Gamma-ray Burst 080913

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 13 Sep 08 06:47:15 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     324561,   Seg_Num: 0
GRB_RA:           65.725d {+04h 22m 54s} (J2000),
                  65.815d {+04h 23m 16s} (current),
                  65.203d {+04h 20m 49s} (1950)
GRB_DEC:         -25.110d {-25d 06' 36"} (J2000),
                 -25.090d {-25d 05' 24"} (current),
                 -25.226d {-25d 13' 32"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4881 [cnts]    Image_Peak=200 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   150     E_range: 25-100 keV
BKG_INTEN:       31519 [cnts]
BKG_TIME:        24396.90 SOD {06:46:36.90} UT
BKG_DUR:         8 [sec]
GRB_DATE:        14722 TJD;   257 DOY;   08/09/13
GRB_TIME:        24414.12 SOD {06:46:54.12} UT
GRB_PHI:         -168.25 [deg]
GRB_THETA:        46.32 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     13.92 [sigma]
IMAGE_SIGNIF:    9.39 [sigma]
MERIT_PARAMS:     +1  +0  +0  +1  +2  +4  +0  +0 +27  +1 
SUN_POSTN:       171.59d {+11h 26m 23s}   +3.63d {+03d 37' 32"}
SUN_DIST:        105.82 [deg]   Sun_angle= 7.1 [hr] (West of Sun)
MOON_POSTN:      327.05d {+21h 48m 13s}  -12.72d {-12d 43' 16"}
MOON_DIST:        92.36 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      223.02,-42.84 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       57.68,-45.86 [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 = 300.99,20.48 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 13 Sep 08 06:48:41 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     324561,   Seg_Num: 0
POINT_RA:         65.725d {+04h 22m 54s} (J2000)
POINT_DEC:       -25.121d {-25d 07' 13"} (J2000)
IMG_START_DATE:  14722 TJD;   257 DOY;   08/09/13
IMG_START_TIME:  24513.61 SOD {06:48:33.61} UT,   99.5 [sec] since BAT Trigger Time
COUNTS:          29    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        4    Max_iter_allowed= 4
ERROR_CODE:      2
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        Algorithm did not converge; too many interations.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 13 Sep 08 06:50:39 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     324561,   Seg_Num: 0
GRB_RA:           65.725d {+04h 22m 54s} (J2000),
                  65.815d {+04h 23m 16s} (current),
                  65.203d {+04h 20m 49s} (1950)
GRB_DEC:         -25.110d {-25d 06' 36"} (J2000),
                 -25.090d {-25d 05' 24"} (current),
                 -25.226d {-25d 13' 32"} (1950)
GRB_DATE:        14722 TJD;   257 DOY;   08/09/13
GRB_TIME:        24414.12 SOD {06:46:54.12} UT
TRIGGER_INDEX:   150
GRB_PHI:         -168.25 [deg]
GRB_THETA:        46.32 [deg]
DELTA_TIME:      38.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     13.92 [sigma]
IMAGE_SIGNIF:    9.39 [sigma]
LC_URL:          sw00324561000msb.lc
SUN_POSTN:       171.60d {+11h 26m 23s}   +3.62d {+03d 37' 29"}
SUN_DIST:        105.82 [deg]   Sun_angle= 7.1 [hr] (West of Sun)
MOON_POSTN:      327.08d {+21h 48m 20s}  -12.71d {-12d 42' 30"}
MOON_DIST:        92.34 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      223.02,-42.84 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       57.68,-45.86 [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 = 300.99,20.48 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 13 Sep 08 06:50:53 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     324561,   Seg_Num: 0
POINT_RA:         65.724d {+04h 22m 54s} (J2000)
POINT_DEC:       -25.121d {-25d 07' 13"} (J2000)
POINT_ROLL:      93.459d
IMG_START_DATE:  14722 TJD;   257 DOY;   08/09/13
IMG_START_TIME:  24519.02 SOD {06:48:39.02} UT,   104.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.263
N_STARS:         61
X_OFFSET:        439 [pixels]
Y_OFFSET:        470 [pixels]
X_MAX:           1398 [pixels]
Y_MAX:           1429 [pixels]
DET_THRESH:      9
PHOTO_THRESH:    4
SL_URL:          sw00324561000msufc0104.fits
SUN_POSTN:       171.60d {+11h 26m 23s}   +3.62d {+03d 37' 29"}
SUN_DIST:        105.82 [deg]   Sun_angle= 7.1 [hr] (West of Sun)
MOON_POSTN:      327.08d {+21h 48m 20s}  -12.71d {-12d 42' 27"}
MOON_DIST:        92.34 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      223.03,-42.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       57.68,-45.87 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 13 Sep 08 06:51:24 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     324561,   Seg_Num: 0
POINT_RA:         65.724d {+04h 22m 54s} (J2000)
POINT_DEC:       -25.121d {-25d 07' 13"} (J2000)
POINT_ROLL:      93.459d
IMG_START_DATE:  14722 TJD;   257 DOY;   08/09/13
IMG_START_TIME:  24519.02 SOD {06:48:39.02} UT,   104.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.263
N_STARS:         61
X_OFFSET:        439 [pixels]
Y_OFFSET:        470 [pixels]
X_MAX:           1398 [pixels]
Y_MAX:           1429 [pixels]
DET_THRESH:      9
PHOTO_THRESH:    4
SL_URL:          sw00324561000msufc0104.fits
SUN_POSTN:       171.60d {+11h 26m 23s}   +3.62d {+03d 37' 28"}
SUN_DIST:        105.82 [deg]   Sun_angle= 7.1 [hr] (West of Sun)
