Gamma-ray Burst 100117A

(All information courtesy of the instrument teams.)

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 17 Jan 10 21:06:33 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     382941,   Seg_Num: 0
GRB_RA:           11.260d {+00h 45m 02s} (J2000),
                  11.388d {+00h 45m 33s} (current),
                  10.621d {+00h 42m 29s} (1950)
GRB_DEC:          -1.594d {-01d 35' 38"} (J2000),
                  -1.539d {-01d 32' 21"} (current),
                  -1.868d {-01d 52' 03"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       508 [cnts]    Image_Peak=57 [image_cnts]
TRIGGER_DUR:     0.064 [sec] 
TRIGGER_INDEX:   10418     E_range: 25-100 keV
BKG_INTEN:       25472 [cnts]
BKG_TIME:        75970.55 SOD {21:06:10.55} UT
BKG_DUR:         8 [sec]
GRB_DATE:        15213 TJD;    17 DOY;   10/01/17
GRB_TIME:        75979.51 SOD {21:06:19.51} UT
GRB_PHI:         169.90 [deg]
GRB_THETA:        32.69 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     21.02 [sigma]
IMAGE_SIGNIF:    7.19 [sigma]
MERIT_PARAMS:     +1  +0  +0  -4  +2  -3  +0  +0 -30  +0 
SUN_POSTN:       299.73d {+19h 58m 54s}  -20.63d {-20d 37' 46"}
SUN_DIST:         72.31 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      326.72d {+21h 46m 52s}  -10.18d {-10d 10' 36"}
MOON_DIST:        45.21 [deg]
MOON_ILLUM:      6 [%]
GAL_COORDS:      119.23,-64.42 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:        9.72, -5.92 [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 = 254.78,6.22 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 17 Jan 10 21:06:37 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      47
TRIGGER_NUM:     285455181
GRB_RA:            6.100d {+00h 24m 24s} (J2000),
                   6.228d {+00h 24m 55s} (current),
                   5.463d {+00h 21m 51s} (1950)
GRB_DEC:          -6.233d {-06d 13' 59"} (J2000),
                  -6.178d {-06d 10' 39"} (current),
                  -6.510d {-06d 30' 36"} (1950)
GRB_ERROR:       11.92 [deg radius, statistical plus systematic]
GRB_INTEN:       615 [cnts/sec]
DATA_SIGNIF:     9.60 [sigma]
INTEG_TIME:      0.128 [sec]
GRB_DATE:        15213 TJD;    17 DOY;   10/01/17
GRB_TIME:        75979.66 SOD {21:06:19.66} UT
GRB_PHI:         293.00 [deg]
GRB_THETA:        80.00 [deg]
DATA_TIME_SCALE: 0.1280 [sec]
HARD_RATIO:      0.31
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      90%  GRB
2nd_MOST_LIKELY:   6%  Distant Particles
DETECTORS:       0,0,0, 1,1,0, 0,0,1, 0,0,0, 0,0,
SUN_POSTN:       299.73d {+19h 58m 54s}  -20.63d {-20d 37' 46"}
SUN_DIST:         65.86 [deg]   Sun_angle= -4.4 [hr] (East of Sun)
MOON_POSTN:      326.72d {+21h 46m 53s}  -10.18d {-10d 10' 35"}
MOON_DIST:        39.29 [deg]
MOON_ILLUM:      6 [%]
GAL_COORDS:      104.62,-68.14 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:        3.11, -8.14 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 194.42,-24.30 [deg].

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 17 Jan 10 21:06:54 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      58
TRIGGER_NUM:     285455181
GRB_RA:            7.760d {+00h 31m 02s} (J2000),
                   7.889d {+00h 31m 33s} (current),
                   7.118d {+00h 28m 28s} (1950)
GRB_DEC:          +2.650d {+02d 38' 60"} (J2000),
                  +2.705d {+02d 42' 19"} (current),
                  +2.374d {+02d 22' 26"} (1950)
GRB_ERROR:       7.80 [deg radius, statistical only]
DATA_SIGNIF:     10.10 [sigma]
DATA_INTERVAL:   0.128 [sec]
GRB_DATE:        15213 TJD;    17 DOY;   10/01/17
GRB_TIME:        75979.66 SOD {21:06:19.66} UT
GRB_PHI:         294.00 [deg]
GRB_THETA:        89.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   413 (Gnd S/W Version number)
SUN_POSTN:       299.73d {+19h 58m 54s}  -20.63d {-20d 37' 46"}
SUN_DIST:         70.66 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      326.72d {+21h 46m 53s}  -10.18d {-10d 10' 32"}
MOON_DIST:        42.96 [deg]
MOON_ILLUM:      6 [%]
GAL_COORDS:      112.76,-59.82 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:        8.17, -0.64 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.
