Gamma-ray Burst 070809

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 09 Aug 07 19:22:39 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     287344,   Seg_Num: 0
GRB_RA:          203.782d {+13h 35m 08s} (J2000),
                 203.886d {+13h 35m 33s} (current),
                 203.096d {+13h 32m 23s} (1950)
GRB_DEC:         -22.134d {-22d 08' 01"} (J2000),
                 -22.173d {-22d 10' 20"} (current),
                 -21.878d {-21d 52' 41"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       5497 [cnts]    Image_Peak=302 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   146     E_range: 25-100 keV
BKG_INTEN:       32658 [cnts]
BKG_TIME:        69725.85 SOD {19:22:05.85} UT
BKG_DUR:         8 [sec]
GRB_DATE:        14321 TJD;   221 DOY;   07/08/09
GRB_TIME:        69737.37 SOD {19:22:17.37} UT
GRB_PHI:         108.68 [deg]
GRB_THETA:        18.80 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     19.15 [sigma]
IMAGE_SIGNIF:    10.98 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  +6  +0  +0 -28  +1 
SUN_POSTN:       139.28d {+09h 17m 08s}  +15.79d {+15d 47' 28"}
SUN_DIST:         73.77 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:       98.75d {+06h 35m 01s}  +27.71d {+27d 42' 27"}
MOON_DIST:       112.92 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:      316.10, 39.62 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      210.16,-11.37 [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 = 269.08,-5.67 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 09 Aug 07 19:23:59 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     287344,   Seg_Num: 0
GRB_RA:          203.7762d {+13h 35m 06.2s} (J2000),
                 203.8807d {+13h 35m 31.3s} (current),
                 203.0905d {+13h 32m 21.7s} (1950)
GRB_DEC:         -22.3200d {-22d 19' 12.0"} (J2000),
                 -22.3587d {-22d 21' 31.4"} (current),
                 -22.0646d {-22d 03' 52.4"} (1950)
GRB_ERROR:       4.3 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       26 [cnts]
IMG_START_DATE:  14321 TJD;   221 DOY;   07/08/09
IMG_START_TIME:  69808.15 SOD {19:23:28.15} UT,   70.8 [sec] since BAT Trigger Time
CENTROID_X:      453.00,  raw= 453  [pixels]
CENTROID_Y:      552.32,  raw= 552  [pixels]
ROLL:            295.19 [deg]
GAIN:            16
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   599.51
GRB_POS_XRT_Z:   355.25
IMAGE_URL:       sw00287344000msxps_rw.img
SUN_POSTN:       139.28d {+09h 17m 08s}  +15.79d {+15d 47' 27"}
SUN_DIST:         73.84 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:       98.77d {+06h 35m 04s}  +27.71d {+27d 42' 22"}
MOON_DIST:       112.98 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:      316.04, 39.44 [deg] galactic lon,lat of the burst
ECL_COORDS:      210.23,-11.54 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 09 Aug 07 19:23:58 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     287344,   Seg_Num: 0
GRB_RA:          203.7762d {+13h 35m 06.2s} (J2000),
                 203.8807d {+13h 35m 31.3s} (current),
                 203.0905d {+13h 32m 21.7s} (1950)
GRB_DEC:         -22.3200d {-22d 19' 12.0"} (J2000),
                 -22.3587d {-22d 21' 31.4"} (current),
                 -22.0646d {-22d 03' 52.4"} (1950)
GRB_ERROR:       4.3 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       3.94e-08 [erg/cm2/sec]
GRB_SIGNIF:      5.09 [sigma]
IMG_START_DATE:  14321 TJD;   221 DOY;   07/08/09
IMG_START_TIME:  69808.15 SOD {19:23:28.15} UT,   70.8 [sec] since BAT Trigger Time
TAM[0-3]:        327.65 237.21 261.41 243.40
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       139.28d {+09h 17m 08s}  +15.79d {+15d 47' 27"}
SUN_DIST:         73.84 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:       98.77d {+06h 35m 04s}  +27.71d {+27d 42' 22"}
MOON_DIST:       112.98 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:      316.04, 39.44 [deg] galactic lon,lat of the burst
ECL_COORDS:      210.23,-11.54 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The object found at this position is either a very bright burst or a cosmic ray hit.  
COMMENTS:        Examine the XRT Image to differentiate (CRs are much more compact; see examples at:  
COMMENTS:        http://www.swift.psu.edu/xrt/XRT_Postage_Stamp_Image_Photo_Gallery.htm .

