Gamma-ray Burst 131026A

(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:     Sat 26 Oct 13 06:40:47 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     575905,   Seg_Num: 0
GRB_RA:           15.547d {+01h 02m 11s} (J2000),
                  15.737d {+01h 02m 57s} (current),
                  14.860d {+00h 59m 26s} (1950)
GRB_DEC:         +32.487d {+32d 29' 13"} (J2000),
                 +32.561d {+32d 33' 40"} (current),
                 +32.218d {+32d 13' 06"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       0 [cnts]    Image_Peak=1326 [image_cnts]
TRIGGER_DUR:     64.000 [sec] 
TRIGGER_INDEX:   20000     E_range: 15-50 keV
BKG_INTEN:       0 [cnts]
BKG_TIME:        0.00 SOD {00:00:00.00} UT
BKG_DUR:         0 [sec]
GRB_DATE:        16591 TJD;   299 DOY;   13/10/26
GRB_TIME:        23972.80 SOD {06:39:32.80} UT
GRB_PHI:         114.46 [deg]
GRB_THETA:         9.52 [deg]
SOLN_STATUS:     0x13
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    7.06 [sigma]
MERIT_PARAMS:     +1  +0  +0  +6  +1  -3  +0  +0 +91  +0 
SUN_POSTN:       210.80d {+14h 03m 11s}  -12.51d {-12d 30' 51"}
SUN_DIST:        155.67 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:      116.26d {+07h 45m 03s}  +15.98d {+15d 58' 55"}
MOON_DIST:        89.99 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      125.56,-30.33 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       27.39, 23.76 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is an image trigger.  (The RATE_SIGNIF & BKG_{INTEN, TIME, DUR} are undefined.)  
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 = 281.72,6.97 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 26 Oct 13 06:41:44 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     575905,   Seg_Num: 0
POINT_RA:         15.547d {+01h 02m 11s} (J2000)
POINT_DEC:       +32.492d {+32d 29' 30"} (J2000)
IMG_START_DATE:  16591 TJD;   299 DOY;   13/10/26
IMG_START_TIME:  24093.91 SOD {06:41:33.91} UT,   121.1 [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:     Sat 26 Oct 13 06:43:33 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     575905,   Seg_Num: 0
GRB_RA:           15.547d {+01h 02m 11s} (J2000),
                  15.737d {+01h 02m 57s} (current),
                  14.860d {+00h 59m 26s} (1950)
GRB_DEC:         +32.487d {+32d 29' 13"} (J2000),
                 +32.561d {+32d 33' 40"} (current),
                 +32.218d {+32d 13' 06"} (1950)
GRB_DATE:        16591 TJD;   299 DOY;   13/10/26
GRB_TIME:        23972.80 SOD {06:39:32.80} UT
TRIGGER_INDEX:   20000
GRB_PHI:         114.46 [deg]
GRB_THETA:         9.52 [deg]
DELTA_TIME:      0.00 [sec]
TRIGGER_DUR:     64.000 [sec] 
SOLN_STATUS:     0x13
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    7.06 [sigma]
LC_URL:          sw00575905000msb.lc
SUN_POSTN:       210.80d {+14h 03m 12s}  -12.52d {-12d 30' 53"}
SUN_DIST:        155.66 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:      116.29d {+07h 45m 09s}  +15.98d {+15d 58' 39"}
MOON_DIST:        90.01 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      125.56,-30.33 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       27.39, 23.76 [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 an image 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 = 281.72,6.97 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 26 Oct 13 06:44:32 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     575905,   Seg_Num: 0
POINT_RA:         15.547d {+01h 02m 11s} (J2000)
POINT_DEC:       +32.492d {+32d 29' 30"} (J2000)
POINT_ROLL:      321.519d
IMG_START_DATE:  16591 TJD;   299 DOY;   13/10/26
IMG_START_TIME:  24100.10 SOD {06:41:40.10} UT,   127.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.148
N_STARS:         103
X_OFFSET:        429 [pixels]
Y_OFFSET:        553 [pixels]
X_MAX:           1388 [pixels]
Y_MAX:           1512 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00575905000msufc0127.fits
