Gamma-ray Burst 081008

(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:     Wed 08 Oct 08 19:58:44 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     331093,   Seg_Num: 0
GRB_RA:          279.987d {+18h 39m 57s} (J2000),
                 280.175d {+18h 40m 42s} (current),
                 278.916d {+18h 35m 40s} (1950)
GRB_DEC:         -57.464d {-57d 27' 50"} (J2000),
                 -57.456d {-57d 27' 20"} (current),
                 -57.510d {-57d 30' 35"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       10112 [cnts]    Image_Peak=382 [image_cnts]
TRIGGER_DUR:     2.048 [sec] 
TRIGGER_INDEX:   486     E_range: 25-100 keV
BKG_INTEN:       88049 [cnts]
BKG_TIME:        71852.84 SOD {19:57:32.84} UT
BKG_DUR:         24 [sec]
GRB_DATE:        14747 TJD;   282 DOY;   08/10/08
GRB_TIME:        71889.38 SOD {19:58:09.38} UT
GRB_PHI:         143.63 [deg]
GRB_THETA:        21.45 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     19.77 [sigma]
IMAGE_SIGNIF:    10.00 [sigma]
MERIT_PARAMS:     +1  +0  +0  +3  +2 +12  +0  +0 -13  +0 
SUN_POSTN:       194.65d {+12h 58m 37s}   -6.26d {-06d 15' 26"}
SUN_DIST:         82.32 [deg]   Sun_angle= -5.7 [hr] (East of Sun)
MOON_POSTN:      304.55d {+20h 18m 11s}  -20.99d {-20d 59' 12"}
MOON_DIST:        40.59 [deg]
MOON_ILLUM:      64 [%]
GAL_COORDS:      338.09,-21.13 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      276.48,-34.25 [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 = 333.09,6.11 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 08 Oct 08 20:00:17 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     331093,   Seg_Num: 0
GRB_RA:          279.9587d {+18h 39m 50.0s} (J2000),
                 280.1463d {+18h 40m 35.1s} (current),
                 278.8878d {+18h 35m 33.0s} (1950)
GRB_DEC:         -57.4312d {-57d 25' 52.3"} (J2000),
                 -57.4227d {-57d 25' 21.6"} (current),
                 -57.4768d {-57d 28' 36.4"} (1950)
GRB_ERROR:       5.0 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       60 [cnts]
IMG_START_DATE:  14747 TJD;   282 DOY;   08/10/08
IMG_START_TIME:  71976.53 SOD {19:59:36.53} UT,   87.1 [sec] since BAT Trigger Time
CENTROID_X:      287.35,  raw= 287  [pixels]
CENTROID_Y:      251.12,  raw= 251  [pixels]
ROLL:            270.55 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -110.50
GRB_POS_XRT_Z:   -35.22
IMAGE_URL:       sw00331093000msxps_rw.img
SUN_POSTN:       194.65d {+12h 58m 37s}   -6.26d {-06d 15' 28"}
SUN_DIST:         82.30 [deg]   Sun_angle= -5.7 [hr] (East of Sun)
MOON_POSTN:      304.56d {+20h 18m 14s}  -20.98d {-20d 58' 57"}
MOON_DIST:        40.58 [deg]
MOON_ILLUM:      64 [%]
GAL_COORDS:      338.12,-21.10 [deg] galactic lon,lat of the burst
ECL_COORDS:      276.46,-34.22 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 08 Oct 08 20:00:08 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     331093,   Seg_Num: 0
GRB_RA:          279.9587d {+18h 39m 50.08s} (J2000),
                 280.1463d {+18h 40m 35.11s} (current),
                 278.8878d {+18h 35m 33.07s} (1950)
GRB_DEC:         -57.4312d {-57d 25' 52.3"} (J2000),
                 -57.4227d {-57d 25' 21.6"} (current),
                 -57.4768d {-57d 28' 36.4"} (1950)
GRB_ERROR:       5.3 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.50e-09 [erg/cm2/sec]
GRB_SIGNIF:      7.74 [sigma]
IMG_START_DATE:  14747 TJD;   282 DOY;   08/10/08
IMG_START_TIME:  71976.53 SOD {19:59:36.53} UT,   87.1 [sec] since BAT Trigger Time
TAM[0-3]:        327.65 237.23 261.34 243.50
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       194.65d {+12h 58m 37s}   -6.26d {-06d 15' 28"}
SUN_DIST:         82.30 [deg]   Sun_angle= -5.7 [hr] (East of Sun)
MOON_POSTN:      304.56d {+20h 18m 14s}  -20.98d {-20d 58' 59"}
MOON_DIST:        40.58 [deg]
MOON_ILLUM:      64 [%]
GAL_COORDS:      338.12,-21.10 [deg] galactic lon,lat of the burst
ECL_COORDS:      276.46,-34.22 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 2.19 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 08 Oct 08 20:00:23 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     331093,   Seg_Num: 0