MOON_POSTN:      327.09d {+21h 48m 21s}  -12.71d {-12d 42' 20"}
MOON_DIST:        92.33 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      223.03,-42.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       57.68,-45.87 [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 13 Sep 08 06:52:45 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     324561,   Seg_Num: 0
POINT_RA:         65.724d {+04h 22m 54s} (J2000)
POINT_DEC:       -25.121d {-25d 07' 13"} (J2000)
ROLL:            93.459d
IMG_START_DATE:  14722 TJD;   257 DOY;   08/09/13
IMG_START_TIME:  24519.02 SOD {06:48:39.02} UT,   104.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     242981322
X_OFFSET:        758 [pixels]
Y_OFFSET:        789 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       918
Y_GRB_POS:       949
BINNING_INDEX:   1
IM_URL:          sw00324561000msuni0104.fits
SUN_POSTN:       171.60d {+11h 26m 23s}   +3.62d {+03d 37' 27"}
SUN_DIST:        105.82 [deg]   Sun_angle= 7.1 [hr] (West of Sun)
MOON_POSTN:      327.10d {+21h 48m 24s}  -12.70d {-12d 42' 01"}
MOON_DIST:        92.33 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      223.03,-42.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       57.68,-45.87 [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 13 Sep 08 06:53:11 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     324561,   Seg_Num: 0
POINT_RA:         65.724d {+04h 22m 54s} (J2000)
POINT_DEC:       -25.121d {-25d 07' 13"} (J2000)
ROLL:            93.459d
IMG_START_DATE:  14722 TJD;   257 DOY;   08/09/13
IMG_START_TIME:  24519.02 SOD {06:48:39.02} UT,   104.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     242981322
X_OFFSET:        758 [pixels]
Y_OFFSET:        789 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       918
Y_GRB_POS:       949
BINNING_INDEX:   1
IM_URL:          sw00324561000msuni0104.fits
SUN_POSTN:       171.60d {+11h 26m 24s}   +3.62d {+03d 37' 27"}
SUN_DIST:        105.82 [deg]   Sun_angle= 7.1 [hr] (West of Sun)
MOON_POSTN:      327.10d {+21h 48m 25s}  -12.70d {-12d 41' 56"}
MOON_DIST:        92.32 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      223.03,-42.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       57.68,-45.87 [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_sources_image.fits.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 13 Sep 08 07:00:00 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     324561,   Seg_Num: 0
POINT_RA:         65.723d {+04h 22m 53s} (J2000)
POINT_DEC:       -25.123d {-25d 07' 21"} (J2000)
POINT_ROLL:      93.462d
IMG_START_DATE:  14722 TJD;   257 DOY;   08/09/13
IMG_START_TIME:  24624.89 SOD {06:50:24.89} UT,   210.8 [sec] since BAT Trigger Time
FILTER:          3, V
BKG_MEAN:        1.281
N_STARS:         78
X_OFFSET:        439 [pixels]
Y_OFFSET:        470 [pixels]
X_MAX:           1398 [pixels]
Y_MAX:           1429 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00324561000msufc0210.fits
SUN_POSTN:       171.60d {+11h 26m 25s}   +3.62d {+03d 37' 20"}
SUN_DIST:        105.83 [deg]   Sun_angle= 7.1 [hr] (West of Sun)
MOON_POSTN:      327.16d {+21h 48m 39s}  -12.67d {-12d 40' 23"}
MOON_DIST:        92.28 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      223.04,-42.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       57.68,-45.88 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 13 Sep 08 07:00:26 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     324561,   Seg_Num: 0
POINT_RA:         65.723d {+04h 22m 53s} (J2000)
POINT_DEC:       -25.123d {-25d 07' 21"} (J2000)
POINT_ROLL:      93.462d
IMG_START_DATE:  14722 TJD;   257 DOY;   08/09/13
IMG_START_TIME:  24624.89 SOD {06:50:24.89} UT,   210.8 [sec] since BAT Trigger Time
FILTER:          3, V
BKG_MEAN:        1.281
N_STARS:         78
X_OFFSET:        439 [pixels]
Y_OFFSET:        470 [pixels]
X_MAX:           1398 [pixels]
Y_MAX:           1429 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00324561000msufc0210.fits
SUN_POSTN:       171.60d {+11h 26m 25s}   +3.62d {+03d 37' 20"}
SUN_DIST:        105.83 [deg]   Sun_angle= 7.1 [hr] (West of Sun)
MOON_POSTN:      327.16d {+21h 48m 40s}  -12.67d {-12d 40' 17"}
MOON_DIST:        92.28 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      223.04,-42.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       57.68,-45.88 [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 13 Sep 08 07:00:56 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     324561,   Seg_Num: 0
GRB_RA:           65.7279d {+04h 22m 54.6s} (J2000),
                  65.8187d {+04h 23m 16.4s} (current),
                  65.2065d {+04h 20m 49.5s} (1950)
GRB_DEC:         -25.1294d {-25d 07' 45.8"} (J2000),
                 -25.1095d {-25d 06' 34.2"} (current),
                 -25.2450d {-25d 14' 41.9"} (1950)
GRB_ERROR:       2.2 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  14722 TJD;   257 DOY;   08/09/13
IMG_START_TIME:  24524.00 SOD {06:48:44.00} UT,   109.9 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       171.60d {+11h 26m 25s}   +3.62d {+03d 37' 19"}
