Gamma-ray Burst 080727B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 27 Jul 08 08:13:38 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     318101,   Seg_Num: 0
GRB_RA:          276.870d {+18h 27m 29s} (J2000),
                 276.979d {+18h 27m 55s} (current),
                 276.235d {+18h 24m 56s} (1950)
GRB_DEC:          +1.172d {+01d 10' 20"} (J2000),
                  +1.178d {+01d 10' 40"} (current),
                  +1.140d {+01d 08' 25"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       841 [cnts]    Image_Peak=112 [image_cnts]
TRIGGER_DUR:     0.064 [sec] 
TRIGGER_INDEX:   10418     E_range: 25-100 keV
BKG_INTEN:       30576 [cnts]
BKG_TIME:        29589.02 SOD {08:13:09.02} UT
BKG_DUR:         8 [sec]
GRB_DATE:        14674 TJD;   209 DOY;   08/07/27
GRB_TIME:        29604.70 SOD {08:13:24.70} UT
GRB_PHI:          28.72 [deg]
GRB_THETA:        27.23 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     38.22 [sigma]
IMAGE_SIGNIF:    10.73 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2 +25  +0  +1 +80  +1 
SUN_POSTN:       127.01d {+08h 28m 02s}  +19.09d {+19d 05' 42"}
SUN_DIST:        144.22 [deg]   Sun_angle= -10.0 [hr] (East of Sun)
MOON_POSTN:       51.61d {+03h 26m 25s}  +24.16d {+24d 09' 32"}
MOON_DIST:       129.23 [deg]
MOON_ILLUM:      32 [%]
GAL_COORDS:       31.24,  5.86 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      277.55, 24.43 [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 = 249.66,15.14 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 27 Jul 08 08:15:17 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     318101,   Seg_Num: 0
POINT_RA:        276.886d {+18h 27m 33s} (J2000)
POINT_DEC:        +1.166d {+01d 09' 59"} (J2000)
IMG_START_DATE:  14674 TJD;   209 DOY;   08/07/27
IMG_START_TIME:  29705.93 SOD {08:15:05.93} UT,   101.2 [sec] since BAT Trigger Time
COUNTS:          18    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        1    Max_iter_allowed= 4
ERROR_CODE:      1
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        No source found in the image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 27 Jul 08 08:16:53 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     318101,   Seg_Num: 0
GRB_RA:          276.870d {+18h 27m 29s} (J2000),
                 276.979d {+18h 27m 55s} (current),
                 276.235d {+18h 24m 56s} (1950)
GRB_DEC:          +1.172d {+01d 10' 20"} (J2000),
                  +1.178d {+01d 10' 40"} (current),
                  +1.140d {+01d 08' 25"} (1950)
GRB_DATE:        14674 TJD;   209 DOY;   08/07/27
GRB_TIME:        29604.95 SOD {08:13:24.95} UT
TRIGGER_INDEX:   10418
GRB_PHI:          28.72 [deg]
GRB_THETA:        27.23 [deg]
DELTA_TIME:      7.00 [sec]
TRIGGER_DUR:     0.064 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     38.22 [sigma]
IMAGE_SIGNIF:    10.73 [sigma]
LC_URL:          sw00318101000msb.lc
SUN_POSTN:       127.01d {+08h 28m 03s}  +19.09d {+19d 05' 40"}
SUN_DIST:        144.21 [deg]   Sun_angle= -10.0 [hr] (East of Sun)
MOON_POSTN:       51.64d {+03h 26m 34s}  +24.17d {+24d 09' 59"}
MOON_DIST:       129.25 [deg]
MOON_ILLUM:      32 [%]
GAL_COORDS:       31.24,  5.86 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      277.55, 24.43 [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 = 249.66,15.14 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 27 Jul 08 08:17:20 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     318101,   Seg_Num: 0