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 09 Aug 07 19:24:04 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     287344,   Seg_Num: 0
GRB_RA:          203.7762d {+13h 35m 06.2s} (J2000),
                 203.8807d {+13h 35m 31.3s} (current),
                 203.0905d {+13h 32m 21.7s} (1950)
GRB_DEC:         -22.3200d {-22d 19' 12.0"} (J2000),
                 -22.3587d {-22d 21' 31.4"} (current),
                 -22.0646d {-22d 03' 52.4"} (1950)
GRB_ERROR:       4.3 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       26 [cnts]
IMG_START_DATE:  14321 TJD;   221 DOY;   07/08/09
IMG_START_TIME:  69808.15 SOD {19:23:28.15} UT,   70.8 [sec] since BAT Trigger Time
CENTROID_X:      453.00,  raw= 453  [pixels]
CENTROID_Y:      552.32,  raw= 552  [pixels]
ROLL:            295.19 [deg]
GAIN:            16
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   599.51
GRB_POS_XRT_Z:   355.25
IMAGE_URL:       sw00287344000msxps_rw.img
SUN_POSTN:       139.28d {+09h 17m 08s}  +15.79d {+15d 47' 27"}
SUN_DIST:         73.84 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:       98.77d {+06h 35m 04s}  +27.71d {+27d 42' 21"}
MOON_DIST:       112.98 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:      316.04, 39.44 [deg] galactic lon,lat of the burst
ECL_COORDS:      210.23,-11.54 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 09 Aug 07 19:25:59 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     287344,   Seg_Num: 0
GRB_RA:          203.782d {+13h 35m 08s} (J2000),
                 203.886d {+13h 35m 33s} (current),
                 203.096d {+13h 32m 23s} (1950)
GRB_DEC:         -22.134d {-22d 08' 01"} (J2000),
                 -22.173d {-22d 10' 20"} (current),
                 -21.878d {-21d 52' 41"} (1950)
GRB_DATE:        14321 TJD;   221 DOY;   07/08/09
GRB_TIME:        69737.37 SOD {19:22:17.37} UT
TRIGGER_INDEX:   146
GRB_PHI:         108.68 [deg]
GRB_THETA:        18.80 [deg]
DELTA_TIME:      -31.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     19.15 [sigma]
IMAGE_SIGNIF:    10.98 [sigma]
LC_URL:          sw00287344000msb.lc
SUN_POSTN:       139.29d {+09h 17m 09s}  +15.79d {+15d 47' 25"}
SUN_DIST:         73.77 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:       98.79d {+06h 35m 09s}  +27.70d {+27d 42' 14"}
MOON_DIST:       112.89 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:      316.10, 39.62 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      210.16,-11.37 [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 = 269.08,-5.67 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 09 Aug 07 19:33:18 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     287344,   Seg_Num: 0
POINT_RA:        203.756d {+13h 35m 02s} (J2000)
POINT_DEC:       -22.128d {-22d 07' 39"} (J2000)
POINT_ROLL:      295.190d
IMG_START_DATE:  14321 TJD;   221 DOY;   07/08/09
IMG_START_TIME:  69810.96 SOD {19:23:30.96} UT,   73.6 [sec] since BAT Trigger Time
FILTER:          3, V
BKG_MEAN:        3.099
N_STARS:         36
X_OFFSET:        0 [pixels]
Y_OFFSET:        0 [pixels]
X_MAX:           959 [pixels]
Y_MAX:           959 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw00287344000msufc0073.fits
SUN_POSTN:       139.29d {+09h 17m 10s}  +15.79d {+15d 47' 20"}
SUN_DIST:         73.74 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:       98.87d {+06h 35m 28s}  +27.70d {+27d 41' 47"}
MOON_DIST:       112.80 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:      316.07, 39.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      210.14,-11.37 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 09 Aug 07 19:33:46 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     287344,   Seg_Num: 0
POINT_RA:        203.756d {+13h 35m 02s} (J2000)
POINT_DEC:       -22.128d {-22d 07' 39"} (J2000)
POINT_ROLL:      295.190d
IMG_START_DATE:  14321 TJD;   221 DOY;   07/08/09
IMG_START_TIME:  69810.96 SOD {19:23:30.96} UT,   73.6 [sec] since BAT Trigger Time
FILTER:          3, V
BKG_MEAN:        3.099
N_STARS:         36
X_OFFSET:        0 [pixels]
Y_OFFSET:        0 [pixels]
X_MAX:           959 [pixels]
Y_MAX:           959 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw00287344000msufc0073.fits
SUN_POSTN:       139.29d {+09h 17m 10s}  +15.79d {+15d 47' 20"}
SUN_DIST:         73.74 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:       98.87d {+06h 35m 29s}  +27.70d {+27d 41' 45"}
MOON_DIST:       112.80 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:      316.07, 39.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      210.14,-11.37 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 09 Aug 07 19:33:47 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     287344,   Seg_Num: 0