SUN_DIST:        105.82 [deg]   Sun_angle= 7.1 [hr] (West of Sun)
MOON_POSTN:      327.17d {+21h 48m 41s}  -12.67d {-12d 40' 11"}
MOON_DIST:        92.28 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      223.05,-42.85 [deg] galactic lon,lat of the burst
ECL_COORDS:       57.68,-45.88 [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

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 13 Sep 08 07:01:21 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     324561,   Seg_Num: 0
POINT_RA:         65.723d {+04h 22m 53s} (J2000)
POINT_DEC:       -25.123d {-25d 07' 21"} (J2000)
ROLL:            93.462d
IMG_START_DATE:  14722 TJD;   257 DOY;   08/09/13
IMG_START_TIME:  24624.89 SOD {06:50:24.89} UT,   210.8 [sec] since BAT Trigger Time
FILTER:          3, V
EXPOSURE_ID:     242981427
X_OFFSET:        758 [pixels]
Y_OFFSET:        789 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       918
Y_GRB_POS:       949
BINNING_INDEX:   1
IM_URL:          sw00324561000msuni0210.fits
SUN_POSTN:       171.60d {+11h 26m 25s}   +3.62d {+03d 37' 19"}
SUN_DIST:        105.83 [deg]   Sun_angle= 7.1 [hr] (West of Sun)
MOON_POSTN:      327.17d {+21h 48m 41s}  -12.67d {-12d 40' 05"}
MOON_DIST:        92.28 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      223.04,-42.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       57.68,-45.88 [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 13 Sep 08 07:01:49 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     324561,   Seg_Num: 0
POINT_RA:         65.723d {+04h 22m 53s} (J2000)
POINT_DEC:       -25.123d {-25d 07' 21"} (J2000)
ROLL:            93.462d
IMG_START_DATE:  14722 TJD;   257 DOY;   08/09/13
IMG_START_TIME:  24624.89 SOD {06:50:24.89} UT,   210.8 [sec] since BAT Trigger Time
FILTER:          3, V
EXPOSURE_ID:     242981427
X_OFFSET:        758 [pixels]
Y_OFFSET:        789 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       918
Y_GRB_POS:       949
BINNING_INDEX:   1
IM_URL:          sw00324561000msuni0210.fits
SUN_POSTN:       171.60d {+11h 26m 25s}   +3.62d {+03d 37' 18"}
SUN_DIST:        105.83 [deg]   Sun_angle= 7.1 [hr] (West of Sun)
MOON_POSTN:      327.18d {+21h 48m 42s}  -12.67d {-12d 39' 59"}
MOON_DIST:        92.27 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      223.04,-42.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       57.68,-45.88 [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_sources_image.fits.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 13 Sep 08 07:04:18 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     324561,   Seg_Num: 0
POINT_RA:         65.723d {+04h 22m 53s} (J2000)
POINT_DEC:       -25.123d {-25d 07' 21"} (J2000)
POINT_ROLL:      93.462d
IMG_START_DATE:  14722 TJD;   257 DOY;   08/09/13
IMG_START_TIME:  25273.98 SOD {07:01:13.98} UT,   859.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.507
N_STARS:         75
X_OFFSET:        439 [pixels]
Y_OFFSET:        470 [pixels]
X_MAX:           1398 [pixels]
Y_MAX:           1429 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00324561000msufc0859.fits
SUN_POSTN:       171.60d {+11h 26m 25s}   +3.62d {+03d 37' 16"}
SUN_DIST:        105.83 [deg]   Sun_angle= 7.1 [hr] (West of Sun)
MOON_POSTN:      327.20d {+21h 48m 47s}  -12.66d {-12d 39' 25"}
MOON_DIST:        92.26 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      223.04,-42.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       57.68,-45.88 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN Circular #8217
P. Schady (MSSL-UCL), A. P. Beardmore (U Leicester), J. R. Cummings (NASA/UMBC), P. A. Evans (U Leicester), O. Godet (U Leicester), C. Gronwall (PSU), C. B. Markwardt (CRESST/GSFC/UMD), K. L. Page (U Leicester), D. M. Palmer (LANL), A. M. Parsons (GSFC), D. Perez (U Leicester), R. L. C. Starling (U Leicester) and E. Troja (INAF-IASFPA) report on behalf of the Swift Team:
At 06:46:54 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 080913 (trigger=324561). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 65.725, -25.110 which is
```
   RA(J2000) = 04h 22m 54s
   Dec(J2000) = -25d 06' 36"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a double-peaked structure with a duration of about 10 sec. The peak count rate was ~800 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 06:48:33.6 UT, 99.5 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 65.72800, -25.12945 which is equivalent to:
```
   RA(J2000)  = 04h 22m 54.72s
   Dec(J2000) = -25d 07' 46.0"
```
with an uncertainty of 2.4 arcseconds (radius, 90% containment). This location is 70 arcseconds from the BAT onboard position, within the BAT error circle.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 3.17e+20 cm^-2 (Kalberla et al. 2005).
UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 105 seconds after the BAT trigger. No afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 25% of the BAT error circle and 100% of the XRT error circle. The 3-sigma upper limit at the XRT position is 20.7 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 0.04.
