Gamma-ray Burst 120927A

(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:     Thu 27 Sep 12 22:42:04 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     534815,   Seg_Num: 0
GRB_RA:          136.600d {+09h 06m 24s} (J2000),
                 136.764d {+09h 07m 03s} (current),
                 135.958d {+09h 03m 50s} (1950)
GRB_DEC:          +0.417d {+00d 25' 02"} (J2000),
                  +0.366d {+00d 21' 56"} (current),
                  +0.619d {+00d 37' 07"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       0 [cnts]    Image_Peak=4448 [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:        16197 TJD;   271 DOY;   12/09/27
GRB_TIME:        81646.30 SOD {22:40:46.30} UT
GRB_PHI:         -15.13 [deg]
GRB_THETA:        37.19 [deg]
SOLN_STATUS:     0x13
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    18.92 [sigma]
MERIT_PARAMS:     +1  +0  +0  +6  +1  +6  +0  +0 -66  +0 
SUN_POSTN:       184.79d {+12h 19m 09s}   -2.07d {-02d 04' 20"}
SUN_DIST:         48.08 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      339.07d {+22h 36m 16s}   -3.42d {-03d 24' 56"}
MOON_DIST:       157.50 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      229.46, 29.84 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      138.92,-15.46 [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 = 184.41,-18.35 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 27 Sep 12 22:43:30 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     534815,   Seg_Num: 0
POINT_RA:        136.633d {+09h 06m 32s} (J2000)
POINT_DEC:        +0.397d {+00d 23' 50"} (J2000)
IMG_START_DATE:  16197 TJD;   271 DOY;   12/09/27
IMG_START_TIME:  81800.02 SOD {22:43:20.02} UT,   153.7 [sec] since BAT Trigger Time
COUNTS:          12    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        3    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:     Thu 27 Sep 12 22:44:53 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     534815,   Seg_Num: 0
GRB_RA:          136.600d {+09h 06m 24s} (J2000),
                 136.764d {+09h 07m 03s} (current),
                 135.958d {+09h 03m 50s} (1950)
GRB_DEC:          +0.417d {+00d 25' 02"} (J2000),
                  +0.366d {+00d 21' 56"} (current),
                  +0.619d {+00d 37' 07"} (1950)
GRB_DATE:        16197 TJD;   271 DOY;   12/09/27
GRB_TIME:        81646.30 SOD {22:40:46.30} UT
TRIGGER_INDEX:   20000
GRB_PHI:         -15.13 [deg]
GRB_THETA:        37.19 [deg]
DELTA_TIME:      0.00 [sec]
TRIGGER_DUR:     64.000 [sec] 
SOLN_STATUS:     0x13
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    18.92 [sigma]
LC_URL:          sw00534815000msb.lc
SUN_POSTN:       184.79d {+12h 19m 10s}   -2.07d {-02d 04' 23"}
SUN_DIST:         48.08 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      339.09d {+22h 36m 22s}   -3.41d {-03d 24' 24"}
MOON_DIST:       157.48 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      229.46, 29.84 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      138.92,-15.46 [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 = 184.41,-18.35 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 27 Sep 12 22:48:36 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     534815,   Seg_Num: 0
POINT_RA:        136.633d {+09h 06m 32s} (J2000)
POINT_DEC:        +0.397d {+00d 23' 50"} (J2000)
POINT_ROLL:      93.151d
IMG_START_DATE:  16197 TJD;   271 DOY;   12/09/27
IMG_START_TIME:  81804.52 SOD {22:43:24.52} UT,   158.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        7.387
N_STARS:         29
X_OFFSET:        209 [pixels]
Y_OFFSET:        571 [pixels]
X_MAX:           1168 [pixels]
Y_MAX:           1530 [pixels]
DET_THRESH:      23
PHOTO_THRESH:    14
SL_URL:          sw00534815000msufc0158.fits
SUN_POSTN:       184.79d {+12h 19m 10s}   -2.07d {-02d 04' 26"}
SUN_DIST:         48.05 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      339.12d {+22h 36m 30s}   -3.40d {-03d 23' 41"}
MOON_DIST:       157.48 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      229.50, 29.86 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      138.96,-15.47 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 27 Sep 12 22:49:09 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     534815,   Seg_Num: 0