COMMENTS:        This Notice was ground-generated -- not flight-generated.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 17 Jan 10 21:08:13 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     382941,   Seg_Num: 0
GRB_RA:           11.2700d {+00h 45m 04.79s} (J2000),
                  11.3984d {+00h 45m 35.62s} (current),
                  10.6311d {+00h 42m 31.45s} (1950)
GRB_DEC:          -1.5945d {-01d 35' 40.2"} (J2000),
                  -1.5397d {-01d 32' 22.7"} (current),
                  -1.8678d {-01d 52' 04.2"} (1950)
GRB_ERROR:       5.4 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.24e-09 [erg/cm2/sec]
GRB_SIGNIF:      7.14 [sigma]
IMG_START_DATE:  15213 TJD;    17 DOY;   10/01/17
IMG_START_TIME:  76059.60 SOD {21:07:39.60} UT,   80.1 [sec] since BAT Trigger Time
TAM[0-3]:        327.63 237.23 261.43 243.37
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       299.73d {+19h 58m 55s}  -20.63d {-20d 37' 45"}
SUN_DIST:         72.32 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      326.73d {+21h 46m 56s}  -10.17d {-10d 10' 16"}
MOON_DIST:        45.21 [deg]
MOON_ILLUM:      6 [%]
GAL_COORDS:      119.25,-64.42 [deg] galactic lon,lat of the burst
ECL_COORDS:        9.73, -5.93 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 0.61 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 17 Jan 10 21:08:23 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     382941,   Seg_Num: 0
GRB_RA:           11.2700d {+00h 45m 04.7s} (J2000),
                  11.3984d {+00h 45m 35.6s} (current),
                  10.6311d {+00h 42m 31.4s} (1950)
GRB_DEC:          -1.5945d {-01d 35' 40.2"} (J2000),
                  -1.5397d {-01d 32' 22.7"} (current),
                  -1.8678d {-01d 52' 04.2"} (1950)
GRB_ERROR:       5.4 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       51 [cnts]
IMG_START_DATE:  15213 TJD;    17 DOY;   10/01/17
IMG_START_TIME:  76059.60 SOD {21:07:39.60} UT,   80.1 [sec] since BAT Trigger Time
CENTROID_X:      302.00,  raw= 302  [pixels]
CENTROID_Y:      329.37,  raw= 329  [pixels]
ROLL:            248.84 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   73.96
GRB_POS_XRT_Z:   -0.69
IMAGE_URL:       sw00382941000msxps_rw.img
SUN_POSTN:       299.73d {+19h 58m 55s}  -20.63d {-20d 37' 45"}
SUN_DIST:         72.32 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      326.73d {+21h 46m 56s}  -10.17d {-10d 10' 14"}
MOON_DIST:        45.21 [deg]
MOON_ILLUM:      6 [%]
GAL_COORDS:      119.25,-64.42 [deg] galactic lon,lat of the burst
ECL_COORDS:        9.73, -5.93 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 17 Jan 10 21:08:33 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     382941,   Seg_Num: 0
GRB_RA:           11.2700d {+00h 45m 04.7s} (J2000),
                  11.3984d {+00h 45m 35.6s} (current),
                  10.6311d {+00h 42m 31.4s} (1950)
GRB_DEC:          -1.5945d {-01d 35' 40.2"} (J2000),
                  -1.5397d {-01d 32' 22.7"} (current),
                  -1.8678d {-01d 52' 04.2"} (1950)
GRB_ERROR:       5.4 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       51 [cnts]
IMG_START_DATE:  15213 TJD;    17 DOY;   10/01/17
IMG_START_TIME:  76059.60 SOD {21:07:39.60} UT,   80.1 [sec] since BAT Trigger Time
CENTROID_X:      302.00,  raw= 302  [pixels]
CENTROID_Y:      329.37,  raw= 329  [pixels]
ROLL:            248.84 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   73.96
GRB_POS_XRT_Z:   -0.69
IMAGE_URL:       sw00382941000msxps_rw.img
SUN_POSTN:       299.73d {+19h 58m 55s}  -20.63d {-20d 37' 45"}
SUN_DIST:         72.32 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      326.73d {+21h 46m 56s}  -10.17d {-10d 10' 12"}
MOON_DIST:        45.21 [deg]
MOON_ILLUM:      6 [%]
GAL_COORDS:      119.25,-64.42 [deg] galactic lon,lat of the burst
ECL_COORDS:        9.73, -5.93 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 17 Jan 10 21:10:21 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     382941,   Seg_Num: 0