Burst Advocate for this burst is P. Schady (ps AT mssl.ucl.ac.uk). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 13 Sep 08 07:04:45 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     324561,   Seg_Num: 0
POINT_RA:         65.723d {+04h 22m 53s} (J2000)
POINT_DEC:       -25.123d {-25d 07' 21"} (J2000)
POINT_ROLL:      93.462d
IMG_START_DATE:  14722 TJD;   257 DOY;   08/09/13
IMG_START_TIME:  25273.98 SOD {07:01:13.98} UT,   859.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.507
N_STARS:         75
X_OFFSET:        439 [pixels]
Y_OFFSET:        470 [pixels]
X_MAX:           1398 [pixels]
Y_MAX:           1429 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00324561000msufc0859.fits
SUN_POSTN:       171.61d {+11h 26m 25s}   +3.62d {+03d 37' 15"}
SUN_DIST:        105.83 [deg]   Sun_angle= 7.1 [hr] (West of Sun)
MOON_POSTN:      327.20d {+21h 48m 48s}  -12.66d {-12d 39' 19"}
MOON_DIST:        92.26 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      223.04,-42.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       57.68,-45.88 [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 13 Sep 08 07:05:31 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     324561,   Seg_Num: 0
POINT_RA:         65.723d {+04h 22m 53s} (J2000)
POINT_DEC:       -25.123d {-25d 07' 21"} (J2000)
ROLL:            93.462d
IMG_START_DATE:  14722 TJD;   257 DOY;   08/09/13
IMG_START_TIME:  25273.98 SOD {07:01:13.98} UT,   859.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     242982077
X_OFFSET:        758 [pixels]
Y_OFFSET:        789 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       918
Y_GRB_POS:       949
BINNING_INDEX:   1
IM_URL:          sw00324561000msuni0859.fits
SUN_POSTN:       171.61d {+11h 26m 25s}   +3.62d {+03d 37' 15"}
SUN_DIST:        105.83 [deg]   Sun_angle= 7.1 [hr] (West of Sun)
MOON_POSTN:      327.21d {+21h 48m 50s}  -12.65d {-12d 39' 08"}
MOON_DIST:        92.25 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      223.04,-42.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       57.68,-45.88 [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 13 Sep 08 07:05:51 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     324561,   Seg_Num: 0
POINT_RA:         65.723d {+04h 22m 53s} (J2000)
POINT_DEC:       -25.123d {-25d 07' 21"} (J2000)
ROLL:            93.462d
IMG_START_DATE:  14722 TJD;   257 DOY;   08/09/13
IMG_START_TIME:  25273.98 SOD {07:01:13.98} UT,   859.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     242982077
X_OFFSET:        758 [pixels]
Y_OFFSET:        789 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       918
Y_GRB_POS:       949
BINNING_INDEX:   1
IM_URL:          sw00324561000msuni0859.fits
SUN_POSTN:       171.61d {+11h 26m 25s}   +3.62d {+03d 37' 14"}
SUN_DIST:        105.83 [deg]   Sun_angle= 7.1 [hr] (West of Sun)
MOON_POSTN:      327.21d {+21h 48m 50s}  -12.65d {-12d 39' 04"}
MOON_DIST:        92.25 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      223.04,-42.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       57.68,-45.88 [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_sources_image.fits.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 13 Sep 08 07:24:11 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     324561,   Seg_Num: 0
POINT_RA:         65.722d {+04h 22m 53s} (J2000)
POINT_DEC:       -25.123d {-25d 07' 21"} (J2000)
POINT_ROLL:      93.462d
IMG_START_DATE:  14722 TJD;   257 DOY;   08/09/13
IMG_START_TIME:  25380.31 SOD {07:03:00.31} UT,   966.2 [sec] since BAT Trigger Time
FILTER:          3, V
BKG_MEAN:        1.824
N_STARS:         93
X_OFFSET:        439 [pixels]
Y_OFFSET:        470 [pixels]
X_MAX:           1398 [pixels]
Y_MAX:           1429 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    6
SL_URL:          sw00324561000msufc0966.fits
SUN_POSTN:       171.62d {+11h 26m 28s}   +3.62d {+03d 36' 57"}
SUN_DIST:        105.84 [deg]   Sun_angle= 7.1 [hr] (West of Sun)
MOON_POSTN:      327.36d {+21h 49m 27s}  -12.58d {-12d 34' 55"}
MOON_DIST:        92.15 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      223.04,-42.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       57.68,-45.88 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 13 Sep 08 07:24:36 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     324561,   Seg_Num: 0
POINT_RA:         65.722d {+04h 22m 53s} (J2000)
POINT_DEC:       -25.123d {-25d 07' 21"} (J2000)
POINT_ROLL:      93.462d
IMG_START_DATE:  14722 TJD;   257 DOY;   08/09/13
IMG_START_TIME:  25380.31 SOD {07:03:00.31} UT,   966.2 [sec] since BAT Trigger Time
FILTER:          3, V
BKG_MEAN:        1.824
N_STARS:         93
X_OFFSET:        439 [pixels]
Y_OFFSET:        470 [pixels]
X_MAX:           1398 [pixels]
Y_MAX:           1429 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    6
SL_URL:          sw00324561000msufc0966.fits
SUN_POSTN:       171.62d {+11h 26m 28s}   +3.62d {+03d 36' 56"}
SUN_DIST:        105.84 [deg]   Sun_angle= 7.1 [hr] (West of Sun)
MOON_POSTN:      327.37d {+21h 49m 28s}  -12.58d {-12d 34' 49"}
MOON_DIST:        92.14 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      223.04,-42.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       57.68,-45.88 [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 13 Sep 08 07:25:30 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     324561,   Seg_Num: 0
POINT_RA:         65.722d {+04h 22m 53s} (J2000)
POINT_DEC:       -25.123d {-25d 07' 21"} (J2000)
ROLL:            93.462d
IMG_START_DATE:  14722 TJD;   257 DOY;   08/09/13
IMG_START_TIME:  25380.31 SOD {07:03:00.31} UT,   966.2 [sec] since BAT Trigger Time
FILTER:          3, V
EXPOSURE_ID:     242982183
X_OFFSET:        758 [pixels]
Y_OFFSET:        789 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       918
Y_GRB_POS:       949
BINNING_INDEX:   1
IM_URL:          sw00324561000msuni0966.fits
SUN_POSTN:       171.62d {+11h 26m 28s}   +3.62d {+03d 36' 56"}
SUN_DIST:        105.84 [deg]   Sun_angle= 7.1 [hr] (West of Sun)
MOON_POSTN:      327.38d {+21h 49m 30s}  -12.58d {-12d 34' 37"}
MOON_DIST:        92.14 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      223.04,-42.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       57.68,-45.88 [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 13 Sep 08 07:25:55 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     324561,   Seg_Num: 0
POINT_RA:         65.722d {+04h 22m 53s} (J2000)
POINT_DEC:       -25.123d {-25d 07' 21"} (J2000)
ROLL:            93.462d
IMG_START_DATE:  14722 TJD;   257 DOY;   08/09/13
IMG_START_TIME:  25380.31 SOD {07:03:00.31} UT,   966.2 [sec] since BAT Trigger Time
FILTER:          3, V
EXPOSURE_ID:     242982183
X_OFFSET:        758 [pixels]
Y_OFFSET:        789 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       918
Y_GRB_POS:       949
BINNING_INDEX:   1
IM_URL:          sw00324561000msuni0966.fits
SUN_POSTN:       171.62d {+11h 26m 28s}   +3.62d {+03d 36' 55"}
SUN_DIST:        105.84 [deg]   Sun_angle= 7.1 [hr] (West of Sun)
MOON_POSTN:      327.38d {+21h 49m 31s}  -12.58d {-12d 34' 32"}
MOON_DIST:        92.14 [deg]
MOON_ILLUM:      95 [%]
GAL_COORDS:      223.04,-42.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       57.68,-45.88 [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_sources_image.fits.gz file does not exist; skipping the attachment.

