Gamma-ray Burst 151228B

(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:     Mon 28 Dec 15 22:47:30 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     668641,   Seg_Num: 0
GRB_RA:          344.441d {+22h 57m 46s} (J2000),
                 344.642d {+22h 58m 34s} (current),
                 343.811d {+22h 55m 15s} (1950)
GRB_DEC:          +8.076d {+08d 04' 34"} (J2000),
                  +8.162d {+08d 09' 43"} (current),
                  +7.808d {+07d 48' 30"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4049 [cnts]    Image_Peak=328 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   146     E_range: 25-100 keV
BKG_INTEN:       20478 [cnts]
BKG_TIME:        82016.38 SOD {22:46:56.38} UT
BKG_DUR:         8 [sec]
GRB_DATE:        17384 TJD;   362 DOY;   15/12/28
GRB_TIME:        82034.94 SOD {22:47:14.94} UT
GRB_PHI:         -86.67 [deg]
GRB_THETA:         1.58 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     26.24 [sigma]
IMAGE_SIGNIF:    11.83 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  +1  +0  +0 -30  +0 
SUN_POSTN:       277.49d {+18h 29m 57s}  -23.26d {-23d 15' 28"}
SUN_DIST:         72.72 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      141.00d {+09h 24m 00s}  +12.24d {+12d 14' 26"}
MOON_DIST:       148.88 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       80.87,-45.31 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      348.86, 13.56 [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 = 258.44,17.26 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(2.0<100sec) coincident with the FERMI_GBM event (trignum=473035636).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Mon 28 Dec 15 22:47:51 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      56
TRIGGER_NUM:     473035636
GRB_RA:          346.910d {+23h 07m 38s} (J2000),
                 347.111d {+23h 08m 27s} (current),
                 346.283d {+23h 05m 08s} (1950)
GRB_DEC:         +12.180d {+12d 10' 48"} (J2000),
                 +12.267d {+12d 16' 00"} (current),
                 +11.909d {+11d 54' 33"} (1950)
GRB_ERROR:       7.09 [deg radius, statistical only]
DATA_SIGNIF:     11.30 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        17384 TJD;   362 DOY;   15/12/28
GRB_TIME:        82032.59 SOD {22:47:12.59} UT
GRB_PHI:         316.00 [deg]
GRB_THETA:       112.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4153 (Gnd S/W Version number)
SUN_POSTN:       277.49d {+18h 29m 57s}  -23.26d {-23d 15' 28"}
SUN_DIST:         76.78 [deg]   Sun_angle= -4.6 [hr] (East of Sun)
MOON_POSTN:      141.00d {+09h 24m 01s}  +12.24d {+12d 14' 23"}
MOON_DIST:       144.34 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       86.92,-43.32 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      352.86, 16.36 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2015/bn151228949/quicklook/glg_lc_medres34_bn151228949.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_473035636.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~4 min after the notice.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(2.0<100sec) coincident with the SWIFT_BAT event (trignum=668641).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Mon 28 Dec 15 22:47:40 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      44
TRIGGER_NUM:     473035636
GRB_RA:          346.917d {+23h 07m 40s} (J2000),
                 347.122d {+23h 08m 29s} (current),
                 346.274d {+23h 05m 06s} (1950)
GRB_DEC:          -1.717d {-01d 43' 00"} (J2000),
                  -1.630d {-01d 37' 47"} (current),
                  -1.988d {-01d 59' 14"} (1950)
GRB_ERROR:       33.45 [deg radius, statistical plus systematic]
GRB_INTEN:       74 [cnts/sec]
DATA_SIGNIF:     4.70 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        17384 TJD;   362 DOY;   15/12/28
GRB_TIME:        82032.59 SOD {22:47:12.59} UT
GRB_PHI:         309.00 [deg]
GRB_THETA:       100.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      -3.19
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      92%  GRB
2nd_MOST_LIKELY:   5%  Cyg X-1
DETECTORS:       0,0,0, 1,1,0, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:       277.49d {+18h 29m 57s}  -23.26d {-23d 15' 28"}
SUN_DIST:         70.68 [deg]   Sun_angle= -4.6 [hr] (East of Sun)
MOON_POSTN:      141.00d {+09h 24m 00s}  +12.24d {+12d 14' 24"}
MOON_DIST:       152.02 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       74.16,-54.45 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      347.29,  3.58 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2015/bn151228949/quicklook/glg_lc_medres34_bn151228949.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 186.90,-15.05 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(2.0<100sec) coincident with the SWIFT_BAT event (trignum=668641).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Mon 28 Dec 15 22:47:48 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      57