GRB_RA:          279.9587d {+18h 39m 50.0s} (J2000),
                 280.1463d {+18h 40m 35.1s} (current),
                 278.8878d {+18h 35m 33.0s} (1950)
GRB_DEC:         -57.4312d {-57d 25' 52.3"} (J2000),
                 -57.4227d {-57d 25' 21.6"} (current),
                 -57.4768d {-57d 28' 36.4"} (1950)
GRB_ERROR:       5.0 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       60 [cnts]
IMG_START_DATE:  14747 TJD;   282 DOY;   08/10/08
IMG_START_TIME:  71976.53 SOD {19:59:36.53} UT,   87.1 [sec] since BAT Trigger Time
CENTROID_X:      287.35,  raw= 287  [pixels]
CENTROID_Y:      251.12,  raw= 251  [pixels]
ROLL:            270.55 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -110.50
GRB_POS_XRT_Z:   -35.22
IMAGE_URL:       sw00331093000msxps_rw.img
SUN_POSTN:       194.65d {+12h 58m 37s}   -6.26d {-06d 15' 28"}
SUN_DIST:         82.30 [deg]   Sun_angle= -5.7 [hr] (East of Sun)
MOON_POSTN:      304.56d {+20h 18m 15s}  -20.98d {-20d 58' 56"}
MOON_DIST:        40.58 [deg]
MOON_ILLUM:      64 [%]
GAL_COORDS:      338.12,-21.10 [deg] galactic lon,lat of the burst
ECL_COORDS:      276.46,-34.22 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 08 Oct 08 20:01:47 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     331093,   Seg_Num: 0
GRB_RA:          279.987d {+18h 39m 57s} (J2000),
                 280.175d {+18h 40m 42s} (current),
                 278.916d {+18h 35m 40s} (1950)
GRB_DEC:         -57.464d {-57d 27' 50"} (J2000),
                 -57.456d {-57d 27' 20"} (current),
                 -57.510d {-57d 30' 35"} (1950)
GRB_DATE:        14747 TJD;   282 DOY;   08/10/08
GRB_TIME:        71889.38 SOD {19:58:09.38} UT
TRIGGER_INDEX:   486
GRB_PHI:         143.63 [deg]
GRB_THETA:        21.45 [deg]
DELTA_TIME:      25.00 [sec]
TRIGGER_DUR:     2.048 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     19.77 [sigma]
IMAGE_SIGNIF:    10.00 [sigma]
LC_URL:          sw00331093000msb.lc
SUN_POSTN:       194.65d {+12h 58m 37s}   -6.26d {-06d 15' 29"}
SUN_DIST:         82.32 [deg]   Sun_angle= -5.7 [hr] (East of Sun)
MOON_POSTN:      304.57d {+20h 18m 18s}  -20.98d {-20d 58' 43"}
MOON_DIST:        40.60 [deg]
MOON_ILLUM:      64 [%]
GAL_COORDS:      338.09,-21.13 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      276.48,-34.25 [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 = 333.09,6.11 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 08 Oct 08 20:02:39 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     331093,   Seg_Num: 0
POINT_RA:        279.977d {+18h 39m 54s} (J2000)
POINT_DEC:       -57.462d {-57d 27' 43"} (J2000)
POINT_ROLL:      270.555d
IMG_START_DATE:  14747 TJD;   282 DOY;   08/10/08
IMG_START_TIME:  71985.30 SOD {19:59:45.30} UT,   95.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.934
N_STARS:         190
X_OFFSET:        424 [pixels]
Y_OFFSET:        560 [pixels]
X_MAX:           1383 [pixels]
Y_MAX:           1519 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    8
SL_URL:          sw00331093000msufc0095.fits
SUN_POSTN:       194.66d {+12h 58m 37s}   -6.26d {-06d 15' 30"}
SUN_DIST:         82.31 [deg]   Sun_angle= -5.7 [hr] (East of Sun)
MOON_POSTN:      304.58d {+20h 18m 19s}  -20.98d {-20d 58' 35"}
MOON_DIST:        40.61 [deg]
MOON_ILLUM:      64 [%]
GAL_COORDS:      338.09,-21.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      276.47,-34.25 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 08 Oct 08 20:04:08 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     331093,   Seg_Num: 0
POINT_RA:        279.977d {+18h 39m 54s} (J2000)
POINT_DEC:       -57.462d {-57d 27' 43"} (J2000)
POINT_ROLL:      270.555d
IMG_START_DATE:  14747 TJD;   282 DOY;   08/10/08
IMG_START_TIME:  71985.30 SOD {19:59:45.30} UT,   95.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.934
N_STARS:         190
X_OFFSET:        424 [pixels]
Y_OFFSET:        560 [pixels]
X_MAX:           1383 [pixels]
Y_MAX:           1519 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    8
SL_URL:          sw00331093000msufc0095.fits
SUN_POSTN:       194.66d {+12h 58m 37s}   -6.26d {-06d 15' 31"}
SUN_DIST:         82.31 [deg]   Sun_angle= -5.7 [hr] (East of Sun)