GRB_RA:           11.260d {+00h 45m 02s} (J2000),
                  11.388d {+00h 45m 33s} (current),
                  10.621d {+00h 42m 29s} (1950)
GRB_DEC:          -1.594d {-01d 35' 38"} (J2000),
                  -1.539d {-01d 32' 21"} (current),
                  -1.868d {-01d 52' 03"} (1950)
GRB_DATE:        15213 TJD;    17 DOY;   10/01/17
GRB_TIME:        75979.57 SOD {21:06:19.57} UT
TRIGGER_INDEX:   10418
GRB_PHI:         169.90 [deg]
GRB_THETA:        32.69 [deg]
DELTA_TIME:      57.00 [sec]
TRIGGER_DUR:     0.064 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     21.02 [sigma]
IMAGE_SIGNIF:    7.19 [sigma]
LC_URL:          sw00382941000msb.lc
SUN_POSTN:       299.73d {+19h 58m 55s}  -20.63d {-20d 37' 44"}
SUN_DIST:         72.31 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      326.75d {+21h 46m 59s}  -10.16d {-10d 09' 51"}
MOON_DIST:        45.18 [deg]
MOON_ILLUM:      6 [%]
GAL_COORDS:      119.23,-64.42 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:        9.72, -5.92 [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 = 254.78,6.22 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 17 Jan 10 21:11:40 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     382941,   Seg_Num: 0
POINT_RA:         11.263d {+00h 45m 03s} (J2000)
POINT_DEC:        -1.575d {-01d 34' 30"} (J2000)
POINT_ROLL:      248.841d
IMG_START_DATE:  15213 TJD;    17 DOY;   10/01/17
IMG_START_TIME:  76067.76 SOD {21:07:47.76} UT,   88.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.018
N_STARS:         38
X_OFFSET:        464 [pixels]
Y_OFFSET:        416 [pixels]
X_MAX:           1423 [pixels]
Y_MAX:           1375 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw00382941000msufc0088.fits
SUN_POSTN:       299.73d {+19h 58m 55s}  -20.63d {-20d 37' 43"}
SUN_DIST:         72.32 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      326.76d {+21h 47m 02s}  -10.16d {-10d 09' 35"}
MOON_DIST:        45.18 [deg]
MOON_ILLUM:      6 [%]
GAL_COORDS:      119.24,-64.40 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        9.73, -5.91 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 17 Jan 10 21:12:09 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     382941,   Seg_Num: 0
POINT_RA:         11.263d {+00h 45m 03s} (J2000)
POINT_DEC:        -1.575d {-01d 34' 30"} (J2000)
POINT_ROLL:      248.841d
IMG_START_DATE:  15213 TJD;    17 DOY;   10/01/17
IMG_START_TIME:  76067.76 SOD {21:07:47.76} UT,   88.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.018
N_STARS:         38
X_OFFSET:        464 [pixels]
Y_OFFSET:        416 [pixels]
X_MAX:           1423 [pixels]
Y_MAX:           1375 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw00382941000msufc0088.fits
SUN_POSTN:       299.73d {+19h 58m 55s}  -20.63d {-20d 37' 43"}
SUN_DIST:         72.32 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      326.76d {+21h 47m 03s}  -10.16d {-10d 09' 29"}
MOON_DIST:        45.18 [deg]
MOON_ILLUM:      6 [%]
GAL_COORDS:      119.24,-64.40 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        9.73, -5.91 [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:     Sun 17 Jan 10 21:11:40 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     382941,   Seg_Num: 0
POINT_RA:         11.263d {+00h 45m 03s} (J2000)
POINT_DEC:        -1.575d {-01d 34' 30"} (J2000)
POINT_ROLL:      248.841d
IMG_START_DATE:  15213 TJD;    17 DOY;   10/01/17
IMG_START_TIME:  76067.76 SOD {21:07:47.76} UT,   88.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.018
N_STARS:         38
X_OFFSET:        464 [pixels]
Y_OFFSET:        416 [pixels]
X_MAX:           1423 [pixels]
Y_MAX:           1375 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw00382941000msufc0088.fits
SUN_POSTN:       299.73d {+19h 58m 55s}  -20.63d {-20d 37' 43"}