POINT_RA:        276.886d {+18h 27m 33s} (J2000)
POINT_DEC:        +1.166d {+01d 09' 59"} (J2000)
POINT_ROLL:      305.897d
IMG_START_DATE:  14674 TJD;   209 DOY;   08/07/27
IMG_START_TIME:  29709.87 SOD {08:15:09.87} UT,   105.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.862
N_STARS:         30
X_OFFSET:        569 [pixels]
Y_OFFSET:        478 [pixels]
X_MAX:           1528 [pixels]
Y_MAX:           1437 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    6
SL_URL:          sw00318101000msufc0105.fits
SUN_POSTN:       127.01d {+08h 28m 03s}  +19.09d {+19d 05' 40"}
SUN_DIST:        144.23 [deg]   Sun_angle= -10.0 [hr] (East of Sun)
MOON_POSTN:       51.64d {+03h 26m 35s}  +24.17d {+24d 10' 03"}
MOON_DIST:       129.25 [deg]
MOON_ILLUM:      32 [%]
GAL_COORDS:       31.24,  5.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      277.57, 24.42 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 27 Jul 08 08:17:48 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     318101,   Seg_Num: 0
POINT_RA:        276.886d {+18h 27m 33s} (J2000)
POINT_DEC:        +1.166d {+01d 09' 59"} (J2000)
POINT_ROLL:      305.897d
IMG_START_DATE:  14674 TJD;   209 DOY;   08/07/27
IMG_START_TIME:  29709.87 SOD {08:15:09.87} UT,   105.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.862
N_STARS:         30
X_OFFSET:        569 [pixels]
Y_OFFSET:        478 [pixels]
X_MAX:           1528 [pixels]
Y_MAX:           1437 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    6
SL_URL:          sw00318101000msufc0105.fits
SUN_POSTN:       127.01d {+08h 28m 03s}  +19.09d {+19d 05' 39"}
SUN_DIST:        144.23 [deg]   Sun_angle= -10.0 [hr] (East of Sun)
MOON_POSTN:       51.65d {+03h 26m 36s}  +24.17d {+24d 10' 07"}
MOON_DIST:       129.25 [deg]
MOON_ILLUM:      32 [%]
GAL_COORDS:       31.24,  5.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      277.57, 24.42 [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:     Sun 27 Jul 08 08:18:40 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     318101,   Seg_Num: 0
POINT_RA:        276.886d {+18h 27m 33s} (J2000)
POINT_DEC:        +1.166d {+01d 09' 59"} (J2000)
ROLL:            305.897d
IMG_START_DATE:  14674 TJD;   209 DOY;   08/07/27
IMG_START_TIME:  29709.87 SOD {08:15:09.87} UT,   105.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     238839312
X_OFFSET:        888 [pixels]
Y_OFFSET:        797 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1048
Y_GRB_POS:       957
BINNING_INDEX:   1
IM_URL:          sw00318101000msuni0105.fits
SUN_POSTN:       127.01d {+08h 28m 03s}  +19.09d {+19d 05' 39"}
SUN_DIST:        144.23 [deg]   Sun_angle= -10.0 [hr] (East of Sun)
MOON_POSTN:       51.66d {+03h 26m 38s}  +24.17d {+24d 10' 14"}
MOON_DIST:       129.26 [deg]
MOON_ILLUM:      32 [%]
GAL_COORDS:       31.24,  5.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      277.57, 24.42 [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:     Sun 27 Jul 08 08:19:05 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     318101,   Seg_Num: 0
POINT_RA:        276.886d {+18h 27m 33s} (J2000)
POINT_DEC:        +1.166d {+01d 09' 59"} (J2000)
ROLL:            305.897d
IMG_START_DATE:  14674 TJD;   209 DOY;   08/07/27
IMG_START_TIME:  29709.87 SOD {08:15:09.87} UT,   105.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     238839312
X_OFFSET:        888 [pixels]