MOON_POSTN:      304.59d {+20h 18m 22s}  -20.97d {-20d 58' 21"}
MOON_DIST:        40.62 [deg]
MOON_ILLUM:      64 [%]
GAL_COORDS:      338.09,-21.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      276.47,-34.25 [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:     Wed 08 Oct 08 20:04:46 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     331093,   Seg_Num: 0
POINT_RA:        279.977d {+18h 39m 54s} (J2000)
POINT_DEC:       -57.462d {-57d 27' 43"} (J2000)
ROLL:            270.555d
IMG_START_DATE:  14747 TJD;   282 DOY;   08/10/08
IMG_START_TIME:  71985.30 SOD {19:59:45.30} UT,   95.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     245188788
X_OFFSET:        953 [pixels]
Y_OFFSET:        1031 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1113
Y_GRB_POS:       1191
BINNING_INDEX:   1
IM_URL:          sw00331093000msuni0095.fits
SUN_POSTN:       194.66d {+12h 58m 38s}   -6.26d {-06d 15' 32"}
SUN_DIST:         82.31 [deg]   Sun_angle= -5.7 [hr] (East of Sun)
MOON_POSTN:      304.60d {+20h 18m 24s}  -20.97d {-20d 58' 15"}
MOON_DIST:        40.62 [deg]
MOON_ILLUM:      64 [%]
GAL_COORDS:      338.09,-21.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      276.47,-34.25 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        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:     Wed 08 Oct 08 20:04:16 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     331093,   Seg_Num: 0
POINT_RA:        279.977d {+18h 39m 54s} (J2000)
POINT_DEC:       -57.462d {-57d 27' 43"} (J2000)
ROLL:            270.555d
IMG_START_DATE:  14747 TJD;   282 DOY;   08/10/08
IMG_START_TIME:  71985.30 SOD {19:59:45.30} UT,   95.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     245188788
X_OFFSET:        953 [pixels]
Y_OFFSET:        1031 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1113
Y_GRB_POS:       1191
BINNING_INDEX:   1
IM_URL:          sw00331093000msuni0095.fits
SUN_POSTN:       194.66d {+12h 58m 37s}   -6.26d {-06d 15' 32"}
SUN_DIST:         82.31 [deg]   Sun_angle= -5.7 [hr] (East of Sun)
MOON_POSTN:      304.59d {+20h 18m 23s}  -20.97d {-20d 58' 20"}
MOON_DIST:        40.62 [deg]
MOON_ILLUM:      64 [%]
GAL_COORDS:      338.09,-21.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      276.47,-34.25 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 08 Oct 08 20:09:08 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     331093,   Seg_Num: 0
GRB_RA:          279.9587d {+18h 39m 50.08s} (J2000),
                 280.1463d {+18h 40m 35.11s} (current),
                 278.8878d {+18h 35m 33.08s} (1950)
GRB_DEC:         -57.4311d {-57d 25' 51.9"} (J2000),
                 -57.4226d {-57d 25' 21.2"} (current),
                 -57.4767d {-57d 28' 36.0"} (1950)
GRB_ERROR:       1.6 [arcsec radius, statistical only]
GRB_MAG:         15.00 +/- 0.50 [mag]
FILTER:          10, White
IMG_START_DATE:  14747 TJD;   282 DOY;   08/10/08
IMG_START_TIME:  71987.00 SOD {19:59:47.00} UT,   97.6 [sec] since BAT Trigger Time
SUN_POSTN:       194.66d {+12h 58m 38s}   -6.26d {-06d 15' 36"}
SUN_DIST:         82.30 [deg]   Sun_angle= -5.7 [hr] (East of Sun)
MOON_POSTN:      304.64d {+20h 18m 33s}  -20.96d {-20d 57' 34"}
MOON_DIST:        40.62 [deg]
MOON_ILLUM:      64 [%]
GAL_COORDS:      338.12,-21.10 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      276.46,-34.22 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT UVOT Position Notice.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.

GCN Circular #8343
E.S. Rykoff (UCSB), report on behalf of the ROTSE collaboration:
ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, responded to GRB 081008 (Swift trigger 331093). The first image was at 19:58:51.3 UT, 41.9 s after the burst (8.3 s after the GCN notice time). The unfiltered images are calibrated relative to USNO A2.0. We detect a 14.5 magnitude, brightening source with coordinates:
18:39:50.0 -57:25:52.0 (J2000), with positional
uncertainty of 1" or better
```
start UT    	mag     mlim(of image)
----------------------------------
19:58:51.3     14.5     16.2
```
This source is not visible in DSS (second epoch), 2MASS or the MPChecker database.