SUN_DIST:         72.32 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      326.76d {+21h 47m 02s}  -10.16d {-10d 09' 35"}
MOON_DIST:        45.18 [deg]
MOON_ILLUM:      6 [%]
GAL_COORDS:      119.24,-64.40 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        9.73, -5.91 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 17 Jan 10 21:13:43 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     382941,   Seg_Num: 0
POINT_RA:         11.263d {+00h 45m 03s} (J2000)
POINT_DEC:        -1.575d {-01d 34' 30"} (J2000)
ROLL:            248.841d
IMG_START_DATE:  15213 TJD;    17 DOY;   10/01/17
IMG_START_TIME:  76067.76 SOD {21:07:47.76} UT,   88.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     285455273
X_OFFSET:        716 [pixels]
Y_OFFSET:        738 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       876
Y_GRB_POS:       898
BINNING_INDEX:   1
IM_URL:          sw00382941000msuni0094.fits
SUN_POSTN:       299.73d {+19h 58m 56s}  -20.63d {-20d 37' 42"}
SUN_DIST:         72.32 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      326.77d {+21h 47m 06s}  -10.15d {-10d 09' 10"}
MOON_DIST:        45.16 [deg]
MOON_ILLUM:      6 [%]
GAL_COORDS:      119.24,-64.40 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        9.73, -5.91 [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:     Sun 17 Jan 10 21:14:01 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     382941,   Seg_Num: 0
POINT_RA:         11.263d {+00h 45m 03s} (J2000)
POINT_DEC:        -1.575d {-01d 34' 30"} (J2000)
ROLL:            248.841d
IMG_START_DATE:  15213 TJD;    17 DOY;   10/01/17
IMG_START_TIME:  76067.76 SOD {21:07:47.76} UT,   88.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     285455273
X_OFFSET:        716 [pixels]
Y_OFFSET:        738 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       876
Y_GRB_POS:       898
BINNING_INDEX:   1
IM_URL:          sw00382941000msuni0094.fits
SUN_POSTN:       299.73d {+19h 58m 56s}  -20.63d {-20d 37' 42"}
SUN_DIST:         72.32 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      326.78d {+21h 47m 06s}  -10.15d {-10d 09' 07"}
MOON_DIST:        45.16 [deg]
MOON_ILLUM:      6 [%]
GAL_COORDS:      119.24,-64.40 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        9.73, -5.91 [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:        All 4 attachments are included.

GCN Circular #10336
M. De Pasquale (UCL-MSSL), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), S. Campana (INAF-OAB), P.A. Curran (MSSL-UCL), N. Gehrels (NASA/GSFC), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), V. Mangano (INAF-IASFPA), R. Margutti (Univ Bicocca&OAB), C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC), C. Pagani (PSU), D. M. Palmer (LANL), P. Romano (INAF-IASFPA), T. Sakamoto (NASA/UMBC), B. Sbarufatti (INAF-OAB/IASFPA), M. H. Siegel (PSU), M. Stamatikos (OSU/NASA/GSFC) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:
At 21:06:19 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 100117A (trigger=382941). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 11.260, -1.594 which is
```
   RA(J2000)  =  00h 45m 02s
   Dec(J2000) = -01d 35' 38"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single spike structure with a duration of about 0.4 sec. The peak count rate was ~4500 counts/sec (15-350 keV), at T_zero.
The XRT began observing the field at 21:07:39.6 UT, 80.1 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 11.26946, -1.59620 which is equivalent to:
```
   RA(J2000)  = 00h 45m 4.67s
   Dec(J2000) = -01d 35' 46.3"
```
with an uncertainty of 4.6 arcseconds (radius, 90% containment). This location is 34 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 (2.66e+20 cm^-2, Kalberla et al. 2005), with an excess column of 4 (+3.65/-2.58) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 1.24e-09 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 88 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 0.02.
