Gamma-ray Burst 151023A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN/BACODINE POSITION NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 23 Oct 15 13:43:30 UT
  NOTICE_TYPE:     Swift-BAT GRB Position
  TRIGGER_NUM:     661253,   Seg_Num: 0
  GRB_RA:          271.019d {+18h 04m 05s} (J2000),
                   271.235d {+18h 04m 56s} (current),
                   270.338d {+18h 01m 21s} (1950)
  GRB_DEC:          -8.323d {-08d 19' 21"} (J2000),
                    -8.321d {-08d 19' 15"} (current),
                    -8.326d {-08d 19' 33"} (1950)
  GRB_ERROR:       3.00 [arcmin radius, statistical only]
  GRB_INTEN:       6165 [cnts]    Image_Peak=260 [image_cnts]
  TRIGGER_DUR:     1.024 [sec] 
  TRIGGER_INDEX:   137     E_range: 15-50 keV
  BKG_INTEN:       38423 [cnts]
  BKG_TIME:        49368.68 SOD {13:42:48.68} UT
  BKG_DUR:         8 [sec]
  GRB_DATE:        17318 TJD;   296 DOY;   15/10/23
  GRB_TIME:        49384.81 SOD {13:43:04.81} UT
  GRB_PHI:         133.11 [deg]
  GRB_THETA:        18.04 [deg]
  SOLN_STATUS:     0x3
  RATE_SIGNIF:     16.73 [sigma]
  IMAGE_SIGNIF:    8.49 [sigma]
  MERIT_PARAMS:     +1  +0  +0  +0  +1  -1  +0  +1 -46  +0 
  SUN_POSTN:       207.75d {+13h 51m 00s}  -11.41d {-11d 24' 39"}
  SUN_DIST:         62.51 [deg]   Sun_angle= -4.2 [hr] (East of Sun)
  MOON_POSTN:      336.18d {+22h 24m 44s}   -7.66d {-07d 39' 21"}
  MOON_DIST:        64.25 [deg]
  MOON_ILLUM:      79 [%]
  GAL_COORDS:       20.05,  6.59 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      271.04, 15.11 [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 = 338.31,-4.34 [deg].  
  

• red DSS finding chart ps-file
  
  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 23 Oct 15 13:44:32 UT
  NOTICE_TYPE:     Swift-XRT Nack-Position
  TRIGGER_NUM:     661253,   Seg_Num: 0
  POINT_RA:        271.005d {+18h 04m 01s} (J2000)
  POINT_DEC:        -8.326d {-08d 19' 33"} (J2000)
  IMG_START_DATE:  17318 TJD;   296 DOY;   15/10/23
  IMG_START_TIME:  49459.59 SOD {13:44:19.59} UT,   74.8 [sec] since BAT Trigger Time
  COUNTS:          1    Min_needed= 20
  STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
  PH2_ITER:        0    Max_iter_allowed= 4
  ERROR_CODE:      1
  COMMENTS:        SWIFT-XRT Nack Position.  
  COMMENTS:        No source found in the image.  
  

• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 23 Oct 15 13:46:55 UT
  NOTICE_TYPE:     Swift-BAT GRB Lightcurve
  TRIGGER_NUM:     661253,   Seg_Num: 0
  GRB_RA:          271.019d {+18h 04m 05s} (J2000),
                   271.235d {+18h 04m 56s} (current),
                   270.338d {+18h 01m 21s} (1950)
  GRB_DEC:          -8.323d {-08d 19' 21"} (J2000),
                    -8.321d {-08d 19' 15"} (current),
                    -8.326d {-08d 19' 33"} (1950)
  GRB_DATE:        17318 TJD;   296 DOY;   15/10/23
  GRB_TIME:        49384.81 SOD {13:43:04.81} UT
  TRIGGER_INDEX:   137
  GRB_PHI:         133.11 [deg]
  GRB_THETA:        18.04 [deg]
  DELTA_TIME:      -11.00 [sec]
  TRIGGER_DUR:     1.024 [sec] 
  SOLN_STATUS:     0x3
  RATE_SIGNIF:     16.73 [sigma]
  IMAGE_SIGNIF:    8.49 [sigma]
  LC_URL:          sw00661253000msb.lc
  SUN_POSTN:       207.75d {+13h 51m 00s}  -11.41d {-11d 24' 42"}
  SUN_DIST:         62.51 [deg]   Sun_angle= -4.2 [hr] (East of Sun)
  MOON_POSTN:      336.22d {+22h 24m 52s}   -7.65d {-07d 38' 45"}
  MOON_DIST:        64.28 [deg]
  MOON_ILLUM:      79 [%]
  GAL_COORDS:       20.05,  6.59 [deg] galactic lon,lat of the burst (or transient)
  ECL_COORDS:      271.04, 15.11 [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 = 338.31,-4.34 [deg].  
  