GRB_RA:          203.7761d {+13h 35m 06.2s} (J2000),
                 203.8806d {+13h 35m 31.3s} (current),
                 203.0904d {+13h 32m 21.6s} (1950)
GRB_DEC:         -22.3200d {-22d 19' 12.0"} (J2000),
                 -22.3587d {-22d 21' 31.4"} (current),
                 -22.0646d {-22d 03' 52.4"} (1950)
GRB_ERROR:       4.0 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       3.94e-08 [erg/cm2/sec]
GRB_SIGNIF:      5.09 [sigma]
IMG_START_DATE:  14321 TJD;   221 DOY;   07/08/09
IMG_START_TIME:  69808.14 SOD {19:23:28.14} UT,   70.8 [sec] since BAT Trigger Time
TAM[0-3]:        327.61 237.19 261.35 242.66
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       139.29d {+09h 17m 10s}  +15.79d {+15d 47' 20"}
SUN_DIST:         73.84 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:       98.87d {+06h 35m 29s}  +27.70d {+27d 41' 45"}
MOON_DIST:       112.88 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:      316.04, 39.44 [deg] galactic lon,lat of the burst
ECL_COORDS:      210.23,-11.54 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        TAM values are not valid.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 09 Aug 07 19:34:42 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     287344,   Seg_Num: 0
POINT_RA:        203.756d {+13h 35m 02s} (J2000)
POINT_DEC:       -22.128d {-22d 07' 39"} (J2000)
ROLL:            295.190d
IMG_START_DATE:  14321 TJD;   221 DOY;   07/08/09
IMG_START_TIME:  69810.96 SOD {19:23:30.96} UT,   73.6 [sec] since BAT Trigger Time
FILTER:          3, V
EXPOSURE_ID:     208380213
X_OFFSET:        0 [pixels]
Y_OFFSET:        164 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       0
Y_GRB_POS:       324
BINNING_INDEX:   1
IM_URL:          sw00287344000msuni0073.fits
SUN_POSTN:       139.29d {+09h 17m 10s}  +15.79d {+15d 47' 19"}
SUN_DIST:         73.74 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:       98.88d {+06h 35m 31s}  +27.69d {+27d 41' 42"}
MOON_DIST:       112.79 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:      316.07, 39.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      210.14,-11.37 [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:     Thu 09 Aug 07 19:35:01 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     287344,   Seg_Num: 0
POINT_RA:        203.756d {+13h 35m 02s} (J2000)
POINT_DEC:       -22.128d {-22d 07' 39"} (J2000)
ROLL:            295.190d
IMG_START_DATE:  14321 TJD;   221 DOY;   07/08/09
IMG_START_TIME:  69810.96 SOD {19:23:30.96} UT,   73.6 [sec] since BAT Trigger Time
FILTER:          3, V
EXPOSURE_ID:     208380213
X_OFFSET:        0 [pixels]
Y_OFFSET:        164 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       0
Y_GRB_POS:       324
BINNING_INDEX:   1
IM_URL:          sw00287344000msuni0073.fits
SUN_POSTN:       139.29d {+09h 17m 10s}  +15.79d {+15d 47' 19"}
SUN_DIST:         73.74 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:       98.88d {+06h 35m 32s}  +27.69d {+27d 41' 40"}
MOON_DIST:       112.78 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:      316.07, 39.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      210.14,-11.37 [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:     Thu 09 Aug 07 19:43:49 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     287344,   Seg_Num: 0
POINT_RA:        203.755d {+13h 35m 01s} (J2000)
POINT_DEC:       -22.126d {-22d 07' 32"} (J2000)
POINT_ROLL:      295.190d
IMG_START_DATE:  14321 TJD;   221 DOY;   07/08/09
IMG_START_TIME:  70608.91 SOD {19:36:48.91} UT,   871.5 [sec] since BAT Trigger Time
FILTER:          3, V
BKG_MEAN:        2.845
N_STARS:         41
X_OFFSET:        0 [pixels]
Y_OFFSET:        0 [pixels]
X_MAX:           959 [pixels]
Y_MAX:           959 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    7
SL_URL:          sw00287344000msufc0871.fits
SUN_POSTN:       139.30d {+09h 17m 11s}  +15.79d {+15d 47' 12"}
SUN_DIST:         73.73 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:       98.98d {+06h 35m 55s}  +27.69d {+27d 41' 07"}
MOON_DIST:       112.70 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:      316.07, 39.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      210.14,-11.37 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 09 Aug 07 19:44:16 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     287344,   Seg_Num: 0
POINT_RA:        203.755d {+13h 35m 01s} (J2000)
POINT_DEC:       -22.126d {-22d 07' 32"} (J2000)
POINT_ROLL:      295.190d
