GCN Circular 10667

E. A. Hoversten (PSU), S. D. Barthelmy (GSFC),
P. A. Evans (U Leicester), C. Guidorzi (U Ferrara),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
W.B Landsman (GSFC), C. B. Markwardt (CRESST/GSFC/UMD),
F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester),
C. Pagani (U Leicester), D. M. Palmer (LANL), M. H. Siegel (PSU) and
M. A. Stark (PSU) report on behalf of the Swift Team:

At 16:32:42 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 100424A (trigger=420367).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 209.453, +1.513 which is 
   RA(J2000)  =  13h 57m 49s
   Dec(J2000) = +01d 30' 48"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT lightcurve shows nothing as is usual
for an image trigger. 

The XRT began observing the field at 16:34:42.1 UT, 119.8 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 209.4467, +1.5366 which is equivalent to:
   RA(J2000)  = 13h 57m 47.20s
   Dec(J2000) = +01d 32' 11.7"
with an uncertainty of 5.1 arcseconds (radius, 90% containment). No
event data are yet available to determine the column density using
X-ray spectroscopy. 

The initial flux in the 2.5 s image was 2.09e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 128 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 19.6 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
0.03. 

Burst Advocate for this burst is E. A. Hoversten (hoversten AT astro.psu.edu). 
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.)