Y_OFFSET:        797 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1048
Y_GRB_POS:       957
BINNING_INDEX:   1
IM_URL:          sw00318101000msuni0105.fits
SUN_POSTN:       127.01d {+08h 28m 03s}  +19.09d {+19d 05' 39"}
SUN_DIST:        144.23 [deg]   Sun_angle= -10.0 [hr] (East of Sun)
MOON_POSTN:       51.66d {+03h 26m 39s}  +24.17d {+24d 10' 18"}
MOON_DIST:       129.26 [deg]
MOON_ILLUM:      32 [%]
GAL_COORDS:       31.24,  5.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      277.57, 24.42 [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:     Sun 27 Jul 08 08:26:18 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     318101,   Seg_Num: 0
POINT_RA:        276.885d {+18h 27m 32s} (J2000)
POINT_DEC:        +1.165d {+01d 09' 53"} (J2000)
POINT_ROLL:      305.895d
IMG_START_DATE:  14674 TJD;   209 DOY;   08/07/27
IMG_START_TIME:  29815.81 SOD {08:16:55.81} UT,   211.1 [sec] since BAT Trigger Time
FILTER:          3, V
BKG_MEAN:        2.001
N_STARS:         65
X_OFFSET:        569 [pixels]
Y_OFFSET:        478 [pixels]
X_MAX:           1528 [pixels]
Y_MAX:           1437 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00318101000msufc0211.fits
SUN_POSTN:       127.02d {+08h 28m 05s}  +19.09d {+19d 05' 35"}
SUN_DIST:        144.23 [deg]   Sun_angle= -10.0 [hr] (East of Sun)
MOON_POSTN:       51.74d {+03h 26m 58s}  +24.19d {+24d 11' 18"}
MOON_DIST:       129.32 [deg]
MOON_ILLUM:      32 [%]
GAL_COORDS:       31.24,  5.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      277.56, 24.42 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 27 Jul 08 08:26:48 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     318101,   Seg_Num: 0
POINT_RA:        276.885d {+18h 27m 32s} (J2000)
POINT_DEC:        +1.165d {+01d 09' 53"} (J2000)
POINT_ROLL:      305.895d
IMG_START_DATE:  14674 TJD;   209 DOY;   08/07/27
IMG_START_TIME:  29815.81 SOD {08:16:55.81} UT,   211.1 [sec] since BAT Trigger Time
FILTER:          3, V
BKG_MEAN:        2.001
N_STARS:         65
X_OFFSET:        569 [pixels]
Y_OFFSET:        478 [pixels]
X_MAX:           1528 [pixels]
Y_MAX:           1437 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00318101000msufc0211.fits
SUN_POSTN:       127.02d {+08h 28m 05s}  +19.09d {+19d 05' 34"}
SUN_DIST:        144.23 [deg]   Sun_angle= -10.0 [hr] (East of Sun)
MOON_POSTN:       51.75d {+03h 26m 59s}  +24.19d {+24d 11' 22"}
MOON_DIST:       129.32 [deg]
MOON_ILLUM:      32 [%]
GAL_COORDS:       31.24,  5.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      277.56, 24.42 [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:     Sun 27 Jul 08 08:27:03 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     318101,   Seg_Num: 0
GRB_RA:          276.8589d {+18h 27m 26.1s} (J2000),
                 276.9677d {+18h 27m 52.2s} (current),
                 276.2239d {+18h 24m 53.7s} (1950)
GRB_DEC:          +1.1630d {+01d 09' 46.8"} (J2000),
                  +1.1687d {+01d 10' 07.4"} (current),
                  +1.1313d {+01d 07' 52.6"} (1950)
GRB_ERROR:       2.5 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  14674 TJD;   209 DOY;   08/07/27
IMG_START_TIME:  29764.00 SOD {08:16:04.00} UT,   159.3 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       127.02d {+08h 28m 05s}  +19.09d {+19d 05' 34"}
SUN_DIST:        144.21 [deg]   Sun_angle= -10.0 [hr] (East of Sun)
MOON_POSTN:       51.75d {+03h 26m 60s}  +24.19d {+24d 11' 24"}
MOON_DIST:       129.35 [deg]
MOON_ILLUM:      32 [%]