POINT_RA:        136.633d {+09h 06m 32s} (J2000)
POINT_DEC:        +0.397d {+00d 23' 50"} (J2000)
POINT_ROLL:      93.151d
IMG_START_DATE:  16197 TJD;   271 DOY;   12/09/27
IMG_START_TIME:  81804.52 SOD {22:43:24.52} UT,   158.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        7.387
N_STARS:         29
X_OFFSET:        209 [pixels]
Y_OFFSET:        571 [pixels]
X_MAX:           1168 [pixels]
Y_MAX:           1530 [pixels]
DET_THRESH:      23
PHOTO_THRESH:    14
SL_URL:          sw00534815000msufc0158.fits
SUN_POSTN:       184.79d {+12h 19m 10s}   -2.07d {-02d 04' 27"}
SUN_DIST:         48.05 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      339.13d {+22h 36m 31s}   -3.39d {-03d 23' 35"}
MOON_DIST:       157.48 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      229.50, 29.86 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      138.96,-15.47 [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:     Thu 27 Sep 12 22:50:15 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     534815,   Seg_Num: 0
POINT_RA:        136.633d {+09h 06m 32s} (J2000)
POINT_DEC:        +0.397d {+00d 23' 50"} (J2000)
ROLL:            93.151d
IMG_START_DATE:  16197 TJD;   271 DOY;   12/09/27
IMG_START_TIME:  81804.52 SOD {22:43:24.52} UT,   158.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     370478614
X_OFFSET:        528 [pixels]
Y_OFFSET:        890 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       688
Y_GRB_POS:       1050
BINNING_INDEX:   1
IM_URL:          sw00534815000msuni0168.fits
SUN_POSTN:       184.79d {+12h 19m 11s}   -2.07d {-02d 04' 28"}
SUN_DIST:         48.05 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      339.14d {+22h 36m 33s}   -3.39d {-03d 23' 23"}
MOON_DIST:       157.47 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      229.50, 29.86 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      138.96,-15.47 [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:     Thu 27 Sep 12 22:50:32 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     534815,   Seg_Num: 0
POINT_RA:        136.633d {+09h 06m 32s} (J2000)
POINT_DEC:        +0.397d {+00d 23' 50"} (J2000)
ROLL:            93.151d
IMG_START_DATE:  16197 TJD;   271 DOY;   12/09/27
IMG_START_TIME:  81804.52 SOD {22:43:24.52} UT,   158.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     370478614
X_OFFSET:        528 [pixels]
Y_OFFSET:        890 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       688
Y_GRB_POS:       1050
BINNING_INDEX:   1
IM_URL:          sw00534815000msuni0168.fits
SUN_POSTN:       184.79d {+12h 19m 11s}   -2.07d {-02d 04' 28"}
SUN_DIST:         48.05 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      339.14d {+22h 36m 33s}   -3.39d {-03d 23' 19"}
MOON_DIST:       157.47 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      229.50, 29.86 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      138.96,-15.47 [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:     Thu 27 Sep 12 22:56:28 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     534815,   Seg_Num: 0
POINT_RA:        136.633d {+09h 06m 32s} (J2000)
POINT_DEC:        +0.400d {+00d 23' 59"} (J2000)
POINT_ROLL:      93.153d
IMG_START_DATE:  16197 TJD;   271 DOY;   12/09/27
IMG_START_TIME:  81963.16 SOD {22:46:03.16} UT,   316.9 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        2.769
N_STARS:         46
X_OFFSET:        0 [pixels]
Y_OFFSET:        331 [pixels]
X_MAX:           1439 [pixels]
Y_MAX:           1770 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    7
SL_URL:          sw00534815000msufc0316.fits
SUN_POSTN:       184.80d {+12h 19m 12s}   -2.08d {-02d 04' 34"}
SUN_DIST:         48.05 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      339.19d {+22h 36m 45s}   -3.37d {-03d 22' 12"}
MOON_DIST:       157.42 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      229.50, 29.86 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      138.96,-15.47 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 27 Sep 12 22:56:57 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     534815,   Seg_Num: 0
