST:        165.89 [deg]   Sun_angle= 11.1 [hr] (West of Sun)
MOON_POSTN:      220.44d {+14h 41m 45s}  -10.52d {-10d 31' 06"}
MOON_DIST:       175.18 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      157.29,-40.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       41.62, -0.15 [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:     Fri 20 Oct 17 23:26:23 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     780845,   Seg_Num: 0
POINT_RA:         39.238d {+02h 36m 57s} (J2000)
POINT_DEC:       +15.173d {+15d 10' 23"} (J2000)
ROLL:            72.668d
IMG_START_DATE:  18046 TJD;   293 DOY;   17/10/20
IMG_START_TIME:  84091.11 SOD {23:21:31.11} UT,   860.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     530234510
X_OFFSET:        946 [pixels]
Y_OFFSET:        749 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1106
Y_GRB_POS:       909
BINNING_INDEX:   1
IM_URL:          sw00780845000msuni0880.fits
SUN_POSTN:       205.78d {+13h 43m 07s}  -10.68d {-10d 40' 33"}
SUN_DIST:        165.89 [deg]   Sun_angle= 11.1 [hr] (West of Sun)
MOON_POSTN:      220.44d {+14h 41m 46s}  -10.52d {-10d 31' 08"}
MOON_DIST:       175.18 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      157.29,-40.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       41.62, -0.15 [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 #22028
K. L. Page (U Leicester), A. P. Beardmore (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), B. Sbarufatti (PSU) and M. H. Siegel (PSU) report on behalf of the Swift Team:
At 23:07:10 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 171020A (trigger=780845). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 39.262, +15.186 which is
```
   RA(J2000) = 02h 37m 03s
   Dec(J2000) = +15d 11' 10"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 50 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~2 sec after the trigger. Note that the BAT light curve might be contaminated by Swift J0243.6+6124, which has a period of 9.86 s (ATel #10809).
The XRT began observing the field at 23:09:35.2 UT, 144.4 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 39.2482, 15.2038 which is equivalent to:
```
   RA(J2000)  = 02h 36m 59.57s
   Dec(J2000) = +15d 12' 13.5"
```
with an uncertainty of 2.2 arcseconds (radius, 90% containment). This location is 80 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 1.55 x 10^21 cm^-2 (Willingale et al. 2013).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 147 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. 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 0.19.
Burst Advocate for this burst is K. L. Page (klp5 AT leicester.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 Circular #22029
D. Malesani (DARK/NBI), M. Stone (Turku Univ.), K. Karhunen (Turku Univ.), A. de Ugarte Postigo (IAA/CSIC and DARK/NBI), and D. Xu (NAOC/CAS), report on behalf of a larger collaboration:
We observed the field of GRB 171020A (Page et al., GCN 22028) with the Nordic Optical Telescope equipped with the AlFOSC imager and spectrograph. Observations were carried out in the r and z filters, starting on 2017 Oct 20.979 UT (22.9 min after the trigger).
Within the XRT error circle, we detect an uncatalogued source at coordinates (J2000):
```
RA = 02:36:59.62
Dec = +15:12:16.0
```
By comparison with nearby stars from the Pan-STARRS catalog, we measure r = 20.98 +- 0.03 AB. As this object is not visible in the deeper, archival Pan-STARRS images, and given the coincidence with the X-ray counterpart, we suggest this object to be the optical afterglow of GRB 171020A.
GCN Circular #22030
S.Karpov, G.Beskin (SAO RAS and Kazan Federal University, Russia), S.Bondar, E.Ivanov, E.Katkova, N.Orekhova, A.Perkov (OJS RPC PSI, Russia), A.Biryukov (SAI MSU and Kazan Federal University, Russia), V.Sasyuk (Kazan Federal University, Russia)
Mini-MegaTORTORA nine-channel wide-field monitoring system with high temporal resolution has been observing the Swift field of view before, during and after the time of Swift BAT trigger corresponding to GRB171020A (Page et al, GCN 22028). The whole burst localization region has been covered since 2017-10-20 23:00:07.90 UT (T0-422 s) and until 2017-10-20 23:10:17.68 UT (T0+187 s, thus including the whole gamma-ray activity interval) with temporal resolution of 0.1 s in white light. Dedicated real-time transient detection pipeline did not detect any events longer than 0.3 s and brighter than approximately V=10.5 mag during this interval. Visual inspection of co-added images with 10 s effective exposure (summation of 100 consecutive frames each) has not revealed any variable source down to V=12.0 mag during that interval. Also, the multi-regime follow-up (when all channels except for the one containing the trigger are repointed towards it and observe it with various exposures with and without photometric and polarimetric filters installed) has been initiated at 2017-10-20 23:08:12.0 UT (T0+61.25 s). The inspection of 10 s exposure frames acquired in white light between 2017-10-20 23:08:12.0 UT (T0+61.25 s) and 2017-10-20 23:09:43 UT (T0+152.25 s) did not reveal any source brighter than V=13.5 mag at the position of the burst.
Mini-MegaTORTORA belongs to Kazan Federal University and is located at Special Astrophysical Observatory near Russian 6-m telescope.