GCN Circular #8218
A. Rossi (Tautenburg Obs.), J. Greiner, T. Kruehler, A. Yoldas (all MPE), S. Klose (Tautenburg Obs.), A. Kuepcue Yoldas (ESO) report on behalf of the GROND team:
We observed the field of GRB 080913 (Swift trigger 324561; Schady et al., GCN #8217), simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile). Observations started at 06:50 UT on September 13, 2008, 3 min after the GRB trigger. We detect a faint optical object inside the 2.4 arcsec Swift/XRT error box (Schady et al., GCN #8217).
We detect the object only in the z'-band and NIR, but not in i'-band or bluer. Preliminary photometry yields the following magnitudes calibrated against USNO-B1 and 2MASS field stars in stacked images:
```
r' > 23.2 mag,
i' > 23.0 mag,
z' = 22.4 mag,
```
not corrected for the expected Galactic foreground reddening of E(B-V) = 0.05 mag (Schlegel et al., 1998).
The non-detection in i' and bluer may indicate a redshift of about 6. We caution however, that the drop-out is only 0.6 mag in depth between our i' and z' bands, and our lack of better sensitivity could make this a wrong interpretation. We encourage deeper observations.
GCN Circular #8219
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team.
Using 2223 s of XRT Photon Counting mode data and 1 UVOT images for GRB 080913, 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 = 65.72775, -25.12950 which is equivalent to:
```
RA (J2000): 04h 22m 54.66s
Dec (J2000): -25d 07' 46.2"
```
with an uncertainty of 1.9 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 http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is an extension of this method.
This circular was automatically generated, and is an official product of the Swift-XRT team.
GCN Circular #8220
P. D'Avanzo, S. Covino, L.A. Antonelli, D. Malesani, D. Fugazza, L. Calzoletti, S. Campana, G. Chincarini, M.L. Conciatore, S. Cutini, V. D'Elia, F. D'Alessio, F. Fiore, P. Goldoni, D. Guetta, C. Guidorzi, G.L. Israel, E. Maiorano, N. Masetti, A. Melandri, E. Meurs, L. Nicastro, E. Palazzi, E. Pian, S. Piranomonte, L. Stella, G. Stratta, G. Tagliaferri, G. Tosti, V.Testa, S.D. Vergani, F. Vitali report on behalf of the REM team:
The robotic 60-cm REM telescope located at La Silla (Chile) observed automatically the field of the GRB 080913 (Schady et al. GCN 8217) on Sep 13 starting about 6 min after the burst. Observations were carried out at high airmass. Coadding a series of 10s, 30s and 60s exposures, at a mean t-t0 ~ 40 min we do not see the object reported by Rossi et al. (GCN 8218) or any other afterglow candidate inside the refined XRT error box (Beardmore et al.; GCN 8219) down to J > 17.1, H > 17.2 and K > 15.8 (3sigma c.l.).
GCN Circular #8221
P.M. Vreeswijk, J.P.U. Fynbo, D. Malesani (DARK/NBI) report on behalf of a larger collaboration:
The field of GRB 080913 (Swift trigger 324561; Schady et al., GCN #8217) was observed in target-of-opportunity mode with VLT+FORS2 using the imaging sequence RzIVBR, starting at 7:31 UT on September 13, 2008, i.e. 45 minutes after the GRB.
In the z-band image a faint source is detected within the Swift/XRT error circle, with magnitude z(AB) = 23.1 (based on a very preliminary calibration), while this object is not detected in any of the other optical filters. Comparison with the z-band magnitude reported by Rossi et al. (GCN #8218) suggests that the object has faded between 3 and 45 minutes after the burst, and therefore is likely the afterglow of GRB 080913.
We are very grateful for the excellent support by the Paranal observatory staff, in particular Rachel Gilmour and Heidi Schmidt.
GCN Circular #8222
M. Stamatikos (GSFC/ORAU), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), P. Schady (MSSL-UCL), J. Tueller (GSFC), T. Ukwatta (GWU)
(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 080913 (trigger #324561) (Schady, et al., GCN Circ. 8217). The BAT ground-calculated position is RA, Dec = 65.741, -25.127 deg which is
```
  RA(J2000)  =  04h 22m 57.9s
  Dec(J2000) = -25d 07' 38.6"
```
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 39%.
The mask-weighted light curve shows multiple overlapping peaks, somewhat smooth in character. T90 (15-350 keV) is 8 +- 1 sec (estimated error including systematics).
The time-averaged spectrum from T-3.8 to T+5.2 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.46 +- 0.70, and Epeak of 93.1 +- 56.1 keV (chi squared 38.53 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 5.6 +- 0.6 x 10-07 erg/cm2 and the 1-sec peak flux measured from T+0.11 sec in the 15-150 keV band is 1.4 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.36 +- 0.15 (chi squared 44.56 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/324561/BA/
GCN Circular #8223
J. Greiner, T. Kruehler (both MPE), A. Rossi (Tautenburg Obs.) report on behalf of the GROND team:
We have analyzed more data of our GROND observing run (Rossi et al. 2008, GCN #8218) of GRB 080913 (Schady et al. 2008, GCN #8217; Stamatikos et al. 2008, GCN #8222). The object reported previously is clearly detected in several epochs. The position is
```
RA (2000.0) = 04:22:54.74 
Decl. (2000.) = -25:07:46.2
```
with an uncertainty of 0.5 arcsec. This position is consistent with the astrometrically corrected Swift X-ray position (Beardmore et al. 2008, GCN #8219).
z'-band data spanning the time period from 3 min to 3 hrs after the burst clearly show a fading source and are well fit with a power law of decay slope 0.6 +- 0.3. This confirms the fading seen with the VLT (Vreeswijk et al. 2008, GCN #8221). If this fading continues, we predict z(AB) ~ 25 mag at 24 hrs after the GRB.