SUN_POSTN:       210.80d {+14h 03m 12s}  -12.52d {-12d 30' 54"}
SUN_DIST:        155.66 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:      116.29d {+07h 45m 11s}  +15.98d {+15d 58' 34"}
MOON_DIST:        90.02 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      125.56,-30.33 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       27.39, 23.76 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 26 Oct 13 06:44:49 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     575905,   Seg_Num: 0
POINT_RA:         15.547d {+01h 02m 11s} (J2000)
POINT_DEC:       +32.492d {+32d 29' 30"} (J2000)
POINT_ROLL:      321.519d
IMG_START_DATE:  16591 TJD;   299 DOY;   13/10/26
IMG_START_TIME:  24100.10 SOD {06:41:40.10} UT,   127.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.148
N_STARS:         103
X_OFFSET:        429 [pixels]
Y_OFFSET:        553 [pixels]
X_MAX:           1388 [pixels]
Y_MAX:           1512 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00575905000msufc0127.fits
SUN_POSTN:       210.80d {+14h 03m 12s}  -12.52d {-12d 30' 54"}
SUN_DIST:        155.66 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:      116.30d {+07h 45m 11s}  +15.98d {+15d 58' 32"}
MOON_DIST:        90.02 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      125.56,-30.33 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       27.39, 23.76 [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:     Sat 26 Oct 13 06:45:59 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     575905,   Seg_Num: 0
POINT_RA:         15.547d {+01h 02m 11s} (J2000)
POINT_DEC:       +32.492d {+32d 29' 30"} (J2000)
ROLL:            321.519d
IMG_START_DATE:  16591 TJD;   299 DOY;   13/10/26
IMG_START_TIME:  24100.10 SOD {06:41:40.10} UT,   127.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     404462511
X_OFFSET:        748 [pixels]
Y_OFFSET:        872 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       908
Y_GRB_POS:       1032
BINNING_INDEX:   1
IM_URL:          sw00575905000msuni0139.fits
SUN_POSTN:       210.80d {+14h 03m 12s}  -12.52d {-12d 30' 55"}
SUN_DIST:        155.66 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:      116.31d {+07h 45m 14s}  +15.97d {+15d 58' 25"}
MOON_DIST:        90.03 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      125.56,-30.33 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       27.39, 23.76 [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:     Sat 26 Oct 13 06:46:21 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     575905,   Seg_Num: 0
POINT_RA:         15.547d {+01h 02m 11s} (J2000)
POINT_DEC:       +32.492d {+32d 29' 30"} (J2000)
ROLL:            321.519d
IMG_START_DATE:  16591 TJD;   299 DOY;   13/10/26
IMG_START_TIME:  24100.10 SOD {06:41:40.10} UT,   127.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     404462511
X_OFFSET:        748 [pixels]
Y_OFFSET:        872 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       908
Y_GRB_POS:       1032
BINNING_INDEX:   1
IM_URL:          sw00575905000msuni0139.fits
SUN_POSTN:       210.80d {+14h 03m 12s}  -12.52d {-12d 30' 55"}
SUN_DIST:        155.66 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:      116.31d {+07h 45m 14s}  +15.97d {+15d 58' 23"}
MOON_DIST:        90.03 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      125.56,-30.33 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       27.39, 23.76 [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:     Sat 26 Oct 13 06:50:55 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     575905,   Seg_Num: 0
POINT_RA:         15.546d {+01h 02m 11s} (J2000)
POINT_DEC:       +32.493d {+32d 29' 36"} (J2000)
POINT_ROLL:      321.516d
IMG_START_DATE:  16591 TJD;   299 DOY;   13/10/26
IMG_START_TIME:  24258.26 SOD {06:44:18.26} UT,   285.5 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.657
N_STARS:         161