TRIGGER_NUM:     473035636
GRB_RA:          348.483d {+23h 13m 56s} (J2000),
                 348.684d {+23h 14m 44s} (current),
                 347.858d {+23h 11m 26s} (1950)
GRB_DEC:         +14.750d {+14d 45' 00"} (J2000),
                 +14.837d {+14d 50' 14"} (current),
                 +14.478d {+14d 28' 39"} (1950)
GRB_ERROR:       16.33 [deg radius, statistical plus systematic]
GRB_INTEN:       107 [cnts/sec]
DATA_SIGNIF:     6.90 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        17384 TJD;   362 DOY;   15/12/28
GRB_TIME:        82032.59 SOD {22:47:12.59} UT
GRB_PHI:         316.00 [deg]
GRB_THETA:       115.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      -1.58
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      91%  GRB
2nd_MOST_LIKELY:   6%  Cyg X-1
DETECTORS:       0,0,0, 1,1,0, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:       277.49d {+18h 29m 57s}  -23.26d {-23d 15' 28"}
SUN_DIST:         79.33 [deg]   Sun_angle= -4.7 [hr] (East of Sun)
MOON_POSTN:      141.00d {+09h 24m 01s}  +12.24d {+12d 14' 23"}
MOON_DIST:       141.47 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       90.50,-41.90 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      355.42, 18.08 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2015/bn151228949/quicklook/glg_lc_medres34_bn151228949.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 186.90,-15.05 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(2.0<100sec) coincident with the SWIFT_BAT event (trignum=668641).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 28 Dec 15 22:48:34 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     668641,   Seg_Num: 0
GRB_RA:          344.4248d {+22h 57m 41.95s} (J2000),
                 344.6263d {+22h 58m 30.31s} (current),
                 343.7949d {+22h 55m 10.78s} (1950)
GRB_DEC:          +8.0807d {+08d 04' 50.5"} (J2000),
                  +8.1665d {+08d 09' 59.3"} (current),
                  +7.8129d {+07d 48' 46.5"} (1950)
GRB_ERROR:       4.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       6.74e-09 [erg/cm2/sec]
GRB_SIGNIF:      13.15 [sigma]
IMG_START_DATE:  17384 TJD;   362 DOY;   15/12/28
IMG_START_TIME:  82084.46 SOD {22:48:04.46} UT,   49.5 [sec] since BAT Trigger Time
TAM[0-3]:        327.69 237.22 261.60 243.73
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       277.49d {+18h 29m 57s}  -23.26d {-23d 15' 28"}
SUN_DIST:         72.71 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      141.01d {+09h 24m 02s}  +12.24d {+12d 14' 17"}
MOON_DIST:       148.90 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       80.85,-45.30 [deg] galactic lon,lat of the burst
ECL_COORDS:      348.85, 13.57 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 0.97 arcmin from the BAT position.  
COMMENTS:        The object found at this position is either a very bright burst or a cosmic ray hit.  
COMMENTS:        Examine the XRT Image to differentiate (CRs are much more compact); see examples at:  
COMMENTS:        http://www.swift.psu.edu/xrt/XRT_Postage_Stamp_Image_Photo_Gallery.htm .

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 28 Dec 15 22:48:44 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     668641,   Seg_Num: 0
GRB_RA:          344.4248d {+22h 57m 41.9s} (J2000),
                 344.6263d {+22h 58m 30.3s} (current),
                 343.7949d {+22h 55m 10.7s} (1950)
GRB_DEC:          +8.0807d {+08d 04' 50.5"} (J2000),
                  +8.1665d {+08d 09' 59.3"} (current),
                  +7.8129d {+07d 48' 46.5"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       173 [cnts]
IMG_START_DATE:  17384 TJD;   362 DOY;   15/12/28
IMG_START_TIME:  82084.46 SOD {22:48:04.46} UT,   49.5 [sec] since BAT Trigger Time
CENTROID_X:      280.32,  raw= 280  [pixels]
CENTROID_Y:      278.35,  raw= 278  [pixels]
ROLL:            242.43 [deg]
GAIN:            4
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -45.83
GRB_POS_XRT_Z:   -58.87
IMAGE_URL:       sw00668641000msxps_rw.img
SUN_POSTN:       277.49d {+18h 29m 57s}  -23.26d {-23d 15' 28"}
SUN_DIST:         72.71 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      141.01d {+09h 24m 02s}  +12.24d {+12d 14' 16"}
MOON_DIST:       148.90 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       80.85,-45.30 [deg] galactic lon,lat of the burst
ECL_COORDS:      348.85, 13.57 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.  