  
• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 23 Oct 15 14:01:19 UT
  NOTICE_TYPE:     Swift-UVOT Source List
  TRIGGER_NUM:     661253,   Seg_Num: 0
  POINT_RA:        271.002d {+18h 04m 01s} (J2000)
  POINT_DEC:        -8.325d {-08d 19' 28"} (J2000)
  POINT_ROLL:      261.426d
  IMG_START_DATE:  17318 TJD;   296 DOY;   15/10/23
  IMG_START_TIME:  50180.98 SOD {13:56:20.98} UT,   796.2 [sec] since BAT Trigger Time
  FILTER:          10, White
  BKG_MEAN:        5.115
  N_STARS:         86
  X_OFFSET:        366 [pixels]
  Y_OFFSET:        607 [pixels]
  X_MAX:           1325 [pixels]
  Y_MAX:           1566 [pixels]
  DET_THRESH:      19
  PHOTO_THRESH:    11
  SL_URL:          sw00661253000msufc0796.fits
  SUN_POSTN:       207.76d {+13h 51m 03s}  -11.42d {-11d 24' 55"}
  SUN_DIST:         62.48 [deg]   Sun_angle= -4.2 [hr] (East of Sun)
  MOON_POSTN:      336.36d {+22h 25m 26s}   -7.60d {-07d 36' 16"}
  MOON_DIST:        64.44 [deg]
  MOON_ILLUM:      79 [%]
  GAL_COORDS:       20.04,  6.60 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      271.03, 15.11 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Source List.  
  

• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 23 Oct 15 14:01:44 UT
  NOTICE_TYPE:     Swift-UVOT Processed Source List
  TRIGGER_NUM:     661253,   Seg_Num: 0
  POINT_RA:        271.002d {+18h 04m 01s} (J2000)
  POINT_DEC:        -8.325d {-08d 19' 28"} (J2000)
  POINT_ROLL:      261.426d
  IMG_START_DATE:  17318 TJD;   296 DOY;   15/10/23
  IMG_START_TIME:  50180.98 SOD {13:56:20.98} UT,   796.2 [sec] since BAT Trigger Time
  FILTER:          10, White
  BKG_MEAN:        5.115
  N_STARS:         86
  X_OFFSET:        366 [pixels]
  Y_OFFSET:        607 [pixels]
  X_MAX:           1325 [pixels]
  Y_MAX:           1566 [pixels]
  DET_THRESH:      19
  PHOTO_THRESH:    11
  SL_URL:          sw00661253000msufc0796.fits
  SUN_POSTN:       207.76d {+13h 51m 03s}  -11.42d {-11d 24' 55"}
  SUN_DIST:         62.48 [deg]   Sun_angle= -4.2 [hr] (East of Sun)
  MOON_POSTN:      336.36d {+22h 25m 27s}   -7.60d {-07d 36' 12"}
  MOON_DIST:        64.44 [deg]
  MOON_ILLUM:      79 [%]
  GAL_COORDS:       20.04,  6.60 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      271.03, 15.11 [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 23 Oct 15 14:02:28 UT
  NOTICE_TYPE:     Swift-XRT Position
  TRIGGER_NUM:     661253,   Seg_Num: 0
  GRB_RA:          270.9846d {+18h 03m 56.30s} (J2000),
                   271.2000d {+18h 04m 48.00s} (current),
                   270.3034d {+18h 01m 12.81s} (1950)
  GRB_DEC:          -8.3164d {-08d 18' 59.0"} (J2000),
                    -8.3147d {-08d 18' 52.9"} (current),
                    -8.3195d {-08d 19' 10.3"} (1950)
  GRB_ERROR:       3.3 [arcsec radius, statistical plus systematic, 90% containment]
  GRB_INTEN:       1.00e-10 [erg/cm2/sec]
  GRB_SIGNIF:      10.00 [sigma]
  IMG_START_DATE:  17318 TJD;   296 DOY;   15/10/23
  IMG_START_TIME:  50148.00 SOD {13:55:48.00} UT,   763.2 [sec] since BAT Trigger Time
  TAM[0-3]:        100.00 100.00 100.00 100.00
  AMPLIFIER:       1
  WAVEFORM:        31
  SUN_POSTN:       207.76d {+13h 51m 03s}  -11.42d {-11d 24' 56"}
  SUN_DIST:         62.46 [deg]   Sun_angle= -4.2 [hr] (East of Sun)
  MOON_POSTN:      336.37d {+22h 25m 29s}   -7.60d {-07d 36' 04"}
  MOON_DIST:        64.47 [deg]
  MOON_ILLUM:      79 [%]
  GAL_COORDS:       20.04,  6.62 [deg] galactic lon,lat of the burst
  ECL_COORDS:      271.01, 15.12 [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:        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 23 Oct 15 14:03:06 UT
  NOTICE_TYPE:     Swift-UVOT Image
  TRIGGER_NUM:     661253,   Seg_Num: 0
  POINT_RA:        271.002d {+18h 04m 01s} (J2000)
  POINT_DEC:        -8.325d {-08d 19' 28"} (J2000)
  ROLL:            261.426d
  IMG_START_DATE:  17318 TJD;   296 DOY;   15/10/23
  IMG_START_TIME:  50180.98 SOD {13:56:20.98} UT,   796.2 [sec] since BAT Trigger Time
  FILTER:          10, White
  EXPOSURE_ID:     467301396
  X_OFFSET:        685 [pixels]
  Y_OFFSET:        926 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       845
  Y_GRB_POS:       1086
  BINNING_INDEX:   1
  IM_URL:          sw00661253000msuni0812.fits
  SUN_POSTN:       207.76d {+13h 51m 03s}  -11.42d {-11d 24' 56"}
  SUN_DIST:         62.48 [deg]   Sun_angle= -4.2 [hr] (East of Sun)
  MOON_POSTN:      336.38d {+22h 25m 30s}   -7.60d {-07d 35' 58"}
  MOON_DIST:        64.46 [deg]
  MOON_ILLUM:      79 [%]
  GAL_COORDS:       20.04,  6.60 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      271.03, 15.11 [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 23 Oct 15 14:03:16 UT
  NOTICE_TYPE:     Swift-UVOT Processed Image
  TRIGGER_NUM:     661253,   Seg_Num: 0
  POINT_RA:        271.002d {+18h 04m 01s} (J2000)
  POINT_DEC:        -8.325d {-08d 19' 28"} (J2000)
  ROLL:            261.426d
  IMG_START_DATE:  17318 TJD;   296 DOY;   15/10/23
  IMG_START_TIME:  50180.98 SOD {13:56:20.98} UT,   796.2 [sec] since BAT Trigger Time
  FILTER:          10, White
  EXPOSURE_ID:     467301396
  X_OFFSET:        685 [pixels]
  Y_OFFSET:        926 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       845
  Y_GRB_POS:       1086
  BINNING_INDEX:   1
  IM_URL:          sw00661253000msuni0812.fits
  SUN_POSTN:       207.76d {+13h 51m 03s}  -11.42d {-11d 24' 56"}
  SUN_DIST:         62.48 [deg]   Sun_angle= -4.2 [hr] (East of Sun)
  MOON_POSTN:      336.38d {+22h 25m 31s}   -7.60d {-07d 35' 56"}
  MOON_DIST:        64.46 [deg]
  MOON_ILLUM:      79 [%]
  GAL_COORDS:       20.04,  6.60 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      271.03, 15.11 [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 23 Oct 15 14:04:28 UT
  NOTICE_TYPE:     Swift-UVOT Source List
  TRIGGER_NUM:     661253,   Seg_Num: 0
  POINT_RA:        271.003d {+18h 04m 01s} (J2000)
  POINT_DEC:        -8.324d {-08d 19' 26"} (J2000)
  POINT_ROLL:      261.425d
  IMG_START_DATE:  17318 TJD;   296 DOY;   15/10/23
  IMG_START_TIME:  50334.38 SOD {13:58:54.38} UT,   949.6 [sec] since BAT Trigger Time
  FILTER:          10, White
  BKG_MEAN:        4.957
  N_STARS:         190
  X_OFFSET:        126 [pixels]
  Y_OFFSET:        367 [pixels]
  X_MAX:           1565 [pixels]
  Y_MAX:           1806 [pixels]
  DET_THRESH:      19
  PHOTO_THRESH:    11
  SL_URL:          sw00661253000msufc0949.fits
  SUN_POSTN:       207.76d {+13h 51m 03s}  -11.42d {-11d 24' 57"}
  SUN_DIST:         62.48 [deg]   Sun_angle= -4.2 [hr] (East of Sun)
  MOON_POSTN:      336.39d {+22h 25m 33s}   -7.60d {-07d 35' 44"}
  MOON_DIST:        64.47 [deg]
  MOON_ILLUM:      79 [%]
  GAL_COORDS:       20.05,  6.60 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      271.03, 15.11 [deg] ecliptic lon,lat of the pointing direction
  COMMENTS:        SWIFT-UVOT Source List.  
  