X_OFFSET:        189 [pixels]
Y_OFFSET:        313 [pixels]
X_MAX:           1628 [pixels]
Y_MAX:           1752 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw00575905000msufc0285.fits
SUN_POSTN:       210.80d {+14h 03m 13s}  -12.52d {-12d 31' 00"}
SUN_DIST:        155.66 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:      116.35d {+07h 45m 23s}  +15.97d {+15d 57' 57"}
MOON_DIST:        90.07 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      125.56,-30.32 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       27.39, 23.76 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 26 Oct 13 06:51:11 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     575905,   Seg_Num: 0
POINT_RA:         15.546d {+01h 02m 11s} (J2000)
POINT_DEC:       +32.493d {+32d 29' 36"} (J2000)
POINT_ROLL:      321.516d
IMG_START_DATE:  16591 TJD;   299 DOY;   13/10/26
IMG_START_TIME:  24258.26 SOD {06:44:18.26} UT,   285.5 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.657
N_STARS:         161
X_OFFSET:        189 [pixels]
Y_OFFSET:        313 [pixels]
X_MAX:           1628 [pixels]
Y_MAX:           1752 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw00575905000msufc0285.fits
SUN_POSTN:       210.80d {+14h 03m 13s}  -12.52d {-12d 31' 00"}
SUN_DIST:        155.66 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:      116.35d {+07h 45m 24s}  +15.97d {+15d 57' 55"}
MOON_DIST:        90.07 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      125.56,-30.32 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       27.39, 23.76 [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:     Sat 26 Oct 13 06:52:24 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     575905,   Seg_Num: 0
POINT_RA:         15.546d {+01h 02m 11s} (J2000)
POINT_DEC:       +32.493d {+32d 29' 36"} (J2000)
ROLL:            321.516d
IMG_START_DATE:  16591 TJD;   299 DOY;   13/10/26
IMG_START_TIME:  24258.26 SOD {06:44:18.26} UT,   285.5 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     404462669
X_OFFSET:        748 [pixels]
Y_OFFSET:        872 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       908
Y_GRB_POS:       1032
BINNING_INDEX:   1
IM_URL:          sw00575905000msuni0297.fits
SUN_POSTN:       210.80d {+14h 03m 13s}  -12.52d {-12d 31' 01"}
SUN_DIST:        155.66 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:      116.36d {+07h 45m 26s}  +15.96d {+15d 57' 48"}
MOON_DIST:        90.08 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      125.56,-30.32 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       27.39, 23.76 [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:     Sat 26 Oct 13 06:52:43 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     575905,   Seg_Num: 0
POINT_RA:         15.546d {+01h 02m 11s} (J2000)
POINT_DEC:       +32.493d {+32d 29' 36"} (J2000)
ROLL:            321.516d
IMG_START_DATE:  16591 TJD;   299 DOY;   13/10/26
IMG_START_TIME:  24258.26 SOD {06:44:18.26} UT,   285.5 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     404462669
X_OFFSET:        748 [pixels]
Y_OFFSET:        872 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       908
Y_GRB_POS:       1032
BINNING_INDEX:   1
IM_URL:          sw00575905000msuni0297.fits
SUN_POSTN:       210.81d {+14h 03m 13s}  -12.52d {-12d 31' 01"}
SUN_DIST:        155.66 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:      116.36d {+07h 45m 27s}  +15.96d {+15d 57' 46"}
MOON_DIST:        90.08 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      125.56,-30.32 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       27.39, 23.76 [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:     Sat 26 Oct 13 06:56:40 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     575905,   Seg_Num: 0
POINT_RA:         15.546d {+01h 02m 11s} (J2000)
POINT_DEC:       +32.493d {+32d 29' 36"} (J2000)
ROLL:            321.516d