The afterglow is detected in z'JHK, but not in g'r'i-bands. After correction for foreground extinction of A_V=0.129, we obtain (AB system)
```
g > 23.3 +- 0.1
r > 23.3 +- 0.1
i > 23.0 +- 0.1
z = 22.52 +- 0.15
J = 20.90 +- 0.06
H = 20.67 +- 0.09
K = 20.54 +- 0.21
```
at 07:13 UT (mid-time of 12 min exposure), 26 min after the GRB. A fit to this simultaneously obtained 7-filter spectral energy distribution, using Hyper-z (Bolzonella et al. 2000) results in a photometric redshift of z = 6.44 +- 0.3. The SED-fit is shown on http://www.mpe.mpg.de/~jcg/grb080913.html

GCN Circular #8224
S. R. Oates and P. Schady report on behalf of the Swift/UVOT team.
The Swift/UVOT began settled observations of the field of GRB 080913 starting 105s after the BAT trigger (Schady et al., GCN 8217). We do not detect an afterglow in any of the UVOT filters inside the UVOT-enhanced XRT error circle (Beardmore et al., GCN 8219).
The 3 sigma upper limits for the finding charts (fc) and summed images are given below:

Filter    T_start(s)  T_stop(s)  Expo(s)  Magnitude (3 sigma UL)
-----------------------------------------------------------------
White (fc)   105        205        98           >20.92
White        105       1964        238          >21.26                 
v (fc)       211        611        393          >20.08
v            211       1858        865          >20.39
b            691       1957        97           >19.62
u            666       1932        117          >19.36
w1           641       1907        117          >19.48
m2           616       1882        78           >18.84
w2           721       1833        58           >18.99
----------------------------------------------------------------

The above magnitudes are not corrected for the Galactic extinction corresponding to a reddening of E_{B-V} = 0.04 mag (Schlegel et al., 1998, ApJS, 500, 525). The photometry is on the UVOT flight system described in Poole et al. (2008,MNRAS,383,627).

GCN Circular #8225
J.P.U. Fynbo (DARK/NBI), J. Greiner, T. Kruehler (both MPE), A. Rossi (Tautenburg Obs), P. Vreeswijk, D. Malesani (both DARK/NBI) report on behalf of a larger collaboration
Based on the rapid determination of an i'-band drop out we triggered VLT/ToO observations (program-ID 081.A-0135; PI Greiner) and obtained spectroscopy with FORS2+Gris600z of the afterglow of GRB080913 (Schady et al. 2008, GCN #8217; Stamatikos et al. 2008, GCN #8222). Observations started at 8:30, about 100 min after the GRB, and continued until morning twilight. We detect a red continuum that disappears bluewards of a break around 9400 AA. Interpreting this break as the onset of the Lyman-alpha forest we infer a redshift of about z=6.7 consistent with the photometric redshift determined by GROND (Greiner et al., GCN #8223).
We are very grateful for the excellent support by the Paranal observatory staff, in particular Rachel Gilmour and Heidi Schmidt.
GCN Circular #8226
A.P. Beardmore (U. Leicester) and P. Schady (MSSL-UCL) report on behalf of the Swift-XRT team :
The Swift-XRT started observing the field of GRB 080913 (trigger number 324561, Schady et al., GCN Circ. 8217) at 2008-09-13 06:48:30 UT, 94 s after the trigger. The best XRT position is the UVOT-enhanced position reported by Beardmore et al. (GCN Circ. 8219).
The X-ray light curve presently spans 5 orbits of photon counting mode data from T+108 s to T+23 ks. The light curve shows a number of small flares in the first orbit, with the largest giving a factor of ~7 increase in count rate at T+1.8 ks, on top of a power-law decay of index 1.20 +0.16 -0.13.
A 2.7 ks exposure X-ray spectrum from T+108 s to T+7.6 ks can be well fit by an absorbed power-law with a photon index of 1.69 +0.46 -0.41 and a column density consistent with the Galactic value of 3.2 x 10^20 cm^-2 in the direction of the burst. The observed 0.3-10.0 keV flux is (3.2 +0.9 -1.6) x 10^-12 erg cm^-2 s^-1 which corresponds to an unabsorbed flux of (3.7 +1.6 -1.7) x 10^-12 erg cm^-2 s^-1. The count to flux conversion factor is 4.6 x 10^-11 erg cm^-2 count^-1.
Providing the source continues to decay at the same rate, we predict a count rate of 2.8 x 10^-4 count s^-1 at T+1 day.
This circular is an official product of the Swift-XRT team.
GCN Circular #8256
V. Pal'shin, S. Golenetskii, R.Aptekar, E. Mazets, D. Frederiks, and T. Cline on behalf of the Konus-Wind team,
T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), D. Palmer (LANL), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), and T. Ukwatta (GWU) on behalf of the Swift-BAT team,
report:
We performed the Konus-Wind and the Swift/BAT joint spectral analysis of GRB 080913 (Swift/BAT trigger #324561: Schady et al., GCN Circ. 8217, Stamatikos et al. GCN Circ. 8222). Since the Konus-Wind observed this GRB in the waiting mode, we only have 3 channel spectral data for the Konus-Wind which cover the energy range from 20 keV to 1.3 MeV. Therefore, the joint spectral analysis of the Konus-Wind and the Swift/BAT data enables to derive the broad-band spectral parameters of this burst.
