[vsnet-grb-info 14132] GRB 131105A: Swift detection of a burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15446
SUBJECT: GRB 131105A: Swift detection of a burst
DATE:    13/11/05 02:17:27 GMT
FROM:    David Palmer at LANL  <palmer at lanl.gov>

J. R. Cummings (NASA/UMBC), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),
N. Gehrels (NASA/GSFC), A. Y. Lien (NASA/GSFC/ORAU),
P. T. O'Brien (U Leicester), K. L. Page (U Leicester),
D. M. Palmer (LANL), T. Sakamoto (AGU) and C. A. Swenson (PSU) report
on behalf of the Swift Team:

At 02:04:44 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 131105A (trigger=576738).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 71.011, -62.981 which is 
   RA(J2000)  =  04h 44m 03s
   Dec(J2000) = -62d 58' 52"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows multple peaks
with a total duration of about 120 sec.  The peak count rate
was ~1100 counts/sec (15-350 keV), at ~44 sec after the trigger. 

The XRT began observing the field at 02:09:35.6 UT, 290.9 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source located at RA, Dec 70.96452, -62.99394 which
is equivalent to:
   RA(J2000)  = 04h 43m 51.48s
   Dec(J2000) = -62d 59' 38.2"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 89 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. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (2.91 x
10^20 cm^-2, Kalberla et al. 2005), with an excess column of 2.2
(+2.11/-1.84) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White 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 5% of
the BAT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
BAT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.03. 

Burst Advocate for this burst is J. R. Cummings (jayc 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.)