IMG_START_DATE:  16591 TJD;   299 DOY;   13/10/26
IMG_START_TIME:  24835.62 SOD {06:53:55.62} UT,   862.8 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     404463246
X_OFFSET:        748 [pixels]
Y_OFFSET:        872 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       908
Y_GRB_POS:       1032
BINNING_INDEX:   1
IM_URL:          sw00575905000msuni0874.fits
SUN_POSTN:       210.81d {+14h 03m 14s}  -12.52d {-12d 31' 04"}
SUN_DIST:        155.66 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:      116.40d {+07h 45m 35s}  +15.96d {+15d 57' 23"}
MOON_DIST:        90.11 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      125.56,-30.32 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       27.39, 23.76 [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:     Sat 26 Oct 13 06:56:54 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     575905,   Seg_Num: 0
POINT_RA:         15.546d {+01h 02m 11s} (J2000)
POINT_DEC:       +32.493d {+32d 29' 36"} (J2000)
ROLL:            321.516d
IMG_START_DATE:  16591 TJD;   299 DOY;   13/10/26
IMG_START_TIME:  24835.62 SOD {06:53:55.62} UT,   862.8 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     404463246
X_OFFSET:        748 [pixels]
Y_OFFSET:        872 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       908
Y_GRB_POS:       1032
BINNING_INDEX:   1
IM_URL:          sw00575905000msuni0874.fits
SUN_POSTN:       210.81d {+14h 03m 14s}  -12.52d {-12d 31' 04"}
SUN_DIST:        155.66 [deg]   Sun_angle= -11.0 [hr] (East of Sun)
MOON_POSTN:      116.40d {+07h 45m 36s}  +15.96d {+15d 57' 22"}
MOON_DIST:        90.11 [deg]
MOON_ILLUM:      57 [%]
GAL_COORDS:      125.56,-30.32 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       27.39, 23.76 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.

GCN Circular #15384
S. B. Cenko (GSFC), S. T. Holland (STScI), L. Izzo (URoma/ICRA), K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/PSU) and M. H. Siegel (PSU) report on behalf of the Swift Team:
At 06:39:32 UT, the Swift Burst Alert Telescope (BAT) and located a possible GRB in an image trigger (trigger=575905). Swift slewed immediately to the location. The BAT on-board calculated location is RA, Dec 15.547, +32.487 which is
```
   RA(J2000) = 01h 02m 11s
   Dec(J2000) = +32d 29' 13"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). As is usual for an image trigger, there is no obvious variation in the BAT lightcurve.
The XRT began observing the field at 06:41:33.9 UT, 121.1 seconds after the BAT trigger. No source was detected in the 2.5-s promptly available image. We are waiting for the full dataset to detect and localise the XRT counterpart.
UVOT took a finding chart exposure of 150 seconds with the White filter starting 127 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 25% of the BAT 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 BAT 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 0.07.
Because the BAT image peak is of marginal significance (7.06 sigma) and because there is only 2.5 seconds of XRT data immediately available, which does not show a counterpart, we cannot yet confirm or deny the reality of this possible GRB. A final determination of the nature of this trigger will require the full set of downlinked data.
Burst Advocate for this burst is S. B. Cenko (brad.cenko 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 Circular #15385
Klotz A., Turpin D. (IRAP-CNRS-OMP), Gendre B., Boer M., Siellez K., Dereli H., Bardho O. (UNS-CNRS-OCA), Atteia J.L. (IRAP-CNRS-OMP) report:
We imaged the field of GRB 131026A detected by SWIFT (trigger 575905) with the TAROT robotic telescope (D=25cm) located at the European Southern Observatory, La Silla observatory, Chile.
The observations started 86.9s after the GRB trigger (13.7s after the notice). The elevation of the field decreased from 12 degrees above horizon and weather conditions were good.
