TITLE:   GCN CIRCULAR
NUMBER:  16910
SUBJECT: GRB 141015A: Swift/XRT localization
DATE:    14/10/15 15:39:14 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

E. Troja (NASA/GSFC/UMCP), S. D. Barthelmy (GSFC),
M. M. Chester (PSU), P. A. Evans (U Leicester), J. A. Kennea (PSU),
K. L. Page (U Leicester), D. M. Palmer (LANL),
J. L. Racusin (NASA/GSFC), M. H. Siegel (PSU) and
R. L. C. Starling (U Leicester) report on behalf of the Swift Team:

At 09:12:59 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 141015A (trigger=615399).  The position was reloaded up to Swift
using the "grb" mode of the TOO command (now that the location is out of Moon
constraint).  As such, Swift responds by generating the standard set
of real-time TDRSS messages (and hence the GCN Notices). 
We are issuing this Circular with the results from XRT and UVOT. 

The XRT began observing the field at 15:07:56.6 UT, 21297.3 seconds
after the BAT trigger. Using promptly downlinked data we find an
uncatalogued X-ray source located at RA, Dec 87.51746, 18.32965 which
is equivalent to:
   RA(J2000)  = 05h 50m 04.19s
   Dec(J2000) = +18d 19' 46.7"
with an uncertainty of 4.0 arcseconds (radius, 90% containment). This
location is 60 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 consistent with the Galactic value of 5.59
x 10^21 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 21238 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 large, but uncertain
extinction expected. 

Burst Advocate for this burst is E. Troja (eleonora.troja 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.)