The message may be cited.
GCN Circular #22031
A. Moskvitin (SAO RAS), O. Spiridonova (SAO RAS), A. Volnova (IKI RAS)
We observed the field of GRB 171020A (Page et al., GCN 22028) with the 1-m telescope of SAO RAS, Zeiss-1000 on 2017.10.20, starting at 23:18 UT, i.e. ~11 minutes after the trigger. The OT (Malesani et al., GCN 22029) is clearly detected in the individual 300 sec. frames. The coordinates of OT: R. A. = 02:36:59.62; Dec. = +15:12:15.6 (J2000).
```
Date       UT start  t - T0       Filter Exp.  OT       Err.  UL
                     (mid, days)         (s)

2017.10.20 23:18:05  0.02016      Rc     6*300 20.9 +/- 0.1   22.3
           23:55:27  0.04827      Rc     7*300 21.5 +/- 0.1   22.5
```
The temporal decay slope is about -0.3, F ~ (t-T0)^alpha.
The calibration were made against the nearby USNO-B1.0 stars (R2 magnitudes):
```
1051-0026883 02:37:00.38 +15:11:09.6 18.59
1052-0027787 02:36:57.49 +15:12:36.8 16.62
1052-0027776 02:36:50.26 +15:12:39.8 18.15
```
GCN Circular #22032
```
TITLE:   GCN CIRCULAR
NUMBER:  22032 
SUBJECT: GRB 171020A: Correction of alpha in GCN 22031
DATE:    17/10/21 03:49:17 GMT 
FROM:    Moskvitin Alexander at SAO RAS  
```
A. Moskvitin (SAO RAS), O. Spiridonova (SAO RAS), A. Volnova (IKI RAS)
In our previous GCN 22031 we reported incorrect slope. The correct decay slope is about -0.6 +/- 0.2.
We apologize for any confusion caused by the earlier report.
GCN Circular #22033
C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell (U. Bath),=20 A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU) on behalf of a large=20 collaboration report:
The 2-m Liverpool Telescope automatically began observing Swift GRB=20 171020A (Page et al. GCN 22028) on October 20, 23:10:12 UT (3.0 minutes=20 from the GRB trigger time) with the RINGO3 polarimeter and the IO:O=20 camera in the SDSS-R filter. We clearly detect the optical afterglow=20 (Malesani et al, GCN 22029; Moskvitin et al., GCN 22031) with the=20 following magnitude:
```
Mid Time=A0=A0=A0=A0=A0 Exposure=A0=A0=A0=A0=A0=A0 Filter=A0=A0=A0=A0=A0=A0=
 Magnitude (AB)
(min)=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 (s)
-------------------------------------------------------
35.8=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0 6x10=A0=A0=A0=A0=A0=A0=A0=A0 SDSS-R=
=A0=A0=A0=A0=A0=A0 21.12 +- 0.14
-------------------------------------------------------
```
as calibrated against nearby Pan-STARRS objects.
GCN Circular #22034
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
Using 5393 s of XRT Photon Counting mode data and 8 UVOT images for GRB 171020A, 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 = 39.24837, +15.20413 which is equivalent to:
```
RA (J2000): 02h 36m 59.61s
Dec (J2000): +15d 12' 14.9"
```
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 #22035
A. Tohuvavohu (PSU), S. J. LaPorte (PSU), J.A. Kennea (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA) and K.L. Page report on behalf of the Swift-XRT team:
We have analysed 7.5 ks of XRT data for GRB 171020A (Page et al. GCN Circ. 22028), from 128 s to 35.4 ks after the BAT trigger. The data comprise 10 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 Evans et al. (GCN Circ. 22034).
The light curve can be modelled with an initial power-law decay with an index of alpha=2.23 (+0.45, -0.21), followed by a break at T+563 s to an alpha of 0.88 (+0.08, -0.07).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.58 (+0.17, -0.15). The best-fitting absorption column is 1.84 (+0.70, -0.28) x 10^21 cm^-2, consistent with the Galactic value of 1.6 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.5 x 10^-11 (5.3 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     1.84 (+0.70, -0.28) x 10^21 cm^-2
Galactic foreground: 1.6 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.58 (+0.17, -0.15)
```
If the light curve continues to decay with a power-law decay index of 0.88, the count rate at T+24 hours will be 5.4 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.4 x 10^-13 (2.9 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/00780845.
This circular is an official product of the Swift-XRT team.
GCN Circular #22037
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), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jes=FAs Gonz=E1lez (UNAM), Carlos Rom=E1n-Z=FA=F1iga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report:
We observed the field of GRB 171020A (Page, et al., GCN 22028) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astron=F3mico Nacional on Sierra San Pedro M=E1rtir from 2017/10 21.16 to 2017/10 21.50 UTC (4.60 to 12.98 hours after the BAT trigger), obtaining a total of 5.30 hours exposure in the r and i bands and 2.20 hours exposure in the Z, Y, J, and H bands.