The first image is trailed with a duration of 60.0s (see the description in Klotz et al., 2006, A&A 451, L39). We do not detect any OT with a limiting magnitude of: t0+86.9s to t0+146.9s : Rlim = 16.8
The second image is 30.0s exposure in tracking mode: t0+160.5s to t0+190.5s : Rlim = 17.4
We co-added a series of exposures: t0+160.5s to t0+451.9s : Rlim = 18.9
Magnitudes were estimated with the nearby NOMAD1 stars and are not corrected for galactic dust extinction.
N.B. Galactic coordinates are lon=125.5580 lat=-30.3300 and the galactic extinction in R band is about 0.2 magnitude estimated from D. Schlegel et al. 1998ApJ...500..525S.
GCN Circular #15386
WeiKang Zheng, Alexei V. Filippenko, Adam Morgan (UC Berkeley), and S. B. Cenko (NASA/Goddard Space Flight Center) report on behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, responded to Swift Trigger 575905 (Cenko et al., GCN 15384) starting at 06:42:00 UT, 148 s after the burst. Observations were performed with an automatic sequence in the V, I, and clear(roughly R) filters, and the exposure time was 20 s per image. Comparing to the SDSS image, we do not detect new sources within BAT error circle. Typical limiting magnitudes of our single clear image is about 18.7.
GCN Circular #15387
F. V. Ferrante, G. Dhungana, and R. Kehoe (SMU) report on behalf of the ROTSE GRB team:
The 0.45-m ROTSE-IIIb, located at McDonald Observatory, Texas, responded to Swift trigger 575905 (Cenko et al., GCN 15384), producing images beginning 7.7 s after the GCN notice time. An automated response took the first image at 06:40:53.8 UT, 81.0 s after the burst, under fair conditions. We took 10 5-sec, 10 20-sec and 60 60-sec exposures. These unfiltered images are calibrated relative to USNO A2.0. Imaging is on going.
GCN Circular #15388
FROM: Valerio D'Elia at ASDC
L. Izzo (URoma/ICRA), V. D'Elia (ASDC), P. D'Avanzo, A. Melandri =20 (INAF-OAB), A. Maselli (INAF-IASFPA) report:
We have analysed 8.93 ks of XRT data for Swift Trigger 575905 (Cenko =20 et al. GCN Circ. 15384). Two sources were detected at SNR>4, inside a =20 region of 3 arcmin from the BAT position at the following coordinates:
```
Source 1 - (1RXS J010222.4+323020)
RA,Dec =3D 01h 02m 22.8s, +32=B0 30' 02.7"

Source 2
RA,Dec =3D 01h 02m 02.6s, +32=B0 30' 00.9",
```
with an uncertainty of 4.1" and 4.6", respectively.
Source 1 matches a catalogued X-ray source (1RXS J010222.4+323020 of =20 the ROSAT/RASSFSC table is 18" away), while source 2 is an =20 uncatalogued source, but below the RASS limit.
We can not say at the present time whether source 2 is fading. The =20 count rate at the position of Source 2 is (4.3 +/- 1.0) x 10^-3 cts/s. =20 This corresponds to an observed 0.3-10 keV flux of 1.54 x 10^-13 =20 erg/cm2/s (assuming a typical GRB spectrum with photon spectral index =20 of 2). If we consider the Galactic absorption in this direction (5.1 x =20 10^20 cm^-2; Kalberla et al. 2005) this corresponds to an unabsorbed =20 flux of 1.78 x 10^-13 erg/cm2/s.
The results of the XRT-team automatic analysis are available at: http://www.swift.ac.uk/possible_GRBs/00575905
This circular is an official product of the Swift-XRT team.
GCN Circular #15389
D. Kuroda, (OAO, NAOJ), H. Hanayama (IAO, NAOJ), K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ), T. Miyaji J. Watanabe, (IAO, NAOJ), S.Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto) and N. Kawai(Tokyo Tech) report on behalf of the MITSuME collaboration:
We observed the field of GRB 1301026A (Swift Trigger 575905) (Cenko et al., GCNC 15384) with the optical three color (g', Rc and Ic) CCD camera attached to the MITSuME 50cm telescope of Okayama Astrophysical Observatory and the Murikabushi 1m telescope of Ishigakijima Astronomical Observatory.
