GCN Circular 10823

M. De Pasquale (UCL-MSSL), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
V. Mangano (INAF-IASFPA), D. M. Palmer (LANL),
P. Romano (INAF-IASFPA), B. Sbarufatti (INAF-OAB/IASFPA),
R. L. C. Starling (U Leicester) and L. Vetere (PSU) report on behalf
of the Swift Team:

At 17:23:30 UT, the Swift Burst Alert Telescope (BAT) detected increased
flux from the Supergiant Fast X-Ray Transient IGR J18410-0535. 
Swift slewed to the source immediately after its detection. 
The BAT on-board calculated location is 
RA, Dec 280.267, -5.615 which is 
   RA(J2000) = 18h 41m 04s
   Dec(J2000) = -05d 36' 53"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty), consistent with the known source location. 
As is typical for long image detections, the immediately available
light curve shows no obvious activity. 

The XRT began observing the field at 17:51:50.5 UT, 1700 seconds
after the BAT trigger. Using promptly downlinked data we find an X-ray
source located at RA, Dec 280.25128, -5.59666 which is equivalent to:
   RA(J2000)  = 18h 41m 0.40s
   Dec(J2000) = -05d 35' 46.5"
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This is
consistent with the identification of this source as IGR J18410-0535. The
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
1.59e+22 cm^-2 (Kalberla et al. 2005). 

UVOT took a finding chart exposure of 150 seconds with the White
filter  starting 1705 seconds after the BAT trigger. No credible
optical transient has been found in the initial data products. No
correction has been made for the large, but uncertain extinction
expected.