COMMENTS:        The object found at this position is either a very bright burst or a cosmic ray hit.  
COMMENTS:        Examine the XRT Image to differentiate (CRs are much more compact); see examples at:  
COMMENTS:        http://www.swift.psu.edu/xrt/XRT_Postage_Stamp_Image_Photo_Gallery.htm .

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 28 Dec 15 22:49:02 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     668641,   Seg_Num: 0
GRB_RA:          344.4248d {+22h 57m 41.9s} (J2000),
                 344.6263d {+22h 58m 30.3s} (current),
                 343.7949d {+22h 55m 10.7s} (1950)
GRB_DEC:          +8.0807d {+08d 04' 50.5"} (J2000),
                  +8.1665d {+08d 09' 59.3"} (current),
                  +7.8129d {+07d 48' 46.5"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       173 [cnts]
IMG_START_DATE:  17384 TJD;   362 DOY;   15/12/28
IMG_START_TIME:  82084.46 SOD {22:48:04.46} UT,   49.5 [sec] since BAT Trigger Time
CENTROID_X:      280.32,  raw= 280  [pixels]
CENTROID_Y:      278.35,  raw= 278  [pixels]
ROLL:            242.43 [deg]
GAIN:            4
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -45.83
GRB_POS_XRT_Z:   -58.87
IMAGE_URL:       sw00668641000msxps_rw.img
SUN_POSTN:       277.49d {+18h 29m 57s}  -23.26d {-23d 15' 28"}
SUN_DIST:         72.71 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      141.01d {+09h 24m 03s}  +12.24d {+12d 14' 14"}
MOON_DIST:       148.90 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       80.85,-45.30 [deg] galactic lon,lat of the burst
ECL_COORDS:      348.85, 13.57 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.  
COMMENTS:        The object found at this position is either a very bright burst or a cosmic ray hit.  
COMMENTS:        Examine the XRT Image to differentiate (CRs are much more compact); see examples at:  
COMMENTS:        http://www.swift.psu.edu/xrt/XRT_Postage_Stamp_Image_Photo_Gallery.htm .

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 28 Dec 15 22:51:00 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     668641,   Seg_Num: 0
GRB_RA:          344.441d {+22h 57m 46s} (J2000),
                 344.642d {+22h 58m 34s} (current),
                 343.811d {+22h 55m 15s} (1950)
GRB_DEC:          +8.076d {+08d 04' 34"} (J2000),
                  +8.162d {+08d 09' 43"} (current),
                  +7.808d {+07d 48' 30"} (1950)
GRB_DATE:        17384 TJD;   362 DOY;   15/12/28
GRB_TIME:        82034.94 SOD {22:47:14.94} UT
TRIGGER_INDEX:   146
GRB_PHI:         -86.67 [deg]
GRB_THETA:         1.58 [deg]
DELTA_TIME:      64.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     26.24 [sigma]
IMAGE_SIGNIF:    11.83 [sigma]
LC_URL:          sw00668641000msb.lc
SUN_POSTN:       277.49d {+18h 29m 57s}  -23.26d {-23d 15' 28"}
SUN_DIST:         72.72 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      141.03d {+09h 24m 07s}  +12.23d {+12d 13' 59"}
MOON_DIST:       148.91 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       80.87,-45.31 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      348.86, 13.56 [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 = 258.44,17.26 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 28 Dec 15 22:51:33 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     668641,   Seg_Num: 0
POINT_RA:        344.445d {+22h 57m 47s} (J2000)
POINT_DEC:        +8.077d {+08d 04' 38"} (J2000)
POINT_ROLL:      242.429d
IMG_START_DATE:  17384 TJD;   362 DOY;   15/12/28
IMG_START_TIME:  82092.88 SOD {22:48:12.88} UT,   57.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.722
N_STARS:         25
X_OFFSET:        512 [pixels]
Y_OFFSET:        552 [pixels]
X_MAX:           1471 [pixels]
Y_MAX:           1511 [pixels]
DET_THRESH:      16
PHOTO_THRESH:    9
SL_URL:          sw00668641000msufc0057.fits
SUN_POSTN:       277.49d {+18h 29m 57s}  -23.26d {-23d 15' 28"}
SUN_DIST:         72.72 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      141.03d {+09h 24m 08s}  +12.23d {+12d 13' 55"}
MOON_DIST:       148.91 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       80.87,-45.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      348.87, 13.56 [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:     Mon 28 Dec 15 22:51:12 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     668641,   Seg_Num: 0
