[vsnet-grb-info 13798] GRB 130822A: Swift detection of a short burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15112
SUBJECT: GRB 130822A: Swift detection of a short burst
DATE:    13/08/22 16:12:35 GMT
FROM:    Jamie A. Kennea at PSU/Swift-XRT  <kennea at swift.psu.edu>

D. Kocevski (NASA/GSFC/ORAU), D. N. Burrows (PSU),
N. Gehrels (NASA/GSFC), S. T. Holland (STScI), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), N. P. M. Kuin (UCL-MSSL),
V. Mangano (PSU), F. E. Marshall (NASA/GSFC), C. Pagani (U Leicester),
K. L. Page (U Leicester), J. L. Racusin (NASA/GSFC),
B. Sbarufatti (INAF-OAB/PSU), R. L. C. Starling (U Leicester) and
G. Tagliaferri (INAF-OAB) report on behalf of the Swift Team:

At 15:54:17 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 130822A (trigger=567163).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 27.940, -3.219 which is 
   RA(J2000) = 01h 51m 46s
   Dec(J2000) = -03d 13' 08"
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 0.1 sec.  The peak count rate
was ~3700 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 15:55:30.7 UT, 73.5 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 27.9218, -3.2085 which
is equivalent to:
   RA(J2000)  = 01h 51m 41.22s
   Dec(J2000) = -03d 12' 30.6"
with an uncertainty of 3.1 arcseconds (radius, 90% containment). This
location is 75 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper.  We
cannot determine whether the source is fading at the present time. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 2.76
x 10^20 cm^-2 (Kalberla et al. 2005). 

UVOT took a finding chart exposure of 250 seconds with the U filter starting
294 seconds after the BAT trigger. No credible afterglow candidate has been
found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the
XRT error circle. The typical 3-sigma upper limit has been about 19.2 mag. The
8'x8' region for the list of sources generated on-board covers 100% of the XRT
error circle. The list of sources is typically complete to about 18.0 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.03. 

Burst Advocate for this burst is D. Kocevski (daniel.kocevski AT 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.)