GCN Circular 10581

S. T. Holland (CRESST/USRA/GSFC), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), S. Campana (INAF-OAB),
M. M. Chester (PSU), P. A. Evans (U Leicester),
N. Gehrels (NASA/GSFC), J. M. Gelbord (PSU), E. A. Hoversten (PSU),
J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA),
N. P. M. Kuin (UCL-MSSL), V. Mangano (INAF-IASFPA), J. Mao (INAF-OAB),
F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL),
J. L. Racusin (NASA/GSFC), A. Rowlinson (U Leicester),
B. Sbarufatti (INAF-OAB/IASFPA), M. H. Siegel (PSU),
M. Stamatikos (OSU/NASA/GSFC), M. A. Stark (PSU),
R. L. C. Starling (U Leicester), M. C. Stroh (PSU),
G. Tagliaferri (INAF-OAB), E. Troja (NASA/GSFC/ORAU) and
T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:

At 17:33:28 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 100413A (trigger=419404).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 266.217, +15.837 which is 
   RA(J2000)  =  17h 44m 52s
   Dec(J2000) = +15d 50' 14"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a single peak
with a duration of about 15 sec.  The peak count rate
was ~700 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 17:35:48.4 UT, 140.0 seconds after
the BAT trigger. Using promptly downlinked data we find a bright, fading,
uncatalogued X-ray source located at RA, Dec 266.22043, 15.83309 which
is equivalent to:
   RA(J2000)  = 17h 44m 52.90s
   Dec(J2000) = +15d 49' 59.1"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 18 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 in excess of the Galactic value (7.3e+20
cm^-2, Kalberla et al. 2005), with an excess column of 2 (+1.81/-1.60)
x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 6.30e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White
filter  starting 149 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  0.11. 

Burst Advocate for this burst is S. T. Holland (Stephen.T.Holland 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.)