POINT_RA:        344.445d {+22h 57m 47s} (J2000)
POINT_DEC:        +8.077d {+08d 04' 38"} (J2000)
POINT_ROLL:      242.429d
IMG_START_DATE:  17384 TJD;   362 DOY;   15/12/28
IMG_START_TIME:  82092.88 SOD {22:48:12.88} UT,   57.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.722
N_STARS:         25
X_OFFSET:        512 [pixels]
Y_OFFSET:        552 [pixels]
X_MAX:           1471 [pixels]
Y_MAX:           1511 [pixels]
DET_THRESH:      16
PHOTO_THRESH:    9
SL_URL:          sw00668641000msufc0057.fits
SUN_POSTN:       277.49d {+18h 29m 57s}  -23.26d {-23d 15' 28"}
SUN_DIST:         72.72 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      141.03d {+09h 24m 08s}  +12.23d {+12d 13' 57"}
MOON_DIST:       148.90 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       80.87,-45.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      348.87, 13.56 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 28 Dec 15 22:53:08 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     668641,   Seg_Num: 0
POINT_RA:        344.445d {+22h 57m 47s} (J2000)
POINT_DEC:        +8.077d {+08d 04' 38"} (J2000)
ROLL:            242.429d
IMG_START_DATE:  17384 TJD;   362 DOY;   15/12/28
IMG_START_TIME:  82092.88 SOD {22:48:12.88} UT,   57.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     473035708
X_OFFSET:        944 [pixels]
Y_OFFSET:        895 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1104
Y_GRB_POS:       1055
BINNING_INDEX:   1
IM_URL:          sw00668641000msuni0073.fits
SUN_POSTN:       277.49d {+18h 29m 58s}  -23.26d {-23d 15' 28"}
SUN_DIST:         72.72 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      141.05d {+09h 24m 12s}  +12.23d {+12d 13' 43"}
MOON_DIST:       148.92 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       80.87,-45.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      348.87, 13.56 [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:     Mon 28 Dec 15 22:53:16 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     668641,   Seg_Num: 0
POINT_RA:        344.445d {+22h 57m 47s} (J2000)
POINT_DEC:        +8.077d {+08d 04' 38"} (J2000)
ROLL:            242.429d
IMG_START_DATE:  17384 TJD;   362 DOY;   15/12/28
IMG_START_TIME:  82092.88 SOD {22:48:12.88} UT,   57.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     473035708
X_OFFSET:        944 [pixels]
Y_OFFSET:        895 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1104
Y_GRB_POS:       1055
BINNING_INDEX:   1
IM_URL:          sw00668641000msuni0073.fits
SUN_POSTN:       277.49d {+18h 29m 58s}  -23.26d {-23d 15' 28"}
SUN_DIST:         72.72 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      141.05d {+09h 24m 12s}  +12.23d {+12d 13' 42"}
MOON_DIST:       148.92 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       80.87,-45.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      348.87, 13.56 [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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 28 Dec 15 22:55:14 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     668641,   Seg_Num: 0
GRB_RA:          344.4243d {+22h 57m 41.83s} (J2000),
                 344.6258d {+22h 58m 30.19s} (current),
                 343.7944d {+22h 55m 10.66s} (1950)
GRB_DEC:          +8.0816d {+08d 04' 53.7"} (J2000),
                  +8.1674d {+08d 10' 02.6"} (current),
                  +7.8138d {+07d 48' 49.8"} (1950)
GRB_ERROR:       0.8 [arcsec radius, statistical only]
GRB_MAG:         19.73 +/- 0.17 [mag]
FILTER:          10, White
IMG_START_DATE:  17384 TJD;   362 DOY;   15/12/28
IMG_START_TIME:  82090.00 SOD {22:48:10.00} UT,   55.1 [sec] since BAT Trigger Time
SUN_POSTN:       277.49d {+18h 29m 58s}  -23.26d {-23d 15' 27"}
SUN_DIST:         72.71 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      141.07d {+09h 24m 16s}  +12.22d {+12d 13' 27"}
MOON_DIST:       148.95 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       80.85,-45.30 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      348.85, 13.58 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT UVOT Position Notice.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The UVOT position is 3.6 arcsec from the XRT position.  