POINT_RA:        136.633d {+09h 06m 32s} (J2000)
POINT_DEC:        +0.400d {+00d 23' 59"} (J2000)
POINT_ROLL:      93.153d
IMG_START_DATE:  16197 TJD;   271 DOY;   12/09/27
IMG_START_TIME:  81963.16 SOD {22:46:03.16} UT,   316.9 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        2.769
N_STARS:         46
X_OFFSET:        0 [pixels]
Y_OFFSET:        331 [pixels]
X_MAX:           1439 [pixels]
Y_MAX:           1770 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    7
SL_URL:          sw00534815000msufc0316.fits
SUN_POSTN:       184.80d {+12h 19m 12s}   -2.08d {-02d 04' 34"}
SUN_DIST:         48.05 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      339.19d {+22h 36m 46s}   -3.37d {-03d 22' 06"}
MOON_DIST:       157.41 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      229.50, 29.86 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      138.96,-15.47 [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:     Thu 27 Sep 12 22:58:01 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     534815,   Seg_Num: 0
POINT_RA:        136.633d {+09h 06m 32s} (J2000)
POINT_DEC:        +0.400d {+00d 23' 59"} (J2000)
ROLL:            93.153d
IMG_START_DATE:  16197 TJD;   271 DOY;   12/09/27
IMG_START_TIME:  81963.16 SOD {22:46:03.16} UT,   316.9 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     370478772
X_OFFSET:        559 [pixels]
Y_OFFSET:        890 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       719
Y_GRB_POS:       1050
BINNING_INDEX:   1
IM_URL:          sw00534815000msuni0326.fits
SUN_POSTN:       184.80d {+12h 19m 12s}   -2.08d {-02d 04' 35"}
SUN_DIST:         48.05 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      339.20d {+22h 36m 48s}   -3.37d {-03d 21' 54"}
MOON_DIST:       157.41 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      229.50, 29.86 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      138.96,-15.47 [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:     Thu 27 Sep 12 22:58:26 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     534815,   Seg_Num: 0
POINT_RA:        136.633d {+09h 06m 32s} (J2000)
POINT_DEC:        +0.400d {+00d 23' 59"} (J2000)
ROLL:            93.153d
IMG_START_DATE:  16197 TJD;   271 DOY;   12/09/27
IMG_START_TIME:  81963.16 SOD {22:46:03.16} UT,   316.9 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     370478772
X_OFFSET:        559 [pixels]
Y_OFFSET:        890 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       719
Y_GRB_POS:       1050
BINNING_INDEX:   1
IM_URL:          sw00534815000msuni0326.fits
SUN_POSTN:       184.80d {+12h 19m 12s}   -2.08d {-02d 04' 36"}
SUN_DIST:         48.05 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      339.21d {+22h 36m 49s}   -3.36d {-03d 21' 49"}
MOON_DIST:       157.40 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      229.50, 29.86 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      138.96,-15.47 [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 #13822
A. Maselli (INAF-IASFPA), W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC), V. D'Elia (ASDC), S. T. Holland (STScI), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), V. Mangano (INAF-IASFPA), C. B. Markwardt (NASA/GSFC) and F. E. Marshall (NASA/GSFC) report on behalf of the Swift Team:
At 22:40:46 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 120927A (trigger=534815). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 136.600, +0.417 which is
```
   RA(J2000) = 09h 06m 24s
   Dec(J2000) = +00d 25' 02"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a broad single-peaked structure with a duration of about 50 sec. The peak count rate was ~1500 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 22:43:20.0 UT, 154 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 136.614125, 0.415722 which is equivalent to:
```
   RA(J2000)  = 09h 06m 27.20s
   Dec(J2000) = +00d 24' 56.6"
```
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This location is 52 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.