The time interval of the spectral data for each instrument is chosen from T0(BAT)-4.1 to T0(BAT)+4.7 sec where T0(BAT) is the trigger time of BAT at 06:46:54.1 UTC. The energy ranges which we used in the joint spectral analysis are 20-1300 keV and 14-150 keV for the Konus-Wind and the Swift/BAT respectively. The spectral data of two instruments are fit with the spectral model multiplied by the constant factor to take into account the systematic effective area uncertainties in the response matrices of each instrument.
The spectrum is well fit with a power-law with exponential cutoff model: dN/dE ~ E^{alpha}*exp(-(2+alpha)*E/Epeak). The constant factors of each instrument agree within 5%. No systematic residual from the best fit model is seen in the spectral data of each instrument. The best fit spectral parameters are: alpha = -0.89(-0.46, +0.65) and Epeak = 131 (-48/+225) keV (chi2/dof = 43.7/58). The best fit spectral parameters for the Band function fixing beta=-2.5 are: alpha = -0.82(-0.53, +0.75) and Epeak = 121 (-39/+232) keV (chi2/dof = 43.9/58). The energy fluence in the 15-1000 keV band calculated by a power-law with exponential cutoff model for this 8.8 sec interval is 8.5(-2.2, +6.0)x10^-7 erg/cm2
All the quoted errors are at the 90% confidence level.
Assuming z = 6.7 (Fynbo et al., GCN Circ. 8225) and a standard cosmology model with H_0 = 71 km/s/Mpc, Omega_M = 0.27, Omega_Lambda = 0.73, the isotropic energy release is E_iso ~7x10^52 erg in 1 keV to 10 MeV at the GRB rest frame extrapolating the best Band function fit fixing beta=-2.5.
Looking only at the parameters of the prompt emission, namely T90~1 sec and Ep ~900 keV in the GRB rest frame, this burst could be classified as a short burst.
GCN Circular #8267
Dong Xu (DARK/NBI) reports
The Swift/BAT data were reduced in a standard way. Making use of the Cross Correlation Function (CCF) for different energy bands over 15-150 keV, we found negligible spectral time lags, being consistent with the values/range of previous Swift short-duration GRBs. Also we note the rest-frame energy band which BAT corresponds to for this burst (z~6.7, Fynbo et al. GCN 8225) is higher than that for previous GRBs.
DX is grateful to R. L. C. Starling, P. T. O'Brien, and K. Page through the SPARTAN program on Swift data reduction.
GCN Report 165.1
GCN_Report 165.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_165_1.pdf by P. Schady at MSSL-UCL titled: "Final Swift report on GRB 080913"
0810.2107from 13 Oct 2008
Perez: Detection of the ultra-high z short GRB 080913 and its implications on progenitors and energy extraction mechanisms
Abstract: Aims: We present multiwavelength observations of the most distant gamma-ray burst detected so far GRB 080913 and study whether it can be considered a short-duration GRB and the implications for the progenitor nature and energy extraction mechanisms.
Methods: Multiwavelength (X-ray/nIR/millimetre) observations were made between 20.7 hours and ~16.8 days after the event.
Results: Whereas a very faint afterglow was seen at the 3.5m CAHA telescope in the nIR, the X-ray afterglow was clearly detected in our XMM-Newton observations. An upper limit is reported in the mm range. At typical redshifts of other bursts, GRB 080913 would be found in the locus of short-duration GRBs on a hardness-duration diagram, thus strengthening its membership of this class. We also report that GRB 080913 shows lower isotropic luminosities than GRB 060121, another likely member of the short-duration class of GRB at z~4.6. Regarding the nature of the progenitor, we find that a NS+BH is slightly preferred over a double NS merger, with the Blandford-Znajek process operating in this subclass of extremely energetic short GRBs.
0810.2314from 13 Oct 2008
Greiner: GRB 080913 at redshift 6.7
Abstract: We report on the detection by Swift of GRB 080913, and subsequent optical/near-infrared follow-up observations by GROND which led to the discovery of its optical/NIR afterglow and the recognition of its high-z nature via the detection of a spectral break between the i' and z' bands. Spectroscopy obtained at the ESO-VLT revealed a continuum extending down to lambda = 9400 A, and zero flux for 7500 A < lambda<9400 A, which we interpret as the onset of a Gunn-Peterson trough at z=6.695+-0.025 (95.5% conf. level), making GRB 080913 the highest redshift GRB to date, and more distant than the highest-redshift QSO. We note that many redshift indicators which are based on promptly available burst or afterglow properties have failed for GRB 080913. We report on our follow-up campaign and compare the properties of GRB 080913 with bursts at lower redshift. In particular, since the afterglow of this burst is fainter than typical for GRBs, we show that 2m-class telescopes can identify most high-redshift GRBs.
0812.2470 from 12 Dec 2008
Belczynski: On The Origin Of The Highest Redshift Gamma-Ray Burst GRB 080913
Abstract: GRB 080913, discovered by SWIFT, is the most distant gamma-ray burst (GRB) known to-date, with a spectroscopically determined redshift of z=6.7. The detection of a burst at such an early epoch of the Universe significantly constrains the nature of GRBs and their progenitors. To evaluate these constraints, we perform population synthesis studies of the formation and evolution of early stars and calculate the resulting formation rates of short- and long-duration GRBs at high redshift. The peak of the GRB rate from Population II stars occurs at z=7 for a model with efficient/fast mixing of metals, while it is found at z=3 for an inefficient/slow metallicity evolution model. We show that for at z=6.7 essentially all GRBs originate from Population II stars, independent of the adopted metallicity evolution model. At this epoch Population III (metal free) stars, representing the very first generation of stars, most likely have already completed their evolution, and Population I stars (representing the present population) have just begun forming. We argue that Population II stars (having small, but non-zero metallicity) are the most likely progenitors of both long GRBs (collapsars) and short GRBs (NS-NS or BH-NS mergers) in the redshift range 6<z<10. Since the predicted rates, after correction for modeling and observational biases, are very similar at these epochs we cannot definitively conclude which of these two progenitor scenarios is more likely in the case of GRB 080913. Further information about these high-z events, such as their spectral energy distribution and host galaxy properties, will be needed for a much larger sample to consolidate the progenitor models considered here.