IMG_START_DATE:  14321 TJD;   221 DOY;   07/08/09
IMG_START_TIME:  70608.91 SOD {19:36:48.91} UT,   871.5 [sec] since BAT Trigger Time
FILTER:          3, V
BKG_MEAN:        2.845
N_STARS:         41
X_OFFSET:        0 [pixels]
Y_OFFSET:        0 [pixels]
X_MAX:           959 [pixels]
Y_MAX:           959 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    7
SL_URL:          sw00287344000msufc0871.fits
SUN_POSTN:       139.30d {+09h 17m 12s}  +15.79d {+15d 47' 12"}
SUN_DIST:         73.73 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:       98.98d {+06h 35m 56s}  +27.68d {+27d 41' 06"}
MOON_DIST:       112.70 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:      316.07, 39.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      210.14,-11.37 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 09 Aug 07 19:45:25 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     287344,   Seg_Num: 0
POINT_RA:        203.755d {+13h 35m 01s} (J2000)
POINT_DEC:       -22.126d {-22d 07' 32"} (J2000)
ROLL:            295.190d
IMG_START_DATE:  14321 TJD;   221 DOY;   07/08/09
IMG_START_TIME:  70608.91 SOD {19:36:48.91} UT,   871.5 [sec] since BAT Trigger Time
FILTER:          3, V
EXPOSURE_ID:     208381011
X_OFFSET:        319 [pixels]
Y_OFFSET:        319 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       479
Y_GRB_POS:       479
BINNING_INDEX:   1
IM_URL:          sw00287344000msuni0871.fits
SUN_POSTN:       139.30d {+09h 17m 12s}  +15.79d {+15d 47' 11"}
SUN_DIST:         73.73 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:       98.99d {+06h 35m 59s}  +27.68d {+27d 41' 01"}
MOON_DIST:       112.68 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:      316.07, 39.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      210.14,-11.37 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 09 Aug 07 19:45:43 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     287344,   Seg_Num: 0
POINT_RA:        203.755d {+13h 35m 01s} (J2000)
POINT_DEC:       -22.126d {-22d 07' 32"} (J2000)
ROLL:            295.190d
IMG_START_DATE:  14321 TJD;   221 DOY;   07/08/09
IMG_START_TIME:  70608.91 SOD {19:36:48.91} UT,   871.5 [sec] since BAT Trigger Time
FILTER:          3, V
EXPOSURE_ID:     208381011
X_OFFSET:        319 [pixels]
Y_OFFSET:        319 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       479
Y_GRB_POS:       479
BINNING_INDEX:   1
IM_URL:          sw00287344000msuni0871.fits
SUN_POSTN:       139.30d {+09h 17m 12s}  +15.79d {+15d 47' 11"}
SUN_DIST:         73.73 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:       99.00d {+06h 35m 60s}  +27.68d {+27d 41' 00"}
MOON_DIST:       112.68 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:      316.07, 39.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      210.14,-11.37 [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 #6728
F. E. Marshall (NASA/GSFC), D. N. Burrows (PSU), M. M. Chester (PSU), J. R. Cummings (NASA/UMBC), P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), C. Guidorzi (Univ Bicocca&INAF-OAB), S. T. Holland (CRESST/GSFC/USRA), J. A. Kennea (PSU), K. L. Page (U Leicester), D. M. Palmer (LANL), P. Romano (Univ. Bicocca & INAF-OAB), T. Sakamoto (NASA/ORAU), G. Sato (GSFC/ISAS), B. Sbarufatti (INAF-IASFPA), M. Stamatikos (NASA/ORAU) and R. L. C. Starling (U Leicester) report on behalf of the Swift Team:
At 19:22:17 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 070809 (trigger=287344). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 203.782, -22.134 which is
```
   RA(J2000) = 13h 35m 08s
   Dec(J2000) = -22d 08' 01"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak structure with a duration of about 2 sec. The peak count rate was ~2500 counts/sec (15-350 keV), at ~0 sec after the trigger. It is currently unclear from the spectral data if this is a short hard burst.
The XRT began observing the field at 19:23:28 UT, 71 seconds after the BAT trigger. Using prompt downlinked data, we found a fading X-ray source located at RA, Dec 203.7708, -22.1408 which is equivalent to
```
   RA(J2000)  =  13h 35m 04.99s
   Dec(J2000) = -22d 08' 26.2"
```
with an uncertainty of 4.0 arcseconds (radius, 90% containment). This location is 44.7 arcseconds from the BAT on-board position, inside the BAT error circle.
UVOT took a finding chart exposure of nominal 400 seconds with the V filter starting 74 seconds after the BAT trigger. However, the 8'x8' region for the list of sources generated on-board does not cover the ground-generated XRT error circle, so no statement can be made regarding an optical counterpart.