GAL_COORDS:       31.23,  5.87 [deg] galactic lon,lat of the burst
ECL_COORDS:      277.54, 24.42 [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:     Sun 27 Jul 08 08:27:47 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     318101,   Seg_Num: 0
POINT_RA:        276.885d {+18h 27m 32s} (J2000)
POINT_DEC:        +1.165d {+01d 09' 53"} (J2000)
ROLL:            305.895d
IMG_START_DATE:  14674 TJD;   209 DOY;   08/07/27
IMG_START_TIME:  29815.81 SOD {08:16:55.81} UT,   211.1 [sec] since BAT Trigger Time
FILTER:          3, V
EXPOSURE_ID:     238839418
X_OFFSET:        888 [pixels]
Y_OFFSET:        797 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1048
Y_GRB_POS:       957
BINNING_INDEX:   1
IM_URL:          sw00318101000msuni0211.fits
SUN_POSTN:       127.02d {+08h 28m 05s}  +19.09d {+19d 05' 34"}
SUN_DIST:        144.22 [deg]   Sun_angle= -10.0 [hr] (East of Sun)
MOON_POSTN:       51.76d {+03h 27m 01s}  +24.19d {+24d 11' 31"}
MOON_DIST:       129.33 [deg]
MOON_ILLUM:      32 [%]
GAL_COORDS:       31.24,  5.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      277.56, 24.42 [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:     Sun 27 Jul 08 08:28:04 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     318101,   Seg_Num: 0
POINT_RA:        276.885d {+18h 27m 32s} (J2000)
POINT_DEC:        +1.165d {+01d 09' 53"} (J2000)
ROLL:            305.895d
IMG_START_DATE:  14674 TJD;   209 DOY;   08/07/27
IMG_START_TIME:  29815.81 SOD {08:16:55.81} UT,   211.1 [sec] since BAT Trigger Time
FILTER:          3, V
EXPOSURE_ID:     238839418
X_OFFSET:        888 [pixels]
Y_OFFSET:        797 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1048
Y_GRB_POS:       957
BINNING_INDEX:   1
IM_URL:          sw00318101000msuni0211.fits
SUN_POSTN:       127.02d {+08h 28m 05s}  +19.09d {+19d 05' 34"}
SUN_DIST:        144.22 [deg]   Sun_angle= -10.0 [hr] (East of Sun)
MOON_POSTN:       51.76d {+03h 27m 02s}  +24.19d {+24d 11' 33"}
MOON_DIST:       129.33 [deg]
MOON_ILLUM:      32 [%]
GAL_COORDS:       31.24,  5.85 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      277.56, 24.42 [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 #8022
S. Immler (CRESST/GSFC/UMD), W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), P. A. Evans (U Leicester), C. Guidorzi (INAF-OAB), S. D. Hunsberger (PSU), W.B Landsman (GSFC), C. B. Markwardt (CRESST/GSFC/UMD), K. L. Page (U Leicester), D. M. Palmer (LANL), A. M. Parsons (GSFC), D. Perez (U Leicester), T. Sakamoto (NASA/UMBC) and R. L. C. Starling (U Leicester) report on behalf of the Swift Team:
At 08:13:24 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 080727B (trigger=318101). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 276.870, +1.172 which is
```
   RA(J2000) = 18h 27m 29s
   Dec(J2000) = +01d 10' 20"
```
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 ~18,000 counts/sec (15-350 keV), at 6 sec after the trigger.
The XRT began observing the field at 08:15:05.9 UT, 101.2 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 276.85898, 1.16304 which is equivalent to:
```
   RA(J2000)  = 18h 27m 26.16s
   Dec(J2000) = +01d 09' 47.0"
```
with an uncertainty of 2.8 arcseconds (radius, 90% containment). This location is 51 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 in excess of the Galactic value (3.64e+21 cm^-2, Kalberla et al. 2005), with an excess column of 4.7 (+4.37/-3.38) x 10^21 cm^-2 (90% confidence).