• GCN NOTICE
  

  TITLE:           GCN/SWIFT NOTICE
  NOTICE_DATE:     Fri 23 Oct 15 14:04:47 UT
  NOTICE_TYPE:     Swift-UVOT Processed Source List
  TRIGGER_NUM:     661253,   Seg_Num: 0
  POINT_RA:        271.003d {+18h 04m 01s} (J2000)
  POINT_DEC:        -8.324d {-08d 19' 26"} (J2000)
  POINT_ROLL:      261.425d
  IMG_START_DATE:  17318 TJD;   296 DOY;   15/10/23
  IMG_START_TIME:  50334.38 SOD {13:58:54.38} UT,   949.6 [sec] since BAT Trigger Time
  FILTER:          10, White
  BKG_MEAN:        4.957
  N_STARS:         190
  X_OFFSET:        126 [pixels]
  Y_OFFSET:        367 [pixels]
  X_MAX:           1565 [pixels]
  Y_MAX:           1806 [pixels]
  DET_THRESH:      19
  PHOTO_THRESH:    11
  SL_URL:          sw00661253000msufc0949.fits
  SUN_POSTN:       207.76d {+13h 51m 03s}  -11.42d {-11d 24' 58"}
  SUN_DIST:         62.48 [deg]   Sun_angle= -4.2 [hr] (East of Sun)
  MOON_POSTN:      336.39d {+22h 25m 34s}   -7.59d {-07d 35' 40"}
  MOON_DIST:        64.47 [deg]
  MOON_ILLUM:      79 [%]
  GAL_COORDS:       20.05,  6.60 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      271.03, 15.11 [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 23 Oct 15 14:05:51 UT
  NOTICE_TYPE:     Swift-UVOT Image
  TRIGGER_NUM:     661253,   Seg_Num: 0
  POINT_RA:        271.003d {+18h 04m 01s} (J2000)
  POINT_DEC:        -8.324d {-08d 19' 26"} (J2000)
  ROLL:            261.425d
  IMG_START_DATE:  17318 TJD;   296 DOY;   15/10/23
  IMG_START_TIME:  50334.38 SOD {13:58:54.38} UT,   949.6 [sec] since BAT Trigger Time
  FILTER:          10, White
  EXPOSURE_ID:     467301549
  X_OFFSET:        685 [pixels]
  Y_OFFSET:        926 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       845
  Y_GRB_POS:       1086
  BINNING_INDEX:   1
  IM_URL:          sw00661253000msuni0965.fits
  SUN_POSTN:       207.76d {+13h 51m 03s}  -11.42d {-11d 24' 59"}
  SUN_DIST:         62.48 [deg]   Sun_angle= -4.2 [hr] (East of Sun)
  MOON_POSTN:      336.40d {+22h 25m 37s}   -7.59d {-07d 35' 29"}
  MOON_DIST:        64.48 [deg]
  MOON_ILLUM:      79 [%]
  GAL_COORDS:       20.05,  6.60 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      271.03, 15.11 [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 23 Oct 15 14:06:04 UT
  NOTICE_TYPE:     Swift-UVOT Processed Image
  TRIGGER_NUM:     661253,   Seg_Num: 0
  POINT_RA:        271.003d {+18h 04m 01s} (J2000)
  POINT_DEC:        -8.324d {-08d 19' 26"} (J2000)
  ROLL:            261.425d
  IMG_START_DATE:  17318 TJD;   296 DOY;   15/10/23
  IMG_START_TIME:  50334.38 SOD {13:58:54.38} UT,   949.6 [sec] since BAT Trigger Time
  FILTER:          10, White
  EXPOSURE_ID:     467301549
  X_OFFSET:        685 [pixels]
  Y_OFFSET:        926 [pixels]
  WIDTH:           160 [pixels]
  HEIGHT:          160 [pixels]
  X_GRB_POS:       845
  Y_GRB_POS:       1086
  BINNING_INDEX:   1
  IM_URL:          sw00661253000msuni0965.fits
  SUN_POSTN:       207.76d {+13h 51m 03s}  -11.42d {-11d 24' 59"}
  SUN_DIST:         62.48 [deg]   Sun_angle= -4.2 [hr] (East of Sun)
  MOON_POSTN:      336.40d {+22h 25m 37s}   -7.59d {-07d 35' 27"}
  MOON_DIST:        64.49 [deg]
  MOON_ILLUM:      79 [%]
  GAL_COORDS:       20.05,  6.60 [deg] galactic lon,lat of the pointing direction
  ECL_COORDS:      271.03, 15.11 [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 #18450
  P. D'Avanzo (INAF-OAB), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), N. Gehrels (NASA/GSFC), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), N. P. M. Kuin (UCL-MSSL), F. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), C. Pagani (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), T. G. R. Roegiers (PSU), B. Sbarufatti (INAF-OAB/PSU), M. H. Siegel (PSU) and R. L. C. Starling (U Leicester) report on behalf of the Swift Team:
  At 13:43:04 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 151023A (trigger=661253). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 271.019, -8.323, which is