Burst Advocate for this burst is F. E. Marshall (marshall AT milkyway.gsfc.nasa.gov). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 09 Aug 07 19:50:26 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     287344,   Seg_Num: 0
POINT_RA:        203.755d {+13h 35m 01s} (J2000)
POINT_DEC:       -22.126d {-22d 07' 32"} (J2000)
POINT_ROLL:      295.191d
IMG_START_DATE:  14321 TJD;   221 DOY;   07/08/09
IMG_START_TIME:  71014.25 SOD {19:43:34.25} UT,   1276.9 [sec] since BAT Trigger Time
FILTER:          4, UVM2
BKG_MEAN:        0.071
N_STARS:         3
X_OFFSET:        0 [pixels]
Y_OFFSET:        0 [pixels]
X_MAX:           959 [pixels]
Y_MAX:           959 [pixels]
DET_THRESH:      4
PHOTO_THRESH:    2
SL_URL:          sw00287344000msufc1276.fits
SUN_POSTN:       139.30d {+09h 17m 13s}  +15.79d {+15d 47' 07"}
SUN_DIST:         73.73 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:       99.05d {+06h 36m 12s}  +27.68d {+27d 40' 42"}
MOON_DIST:       112.64 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:      316.07, 39.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      210.14,-11.37 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 09 Aug 07 19:50:51 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     287344,   Seg_Num: 0
POINT_RA:        203.755d {+13h 35m 01s} (J2000)
POINT_DEC:       -22.126d {-22d 07' 32"} (J2000)
POINT_ROLL:      295.191d
IMG_START_DATE:  14321 TJD;   221 DOY;   07/08/09
IMG_START_TIME:  71014.25 SOD {19:43:34.25} UT,   1276.9 [sec] since BAT Trigger Time
FILTER:          4, UVM2
BKG_MEAN:        0.071
N_STARS:         3
X_OFFSET:        0 [pixels]
Y_OFFSET:        0 [pixels]
X_MAX:           959 [pixels]
Y_MAX:           959 [pixels]
DET_THRESH:      4
PHOTO_THRESH:    2
SL_URL:          sw00287344000msufc1276.fits
SUN_POSTN:       139.30d {+09h 17m 13s}  +15.79d {+15d 47' 07"}
SUN_DIST:         73.73 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:       99.05d {+06h 36m 13s}  +27.68d {+27d 40' 41"}
MOON_DIST:       112.63 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:      316.07, 39.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      210.14,-11.37 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_srclist.fits.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 09 Aug 07 19:51:51 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     287344,   Seg_Num: 0
POINT_RA:        203.755d {+13h 35m 01s} (J2000)
POINT_DEC:       -22.126d {-22d 07' 32"} (J2000)
ROLL:            295.191d
IMG_START_DATE:  14321 TJD;   221 DOY;   07/08/09
IMG_START_TIME:  71014.25 SOD {19:43:34.25} UT,   1276.9 [sec] since BAT Trigger Time
FILTER:          4, UVM2
EXPOSURE_ID:     208381416
X_OFFSET:        319 [pixels]
Y_OFFSET:        319 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       479
Y_GRB_POS:       479
BINNING_INDEX:   1
IM_URL:          sw00287344000msuni1276.fits
SUN_POSTN:       139.30d {+09h 17m 13s}  +15.79d {+15d 47' 06"}
SUN_DIST:         73.73 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:       99.06d {+06h 36m 15s}  +27.68d {+27d 40' 37"}
MOON_DIST:       112.62 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:      316.07, 39.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      210.14,-11.37 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 09 Aug 07 19:52:10 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     287344,   Seg_Num: 0
POINT_RA:        203.755d {+13h 35m 01s} (J2000)
POINT_DEC:       -22.126d {-22d 07' 32"} (J2000)
ROLL:            295.191d
IMG_START_DATE:  14321 TJD;   221 DOY;   07/08/09
IMG_START_TIME:  71014.25 SOD {19:43:34.25} UT,   1276.9 [sec] since BAT Trigger Time
FILTER:          4, UVM2
EXPOSURE_ID:     208381416
X_OFFSET:        319 [pixels]
Y_OFFSET:        319 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       479
Y_GRB_POS:       479
BINNING_INDEX:   1
IM_URL:          sw00287344000msuni1276.fits
SUN_POSTN:       139.30d {+09h 17m 13s}  +15.79d {+15d 47' 06"}
SUN_DIST:         73.73 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:       99.07d {+06h 36m 16s}  +27.68d {+27d 40' 36"}
MOON_DIST:       112.62 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:      316.07, 39.63 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      210.14,-11.37 [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.  
COMMENTS:        The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.

GCN Circular #6729
E.S. Rykoff (U Mich), F. Yuan (U Mich), C. Akerlof (U Mich), H. Swan (U Mich), B. E. Schaefer (Louisiana State), R. Quimby (U Texas), report on behalf of the ROTSE collaboration:
ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, responded to GRB 070809 (Swift trigger 287344; Marshall, et al., GCN 6728), producing images beginning 10.2 s after the GCN notice time. An automated response took the first image at 19:22:48.2 UT, 30.9 s after the burst, under excellent conditions. We took 10 5-sec, 10 20-sec and 10 60-sec exposures. These unfiltered images are calibrated relative to USNO A2.0 (R). Imaging is on going.