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 typical 3-sigma upper limit has been about 18.5 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 1.94.
Burst Advocate for this burst is S. Immler (immler 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 Circular #8023
P. D'Avanzo, S. Covino, L.A. Antonelli, 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 080727B (Immler et al. GCN 8022) on July 27 starting at 08:14:25 UT (61 seconds after the burst). Observations were carried out at high airmass. In a series of 10s and 30s exposures we do not see any afterglow candidate inside the XRT error box down to R > 16.0 and H > 13.0 (3sigma c.l.).
GCN Circular #8024
W. Li, R. Chornock, D. A. Perley, J. S. Bloom, and A. V. Filippenko, University of California at Berkeley, on behalf of the KAIT GRB team, report:
The robotic 0.8-m KAIT located at Lick Observatory responded to GRB 080727B (Immler et al. GCN 8022) automatically on July 27 starting at 08:14:12 UT (48 seconds after the burst). A series of images were taken in the V, I, and clear filters. We detected a fading new object at the following location:
```
RA  (J2000) =  18h27m26.05s   +/- 0.3"
Dec (J2000) = +01d09'47.7"    +/- 0.3" , 
```
suggesting that this is the optical afterglow of the GRB. We report the following preliminary photometry (calibrated to USNO B1):
```
UT start  exptime  filter     mag     err

08:14:12  2 s      clear   18.20    0.16
08:14:17  2 s      clear   18.38    0.16
08:14:20  2 s      clear   18.45    0.23
```
The power-law decay index between t = 49 s and 72 s after the burst is -1.44 +/- 0.59. Further analysis is ongoing.
GCN Circular #8026
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 2097 s of XRT Photon Counting mode data and 1 UVOT images for GRB 080727B, 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 = 276.85851, +1.16272 which is equivalent to:
```
RA (J2000): 18h 27m 26.04s
Dec (J2000): +01d 09' 45.8"
```
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 #8030
W. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC), 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), 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+182 sec from the recent telemetry downlink, we report further analysis of BAT GRB 080727B (trigger #318101) (Immler, et al., GCN Circ. 8022). The BAT ground-calculated position is RA, Dec = 276.871, 1.173 deg which is
```
   RA(J2000)  =  18h 27m 29.1s 
   Dec(J2000) = +01d 10' 23.2" 
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 69%.
The mask-weighted light curve shows two big FRED-like pulses from T-0.5 to T+3 sec and from T+5.5 to T+9.5 sec. There are several pulses starting at T+2.5, T+7.2, T+7.5, and T+8.8 sec. T90 (15-350 keV) is 8.6 +- 0.2 sec (estimated error including systematics).
The time-averaged spectrum from T-0.2 to T+9.4 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.80 +- 0.17, and Epeak of 226.6 +- 120.2 keV (chi squared 43.60 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 3.1 +- 0.1 x 10^-06 erg/cm2 and the 1-sec peak flux measured from T-0.04 sec in the 15-150 keV band is 7.6 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.12 +- 0.04 (chi squared 54.09 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/318101/BA/
GCN Circular #8031
P.A. Evans (U. Leicester) and S. Immler (CRESST/GSFC/UMD) report on behalf of the Swift-XRT team:
We have analysed 1.6 ks of XRT data for GRB 080727B (Immler et al., GCN Circ 8022). The data were taken in two snapshots; the first started 105 s after the trigger and contained 51 s of Windowed Timing mode data followed by 500 s of Photon Counting (PC) mode data. The second snapshot began at T0+11 ks, and contained 1.2 ks of data, all in PC mode.
The UVOT-enhanced XRT position has been given by Goad et al. (GCN Circ. 8026).
The light curve shows an initial steep decay with a power-law index of 2.47 (+1.38, -0.39), with a break to a shallower decay of 1.05 (+0.20, -0.13). The break occurred at T0+267 (+89, -100) s.