We did not find any new point source within the BAT error circle (Cenko et al., GCNC 15384) in all the three bands.
Three sigma upper limits of the OT are listed below. We used GSC2.3 catalog for flux calibration.
Okayama Astrophysical Observatory: The observation started on 2013-10-26 10:01:09 UT (~3.4 h after the burst).
```
T0+[day]   MID-UT   T-EXP[sec]    g'     Rc     Ic
------------------------------------------------------
0.24326    12:29:49    6300.0    >19.7  >19.6  >18.6
------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]
```
Ishigakijima Astronomical Observatory: The observation started on 2013-10-26 13:13:44 UT (~6.6 h after the burst).
```
T0+[day]   MID-UT   T-EXP[sec]    g'     Rc     Ic
------------------------------------------------------
0.30110    13:53:07    3360.0    >21.6  >21.0  >20.4
------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]
```
GCN Circular #15394
J. R. Cummings and Valerio D'Elia on behalf of the Swift science team
Swift-BAT trigger 575905 (Cenko et al., GCN 15384) is probably due to a fluctuation in the image domain, not to any astrophysical source. While the BAT significance level (7.0 sigma) usually is high enough to indicate a real source, in this case the peak in the image is not robust with respect to very slight changes in parameters.
The total XRT exposure for this field is 15ks. The source number 2 reported in Izzo et al. (GCN 15388), that was uncatalogued but below the RASS limit, has a bright star as optical counterpart. We thus conclude that source 2 is not related to the BAT emission, and that the slight variability observed for this object in the X-ray band is due to normal stellar activity.
GCN Circular #15394
A. Volnova (IKI), R. Inasaridze (AAO), G. Inasaridze (AAO), V. Zhuzhunadze (AAO), Yu. Krugly (IA KhNU), I. Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of Swift Trigger 575905/GRB 131026A (Cenko et al., GCN 15384) with AS-32 telescope of Abastumani Observatory starting Oct., 26 (UT) 21:06:35. We obtained several unfiltered images with exposures of 180 s. We investigated stacked image and found that both XRT sources (Izzo et al., GCN 15388) coincide with known optical sources, i.e.
```
source 1 (XRT) = SDSS J010222.74+323005.0 (01:02:22.75 +32:30:05.0)
source 2 (XRT) = TYC 2281-1221-1 (01 02 02.468 +32 30 01.53)
```
Within BAT error circle (Cenko et al., GCN 15384) we found a point-like source which is not presented in SDSS catalog. Coordinates of the source are (J2000) RA= 01 02 14.64, Dec = +32 30 35.7 with uncertainties of 0.2 arcsec in both coordinates. The details of the photometry of the source are the following:
```
UT start    t-T0       Filter Exp.     OT              UL (3 sigma)
            (mid, days)         (s)

21:06:35   0.64270     None   32x180   21.67 +/- 0.08  22.6
```
The photometry is based SDSS stars, R (gri -> R transformations by Lupton 2005):
```
SDSS id                   R(Lupton)
J010212.32+323137.9       18.988
J010208.62+323107.7       17.448
J010155.76+322851.8       17.317
```
We subdivide total number of images in two combined images and compare astrometry and photometry of the two combined images. One can conclude that the upper limit of a proper motion of the source is 3 arcsec per 50 minutes, and one can marginally suggest that brightness of the source is increased at ~0.3m between the two combined images.
Finding chart can be found in http://grb.rssi.ru/GRB131026A_Swift_575905/GRB131026A_chart2.png
Additional observations in optic and X-ray are encouraged.

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Jochen Greiner, last update: 28-Oct-2013 [Disclaimer]