GCN Circular #9321
D. A. Riechers (Caltech), F. Walter (MPIA Heidelberg), F. Bertoldi (AIfA Bonn), C. L. Carilli (NRAO), P. Cox (IRAM) report:
"We used the Max-Planck-Millimeter Bolometer (MAMBO-2) array at the IRAM 30-m telescope to observe the field of view toward the host galaxy of GRB 080913 (GCN 8217) at redshift z=6.7 (GCN 8225), RA 04:22:54.74, Dec -25:07:46.2 (J2000) at 250 GHz. Observations were carried out for 3.7 hr between 2008 November 13 and 15. We obtained a non-detection of
S_nu(250 GHz,1.20 mm) = 0.34 +/- 0.45 mJy
(1 sigma error), i.e. a 3 sigma upper flux density limit of 1.35 mJy on the dust continuum in the GRB host galaxy at 1.2 mm (rest-frame 156 um). The 117-element MAMBO-2 bolometer detectors cover 210-290 GHz (half power). The bolometers have a FWHM beam size of 10.7 arcsec, at a pixel spacing of 20 arcsec. Observations were carried out in ON-OFF observing mode under good weather conditions. Calibrations were performed on J0348-278 and J0609-157.
We acknowledge the excellent support of the staff at IRAM. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). This message may be cited."
1001.0598 from 6 Jan 10
Houjun Lv et al.: A New Classification Method for Gamma-Ray Bursts
The traditional long vs. short GRB classification scheme is found not always to match the physical classification scheme Type II (massive star origin) vs. Type I (compact star mergers), respectively. We propose a new classification method of GRBs by introducing a new parameter varepsilon=E_{gamma, iso,52}/E^{5/3}_{p,z,2}, where E_{gamma, iso,52} is the isotropic gamma-ray energy (in units of 10^{52} erg), and E_{p,z} is the cosmic rest frame spectral peak energy (in units of 100 keV). For those GRBs with "extended emission", both quantities are defined for the short/hard spike only. The varepsilon parameter shows a clear bimodal distribution with a separation at varepsilon ~ 0.03. The high-varepsilon region encloses all the high-luminosity long GRBs including the high-z GRBs with intrinsic short durations (such as GRB 090423 and GRB 080913) as well as some high-z short GRBs (such as GRB 090426), which matches the Type II GRBs very well. The low-varepsilon region is represented by all known Type I GRBs and some low luminosity long GRBs. With an additional criterion T_{90,z}< 5 s in the Swift/BAT band, a Type I GRB can be identified in the low-varepsilon region at 3 sigma confidence level. We suggest that the new classification scheme can better match the physically-motivated Type II/I classification scheme.
1101.1503 from 10 Jan 11
Tayyaba Zafar et al.: Exploring dust extinction at the edge of reionization
((1) DARK, (2) Univ. Leicester, (3) Univ. Warwick) The brightness of gamma-ray burst (GRB) afterglows and their occurrence in young, blue galaxies make them excellent probes to study star forming regions in the distant Universe. We here elucidate dust extinction properties in the early Universe through the analysis of the afterglows of all known z > 6 GRBs: GRB 090423, 080913 and 050904, at z = 8.2, 6.69, and 6.295, respectively. We gather all available optical and near-infrared photometry, spectroscopy and X-ray data to construct spectral energy distributions (SEDs) at multiple epochs. We then fit the SEDs at all epochs with a dust-attenuated power-law or broken power-law. We find no evidence for dust extinction in GRB 050904 and GRB 090423, with possible evidence for a low level of extinction in GRB 080913. We compare the high redshift GRBs to a sample of lower redshift GRB extinctions and find a lack of even moderately extinguished events (AV ~ 0.3) above z > 4. In spite of the biased selection and small number statistics, this result hints at a decrease in dust content in star-forming environments at high redshifts.
1201.6383 from 1 Feb 12
S. Basa et al.: Constraining the nature of the most distant Gamma-Ray Burst host galaxies
Long duration Gamma-Ray Bursts (GRBs) allow us to explore the distant Universe, and are potentially the best tracer of the most distant objects. Our current knowledge of the properties of GRB host galaxies at redshifts > 5 is very scarce, and more observations of high-redshift hosts are required to better understand their properties and the implications of using GRBs as probes of the high-redshift universe. We performed very deep photometric observations of three high-redshift GRB host galaxies, GRB 080913 at z = 6.7, GRB 060927 at z = 5.5 and GRB 060522 at z = 5.1. Our FORS2 and HAWK-I observations at the VLT targeted the rest-frame UV continuum of these galaxies, allowing us to constrain their star formation rates. In addition, we performed deep spectroscopic observations of the GRB080913 host galaxy with X-Shooter at the VLT to search for Ly-{\alpha} emission. For the sake of the discussion, we make use of published results on another GRB host, GRB 050904 at z = 6.3. The sample of GRB host galaxies studied in this paper consists of 4 out of the 6 spectroscopically confirmed GRB host galaxies at z > 5. Despite being the deepest observations ever reported of high-redshift GRB host galaxies, we do not detect any of the hosts, neither in photometry nor in spectroscopy in the case of GRB 080913. These observations indicate that the GRB host galaxies seem to evolve with time and to have lower star formation rates (SFR) at z > 5 than they have at z < 2. In addition, the host galaxy of GRB 080913 at z = 6.7 does not show Ly-{\alpha} emission. While the measured properties of the galaxies in our sample are in agreement with the properties of the general galaxy population at z > 5, our observations are not sensitive enough to allow us to infer further conclusions on whether this specific population is representative of the general one.

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Jochen Greiner, last update: 24-Feb-2016 [Disclaimer]