We detect the NOT optical transient (Malesani, et al., GCN 22029), which continues to fade (see also, Moskvitin, et al., GCN 22031). In comparison with the USNO-B1 and 2MASS catalogs, we obtain the following detections and upper limit (3-sigma):
```
 r = 22.91 +/- 0.12
 i = 22.76 +/- 0.11
 Z > 21.44
 Y = 21.72 +/- 0.35
 J = 21.54 +/- 0.23
 H = 21.69 +/- 0.35
```
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=F3mico Nacional in San Pedro M=E1rtir.
GCN Circular #22038
H. A. Krimm (NSF/USRA), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), K. L. Page (U Leicester) D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 171020A (trigger #780845) (Page et al., GCN Circ. 22028). The BAT ground-calculated position is RA, Dec = 39.260, 15.199 deg which is
```
  RA(J2000)  =  02h 37m 02.3s 
  Dec(J2000) = +15d 11' 57.0" 
```
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 48%.
The mask-weighted light curve shows a weak pulse that starts at ~T0 and ends at ~ T+45 s. T90 (15-350 keV) is 41.9 +- 9.2 sec (estimated error including systematics).
The time-averaged spectrum from T-0.97 to T+46.68 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.04 +- 0.20. The fluence in the 15-150 keV band is 1.2 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+19.92 sec in the 15-150 keV band is 0.7 +- 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/780845/BA/
GCN Circular #22039
D. Malesani (DARK/NBI), J. P. U. Fynbo (NBI), K. E. Heintz (Univ. Iceland and DARK/NBI), M. Stone (Turku Univ.), K. Karhunen (Turku Univ.), report on behalf of a larger collaboration:
Following our imaging sequence (Malesani et al., GCN 22029), we secured spectra of the optical afterglow of GRB 171020A (Page et al., GCN 22028), using the AlFOSC spectrograph at the Nordic Optical Telescope. A total of 4x1200 s exposure was secured using grism #4, covering the wavelength range ~3600-9400 AA. Spectroscopy started on 2017 Oct 21.005 UT (1 hr after the trigger).
A faint trace is detected down to at least ~4000 A. Several weak absorption features are detected, which we interpret as due to Mg II, Fe II, and C IV all at a common redshift z = 1.87.
We thank the NOT staff for support, in particular Amanda Djupvik and Sergio Armas.
GCN Circular #22040
GRB 171020A: Swift/UVOT Upper Limits
S. J. LaPorte (PSU) and K. L. Page (U. Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 171020A 147 s after the BAT trigger (Page et al., GCN Circ. 22028). No optical afterglow consistent with the XRT position (Page et al. GCN Circ. 22028) 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           147          297          147         >20.6
u_FC               306          556          246         >20.2
white              147         7652          811         >21.4
v                  636         6640          338         >19.4
b                  562         7460          529         >20.8
u                  306         7254          756         >20.2
w1                 686         7050          491         >20.7
m2                6645         6845          197         >20.3
w2                1016         6435          216         >20.3
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.19 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #22041
Klotz A., Noysena.K., Atteia J.L. (CNRS-OMP-IRAP), Boer, M., Eymar, L. (CNRS-ARTEMIS), Gendre B. (UVI - Etelman Obs.) report:
We imaged the field of GRB 171020A detected by SWIFT (trigger 780845) with the TAROT robotic telescope (D=25cm) located at the Calern observatory, France.
The observations started 68s after the GRB trigger (13s after the notice). The elevation of the field increased from 58 degrees above horizon and weather conditions were good.
The first image is trailed with a duration of 60.0s (see the description in Klotz et al., 2006, A&A 451, L39). We do not detect any OT with a limiting magnitude of: t0+68s to t0+128s : Rlim = 17.5
The OT (Malesani et al., GCN 22029) is detected in the median of three individual frames: t0+141s to t0+251s : R = 18.7 +/- 0.35
We co-added a series of exposures. The OT is no longer detected: t0+262s to t0+533s : Rlim = 18.9
Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction.
GCN Circular #22042
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), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jes=FAs Gonz=E1lez (UNAM), Carlos Rom=E1n-Z=FA=F1iga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report:
We observed the field of GRB 171020A (Page, et al., GCN 22028) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astron=F3mico Nacional on Sierra San Pedro M=E1rtir from 2017/10 22.13 to 2017/10 22.47 UTC (27.94 to 36.23 hours after the BAT trigger), obtaining a total of 5.27 hours exposure in the r and i bands and 2.21 hours exposure in the Z and Y bands.
We contine to detect the optical transient (Malesani, et al., GCN 22029; also, Moskvitin, et al., GCN 22031; Butler, et al., GCN 22037). In comparison with the USNO-B1 and 2MASS catalogs, we obtain the following detections and upper limits (3-sigma):
```
 r = 23.25 +/- 0.14
 i = 23.01 +/- 0.11
 Z > 21.75
 Y > 22.05
```
These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. Compared to our observations last night, these data suggest either a slow afterglow fade (~t^-0.2) or that our measured flux contains flux from the GRB host galaxy.
We thank the staff of the Observatorio Astron=F3mico Nacional in San Pedro M=E1rtir.

Back to JG's homepage

Jochen Greiner, last update: 22-Oct-2017 [Disclaimer]