Burst Advocate for this burst is M. De Pasquale (mdp AT mssl.ucl.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:     Sun 17 Jan 10 21:19:38 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     382941,   Seg_Num: 0
POINT_RA:         11.262d {+00h 45m 03s} (J2000)
POINT_DEC:        -1.574d {-01d 34' 26"} (J2000)
POINT_ROLL:      248.840d
IMG_START_DATE:  15213 TJD;    17 DOY;   10/01/17
IMG_START_TIME:  76280.76 SOD {21:11:20.76} UT,   301.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        1.371
N_STARS:         39
X_OFFSET:        396 [pixels]
Y_OFFSET:        418 [pixels]
X_MAX:           1355 [pixels]
Y_MAX:           1377 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00382941000msufc0301.fits
SUN_POSTN:       299.74d {+19h 58m 57s}  -20.63d {-20d 37' 39"}
SUN_DIST:         72.31 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      326.82d {+21h 47m 16s}  -10.13d {-10d 08' 00"}
MOON_DIST:        45.12 [deg]
MOON_ILLUM:      6 [%]
GAL_COORDS:      119.23,-64.40 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        9.73, -5.90 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 17 Jan 10 21:19:59 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     382941,   Seg_Num: 0
POINT_RA:         11.262d {+00h 45m 03s} (J2000)
POINT_DEC:        -1.574d {-01d 34' 26"} (J2000)
POINT_ROLL:      248.840d
IMG_START_DATE:  15213 TJD;    17 DOY;   10/01/17
IMG_START_TIME:  76280.76 SOD {21:11:20.76} UT,   301.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        1.371
N_STARS:         39
X_OFFSET:        396 [pixels]
Y_OFFSET:        418 [pixels]
X_MAX:           1355 [pixels]
Y_MAX:           1377 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00382941000msufc0301.fits
SUN_POSTN:       299.74d {+19h 58m 57s}  -20.63d {-20d 37' 39"}
SUN_DIST:         72.31 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      326.82d {+21h 47m 17s}  -10.13d {-10d 07' 56"}
MOON_DIST:        45.11 [deg]
MOON_ILLUM:      6 [%]
GAL_COORDS:      119.23,-64.40 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        9.73, -5.90 [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:     Sun 17 Jan 10 21:19:38 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     382941,   Seg_Num: 0
POINT_RA:         11.262d {+00h 45m 03s} (J2000)
POINT_DEC:        -1.574d {-01d 34' 26"} (J2000)
POINT_ROLL:      248.840d
IMG_START_DATE:  15213 TJD;    17 DOY;   10/01/17
IMG_START_TIME:  76280.76 SOD {21:11:20.76} UT,   301.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        1.371
N_STARS:         39
X_OFFSET:        396 [pixels]
Y_OFFSET:        418 [pixels]
X_MAX:           1355 [pixels]
Y_MAX:           1377 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00382941000msufc0301.fits
SUN_POSTN:       299.74d {+19h 58m 57s}  -20.63d {-20d 37' 39"}
SUN_DIST:         72.31 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      326.82d {+21h 47m 16s}  -10.13d {-10d 08' 00"}
MOON_DIST:        45.12 [deg]
MOON_ILLUM:      6 [%]
GAL_COORDS:      119.23,-64.40 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        9.73, -5.90 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 17 Jan 10 21:20:55 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     382941,   Seg_Num: 0
POINT_RA:         11.262d {+00h 45m 03s} (J2000)
POINT_DEC:        -1.574d {-01d 34' 26"} (J2000)
ROLL:            248.840d
IMG_START_DATE:  15213 TJD;    17 DOY;   10/01/17
IMG_START_TIME:  76280.76 SOD {21:11:20.76} UT,   301.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     285455486
X_OFFSET:        716 [pixels]
Y_OFFSET:        738 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       876
Y_GRB_POS:       898
BINNING_INDEX:   1
IM_URL:          sw00382941000msuni0307.fits
SUN_POSTN:       299.74d {+19h 58m 57s}  -20.63d {-20d 37' 39"}
SUN_DIST:         72.31 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      326.83d {+21h 47m 19s}  -10.13d {-10d 07' 44"}
MOON_DIST:        45.11 [deg]
MOON_ILLUM:      6 [%]
GAL_COORDS:      119.23,-64.40 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        9.73, -5.90 [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:     Sun 17 Jan 10 21:21:11 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     382941,   Seg_Num: 0
POINT_RA:         11.262d {+00h 45m 03s} (J2000)
POINT_DEC:        -1.574d {-01d 34' 26"} (J2000)
ROLL:            248.840d
IMG_START_DATE:  15213 TJD;    17 DOY;   10/01/17
IMG_START_TIME:  76280.76 SOD {21:11:20.76} UT,   301.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     285455486
X_OFFSET:        716 [pixels]
Y_OFFSET:        738 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       876
Y_GRB_POS:       898
BINNING_INDEX:   1
IM_URL:          sw00382941000msuni0307.fits
SUN_POSTN:       299.74d {+19h 58m 57s}  -20.63d {-20d 37' 39"}
SUN_DIST:         72.31 [deg]   Sun_angle= -4.8 [hr] (East of Sun)
MOON_POSTN:      326.83d {+21h 47m 19s}  -10.13d {-10d 07' 41"}
MOON_DIST:        45.10 [deg]
MOON_ILLUM:      6 [%]
GAL_COORDS:      119.23,-64.40 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        9.73, -5.90 [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 Circular #10337
D. Xu (WIS, DARK/NBI), D. Malesani, G. Leloudas, J.P.U. Fynbo (DARK/NBI), A.A. Djupvik, R. Karjalainen (NOT), N.R. Tanvir (U. Leicester), P. Jakobsson (Univ. of Iceland) report on behalf of a larger collaboration:
We observed the field of GRB100117A (De Pasquale et al., GCN 10336) with the Nordic Optical Telescope equipped with StanCam and NOTCam, starting at 21:26:40 UT on Jan 17th, 20.35 mins after the burst trigger. The observations were carried out at high airmass (~2) and in poor seeing.