UVOT took a finding chart exposure of 150 seconds with the White filter starting 158 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the BAT and XRT error circles. 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 0.04.
Burst Advocate for this burst is A. Maselli (maselli AT ifc.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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 27 Sep 12 23:35:20 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     534815,   Seg_Num: 0
GRB_RA:          136.6141d {+09h 06m 27.38s} (J2000),
                 136.7777d {+09h 07m 06.64s} (current),
                 135.9718d {+09h 03m 53.24s} (1950)
GRB_DEC:          +0.4159d {+00d 24' 57.2"} (J2000),
                  +0.3643d {+00d 21' 51.4"} (current),
                  +0.6172d {+00d 37' 01.7"} (1950)
GRB_ERROR:       2.0 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-09 [erg/cm2/sec]
GRB_SIGNIF:      5.00 [sigma]
IMG_START_DATE:  16197 TJD;   271 DOY;   12/09/27
IMG_START_TIME:  81800.02 SOD {22:43:20.02} UT,   153.7 [sec] since BAT Trigger Time
TAM[0-3]:        327.61 237.19 261.35 242.66
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       184.82d {+12h 19m 17s}   -2.09d {-02d 05' 12"}
SUN_DIST:         48.10 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      339.52d {+22h 38m 04s}   -3.25d {-03d 14' 48"}
MOON_DIST:       157.09 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      229.47, 29.86 [deg] galactic lon,lat of the burst
ECL_COORDS:      138.94,-15.46 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        TAM values are not valid.

GCN Circular #13824
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team.
Using 4566 s of XRT Photon Counting mode data and 10 UVOT images for GRB 120927A, 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 = 136.61376, +0.41620 which is equivalent to:
```
RA (J2000): 09h 06m 27.30s
Dec (J2000): +00d 24' 58.3"
```
with an uncertainty of 1.4 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 #13826
M.C. Stroh (PSU), D.N. Burrows (PSU), P.A. Evans (U. Leicester), O.M. Littlejohns (U. Leicester), J.P. Osborne (U. Leicester), G. Stratta (ASDC), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), J.A. Kennea (PSU) and A. Maselli report on behalf of the Swift-XRT team:
We have analysed 7.9 ks of XRT data for GRB 120927A (Maselli et al. GCN Circ. 13822), from 138 s to 29.1 ks after the BAT trigger. The data comprise 8 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN. Circ 13824).
The light curve can be modelled with an initial power-law decay with an index of alpha=0.94 (+0.04, -0.06), followed by a break at T+11.5 ks to an alpha of 2.6 (+1.7, -0.7).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.75 (+0.18, -0.17). The best-fitting absorption column is 2.8 (+/-0.7) x 10^21 cm^-2, in excess of the Galactic value of 3.2 x 10^20 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.7 x 10^-11 (6.5 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     2.8 (+/-0.7) x 10^21 cm^-2
Galactic foreground: 3.2 x 10^20 cm^-2
Excess significance: 6.2 sigma
Photon index:	     1.75 (+0.18, -0.17)
```
If the light curve continues to decay with a power-law decay index of 2.6, the count rate at T+24 hours will be 2.1 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.8 x 10^-14 (1.3 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/00534815.
This circular is an official product of the Swift-XRT team.
GCN Circular #13827
A. Rossi (TLS Tautenburg), P. Schady and J. Greiner (MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 120927A (Swift trigger 534815; Maselli et al., GCN 13822) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m MPG/ESO telescope at La Silla Observatory (Chile).
