[vsnet-grb-info 9746] GRB 100905A: Swift detection of a burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  11214
SUBJECT: GRB 100905A: Swift detection of a burst
DATE:    10/09/05 15:24:02 GMT
FROM:    David Palmer at LANL  <palmer at lanl.gov>

F. E. Marshall (NASA/GSFC), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), D. N. Burrows (PSU),
P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC),
J. M. Gelbord (PSU), C. Guidorzi (U Ferrara),
S. T. Holland (CRESST/USRA/GSFC), P. T. O'Brien (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL),
A. Rowlinson (U Leicester), B. Sbarufatti (INAF-OAB/IASFPA),
M. H. Siegel (PSU), E. Troja (NASA/GSFC/ORAU) and
T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:

At 15:08:14 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 100905A (trigger=433442).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 31.530, +14.932 which is 
   RA(J2000) = 02h 06m 07s
   Dec(J2000) = +14d 55' 54"
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 6 sec.  The peak count rate
was ~1500 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 15:09:29.9 UT, 75.2 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 31.5505, 14.9300 which
is equivalent to:
   RA(J2000)  = 02h 06m 12.12s
   Dec(J2000) = +14d 55' 47.9"
with an uncertainty of 2.3 arcseconds (radius, 90% containment). This
location is 71 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 consistent with the Galactic value of 5.35
x 10^20 cm^-2 (Kalberla et al. 2005). 

UVOT took a finding chart exposure of 150 seconds with the White 
filter starting 77 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 3-sigma 
upper limit is typically 19.3 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 mag. No correction
has been  made for the expected extinction corresponding to E(B-V) of
0.06. 

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.)