In a 900 s R-band image, starting at 21:48:42 UT, we notice the presence of a faint, marginally significant object at coordinates:
```
RA(J2000)=00h 45m 04.75s
Dec(J2000)=-01d 35' 47.4"
```
with an error circle of 0.5 arcsec. If real, its magnitude is R = 22.5+/-0.5.
The co-addition of a series of K-band images doesn't show any convincing counterpart on the position.
GCN Circular #10338
C. B. Markwardt (GSFC/UMD), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), M. De Pasquale (UCL-MSSL), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+484 sec from the recent telemetry downlink, we report further analysis of BAT GRB 100117A (trigger #382941) (De Pasquale, et al., GCN Circ. 10336). The BAT ground-calculated position is RA, Dec = 11.280, -1.586 deg which is
```
   RA(J2000)  =  00h 45m 07.1s 
   Dec(J2000) = -01d 35' 11.1" 
```
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 66%.
The mask-weighted light curve shows a single peak starting at T+0.0 and ending at T+0.4 sec. T90 (15-350 keV) is 0.3 +- 0.05 sec (estimated error including systematics).
The time-averaged spectrum from T-0.0 to T+0.3 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 0.88 +- 0.22. The fluence in the 15-150 keV band is 9.3 +- 1.3 x 10^-8 erg/cm2. The 1-sec peak photon flux measured from T-0.35 sec in the 15-150 keV band is 2.9 +- 0.4 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/382941/BA/
GCN Circular #10339
S. B. Cenko, D. A. Perley, J. S. Bloom, B. E. Cobb, and A. N. Morgan (UC Berkeley) report on behalf of a larger collaboration:
We have obtained pre-explosion images of the field of GRB100117A from the Canada-France-Hawaii MegaCam archive. Images were obtained in the g', r', and z' filters on 26 December 2005, and in the i' filter on 12 November 2007. Exposure times ranged from 240 s in g'-band to 500 s in i'-band.
Inside the candidate XRT afterglow localization (de Pasquale; GCN 10336), we find four sources, with the following positions and R- and I-band magnitudes (calibrated relative to several USNO-B1 sources in the field; expected systematic uncertainty ~ 0.3 mag):
```
Source 	RA		Dec (J2000.0)		R	I
----------------------------------------------------------------------
S1	00:45:04.82 	-01:35:47.7 		23.1	21.0
S2	00:45:04.78 	-01:35:45.5 		23.6	22.9
S3	00:45:04.70 	-01:35:42.0 		24.5	22.9
S4	00:45:04.53 	-01:35:49.2 		> 24.7	23.6
```
We have also obtained a single epoch of acquisition imaging in i'-band of the field with GMOS on Gemini South beginning at 00:46 on 18 January 2010 (~ 4.7 hours after the burst). We detect only S1 in this image, at a magnitude consistent with the value derived from the CFHT image.
Furthermore, given the uncertainty in our astrometry (~ 0.5" in each coordinate), we believe it likely this is the same source identified by Xu et al. (GCN 10337) at R = 22.5 +/- 0.5. We therefore have no evidence that this source has varied.
Further observations are planned.
We wish to thank the Gemini Observatory staff, in particular Peter Pessev, for assistance with these observations.
GCN Circular #10340
R. Chornock, E. Berger (Harvard), R. Williams, and D. Kelson (OCIW) report:
"We observed the location of the short GRB 100117A (GCN 10336) with IMACS on the Magellan/Baade 6.5-m telescope starting on 2010 Jan 18.042 UT (3.9 hours after the burst). In a 1200 sec stacked R-band image with a seeing of about 1" we detect the same four objects within the XRT error circle (GCN 10336) found in archival CFHT images by Cenko et al. and listed in GCN 10339. All four objects appear to be extended in our image, indicating that one of them may represent the GRB host galaxy. No new sources appear to be present within the XRT error circle, with a 3-sigma limiting magnitude of approximately R=24.7."
GCN Circular #10341
A. Cucchiara, D. B. Fox (PSU), E. Berger, R. Chornok (Harvard), A. Fruchter, J. Graham (STScI) report on a larger collaboration:
"We observed the location of the short GRB 100117A (GCN 10336) with GMOS on the Gemini-North 8-m telescope starting on 2010 Jan 18.208 UT (7.9 hours after the burst). In a 2700 sec stacked r-band image with a seeing of about 1" we detect the same four objects within the XRT error circle (GCN 10336) found in archival CFHT images by Cenko et al. and listed in GCN 10339 (see also GCN 10340). As in the Magellan/IMACS image (GCN 10340) all four objects appear to be extended in the Gemini-North/GMOS data, indicating that one of them may represent the GRB host galaxy. No new sources appear to be present within the XRT error circle, with a 3-sigma limiting magnitude of approximately r=26.5."