A spectrum formed from all available PC mode data can be modelled by an absorbed power law with a photon index on 1.61 (+0.43, -0.38). The best fitting absorption column is 8.7 (+4.1, -2.9) x 10^21 cm^-2, in excess of the Galactic value in the direction of the burst (3.6 x 10^21, Kalberla et al. 2005). The counts to observed 0.3-10 keV flux conversion factor deduced from this spectrum is 5.0 x 10^-11 erg cm^-2 s^-1 count^-1.
If the light curve continues to decay with a slope of 1.05, the count rate at 24 hours post-trigger will be 1.8 x 10^-3, corresponding to an observed (unabsorbed) flux of 9.0 x 10^-14 (4.2 x 10^-13) erg cm^-2 s^-1.
This circular is an official product of the Swift-XRT team.
GCN Circular #8033
W.B. Landsman (NASA/GSFC/Adnet) and S. Immler (PSU) report on behalf of the Swift/UVOT team:
The Swift/UVOT observed the field of GRB 080727B starting 105s after the BAT trigger (Immler et al., GCN Circ. 8022). We do not find any source, in any of the UVOT observations, at either the UVOT-enhanced XRT position of the afterglow (Goad et al. GCN Circ. 8026) or the proposed KAIT afterglow position (Li et al., GCN 8024). The 3-sigma upper limits for detecting a source at this location in single exposures are:
```
Filter       T_start      Exp(s)    Mag (3-sigma upper limit)
----------------------------------------------------------
   v          211        393     >20.6
  uvw1        642         15     >17.9
  uvm2        617         19     >17.6
  white       105         98     >21.0
----------------------------------------------------------
```
The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight corresponding to a large reddening of E_{B-V} = 1.9 mag. All photometry is on the UVOT flight system described in Poole et al. (2008, MNRAS, 383, 627).
Combining the UVOT upper limits with the KAIT detection at R~18.3 (Li et al., GCN 8024) suggest that there is either high extinction, very fast decline in brightness (the UVOT observations began 57 seconds after the KAIT observations ), or high redshift. The UVOT results are obtained at shorter wavelengths, and for example, the UVOT v filter is expected to suffer an additional ~1.4 mag of extinction, assuming that E(B-V) = 1.9 and that the KAIT clear filter corresponds roughly to the R band. The results may also be consistent with a high redshift burst (5.5 < z <6.5) which is only observable at wavelengths longward of ~6000 A.
GCN Circular #8037
P. D'Avanzo, S. Covino, L.A. Antonelli, D. Malesani, D. Fugazza, L. =20 Calzoletti, S. Campana, G. Chincarini, M.L. Conciatore, S. Cutini, V.=20 D'Elia, F. D'Alessio, F. Fiore, P. Goldoni, D. Guetta, C. Guidorzi,=20 G.L. Israel, E. Maiorano, N. Masetti, A. Melandri, E. Meurs, L.=20 Nicastro, E. Palazzi, E. Pian, S. Piranomonte, L. Stella, G. Stratta,=20 G. Tagliaferri, G. Tosti, V.Testa, S.D. Vergani, F. Vitali report on=20 behalf of the REM team:
Following the KAIT detection of the optical afterglow of GRB 080727B (Li=20 et al. GCN 8024) we performed a detailed off-line analysis of our REM=20 images (D'Avanzo et al., GCN 8023). While we confirm the non-detection=20 of the optical afterglow in the R-band down to the 16th magnitude (30 s=20 of total exposure), we find a barely visible object in our coadded=20 H-band frame (50 s of total exposure) with a magnitude of H =3D 11.8 =B1 = 0.2 (calibrated against the 2MASS catalogue) at a position consistent with=20 the one reported by Li et al.
Unfortunately, just after taking the first R and H-band images, the=20 telescope experienced tracking problems, due to the low altitude of the=20 object with respect to the horizon, and we do not have more images of=20 this GRB. The inferred unabsorbed color (R-H =3D 3.24 mag) is consistent with the hypothesis of an highly absorbed or high redshift event=20 (Landsman et al. GCN 8033).