     RA(J2000)  =  18h 04m 05s
     Dec(J2000) = -08d 19' 21"
  

  with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single peak with a duration of about 15 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger.
  The XRT began observing the field at 13:44:19.5 UT, 74.8 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 270.9847, -8.3165 which is equivalent to:

     RA(J2000)  = 18h 03m 56.33s
     Dec(J2000) = -08d 18' 59.4"
  

  with an uncertainty of 3.3 arcseconds (radius, 90% containment). This location is 124 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 consistent with the Galactic value of 4.10 x 10^21 cm^-2 (Willingale et al. 2013).
  UVOT took a finding chart exposure of 150 seconds with the White filter starting 796 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 none of the XRT error circle. 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 1.42.
  Burst Advocate for this burst is P. D'Avanzo (paolo.davanzo AT brera.inaf.it). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.)
• GCN Circular #18459
  P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
  Using 1446 s of XRT Photon Counting mode data and 2 UVOT images for GRB 151023A, 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 = 270.98458, -8.31640 which is equivalent to:

  RA (J2000): 18h 03m 56.30s
  Dec (J2000): -08d 18' 59.0"
  

  with an uncertainty of 2.3 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 #18461
  F. Knust (MPE Garching), S. Klose (TLS Tautenburg), and J. Greiner (MPE Garching) report on behalf of the GROND team:
  We observed the field of GRB 151023A (Swift trigger 661253; D'Avanzo et al., GCN #18450) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile). Observations started at 23:52 UT on Oct. 23rd 2015, 10 hrs after the GRB trigger, and are continuing. They were performed at an average seeing of 1.6" and at an average airmass of 1.6 We found a single point source within the 2.3" Swift-XRT error circle reported by Evans et al. (GCN #18459) at

  RA (J2000.0) = 18:03:56.244    
  Dec. (J2000.0) = -08:18:57.42 
  

  with an uncertainty of 0.2" in each coordinate. Based on the first 4.4 min of total exposures in g'r'i'z' and 4.0 min in JHK, we estimate preliminary magnitudes (all in AB system) of

  g'> 22.1 mag,
  r' = 20.2 +/- 0.1 mag,
  i' = 19.1 +/- 0.1 mag,
  z' =18.4 +/- 0.1 mag,
  J = 17.6 +/- 0.2 mag,
  H = 17.0 +/- 0.1 mag, and
  K = 17.3 +/- 0.2 mag. 
  