A jpeg image is available at http://www.rotse.net/images/gsb331093_3c00_img.jpg
Continuing observations are in progress.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 08 Oct 08 20:10:19 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     331093,   Seg_Num: 0
POINT_RA:        279.974d {+18h 39m 54s} (J2000)
POINT_DEC:       -57.461d {-57d 27' 37"} (J2000)
POINT_ROLL:      270.555d
IMG_START_DATE:  14747 TJD;   282 DOY;   08/10/08
IMG_START_TIME:  72143.34 SOD {20:02:23.34} UT,   254.0 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.867
N_STARS:         173
X_OFFSET:        633 [pixels]
Y_OFFSET:        711 [pixels]
X_MAX:           1592 [pixels]
Y_MAX:           1670 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    4
SL_URL:          sw00331093000msufc0253.fits
SUN_POSTN:       194.66d {+12h 58m 38s}   -6.26d {-06d 15' 37"}
SUN_DIST:         82.31 [deg]   Sun_angle= -5.7 [hr] (East of Sun)
MOON_POSTN:      304.65d {+20h 18m 35s}  -20.96d {-20d 57' 23"}
MOON_DIST:        40.65 [deg]
MOON_ILLUM:      64 [%]
GAL_COORDS:      338.09,-21.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      276.47,-34.25 [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:     Wed 08 Oct 08 20:09:51 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     331093,   Seg_Num: 0
POINT_RA:        279.974d {+18h 39m 54s} (J2000)
POINT_DEC:       -57.461d {-57d 27' 37"} (J2000)
POINT_ROLL:      270.555d
IMG_START_DATE:  14747 TJD;   282 DOY;   08/10/08
IMG_START_TIME:  72143.34 SOD {20:02:23.34} UT,   254.0 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.867
N_STARS:         173
X_OFFSET:        633 [pixels]
Y_OFFSET:        711 [pixels]
X_MAX:           1592 [pixels]
Y_MAX:           1670 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    4
SL_URL:          sw00331093000msufc0253.fits
SUN_POSTN:       194.66d {+12h 58m 38s}   -6.26d {-06d 15' 37"}
SUN_DIST:         82.31 [deg]   Sun_angle= -5.7 [hr] (East of Sun)
MOON_POSTN:      304.64d {+20h 18m 34s}  -20.96d {-20d 57' 27"}
MOON_DIST:        40.65 [deg]
MOON_ILLUM:      64 [%]
GAL_COORDS:      338.09,-21.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      276.47,-34.25 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 08 Oct 08 20:12:26 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     331093,   Seg_Num: 0
POINT_RA:        279.974d {+18h 39m 54s} (J2000)
POINT_DEC:       -57.461d {-57d 27' 37"} (J2000)
ROLL:            270.555d
IMG_START_DATE:  14747 TJD;   282 DOY;   08/10/08
IMG_START_TIME:  72143.34 SOD {20:02:23.34} UT,   254.0 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     245188946
X_OFFSET:        953 [pixels]
Y_OFFSET:        1031 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1113
Y_GRB_POS:       1191
BINNING_INDEX:   1
IM_URL:          sw00331093000msuni0253.fits
SUN_POSTN:       194.66d {+12h 58m 39s}   -6.26d {-06d 15' 39"}
SUN_DIST:         82.31 [deg]   Sun_angle= -5.7 [hr] (East of Sun)
MOON_POSTN:      304.67d {+20h 18m 40s}  -20.95d {-20d 57' 03"}
MOON_DIST:        40.66 [deg]
MOON_ILLUM:      64 [%]
GAL_COORDS:      338.09,-21.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      276.47,-34.25 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        This notice was forced out after watchdog timer expiring -- most likely due to missing packet(s);  
COMMENTS:        as a consequence some of the fields may be incoorect (eg TRIGGER_NUM,RA,DEC).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 08 Oct 08 20:12:43 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     331093,   Seg_Num: 0
POINT_RA:        279.974d {+18h 39m 54s} (J2000)
POINT_DEC:       -57.461d {-57d 27' 37"} (J2000)
ROLL:            270.555d
IMG_START_DATE:  14747 TJD;   282 DOY;   08/10/08
IMG_START_TIME:  72143.34 SOD {20:02:23.34} UT,   254.0 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     245188946
X_OFFSET:        953 [pixels]
Y_OFFSET:        1031 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1113
Y_GRB_POS:       1191
BINNING_INDEX:   1
IM_URL:          sw00331093000msuni0253.fits
SUN_POSTN:       194.66d {+12h 58m 39s}   -6.26d {-06d 15' 40"}
SUN_DIST:         82.31 [deg]   Sun_angle= -5.7 [hr] (East of Sun)
MOON_POSTN:      304.67d {+20h 18m 40s}  -20.95d {-20d 57' 00"}
MOON_DIST:        40.66 [deg]
MOON_ILLUM:      64 [%]
GAL_COORDS:      338.09,-21.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      276.47,-34.25 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_sources_image.fits.gz file does not exist; skipping the attachment.  