Observations started at 09:05 UT on Sep 28, 10.4 hrs after the GRB trigger, as soon the target became visible from La Silla. They were performed at an average seeing of 2.6 arcsec and at an average airmass of 2.3. It was only possible to observe for a total exposure time of 7.2 min in the g'r'i'z' bands during morning twilight, whereas in the JHK bands we were able to observe for a total of 32 min.
Using our full data set, we do not detect any source within the refined XRT error circle (Beardmore et al., GCN 13824) in our stacked GROND images down to the following 3 sigma limiting magnitudes (AB) mags:
```
g' > 22.4
r' > 22.5
i' > 21.9
z' > 21.9
J  > 21.3
H  > 21.0
K  > 19.4
```
The g'r'i'z and JHK bands are calibrated against SDSS and 2MASS, respectively, and the above limits are not corrected for the Galactic foreground reddening of E_(B-V)= 0.04 mag in the direction of the burst (Schlegel et al. 1998).
We note the presence of a source south of the enhanced XRT position, which is already present in DSS2 images.
GCN Circular #13828
GRB 120927A, Swift-BAT refined analysis
D. M. Palmer (LANL), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), A. Maselli (INAF-IASFPA), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (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 120927A (trigger #534815) (Maselli, et al., GCN Circ. 13822). The BAT ground-calculated position is RA, Dec = 136.606, 0.420 deg which is
```
    RA(J2000)  =  09h 06m 25.3s
    Dec(J2000) = +00d 25' 13.5"
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 64%.
The mask-weighted light curve shows multiple overlapping peaks with an overall FRED profile starting about T-15 seconds and significant until about T+32 seconds. T90 (15-350 keV) is 43 +- 18 sec (estimated error including systematics).
The time-averaged spectrum from T-37.94 to T+41.04 sec is best fit by a power lawwith an exponential cutoff. This fit gives a photon index 0.63 +- 0.38, and Epeak of 66.1 +- 9.6 keV (chi squared 50.98 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 2.6 +- 0.3 x 10^-06 erg/cm2 and the 1-sec peak flux measured from T-3.93 sec in the 15-150 keV band is 1.6 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.64 +- 0.08 (chi squared 77.30 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/534815/BA/
GCN Circular #13829
S. Immler (NASA/CRESST/GSFC) and A. Maselli (INAF-IASFPA) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 120927A 158 s after the BAT trigger (Maselli et al., GCN Circ. 13822). No optical afterglow consistent with the enhanced XRT position (Beardmore et al. GCN Circ. 13824) 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) and subsequent exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           158          308          147         >20.3
u_FC               317          567          246         >19.5
white              158         6331          580         >21.0
v                  648         6625          317         >19.1
b                  572         6127          432         >20.1
u                  317         5921          659         >20.2
w1                 697         5717          413         >19.6
m2                 672         5511          225         >19.6
w2                 623         6537          432         >20.3
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.04 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #13842
M. Andreev, A. Sergeev (Terskol Branch of Institute of Astronomy), A. Pozanenko (IKI) on behalf of larger GRB follow up collaboration report:
We observed field of the Swift GRB 120927A (Maselli et al. GCN 13822) with Zeiss-600 telescope of Mt.Terskol observatory starting on Sep. 28 (UT) 01:31:05. Several unfiltered images were taken under favorable weather conditions. We do not detect any sources in the enhanced XRT error circle (Beardmore et al. GCN 13824). Photometry is based on nearby USNO-B1.0 (R2) stars:
```
  T0+,     Filter      Exposure,  OT,     UL (3 sigma)
  mid, d                (s)

0.1292    none      30x60         n/d     22.0 
```
GCN Report 396.1
GCN_Report 396.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_396_1.pdf by A. Maselli at INAF IASFPa titled: "Swift Observations of GRB 120927A"

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Jochen Greiner, last update: 05-Oct-2012 [Disclaimer]