  Given magnitudes are calibrated against GROND zeropoints as well as 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=1.38 mag in the direction of the burst (Schlegel et al. 1998).
• GCN Circular #18462
  M. H. Siegel (PSU), B. G. Balzer (PSU) and P. D'Avanzo (INAF-OAB) report on behalf of the Swift/UVOT team:
  The Swift/UVOT began settled observations of the field of GRB 151023A 796 s after the BAT trigger (D'Avanzo et al., GCN Circ. 18450). No optical afterglow consistent with the XRT position (D'Avanzo et al. GCN Circ. 18450) 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           796          946          147         >19.6
  white              796         2140          411         >20.0
  v                 1130         2191          136         >18.5
  b                 1229         2116          117         >19.3
  w1                1354         1374           19         >18.2
  

  The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 1.42 in the direction of the burst (Schlegel et al. 1998).
• GCN Circular #18463
  J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A. Melandri (INAF-OAB), V. D'Elia (ASDC), D.N. Burrows (PSU), T.G.R. Roegiers (PSU), L.M. McCauley (PSU), C. Pagani (U. Leicester) and P. D'Avanzo report on behalf of the Swift-XRT team:
  We have analysed 7.4 ks of XRT data for GRB 151023A (D'Avanzo et al. GCN Circ. 18450), from 756 s to 35.7 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 18459).
  The light curve can be modelled with a power-law decay with a decay index of alpha=1.32 (+0.27, -0.21).
  A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.7 (+1.1, -0.8). The best-fitting absorption column is 2.7 (+1.8, -1.4) x 10^22 cm^-2, in excess of the Galactic value of 4.1 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 4.9 x 10^-11 (2.6 x 10^-10) erg cm^-2 count^-1.
  A summary of the PC-mode spectrum is thus:

  Total column:	     2.7 (+1.8, -1.4) x 10^22 cm^-2
  Galactic foreground: 4.1 x 10^21 cm^-2
  Excess significance: 2.7 sigma
  Photon index:	     2.7 (+1.1, -0.8)
  

  If the light curve continues to decay with a power-law decay index of 1.32, the count rate at T+24 hours will be 2.5 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.2 x 10^-14 (6.4 x 10^-14) erg cm^-2 s^-1.
  The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00661253.
  This circular is an official product of the Swift-XRT team.
• GCN Circular #18464
  Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), Willia= m H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (UCB), J. Xavier Proch= aska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (GSFC/STScI), Eleonora = Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jos=EF=BF= =BD A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes=EF=BF=BDs Gonz=EF=BF=BD= lez (UNAM), Carlos Rom=EF=BF=BDn-Z=EF=BF=BD=EF=BF=BDiga (UNAM), Neil Gehr= els (GSFC), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (AS= U), and Vicki Toy (UMD) report:
  We observed the field of GRB 151023A (D'Avanzo, et al., GCN 18450) with t= he Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on = the 1.5m Harold Johnson Telescope at the Observatorio Astron=EF=BF=BDmico= Nacional on Sierra San Pedro M=EF=BF=BDrtir from 2015/10 24.09 to 2015/1= 0 24.14 UTC (12.35 to 13.66 hours after the BAT trigger), obtaining a tot= al of 1.07 hours exposure in the r, i, and z bands.
  We detect the GROND source (Knust, et al., GCN 18461) at a similar bright= ness level. In comparison with the USNO-B1 catalog, we find:

     r 20.27 +/- 0.04
     i 19.10 +/- 0.02
     z 18.29 +/- 0.09
  

  These magnitudes are in the AB system and are not corrected for Galactic = extinction in the direction of the GRB.
  We note that this source is present in the DSS at a comparable brightness= level and may not, therefore, be the GRB afterglow.
  We thank the staff of the Observatorio Astron=EF=BF=BDmico Nacional in San Pedro M=EF=BF=BDrtir.
• GCN Circular #18469
  C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), P. D'Avanzo (INAF-OAB), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), 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-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 151023A (trigger #661253) (D'Avanzo, et al., GCN Circ. 18450). The BAT ground-calculated position is RA, Dec = 271.012, -8.289 deg which is

    RA(J2000)  =  18h 04m 02.9s
    Dec(J2000) = -08d 17' 19.7"
  

  with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 83%.
  The mask-weighted light curve shows a single-pulse structure that starts at ~ T-1 s, peaks at ~T0, and ends at ~ T+10 s. T90 (15-350 keV) is 10.66 +- 4.41 sec (estimated error including systematics).
  The time-averaged spectrum from T-0.65 to T+12.16 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.24 +- 0.24. The fluence in the 15-150 keV band is 2.6 +- 0.4 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.03 sec in the 15-150 keV band is 1.1 +- 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/661253/BA/