GCN Circular #10342
B. Sbarufatti, R. Margutti (INAF/OAB) and M. De Pasquale (UCL-MSSL) report on behalf of the Swift-XRT team:
We have analysed 5.5 ks of XRT data for GRB 100117A (De Pasquale et al. GCN Circ. 10336), from 69 s to 18.9 ks after the BAT trigger. The data comprise 180 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode.
The best position is the SPER UVOT enhanced position: RA,Dec = 11.2690, -1.5949 (degrees) which is equivalent to:
```
RA (J2000) = 00 45 4.56
Dec (J2000) = -01 35 41.7
```
with an uncertainty of 2.4 arcsec (radius, 90% containment). This location is 50.8 arcseconds from the BAT ground position, inside the BAT error circle.
After the initial flaring activity the light curve can be modeled with a power-law decay with a decay index of alpha=3.5 (+/-0.2). The afterglow is not detected after the first snapshot of data (ending 500 s after the trigger), with an upper limit of 5E-3 count/sec at ~12 ks after the trigger
The spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.6 (+/-0.13). The best-fitting absorption column is 1.2 (+/-0.4) x 10^21 cm^-2, in excess of the Galactic value of 2.7 x 10^20 cm^-2 (Kalberla et al. 2005). The observed (unabsorbed) 0.3-10 keV flux is 4.14 (4.84) x 10^-10 erg cm^-2 s^-1.
The spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.3 (-0.5+0.6). The best-fitting absorption column is 1.1 (+1.3-0.9) x 10^21 cm^-2, slightly in excess of the Galactic value of 2.7 x 10^20 cm^-2 (Kalberla et al. 2005). The observed (unabsorbed) 0.3-10 keV flux is 2.40 (3.54) x 10^-12 erg cm^-2 s^-1.
The count-rate to flux conversion factor is 6.0E-11 erg cm^-2 count^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00382941 .
This circular is an official product of the Swift-XRT team.
GCN Circular #10343
D. Alexander Kann (TLS Tautenburg), D. Malesani (DARK/NBI), D. Xu (WIS, DARK/NBI) report on behalf of a larger collaboration:
Using the improved XRT position (B. Sbarufatti et al. GCN 10342) for the Swift short/hard GRB 100117A (M. de Pasquale et al., GCN 10336), we find that the afterglow candidate reported from NOT observations (D. Xu et al., GCN 10337), which is probably identical to source "S1" from S. B. Cenko et al. (GCN 10339), lies outside the error circle. We therefore consider it unlikely that this object is related to the GRB, also considering the lack of pronounced variability (S. B. Cenko et al. GCN 10339).
Of the four sources reported by S. B. Cenko et al. (GCN 10339) and confirmed by R. Chornock et al. (GCN 10340) and A. Cucchiara et al. (GCN 10341), only source "S3" still lies within the new XRT error circle. Source S3, which is extended according to the above reports, may be the host galaxy of GRB 100117A, although lack of variability does not allow a conclusive statement.
An additional image epoch to perform image subtraction is encouraged.
This message may be cited.
GCN Circular #10344
M. De Pasquale (MSSL/UCL), S. T. Holland (NASA/GSFC), S. Oates (MSSL) report, on the behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 100117A 89s after the BAT trigger (De Pasquale et al., GCN 10336). We do not detect any source in the UVOT-enhanced XRT error circle (Sbarufatti et al. GCN 10342) in the initial finding chart in the white filter, nor in the other filters. We do not detect the the S3 source of Cenko et al. (GCN 10339). UVOT magnitude 3-sigma upper limits are reported in the following table:
```
Filter   T_start   T_stop   Exp(s)  Mag (3-sigma upper limit)
-------------------------------------------------------------
WHITE        89      238     147          > 20.4
WHITE        89    11957    1228          > 21.4
v          5589    17747    1082          > 19.8
b           557     6607     216          > 19.9
u           302     6402     442          > 19.9
uvw1       5999    18941     474          > 20.1
uvm2       5793    18652    1082          > 20.8
uvw2       5384    12757     978          > 20.9
```
No UVOT source has been found at the position of the NOT source (Xu et al., GCN 10337) outside the XRT error circle.
The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight of E_(B-V) = 0.02 mag (Schlegel et al. 1998). All photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383, 627).