COMMENTS:        Result based on Genie data.  
COMMENTS:        Notice generated automatically.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 28 Dec 15 22:59:27 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     668641,   Seg_Num: 0
POINT_RA:        344.446d {+22h 57m 47s} (J2000)
POINT_DEC:        +8.077d {+08d 04' 39"} (J2000)
POINT_ROLL:      242.428d
IMG_START_DATE:  17384 TJD;   362 DOY;   15/12/28
IMG_START_TIME:  82304.79 SOD {22:51:44.79} UT,   269.8 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.965
N_STARS:         13
X_OFFSET:        624 [pixels]
Y_OFFSET:        575 [pixels]
X_MAX:           1583 [pixels]
Y_MAX:           1534 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    4
SL_URL:          sw00668641000msufc0269.fits
SUN_POSTN:       277.50d {+18h 29m 59s}  -23.26d {-23d 15' 27"}
SUN_DIST:         72.72 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      141.10d {+09h 24m 25s}  +12.22d {+12d 12' 54"}
MOON_DIST:       148.97 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       80.87,-45.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      348.87, 13.56 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 28 Dec 15 22:59:49 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     668641,   Seg_Num: 0
POINT_RA:        344.446d {+22h 57m 47s} (J2000)
POINT_DEC:        +8.077d {+08d 04' 39"} (J2000)
POINT_ROLL:      242.428d
IMG_START_DATE:  17384 TJD;   362 DOY;   15/12/28
IMG_START_TIME:  82304.79 SOD {22:51:44.79} UT,   269.8 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.965
N_STARS:         13
X_OFFSET:        624 [pixels]
Y_OFFSET:        575 [pixels]
X_MAX:           1583 [pixels]
Y_MAX:           1534 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    4
SL_URL:          sw00668641000msufc0269.fits
SUN_POSTN:       277.50d {+18h 29m 59s}  -23.26d {-23d 15' 27"}
SUN_DIST:         72.72 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      141.11d {+09h 24m 26s}  +12.21d {+12d 12' 52"}
MOON_DIST:       148.97 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       80.87,-45.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      348.87, 13.56 [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:     Mon 28 Dec 15 23:00:05 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     668641,   Seg_Num: 0
GRB_RA:          344.4243d {+22h 57m 41.83s} (J2000),
                 344.6258d {+22h 58m 30.19s} (current),
                 343.7944d {+22h 55m 10.66s} (1950)
GRB_DEC:          +8.0815d {+08d 04' 53.4"} (J2000),
                  +8.1673d {+08d 10' 02.2"} (current),
                  +7.8137d {+07d 48' 49.4"} (1950)
GRB_ERROR:       2.7 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  17384 TJD;   362 DOY;   15/12/28
IMG_START_TIME:  82286.00 SOD {22:51:26.00} UT,   251.1 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       277.50d {+18h 29m 59s}  -23.26d {-23d 15' 27"}
SUN_DIST:         72.70 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      141.11d {+09h 24m 26s}  +12.21d {+12d 12' 50"}
MOON_DIST:       148.99 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       80.85,-45.30 [deg] galactic lon,lat of the burst
ECL_COORDS:      348.85, 13.58 [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:     Mon 28 Dec 15 23:00:52 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     668641,   Seg_Num: 0
POINT_RA:        344.446d {+22h 57m 47s} (J2000)
POINT_DEC:        +8.077d {+08d 04' 39"} (J2000)
ROLL:            242.428d
IMG_START_DATE:  17384 TJD;   362 DOY;   15/12/28
IMG_START_TIME:  82304.79 SOD {22:51:44.79} UT,   269.8 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     473035920
X_OFFSET:        944 [pixels]
Y_OFFSET:        895 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1104
Y_GRB_POS:       1055
BINNING_INDEX:   1
IM_URL:          sw00668641000msuni0285.fits
SUN_POSTN:       277.50d {+18h 29m 59s}  -23.26d {-23d 15' 27"}
SUN_DIST:         72.72 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      141.12d {+09h 24m 28s}  +12.21d {+12d 12' 44"}
MOON_DIST:       148.98 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       80.87,-45.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      348.87, 13.56 [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:     Mon 28 Dec 15 23:01:13 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     668641,   Seg_Num: 0
POINT_RA:        344.446d {+22h 57m 47s} (J2000)
POINT_DEC:        +8.077d {+08d 04' 39"} (J2000)