COMMENTS:        This notice was forced out after watchdog timer expiring -- most likely due to missing packet(s);  
COMMENTS:        as a consequence some of the fields may be incoorect (eg TRIGGER_NUM,RA,DEC).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 08 Oct 08 20:30:31 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     331093,   Seg_Num: 0
POINT_RA:        279.974d {+18h 39m 54s} (J2000)
POINT_DEC:       -57.461d {-57d 27' 38"} (J2000)
POINT_ROLL:      270.555d
IMG_START_DATE:  14747 TJD;   282 DOY;   08/10/08
IMG_START_TIME:  72745.83 SOD {20:12:25.83} UT,   856.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.985
N_STARS:         190
X_OFFSET:        393 [pixels]
Y_OFFSET:        471 [pixels]
X_MAX:           1832 [pixels]
Y_MAX:           1910 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    8
SL_URL:          sw00331093000msufc0856.fits
SUN_POSTN:       194.67d {+12h 58m 41s}   -6.27d {-06d 15' 56"}
SUN_DIST:         82.30 [deg]   Sun_angle= -5.7 [hr] (East of Sun)
MOON_POSTN:      304.82d {+20h 19m 17s}  -20.90d {-20d 54' 12"}
MOON_DIST:        40.75 [deg]
MOON_ILLUM:      64 [%]
GAL_COORDS:      338.09,-21.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      276.47,-34.25 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 08 Oct 08 20:31:03 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     331093,   Seg_Num: 0
POINT_RA:        279.974d {+18h 39m 54s} (J2000)
POINT_DEC:       -57.461d {-57d 27' 38"} (J2000)
POINT_ROLL:      270.555d
IMG_START_DATE:  14747 TJD;   282 DOY;   08/10/08
IMG_START_TIME:  72745.83 SOD {20:12:25.83} UT,   856.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.985
N_STARS:         190
X_OFFSET:        393 [pixels]
Y_OFFSET:        471 [pixels]
X_MAX:           1832 [pixels]
Y_MAX:           1910 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    8
SL_URL:          sw00331093000msufc0856.fits
SUN_POSTN:       194.67d {+12h 58m 42s}   -6.27d {-06d 15' 57"}
SUN_DIST:         82.30 [deg]   Sun_angle= -5.7 [hr] (East of Sun)
MOON_POSTN:      304.83d {+20h 19m 18s}  -20.90d {-20d 54' 07"}
MOON_DIST:        40.76 [deg]
MOON_ILLUM:      64 [%]
GAL_COORDS:      338.09,-21.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      276.47,-34.25 [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:     Wed 08 Oct 08 20:32:07 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     331093,   Seg_Num: 0
POINT_RA:        279.974d {+18h 39m 54s} (J2000)
POINT_DEC:       -57.461d {-57d 27' 38"} (J2000)
ROLL:            270.555d
IMG_START_DATE:  14747 TJD;   282 DOY;   08/10/08
IMG_START_TIME:  72745.83 SOD {20:12:25.83} UT,   856.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     245189548
X_OFFSET:        952 [pixels]
Y_OFFSET:        1030 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1112
Y_GRB_POS:       1190
BINNING_INDEX:   1
IM_URL:          sw00331093000msuni0856.fits
SUN_POSTN:       194.67d {+12h 58m 42s}   -6.27d {-06d 15' 58"}
SUN_DIST:         82.29 [deg]   Sun_angle= -5.7 [hr] (East of Sun)
MOON_POSTN:      304.83d {+20h 19m 20s}  -20.90d {-20d 53' 57"}
MOON_DIST:        40.76 [deg]
MOON_ILLUM:      64 [%]
GAL_COORDS:      338.09,-21.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      276.47,-34.25 [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:     Wed 08 Oct 08 20:32:23 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     331093,   Seg_Num: 0
POINT_RA:        279.974d {+18h 39m 54s} (J2000)
POINT_DEC:       -57.461d {-57d 27' 38"} (J2000)
ROLL:            270.555d
IMG_START_DATE:  14747 TJD;   282 DOY;   08/10/08
IMG_START_TIME:  72745.83 SOD {20:12:25.83} UT,   856.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     245189548
X_OFFSET:        952 [pixels]
Y_OFFSET:        1030 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1112
Y_GRB_POS:       1190
BINNING_INDEX:   1
IM_URL:          sw00331093000msuni0856.fits
SUN_POSTN:       194.67d {+12h 58m 42s}   -6.27d {-06d 15' 58"}
SUN_DIST:         82.29 [deg]   Sun_angle= -5.7 [hr] (East of Sun)
MOON_POSTN:      304.84d {+20h 19m 21s}  -20.90d {-20d 53' 54"}
MOON_DIST:        40.76 [deg]
MOON_ILLUM:      64 [%]
GAL_COORDS:      338.09,-21.12 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      276.47,-34.25 [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 #8344
J. L. Racusin (PSU), W. H. Baumgartner (GSFC/UMBC), P. J. Brown (PSU), D. N. Burrows (PSU), P. A. Evans (U Leicester), D. Grupe (PSU), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), J. A. Kennea (PSU), V. La Parola (INAF-IASFPA), F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester), J. P. Osborne (U Leicester), A. M. Parsons (GSFC), M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester), G. Tagliaferri (INAF-OAB), T. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU) report on behalf of the Swift Team:
At 19:58:09 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 081008 (trigger=331093). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 279.987, -57.464 which is
```
   RA(J2000) = 18h 39m 57s
   Dec(J2000) = -57d 27' 50"
```
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 150 sec. The peak count rate was ~2500 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 19:59:36.5 UT, 87.1 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 279.9587, -57.4312 which is equivalent to:
```
   RA(J2000)  = 18h 39m 50.08s
   Dec(J2000) = -57d 25' 52.3"
```
with an uncertainty of 5.3 arcseconds (radius, 90% containment). This location is 130 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy.
UVOT took a finding chart exposure of 150 seconds with the White (160-650 nm) filter starting 96 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at
```
  RA(J2000)  =	18:39:50.11 = 279.9588
  DEC(J2000) = -57:25:52.3  = -57.4312
```
with a 1-sigma error radius of about 1.6 arc sec. This position is 0.3 arcseconds from the center of the XRT error circle. The estimated magnitude is 15.0 with a 1-sigma error of about 0.5 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.10.
Burst Advocate for this burst is J. L. Racusin (racusin AT astro.psu.edu). 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 #8345
P. D'Avanzo (INAF-OAB), V. D'Elia (INAF-OAR), S. Covino (INAF-OAB) report, on behalf of the MISTICI collaboration:
Following the detection of GRB 081008 (Rykoff, GCN 8343; Racusin et al., GCN 8344), we triggered observations with the FORS2 camera, mounted at ESO-VLT. The observations were performed using the 600B grism. We took a 900 s spectrum starting around Oct 09 at 00:20 UT (about 4.5 hours after the burst) and covering the range 380-620 nm.