GCN Circular #10345
W. Paciesas (UAH) reports on behalf of the Fermi GBM Team:
"At 21:06:19.66 UT on 17 January 2010, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 100117A (trigger 285455181 / 100117879) which was also detected by the Swift-BAT (De Pasquale et al. 2010, GCN 10336). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 86 degrees.
The GBM light curve consists of one pulse with a duration (T90) of about 0.4 s. The time-averaged spectrum from T0-0.128 s to T0+0.256 s is adequately fit by a power law function with an exponential high energy cutoff. The power law index is -0.14 (+0.33 / -0.27) and the cutoff energy, parameterized as Epeak, is 287 (+74 / -50) keV (CSTAT 548 for 484 d.o.f.).
The event fluence (8-1000 keV) in this time interval is (4.1 +/- 0.5 )E-07 erg/cm^2. The 0.256-sec peak photon flux measured starting from T0-0.128 s in the 8-1000 keV band is 6.1 +/- 0.4 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN Circular #10346
E. Berger, R. Chornock (Harvard), A. Cucchiara, D. B. Fox (PSU) report:
"Starting on 2010 Jan 19.22 UT we used the GMOS spectrograph on the Gemini North 8-m telescope to obtain spectroscopic observations of several extended objects (GCNs 10339, 10340, 10341) located inside and near the revised XRT error circle (GCN 10342) of the short GRB 100117A (GCN 10336). The slit was aligned so that it covered sources S1, S2, and S3 (GCN 10339). Preliminary inspection of the combined 3000 sec spectrum covering the wavelength range 4000-8000 A reveals that source S1 is an M dwarf star. We detect continuum emission from sources S2 and S3 redward of about 5000 and 5600 A, respectively, but no clear emission or absorption features are identified."
GCN Circular #10349
A.J. Levan (Warwick), J. Graham, A. Fruchter (STScI), N. Tanvir (Leicester) A. Cucchiara, D. Fox (PSU), E. Berger, R. Chornock (Harvard) report for a larger collaboration:
"We obtained a second epoch of Gemini North imaging of the short duration GRB 100117A (De Pasquale et al. GCN 10336) beginning at 06:17 UT. A total of 2700s of observations were acquired in the r-band.
Comparison with our first epoch of observations (Cucchiara et al. GCN 10341) reveals that source S3 identifed by Cenko et al. (GCN 10339) has faded by 0.23 +/- 0.06 magnitudes in the timeframe between the two epochs of observation (approximately 25 hours). This is confirmed by image subtraction, which shows an offset from the centre of S3 by ~0.6".
We suggest this is the afterglow of GRB 100117A. "
GCN Report 269.1
GCN_Report 269.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_269_1.pdf by M. De Pasquale at UCL/MSSL titled: "Final Swift Observations of GRB 100117A"
Redshift of 0.92 is cited in http://arxiv.org/abs//1007.0003 as "Fong et al. 2010 (in prep.)"
1012.4009 from 21 Dec 10; ApJ 730 (2011) 26
Wen-fai Fong et al.: The Optical Afterglow and z=0.92 Early-type Host Galaxy of the Short GRB 100117A
We present the discovery of the optical afterglow and early-type host galaxy of the short-duration GRB 100117A. The faint afterglow is detected 8.3 hr after the burst with r_AB = 25.46 +/- 0.20 mag. Follow-up optical and near-IR observations uncover a coincident compact red galaxy, identified as an early-type galaxy at a photometric redshift of z~0.6-0.9 (2-sigma) with a mass of 3x10^10 M_Sun, an age of ~1 Gyr, and a luminosity of L_B~0.5L_star. Spectroscopic observations of the host reveal a notable break corresponding to the Balmer 4000-Angstrom break at z~0.9, and stellar population spectral evolution template fits indicate z~0.915, which we adopt as the redshift of the host, with stellar population ages of ~1-3 Gyr. From a possible weak detection of [OII]-3727 emission at z=0.915 we infer an upper bound on the star formation rate of ~0.1 M_Sun per yr, leading to a specific star formation rate of <0.004 per Gyr. Thus, GRB 100117A is only the second short burst to date with a secure early-type host (the other being GRB 050724 at z=0.257) and it has one of the highest short GRB redshifts. The offset between the host center and the burst position, 470 +/- 310 pc, is the smallest to date. Combined with the old stellar population age, this indicates that the burst likely originated from a progenitor with no significant kick velocity. However, from the brightness of the optical afterglow we infer a relatively low density of n~3x10^-4 cm^-3 when epsilon_e and epsilon_B = 0.1. The combination of an optically faint afterglow and host suggest that previous such events may have been missed, thereby potentially biasing the known short GRB host population against z>1 early-type hosts.

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Jochen Greiner, last update: 20-Apr-2024 [Disclaimer]