ROLL:            242.428d
IMG_START_DATE:  17384 TJD;   362 DOY;   15/12/28
IMG_START_TIME:  82304.79 SOD {22:51:44.79} UT,   269.8 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     473035920
X_OFFSET:        944 [pixels]
Y_OFFSET:        895 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1104
Y_GRB_POS:       1055
BINNING_INDEX:   1
IM_URL:          sw00668641000msuni0285.fits
SUN_POSTN:       277.50d {+18h 29m 59s}  -23.26d {-23d 15' 27"}
SUN_DIST:         72.72 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      141.12d {+09h 24m 29s}  +12.21d {+12d 12' 41"}
MOON_DIST:       148.98 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       80.87,-45.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      348.87, 13.56 [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 #18739
A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), F. E. Marshall (NASA/GSFC), L. M. McCauley (PSU) and K. L. Page (U Leicester) report on behalf of the Swift Team:
At 22:47:14 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 151228B (trigger=668641). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 344.441, +8.076, which is
```
   RA(J2000)  =  22h 57m 46s
   Dec(J2000) = +08d 04' 34"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows FRED-like peak structure with a duration of about 40 sec. The peak count rate was ~2500 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 22:48:04.4 UT, 49.6 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source with an enhanced position: RA, Dec 344.4247, 8.0816 which is equivalent to:
```
   RA(J2000)  = 22h 57m 41.93s
   Dec(J2000) = +08d 04' 53.7"
```
with an uncertainty of 2.7 arcseconds (radius, 90% containment). This location is 61 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 5.74 x 10^20 cm^-2 (Willingale et al. 2013).
The initial flux in the 2.5 s image was 6.74e-09 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 57 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at
```
  RA(J2000)  =  22:57:41.85 = 344.42437
  DEC(J2000) = +08:04:54.0  =   8.08166
```
with a 90%-confidence error radius of about 0.80 arc sec. This position is 3.8 arc sec. from the center of the XRT error circle. The estimated magnitude is 19.74 with a 1-sigma error of about 0.17. No correction has been made for the expected extinction corresponding to E(B-V) of 0.06.
Burst Advocate for this burst is A. Y. Lien (amy.y.lien AT nasa.gov). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 28 Dec 15 23:07:17 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     668641,   Seg_Num: 0
POINT_RA:        344.446d {+22h 57m 47s} (J2000)
POINT_DEC:        +8.078d {+08d 04' 40"} (J2000)
POINT_ROLL:      242.428d
IMG_START_DATE:  17384 TJD;   362 DOY;   15/12/28
IMG_START_TIME:  82906.90 SOD {23:01:46.90} UT,   872.0 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.498
N_STARS:         58
X_OFFSET:        384 [pixels]
Y_OFFSET:        335 [pixels]
X_MAX:           1823 [pixels]
Y_MAX:           1774 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw00668641000msufc0871.fits
SUN_POSTN:       277.50d {+18h 30m 00s}  -23.26d {-23d 15' 26"}
SUN_DIST:         72.71 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      141.17d {+09h 24m 41s}  +12.20d {+12d 11' 54"}
MOON_DIST:       149.03 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       80.87,-45.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      348.87, 13.56 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 28 Dec 15 23:07:47 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     668641,   Seg_Num: 0
POINT_RA:        344.446d {+22h 57m 47s} (J2000)
POINT_DEC:        +8.078d {+08d 04' 40"} (J2000)
POINT_ROLL:      242.428d
IMG_START_DATE:  17384 TJD;   362 DOY;   15/12/28
IMG_START_TIME:  82906.90 SOD {23:01:46.90} UT,   872.0 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.498
N_STARS:         58
X_OFFSET:        384 [pixels]
Y_OFFSET:        335 [pixels]
X_MAX:           1823 [pixels]
Y_MAX:           1774 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw00668641000msufc0871.fits
SUN_POSTN:       277.50d {+18h 30m 00s}  -23.26d {-23d 15' 26"}
SUN_DIST:         72.71 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      141.18d {+09h 24m 42s}  +12.20d {+12d 11' 51"}
MOON_DIST:       149.03 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       80.87,-45.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      348.87, 13.56 [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:     Mon 28 Dec 15 23:08:40 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     668641,   Seg_Num: 0