The non-detection of Ly-alpha sets an upper limit of z ~ 2 to the GRB redshift. We detect a double horned absorption feature around lambda 4600 A which we identify as the MgII doublet at 2796-2803 A. This implies a redshift of the absorber of z = 0.64. We also detect two absorption features around lambda 4530-4550 A which we identify as FeII 2586 and FeII 2600 A. We possibly interpret this signature as another absorption system at z = 0.75.
However, at the present stage, the most robust redshift range that we can set for GRB 081008 is 0.64 < z < 2.
Further analysis is in progress.
We are very grateful for the excellent support of the VLT staff.
GCN Circular #8346
A. Cucchiara, D. B. Fox (Penn State), S. B. Cenko (Berkeley) and E. Berger (Harvard) report on behalf of a larger collaboration:
Starting at 00:20 UT on 2008 October 9 (T0+5h) we observed the optical counterpart of GRB 081008 (Racusin et al., GCN 8344, Rykoff et al., GCN 83433) using Gemini-South with the GMOS-South spectrograph (R~1600). We acquired 2x900s spectra covering the wavelength range 3800A-6700A.
We clearly detect several metal absorption features which we interpret as SiIV(1393,1402), SiII1526, SiII*1816, CIV(1548,1550), FeII1608, AlII1670, NiII1703, AlIII(1854,1862), MgI2026 at the common redshift of z = 1.967.
The absorption system identified by D'Avanzo et al. (GCN 8345) can be explained by the CIV and SiII/SiII* doublets at this redshift.
We thank the Gemini staff for conducting these observations.
GCN Circular #8347
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
Using 8661 s of XRT Photon Counting mode data and 8 UVOT images for GRB 081008, 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 = 279.95776, -57.43188 which is equivalent to:
```
RA (J2000): 18h 39m 49.86s
Dec (J2000): -57d 25' 54.8"
```
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 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 #8348
P. Schady (MSSL-UCL) and J. L. Racusin (PSU) report on behalf of the=20 Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 081008 96 s= =20 after the BAT trigger (Racusin et al., GCN Circ. 8344), using a newly=20 implemented observing sequence. The new sequence takes a 150s white-band=20 finding chart exposure, followed by a 250s u-band exposure, after which=20 the filter wheel rotates through all filters, taking short 20s exposures.
A new fading source is detected at the ROTSE position (Rykoff et al., GCN= =20 Circ 8343) in the white, v, b, u and uvw1 filters, consistent with a=A0=20 redshift of z=3D1.967 reported by Cucchiara et al., (GCN Circ 8346). The=20 source is decaying at a constant rate of 0.90+/-0.03 for the duration of=20 intial UVOT observations, out to ~700s after the BAT trigger. The UVOT=20 refined position is
```
RA(J2000) =3D 18:39:49.877 (279.95833 deg)
Dec(J2000) =3D -57:25:52.87 (-57.431111 deg)
```
with an estimated uncertainty of 0.6 arcsec (radius, 90% confidence).
The detections and 3 sigma upper limits of the fading afterglow are=20 reported below, where T_start and T_stop represent the elapsed time since= =20 the BAT trigger in seconds, and fc indicate finding chart exposures
```
Filter      T_start(s) T_stop  Exp(s)   Mag or 3 Sigma Limit

white (fc)   96         246     146      14.96 +/- 0.01
white        534        554     19       15.87 +/- 0.03
u (fc)       254        504     246      15.19 +/- 0.02
u            658        678     19       15.81 +/- 0.08
v            584        604     19       15.64 +/- 0.10
b            510        530     19       15.79 +/- 0.05
uvw1         633        653     19       17.03 +/- 0.22
uvm2         608        1601    117      > 19.16
uvw2         559        1717    128      > 19.53
```
The above magnitudes are not corrected for the Galactic extinction=20 corresponding to a reddening of E(B-V) =3D 0.10 mag (Schlegel et al., 199= 8,=20 ApJS, 500, 525).=A0 The photometry is on the UVOT photometric system=20 described in Poole et al. (2008, MNRAS, 383,627).
GCN Circular #8349
J. L. Racusin (PSU) reports on behalf of the Swift-XRT team:
We have analyzed the first 7 orbits of XRT data for GRB 081008 (Racusin et al., GCN 8344), including 315 s of WT data and 6.9 ks of PC data. The UVOT-enhanced position was given by Evans et al. (GCN 8347). The results of the automatic analysis of the XRT data are available at http://www.swift.ac.uk/xrt_products.
The 0.3-10.0 keV lightcurve shows three bright flares superimposed on a steep decay, followed by a plateau with a decay index of 0.9 +/- 0.1, breaking at 16 +/- 14 ks to a decay index of 2.0 {+1.8,-0.9}.
The WT spectrum, for which changes in the hardness ratio during the flares suggests spectral evolution, can be fit by an absorbed power-law, with photon index = 1.81 +/- 0.03 and NH = (6.7 +/- 0.8)e21 cm^-2 at z = 1.967 (Cucchiara et al., GCN 8346), in addition to the Galactic value of 7.1e20 cm^-2. The observed (unabsorbed) flux over this time (93-408 s after the trigger) is 3.1e-9 (3.9e-9) erg cm^-2 s^-1.