Comparison to the DSS (second epoch) reveals no new sources within the 3-sigma Swift/BAT error circle or the XRT error circle, for both single images and coadding into sets of 10. Individual images have limiting magnitudes ranging from 15.8-17.4; we set the following specific limits.
```
  start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
  --------------------------------------------------------------------
  19:22:48.2   19:22:53.2         5     16.1           30.9       N
  19:22:48.2   19:24:06.2        78     17.5           30.9       Y
  19:24:19.9   19:29:06.8       286     18.1          122.6       Y
  19:29:16.6   19:40:41.9       685     18.4          419.3       Y
```
GCN Circular #6731
D. A. Perley (UC Berkeley), P. Nugent (LBL), and J. S. Bloom (UCB) report:
We have created a stacked image through the co-addition of 8 unfiltered images taken by the NEAT collaboration and 13 images in the RG610 filter taken by the Palomar-Quest Consortium at the Palomar Oschin Schmidt telescope (obtained from 2002-2006) of GRB 070809 (Marshall et al., GCN 6728), possibly a short-hard burst.
No object is detected within the XRT error circle (GCN 6728) to a limiting magnitude (3-sigma) of R~22.3.
This message may be cited.
GCN Circular #6732
H. Krimm (GSFC/USRA), L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), C. Markwardt (GSFC/UMD), F. E. Marshall (NASA/GSFC), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU) (i.e. the Swift-BAT team):
Using the data set from T-120 to T+183 sec from the recent telemetry downlink, we report further analysis of BAT GRB 070809 (trigger #287344) (Marshall, et al., GCN Circ. 6728). The BAT ground-calculated position is RA, Dec = 203.767, -22.119 deg which is
```
   RA(J2000)  =  13h 35m 4.2s 
   Dec(J2000) = -22d 7' 7" 
```
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 74%.
The mask-weighted light curve consists of a single peak starting at ~T-0.3 and ending at ~T+1.2 sec. T90 (15-350 keV) is 1.3 +- 0.1 sec (estimated error including systematics).
The time-averaged spectrum from T-0.4 to T+1.1 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.69 +- 0.22. The fluence in the 15-150 keV band is 1.0 +- 0.1 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+0.08 sec in the 15-150 keV band is 1.2 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. We note that the T90-hardness_ratio for this burst falls in between the SHB and LSB clusters in the T90-HR scatter plot for Swift-BAT.
GCN Circular #6737
P.A. Evans, K.L. Page (U. Leicester) and F. E. Marshall (NASA/GSFC) report on behalf of the Swift-XRT team:
We have analysed the first 11 ks of Swift XRT data for GRB 070809 (Marshall et al. GCN Circ 6728), all of which is in Photon Counting (PC) mode. We find a refined XRT position of RA, Dec = 203.7699, -22.1416 degrees, which is equivalent to:
```
RA (J2000) = 13h 35m 4.78s
Dec(J2000) = -22d 08' 29.8"
```
with an estimated uncertainty of 3.5 arcsec (radius, 90% containment including systematics). This is 81.9" from the refined BAT position (Krimm et al. GCN Circ 6732) and 4.2" from the XRT position reported in GCN Circ 6728.
The XRT light curve shows fading behaviour which is well fitted by a power-law with two breaks. The initial decay followed a slope of alpha=2.3 (+0.7/-1.1), and then broke at ~T0+200 s to a shallow decay with alpha=0.28 (+/-0.13). The shallow phase ended at approximately T0+10000 s and the current decay follows a slope of alpha=1.35 (+0.80/-0.72).
The PC mode spectrum from T0+85-25000 s is well fitted by an absorbed power-law with a column density of 6.7e20 (+7.0e20/-5.3e20) cm^-2, consistent with the Galactic value of 6.40e20 cm^-2 (Kalberla et al. 2005). The spectral slope was gamma=1.49 (+0.25/-0.22), consistent with the BAT value (GCN Circ 6732). The observed (unabsorbed) 0.3-10 keV flux is 1.64e-12 (1.79e-12) erg cm^-2 s^-1.
If the source continues to decay with alpha=1.35, we predict a count rate of 1.7e-3 counts s^-1 at T0+24 hours, which corresponds to an observed (unabsorbed) flux of 1.09e-13 (1.20e-13) erg cm^2 s^-1.
This circular is an official product of the Swift/XRT team.
GCN Circular #6739
D. A. Perley (UC Berkeley), C. C. Thoene (DARK, UCB), J. Cooke (UC Irvine), J. S. Bloom (UCB), and E. Barton (UCI) report:
Starting at 06:21:52 UT (2007-08-10), we imaged the field of GRB 070809 (GCN 6728), a short or intermediate-duration (GCN 6732) burst, with the Keck I telescope (+LRIS). We obtained under very high airmass (>2.6) and intervening cirrus 4x300 seconds of imaging in R band and 4x330 seconds in g band.