POINT_RA:        344.446d {+22h 57m 47s} (J2000)
POINT_DEC:        +8.078d {+08d 04' 40"} (J2000)
ROLL:            242.428d
IMG_START_DATE:  17384 TJD;   362 DOY;   15/12/28
IMG_START_TIME:  82906.90 SOD {23:01:46.90} UT,   872.0 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     473036522
X_OFFSET:        943 [pixels]
Y_OFFSET:        894 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1103
Y_GRB_POS:       1054
BINNING_INDEX:   1
IM_URL:          sw00668641000msuni0887.fits
SUN_POSTN:       277.50d {+18h 30m 01s}  -23.26d {-23d 15' 26"}
SUN_DIST:         72.71 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      141.18d {+09h 24m 44s}  +12.20d {+12d 11' 44"}
MOON_DIST:       149.04 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       80.87,-45.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      348.87, 13.56 [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:     Mon 28 Dec 15 23:08:56 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     668641,   Seg_Num: 0
POINT_RA:        344.446d {+22h 57m 47s} (J2000)
POINT_DEC:        +8.078d {+08d 04' 40"} (J2000)
ROLL:            242.428d
IMG_START_DATE:  17384 TJD;   362 DOY;   15/12/28
IMG_START_TIME:  82906.90 SOD {23:01:46.90} UT,   872.0 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     473036522
X_OFFSET:        943 [pixels]
Y_OFFSET:        894 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1103
Y_GRB_POS:       1054
BINNING_INDEX:   1
IM_URL:          sw00668641000msuni0887.fits
SUN_POSTN:       277.50d {+18h 30m 01s}  -23.26d {-23d 15' 26"}
SUN_DIST:         72.71 [deg]   Sun_angle= -4.5 [hr] (East of Sun)
MOON_POSTN:      141.19d {+09h 24m 45s}  +12.19d {+12d 11' 42"}
MOON_DIST:       149.04 [deg]
MOON_ILLUM:      87 [%]
GAL_COORDS:       80.87,-45.31 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      348.87, 13.56 [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 #18743
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 2601 s of XRT Photon Counting mode data and 4 UVOT images for GRB 151228B, 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 = 344.42460, +8.08148 which is equivalent to:
```
RA (J2000): 22h 57m 41.90s
Dec (J2000): +08d 04' 53.3"
```
with an uncertainty of 1.8 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 #18749
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A. D'Ai (INAF-IASFPA), A. Maselli (INAF-IASFPA), A. Melandri (INAF-OAB), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), C. Pagani (U. Leicester) and A.Y. Lien report on behalf of the Swift-XRT team:
We have analysed 10 ks of XRT data for GRB 151228B (Lien et al. GCN Circ. 18739), from 40 s to 29.0 ks after the BAT trigger. The data comprise 194 s in Windowed Timing (WT) mode (the first 8 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN Circ. 18743).
The late-time light curve (from T0+4.7 ks) can be modelled with a power-law decay with a decay index of alpha=0.68 (+0.22, -0.21).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.43 (+/-0.08). The best-fitting absorption column is 1.78 (+0.21, -0.20) x 10^21 cm^-2, in excess of the Galactic value of 5.7 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.94 (+0.14, -0.12) and a best-fitting absorption column consistent with the Galactic value. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.4 x 10^-11 (3.7 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     5.7 (+2.3, -0.0) x 10^20 cm^-2
Galactic foreground: 5.7 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.94 (+0.14, -0.12)
```
If the light curve continues to decay with a power-law decay index of 0.68, the count rate at T+24 hours will be 8.8 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.0 x 10^-13 (3.2 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/00668641.
This circular is an official product of the Swift-XRT team.
GCN Circular #18752
H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), 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-61 to T+243 sec from the recent telemetry downlinks, we report further analysis of BAT GRB 151228B (trigger #668641) (Lien, et al., GCN Circ. 18739). The BAT ground-calculated position is RA, Dec = 344.431, 8.081 deg, which is
```
   RA(J2000)  =  22h 57m 43.4s 
   Dec(J2000) = +08d 04' 52.4" 
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%.