The PC spectrum can be fit by an absorbed power-law, with photon index = 1.91 +/- 0.07 and NH = (5.9 {+15.1, -5.9})e20 cm^-2 at z = 1.967, consistent with the Galactic value. The observed (unabsorbed) flux over this time (412 s - 11.9 ks after the trigger) is 3.4e-11 (4.0e-11) erg cm^-2 s^-1.
Assuming the X-ray emission continues to decline at the same rate, we predict a 0.3-10.0 keV XRT count rate of 3.6e-3 counts/s at T+24hr, which corresponds to an observed (unabsorbed) flux of 1.4e-13 (1.7e-13) ergs cm^-2 s^-1.
This Circular is an official product of the Swift-XRT team.
GCN Circular #8350
P. D'Avanzo (INAF-OAB), V. D'Elia (INAF-OAR), S. Covino (INAF-OAB) report, on behalf of the MISTICI collaboration:
We observed the optical afterglow of GRB 081008 (Rykoff, GCN 8343; Racusin et al., GCN 8344), with the ESO VLT on Oct 09 starting about 4.5 hours after the burst with UVES. In the UVES spectrum we clearly detect the Ly-alpha around lambda 3600 A at a redshift z = 1.96, further analysis of this spectrum are ongoing. In light of this, from a refined analysis of our VLT/FORS2 spectrum of this GRB (D'Avanzo et al. GCN 8345), we can identify the metal lines reported by Cucchiara et al. (GCN 8346) and the absorption lines CrII(2056, 2062,2066) and ZnII(2062) all at a redshift z = 1.9685.
Our results are thus in agreement with what reported by Cucchiara et al.
GCN Circular #8351
GRB 081008, 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/UMD), K. McLean (GSFC/UMD), A. M. Parsons (GSFC), J. L. Racusin (PSU), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU); (i.e. the Swift-BAT team):
Using the data set from T-240 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 081008 (trigger #331093) (Racusin et al., GCN Circ. 8344). The BAT ground-calculated position is RA, Dec = 279.968, -57.433 deg which is
```
    RA(J2000)  =  18h 39m 52.4s
    Dec(J2000) = -57d 25' 58.8"
```
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 81%.
The mask-weighted lightcurve shows two strong peaks at T+0 and T+110s. T90 (15-350 keV) is 185.5 +- 40.3 sec (estimated error including systematics).
The time-averaged spectrum from T-65 to T+201 sec is best fit by a simple power-law model. A cutoff-power law model is also an acceptable fit with an E_peak of 88 keV. The power law index of the time-averaged spectrum is 1.69 +- 0.07. The fluence in the 15-150 keV band is 4.3 +- 0.2 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+7.52 sec in the 15-150 keV band is 1.3 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/331093/BA/
GCN Circular #8356
B. E. Cobb (UC Berkeley) reports:
Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained optical/IR imaging of the error region of GRB 081008 (GCN 8344, Racusin et al.). Several dithered images were obtained in each filter, with total summed exposure times of 180s in each of BRIJK and 120s in each of H and V.
```
At a mid-exposure time of 2008-10-08 23:53 (3.9 hrs post-burst),
the GRB afterglow (GCN 8343, Rykoff et al. and GCN 8344, Racusin et al.)
is detected with the following magnitudes:
B = 19.86 +/- 0.07
R = 18.46 +/- 0.04
I = 18.09 +/- 0.05
J = 17.13 +/- 0.97
H = 16.52 +/- 0.77
K = 16.08 +/- 0.90
```
Observations were obtained under non-photometric conditions. In optical, these preliminary magnitudes are calibrated against several USNO-B1.0 stars in the field, so there is likely an additional photometric calibration error of ~0.2 magnitudes. In the IR, calibration is against 2MASS stars.
Additional observations were obtained at 5.0 hrs and 6.4 hrs post-burst. Between 3.9 hrs and 6.4 hours post-burst, the afterglow decays rapidly with an approximate optical decay rate of alpha~-1.5 (where afterglow flux is proportional to t^alpha).
GCN Circular #8367
Peter Nelson (Ellinbank, Victoria, Australia) reports to the AAVSO International High Energy Network the following optical observation of GRB081008 (GCN #8344 Racusin et al.; GCN #8343 Rykoff et al.):
Peter Nelson has obtained a limiting magnitude on the optical afterglow of GRB081008 (Racusin et al., GCN #8344). The optical afterglow position RA: 18:39:50, Dec: -57:25:52 found by Rykoff et al. (GCN #8343) was observed for a total of 480 seconds using a 0.32-meter Newtonian with an SBIG ST8XE CCD and an R filter. The mid-point of the observations was 2008 Oct 09.4150 UT, approximately 14 hours after the burst. The afterglow was not detected to an upper limit of R=18.2, using USNO-A2.0 star 0300-34687382 (R=11.8) as the comparison. This upper limit is consistent with the R-band magnitude of R=18.46 on 2008 Oct 08.9951 observed by Cobb et al. (GCN #8356).