At the edge of the refined XRT error circle (GCN 6737) we detect a single, faint source in both filters, with coordinates:
```
RA = 13:35:04.55
dec = -22:08:30.8
(err: 0.4")
```
Relative to the USNO B1.0 star at 13:35:09.80 -22:09:15.9 (R2=19.55) we measure a preliminary magnitude of R~24.0. It is not possible to tell whether the object is fading, but it does not appear visibly extended.
We note also the presence of an edge-on galaxy near the error circle, at coordiates of 13:35:04.25, -22:08:26.8.
No other objects are present in or near the error circle to a limiting magnitude of R~25.5.
An image of the field is available at http://lyra.berkeley.edu/~dperley/070809/070809keckR.png
GCN Circular #6744
M.M. Chester (PSU) and F.E. Marshall (NASA/GSFC) report on behalf of the Swift UVOT team:
The Swift/UVOT observed the field of GRB 070809 (Marshall et al., GCN Circ. 6728) beginning 2007-08-09, 20:50:54, 5317 seconds after the BAT trigger.
We do not find any new source in any of the UVOT observations inside the Swift/XRT error circle (RA,DEC(J2000)= 203.7708, -22.1408).
The 3-sigma upper limits for detecting a source inside the XRT error circle in the co-added frames are:
```
Filter   Tstart   Tstop    Exp     Magnitude
            (s)     (s)     (s)    (3-sigma UL)
v        6344     18560   1251       20.8
b        5932     24593    614       21.3
u        5727     24363   1911       21.7
uvw1     5523     23449   2164       21.7
uvm2     5317     19316   2018       21.7
uvw2     6139     17646   1279       21.6
```
The values quoted above are not corrected for the expected Galactic extinction corresponding to a reddening of E_{B-V} = 0.09 mag in the direction of the burst (Schlegel et al. 1998).
GCN Circular #6751
M.M. Chester (PSU) and F.E. Marshall (NASA/GSFC) report on behalf of the Swift UVOT team:
We have identified an additional exposure of GRB 070809 made by the Swift/UVOT that covers the XRT error circle, and can now provide an optical upper limit at a much earlier time, 74 seconds after the BAT trigger. In addition, an error in the photometry analysis previously reported (Chester et al., GCN Circ. 6744) has been identified, and corrected upper limits are reported below.
```
Filter   Tstart   Tstop    Exp     Magnitude
           (s)      (s)     (s)    (3-sigma UL)
v (FC)     74      474    394       19.1
v        6344    18560   1251       20.2
b        5932    24593    614       20.4
u        5727    24363   1911       20.6
uvw1     5523    23449   2164       20.6
uvm2     5317    19316   2018       21.0
uvw2     6139    17646   1279       20.6
```
GCN Report 80.1
GCN_Report 80.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_80_1.pdf by F.E. Marshall at NASA/GSFC titled: "Swift Observations of GRB 070809"
GCN Circular #6774
D. A. Perley (UC Berkeley), C. C. Thoene (DARK, UCB), and J. S. Bloom (UCB) report:
After our initial observations (GCN 6739) of the possibly short GRB 070809 (Palmer et al., GCN 6728), we obtained a second series of imaging the following night using the Keck I telescope (+LRIS).
We imaged the field for a total of 640s (R) and 880s (g) simultaneously in a series of images starting at 06:20:17 UT (2007-08-11) at very high airmass.
The point-like source reported in GCN 6739 visible the first night has significantly faded, and is detectable only at the 3 sigma level in R-band and is undetected in g-band. Using an absolute calibration relative to Landolt standard stars, we calculate magnitudes of this source of:
```
UT (mid-time)     t_burst (hr)  magnitude
2007-08-10 06:35  11.21         R = 24.1 +/- 0.2
                                g = 25.7 +/- 0.2
2007-08-11 06:31  35.14         R = 25.0 +/- 0.3
                                g > 26.0 (3-sigma)
```
We caution that the source is very close to a bright (R~13) star and slightly blended with a diffraction spike in our imaging. This and the very high airmass of the observations may create additional uncertainties in the photometry.
In addition, we acquired a 2x600s spectrum of the nearby edge-on galaxy noted in GCN 6739 during twilight starting at 05:46 UT (2007-08-11), covering the wavelength range from about 3800 to 9200 AA. No obvious emission lines are detected.
GCN Circular #6788
S.D. Barthelmy (GSFC), T. Sakamoto (GSFC), J. Norris (SLAC), N. Gehrels (GSFC) report:
GRB 070809 (Marshall GCN 6728 and Krimm GCN 6732) is very likely a short burst. We base this on four results:
1) The spectral lag in 25-50 to 100-350 keV bands is consistent with zero: +11 ms +38-61 ms for 8 ms binning.