The mask-weighted light curve shows a FreD-like peak starting at ~T-10 sec, peaking at ~T+3 sec, and ending at ~T+65 sec. T90 (15-350 keV) is 48.0 +- 16.0 sec (estimated error including systematics).
The time-averaged spectrum from T-12.56 to T+67.44 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.09 +- 0.34, and Epeak of 78.1 +- 27.0 keV (chi squared 52.3 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 2.4 +- 0.1 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+10.94 sec in the 15-150 keV band is 1.0 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.66 +- 0.08 (chi squared 61.6 for 57 d.o.f.). 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/668641/BA/
GCN Circular #18755
P Veres (UAH) reports on behalf of the Fermi GBM Team:
"At 22:47:12.59 UT on 28 December 2015, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 151228B (trigger 473035636 / 151228949). which was also detected by the Swift/BAT (Lien et al. 2008, GCN 18739). The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 107 degrees.
The GBM light curve shows of a single pulse with a duration (T90) of about 29 s (50-300 keV). There was a Solar flare coincident with this GRB which affected the low energy channels of GBM. For this reason the spectral analysis was carried out for photon energies above 40 keV. The time-averaged spectrum from T0-6.1 s to T0+21.5 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -1.1 +/- 0.4 and the cutoff energy, parameterized as Epeak, is 93 +/- 9 keV.
The event fluence (10-1000 keV) in this time interval is (3.6 +/- 0.4)E-6 erg/cm^2. The 1-sec peak photon flux measured starting from T0+2.3 s in the 10-1000 keV band is 7.6 +/- 0.9 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN Circular #18758
Y.Muraki, T.Fujiwara, T. Yoshii, Y. Saito, Y. Tachibana, Y.Yano, S.Harita, Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:
We searched for the optical counterpart of GRB 151228B (A. Y. Lien et al., GCN Circular #18739) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan.
The observation started on 2015-12-29 09:55:19 UT (~11.1 h after the burst). We did not find any new point source within Swift/XRT circle in all three bands.
We obtained following limits for the magnitudes.
```
T0+[sec] MID-UT T-EXP[sec] g' Rc Ic
-------------------------------------------------------------
40085  10:37:06  2507  > 20.9  > 20.6  > 19.6
-------------------------------------------------------------
T0+ : Elapsed time after the burst 
T-EXP: Total Exposure time 
```
We used GSC2.3 catalog for flux calibration.
GCN Circular #18766
A.A. Breeveld (UCL-MSSL), S.W.K. Emery (UCL-MSSL) and A.Y. Lien (GSFC/UMBC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 151228B 49 s after the BAT trigger (Lien et al., GCN Circ. 18739). A fading source consistent with the XRT position (Goad et al. GCN Circ. 18743) is detected in the initial UVOT exposures in the white filter.
The preliminary UVOT position is:
```
     RA  (J2000) =3D  22:57:41.87 =3D 344.42446 (deg.)
     Dec (J2000) =3D +08:04:53.7  =3D   8.08159 (deg.)
```
with an estimated uncertainty of 0.58 arc sec. (radius, 90% confidence).
Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white               70          220          147         19.62 =B1 0.19
v                   49         6132          306        >19.2
b                  537         5514          274        >20.0
u                  282         5309          520        >20.1
w1                 661         6373          303        >20.1
m2                6137         6337          197        >19.9
w2                1386         5927          216        >20.8
```
The magnitudes in the table are not corrected for the Galactic=20 extinction due to the reddening of E(B-V) =3D 0.06 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #18891
E. Mazaeva (IKI), R. Inasaridze (AbAO), V. Ayvazian (AbAO), A. Volnova (IKI), I. Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of the Swift GRB 151228B (Lien et al., GCN 18739) with AS-32 (0.7m) telescope of Abastumani Observatory starting on Dec. 29 (UT) 14:38:28. We do not detect any source within enhanced XRT error circle (Goad et al., GCN 18743):
```
Date       UT start     t-T0          Filter Exp.    UL(3 sigma)
            (mid, days)                       (s)

2015-12-29 14:38:28     0.69297       None  35*120   22.1
```
The photometry is based on nearby SDSS-DR9 stars:
```
SDSS-DR9_id             R_Lupton
J225738.02+080336.8 18.18
J225747.18+080340.7 16.86
J225736.71+080628.4 17.72
J225752.89+080438.1 17.46
J225726.79+080540.6 16.99
```

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Jochen Greiner, last update: 18-Jan-2016 [Disclaimer]