A detailed report of these observations is available on the AAVSO website at ftp://ftp.aavso.org/grb/PeterNelson_081008_2454752.03073_.txt
A fits image is available at ftp://ftp.aavso.org/grb/PeterNelson_081008_2454752.03073_.fits
The AAVSO thanks the Curry Foundation for their continued support of the AAVSO International High Energy Network.
GCN Circular #8372
A. Cucchiara, D. B. Fox (Penn State), S. B. Cenko (Berkeley) and E. Berger (Harvard) report on behalf of a larger collaboration:
"Analysis of the Gemini-South GMOS r-band acquisition image taken on October 8 (Cucchiara et al., 8346) shows the presence of an extended source at 2-arcsec distance from the afterglow of GRB 081008. The source is serendipitously located in the GMOS slit during our spectroscopic observations.
Extracting the spectrum of this object reveals the presence of metal absorption features including FeII(1608), AlII(1670), NiII(1703), AlIII(1854), and CrII(2056,2062,2066) at a common redshift z=1.967. We conclude that this galaxy is associated with the strong z=1.967 absorber observed in the GRB afterglow spectrum, and is a candidate host galaxy to the GRB.
The galaxy is located at (J2000) RA 18:39:49.64, Dec -57:25:53.41. At z=1.967 its 2.1-arcsec offset from the line of sight to GRB 081008 corresponds to 16 kpc in projection.
We report the R-band magnitude of the GRB and the Host, calibrated using USNO catalog magnitudes of 4 nearby USNO stars: At the time of the acquisition image, 00:01 UT, we find R=18.32 +- 0.1 mag for the GRB afterglow, and R=20.75 +- 0.1 mag for the galaxy.
The observed host galaxy magnitude corresponds to an absolute AB magnitude (at central wavelength 220 nm in the host galaxy frame) of M_220(AB) = -21.5 mag; assuming a comparable rest-frame B-band luminosity would place this galaxy among the brightest GRB host galaxies if it is the host galaxy of GRB 081008 (Berger et al., Apj 2007, 657).
While we cannot confirm a host identification at this time, we note that the presence of an associated DLA in the VLT/FORS2 spectrum (d'Avanzo et al., GCN 8350), along with the reported absence of any absorption signature due to neutral hydrogen at z>1.967, both support this suggestion."
GCN Report 173.1
GCN_Report 173.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_173_1.pdf by J. Racusin at PSU titled: "Final Swift report on GRB 081008"
GCN Circular #8633
Aquib Moin (Curtin Institute of Radio Astronomy / Australia Telescope National Facility), Steven Tingay (Curtin Institute of Radio Astronomy), Chris Phillips (Australia Telescope National Facility), Gregory Taylor (University of New Mexico), Mark Wieringa (Australia Telescope National Facility) and Ralph Martin (Perth Observatory) report:
We observed the SWIFT/UVOT refined position of the GRB 081008 optical afterglow (GCN 8348) at 4.800 and 4.928 GHz with the Australia Telescope Compact Array (ATCA) between 01:15:05 UT, November 24, 2008 and 20:35:30 UT, November 25, 2008.
We did not detect a radio source at the optical afterglow position of the GRB 081008 (GCN 8348). The data at 4.800 and 4.928 GHz were merged and the radio flux density at the afterglow position found out to be -0.151 +/- 0.156 mJy/beam (1-sigma).
The Australia Telescope Compact Array (/ Parkes telescope / Mopra telescope / Long Baseline Array) is part of the Australia Telescope which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.
See the 4.800 & 4.928 GHz combined image at:
http://cira.ivec.org/dokuwiki/doku.php/grb/grb081008_field_image
1108.1049 from 5 Aug 11
V. D'Elia et al.: UVES and FORS2 spectroscopy of GRB081008
We study the GRB 081008 environment with simultaneous high- and low-resolution spectroscopy using UVES and FORS2 data acquired ~5 hr after the Swift trigger. The interstellar medium (ISM) of the host galaxy at z=1.9683 is constituted by at least three components which contribute to the line profiles. Component I is the redmost one, and is 20 km/s and 78 km/s redward component II and III, respectively. We detect several ground state and excited absorption features in components I and II. These features have been used to compute the distances between the GRB and the absorbers. Component I is found to be 52 +/-6 pc away from the GRB, while component II presents few excited transitions and its distance is 200+60-80 pc. Component III only features a few, low ionization and saturated lines suggesting that it is even farther from the GRB. The hydrogen column density associated to GRB 081008 is log N_H/cm^-2 = 21.11 +/- 0.10, and the metallicity of the host galaxy is in the range [X/H] = -1.29 to -0.52. In particular, we found [Fe/H]=-1.19 +/- 0.11 and [Zn/H]=-0.52+/- 0.11 with respect to solar values. This discrepancy can be explained by the presence of dust in the GRB ISM, given the opposite refractory properties of iron and zinc. By deriving the depletion pattern for GRB 081008, we find the optical extinction in the visual band to be A_V ~0.19 mag. The Curve of Growth analysis applied to the FORS2 spectra brings column densities consistent at the 3 sigma level to that evaluated from the UVES data using the line fitting procedure. This reflects the low saturation of the detected GRB 081008 absorption features.

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Jochen Greiner, last update: 05-Aug-2011 [Disclaimer]