GCN Circular 10775

M. Stamatikos (OSU/NASA/GSFC), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), M. M. Chester (PSU),
P. A. Evans (U Leicester), J. M. Gelbord (PSU), J. A. Kennea (PSU),
C. Pagani (U Leicester), J. L. Racusin (NASA/GSFC) and L. Vetere (PSU)
report on behalf of the Swift Team:

Swift began a target of opportunity observation of GRB 100518A on May
18, 2010 at 14:10 UT, approximately 2.6 hours after the burst was
detected by INTEGRAL. Swift data for these observations utilize Target
ID 20138. 

The XRT began observing the field at 14:12:42.5 UT, 9.5 ks after the
INTEGRAL trigger. Using promptly downlinked data we find an
uncatalogued X-ray source located at RA, Dec 304.78875, -24.55459 which
is equivalent to:
   RA(J2000)  = 20h 19m 9.30s
   Dec(J2000) = -24d 33' 16.5"
with an uncertainty of 4.1 arcseconds (radius, 90% containment). This
location is 42 arcseconds from the INTEGRAL position, within the
INTEGRAL 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
6.4e+20 cm^-2 (Kalberla et al. 2005). 

UVOT took a finding chart exposure of 150 seconds with the White  
filter starting 9551 seconds after the INTEGRAL 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  19.6  mag. The 8'x8' region for 
the list of sources generated on-board is typically  complete to about
18  mag.  No correction has been made for the  expected extinction
corresponding  to  E(B-V) of 0.07. 

Burst Advocate for this burst is M. Stamatikos (Michael.Stamatikos-1 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.)