GCN Circular #8042
S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, report:
The long GRB 080727B (Swift-BAT trigger #318101: Immler et al., GCN 8022, Baumgartner et al., GCN 8030) triggered Konus-Wind at T0=29609.825 s UT (08:13:29.825).
The burst light curve shows two multipeaked pulses with a total duration of ~9 s.
As observed by Konus-Wind the burst had a fluence of 9.46(-0.84, +0.98)x10^-6 erg/cm2, and a 64-ms peak flux measured from T0+6.080 s of 5.14(-0.10, +0.11)x10^-6 erg/cm2/s (both in the 20 keV - 2 MeV energy range).
The time-integrated spectrum of the burst (from T0 to T0+8.448 s) is well be fitted (in the 20 keV - 2 MeV range) by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.85(-0.18, +0.16), and Ep = 282(-37, +52) keV (chi2 = 56.6/60 dof). Fitting by GRBM (Band) model yields: the low-energy photon index is alpha = -0.73(-0.24, +0.29), the high energy photon index beta < -2.08, the peak energy Ep = 242(-48, +69) keV (chi2 = 54.8/59 dof).
All the quoted errors are at the 90% confidence level.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.rssi.ru/LEA/GRBs/GRB080727_T29609/
GCN Circular #8045
T. Kruehler, J. Greiner, F. Schrey, C. Clemens, A. Yoldas (all MPE Garching), A. Kupcu Yoldas (ESO) and G. Szokoly (Eoetvoes Univ., Budapest) report on behalf of the GROND team:
Since telescope pointing constraints did not allow a prompt observation of GRB 080727B (Swift trigger 318101, Immler et al. 2008, GCN #8022), GROND (Greiner et al. 2008, PASP 120, 405), mounted at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile), started observations in g'r'i'z'JHK only on Jul 27, 23:08 UT, nearly 15 hrs after the burst. Under mediocre conditions a total of 90 min effective exposure in g'r'i'z' and 76 min in JHK was collected. Correcting for foreground extinction of A_V = 6.15 (Schlegel et al. 1998), we measure the following AB magnitudes/limits: g'>17.7, r'>19.7, i'>19.9, z'=19.8+-0.1, J=19.45+-0.15, H=19.2+-0.1, K=19.0+-0.15.
The corresponding SED is well fit by a single power law with slope 0.85, with no evidence of additional (intrinsic) extinction, and with the i'-limit being consistent with that power law. Our SED power law has an extinction-corrected R-H=1.0. The best fit Hyper-z redshift to our data gives z=5.5-6.5, with a firm upper limit of 6.7. Given the non-constraining upper limits at i' and bluer, no lower limit can be placed. If the color R-H = 3.24 mag from the combination of KAIT (Li et al. 2008, GCN #8024) and REM data (D'Avanzo et al. 2008, GCN #8037) is correct, then the redshift of GRB 080727B would be larger than 5.8.
GCN Circular #8046
W. Li, R. Chornock, D. A. Perley, J. S. Bloom, and A. V. Filippenko, University of California at Berkeley, on behalf of the KAIT GRB team; D. A. Kann, TLS Tautenburg, report:
We have analyzed the KAIT observations of the OA of GRB 080727B as reported in Li et al. (GCN 8024). The imaging sequence started with 10 x 2 s unfiltered exposures, with the OA detected on each frame. A series of 20 s V, I, and unfiltered images were then obtained, and the OA was detected in the first couple of I and unfiltered images. Additional photometry (calibrated to USNO B1):
```
UT start  exptime  filter     mag     err

08:14:46  2  s      clear   18.98    0.28
08:16:03  20 s      clear   19.64    0.07
08:17:35  20 s      clear   20.68    0.23 
```
Our GRB pipeline used more than 100 USNO B1 stars in calculating the photometric zero point. However, we suspect that the USNO B1 calibration for the GRB field may be significantly off. Based on our experience in the limiting magnitude of the KAIT 2 s and 20 s unfiltered images, we estimate that the above photometry and those reported in GCN 8024 should be made brighter by 1.0 - 2.0 mag. The corrected KAIT photometry, together with the REM NIR detection (D'Avanzo et al. GCN 8037), suggests an optical - NIR color of R-H (Vega) = 1.2 to 2.2 mag, which is consistent with the SED fit from the GROND observations (predicted R-H (AB) = 1.0 mag; Kruehler et al. GCN 8045).