2) The T90 was 1.3 +- 0.1 sec which is in the 'short' range of BAT burst durations (see figure 9 of the BAT1 catalog paper; Sakamoto et al., accepted in ApJS, arXiv:0707.4626)
3) The fluence hardness ratio S(50-100 keV)/S(25-50 keV) is 1.24 +- 0.27 (90% error), which is consistent with the BAT short GRB population (see figure 10 of the BAT1 catalog paper; Sakamoto et al., accepted in ApJS, arXiv:0707.4626).
4) The XRT light curve showed a flat phase often seen with long bursts. However, some short bursts also have such a phase (GRB 050724 and 051221A).
GCN Circular #7889
D. A. Perley, J. S. Bloom, M. Modjaz, A. A. Miller, J. Shiode, J. Brewer, D. Starr, and R. Kennedy (UC Berkeley) report:
GRB 070809 was a short-hard burst (Barthelmy et al., GCN 6788) detected by Swift. In our observations on 2007-08-10 and 2007-08-11 we detected a very faint optical afterglow candidate and presented evidence (at about the 3-sigma level) for fading between the two nights. (GCNs 6739, GCN 6774).
On the night of 2008-02-10, we re-imaged the field using Keck I (+LRIS), again in R and g filters simultaneously, for a combined 2550s (R) and 2820s (g). We unambiguously confirm the fading behavior of the optical transient, with no detection in either filter to R > 25.0, g > 26.3. We rule out the presence of a host galaxy coincident with the transient location to the same level. (An color image of the field is posted to http://lyra.berkeley.edu/~dperley/070809/070809host.png. A comparison between the early- and late-time imaging is available at http://lyra.berkeley.edu/~dperley/070809/070809compare.png)
Several other short bursts with no strictly coincident host galaxy have been found to be close in physical projection to relatively low-redshift galaxies (e.g. Bloom et al. 2006, 2007, Stratta et al. 2007, Troja et al. 2008). This burst is not an exception, with an edge-on spiral galaxy centered at an offset of 5.6" to the northwest. Photometry of this source gives magnitudes of R = 21.7 +/- 0.3, g = 22.7 +/- 0.2 (the relatively large uncertainties are due to the extended nature of the source and the variable background due to the presence of a nearby bright star).
On the night of 2008-06-07 we obtained 2x900s of spectroscopy of this source using Keck I (+LRIS), with a PA aligned with the orientation of the galaxy. The galaxy is well contained within the 1 arcsec slit. Two relatively bright emission lines are detected - one at 4542.0 A and one at 6100.1 A. Associating these lines with [O II] and [O III], respectively, the redshift of this galaxy is z=0.2187. No other emission lines are significantly detected.
The line flux of the [O II] doublet is ~2 x 10^-16 erg/s/cm^2 (correcting for Galactic extinction of E(B-V) = 0.09), corresponding to an uncorrected star formation rate (Kewley et al. 2002) of ~0.15 M_sun/year. As the galaxy is edge-on this is likely to be well below the actual value. The velocity dispersion of the galaxy along the slit axis is 110 +/- 20 km/s, which over the observed radius of 1.8" (=6.3 kpc) gives a mass of 1.8 x 10^10 M_sun. These values suggest a relatively small spiral galaxy.
While this galaxy is not particularly massive or luminous, the close proximity (20 kpc in projection at z=0.2187) and lack of a coincident host is strongly suggestive of association given previous short bursts. However, we issue several caveats:
- Some short bursts have been shown to have secure hosts at z~1 (e.g. 060801, 070429B and 070714B: Berger et al. 2007, GCN 6836, GCN7140, Cenko et al. 2008.; see Berger 2008 for a review), and our limiting magnitudes do not rule out relatively underluminous galaxies at this redshift.
- One other probable galaxy is present somewhat closer to the afterglow, a very faint (R = 24.6, g = 25.7) source 2.3" away from the OT position. The probability of chance association of the afterglow position with this source (if it is a galaxy) based on galaxy count/offset statistics is higher than the probability of association with the spiral (~10% vs. ~5%), though they are comparable. The source is at unknown redshift.
- It is possible (but unlikely, GCN 6788) that this event is not a short burst, in which case a even higher-redshift origin would not be surprising.
At a redshift of z=0.2187, the isotropic energy release for this burst would be E_iso = 1.1 * 10^49 erg in the observed 15-150 keV band.
References:
```
Bloom et al. 2006 - ApJ 638,354
Bloom et al. 2007 - ApJ 654,878
Stratta et al. 2007 - A&A 474,827
Troja et al. 2008 - MNRAS 385L,10
Cenko et al. 2008 - arXiv 0802.0874
Berger et al. 2007 - ApJ 664,1000
Berger 2008 - arXiv 0805.0306
```

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Jochen Greiner, last update: 21-Jun-2008 [Disclaimer]