The KAIT unfiltered light curve of GRB 080727B can be well fit by a broken power-law with an index of 1.08 +/- 0.07 between t = 49 s to 169 s, and 1.88 +/- 0.21 between t= 169 s and 524 s. Such an early break in the light curve is quite extraordinary.
We plan to obtain photometric calibrations of the GRB field in the upcoming photometric nights at Lick Observatory.
GCN Circular #8049
A.J. Levan (U. Warwick) and K. Wiersema (U. Leicester) report for a larger collaboration:
We observed the location of GRB 080727B (Immler et al. GCN 8022) using UKIRT. The automatic observations begin at 08:27:13 UT, roughly 800 seconds after the burst. An initial set of K-band observations were acquired, followed by a shallower JHK sequence. At the location of the X-ray (Goad et al. GCN 8026) and optical/IR afterglows (D'Avanzo et al. GCN 8023; Li et al. GCN 8024) we clearly identify the fading afterglow of GRB080727B in all filters. The photometry, calibrated against several 2MASS stars within the field of view is shown below:
```
===========================================
T_s T_s-T_b     Band    Mag     err
===========================================
08:27:13 0.00959        K       13.952 0.03
08:31:38 0.01266        K       14.243 0.03
08:36:03 0.01573        K       14.392 0.03
08:50:08 0.02551        K       14.952 0.05
09:00:10 0.03248        K       15.276 0.05
09:10:09 0.03940        K       15.549 0.05
===========================================
08:47:04 0.023389       H       16.144 0.06
08:58:06 0.031042       H       16.560 0.06
09:07:05 0.037280       H       16.775 0.08
==========================================
08:43:13 0.02071        J       17.855 0.10
08:53:15 0.02767        J       18.300 0.10
09:03:16 0.03463        J       18.626 0.11
===========================================
```
*Data have not been corrected for the significant foreground extinciton
The K-band is suggestive of a break occurring at t_b ~ 1600s, with pre- and post-break slopes of alpha_1 =0.84 and alpha_2 =1.26. The initial slope is significantly shallower than that suggested by the KAIT observations (Li et al GCN 8046), and implies either that the afterglow decay flatenned after those observations, or that the optical and IR were not tracking eachother in this case.
We thank the staff of UKIRT for their rapid response to these alerts.
GCN Circular #8074
T. Kruehler, J. Greiner (MPE Garching) and S. Klose (Tautenburg) report:
We triggered VLT/FORS imaging of the field of the Swift GRB 080727B (Immler et al. 2008, GCN #8022). A series of exposures were obtained in Rc (6*120s), Bessel I (5*120s) and Gunn z (4*120s) starting from 06:19 UT on 2008-07-29, roughly 46 hours after the burst. We marginally detect the optical afterglow (Li et al, 2008, GCN #8024) in the stacked I and z frames at 24.7 +- 0.3 mag (I) and 23.9 +- 0.5 mag (z), calibrated against USNO-B1 stars.
Given the large errors and the uncertain and high foreground extinction, this is consistent with the power law reported in Kruehler et al (2008, GCN #8045) and puts the upper redshift limit to ~5. The 3 sigma upper limit in Rc (>25.5 mag) is above that power law and does not constrain the shape of the spectral energy distribution or the redshift.
We thank the ESO/VLT staff for the perfect support.

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Jochen Greiner, last update: 06-Aug-2008 [Disclaimer]