GCN Circular 17376

H. A. Krimm (CRESST/GSFC/USRA), S. D. Barthelmy (GSFC),
M. M. Chester (PSU), J. A. Kennea (PSU), K. L. Page (U Leicester),
D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/PSU) and
T. N. Ukwatta (LANL) report on behalf of the Swift Team:

At 23:10:02 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150202A (trigger=629547).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 39.236, -33.150, which is 
   RA(J2000)  =  02h 36m 57s
   Dec(J2000) = -33d 08' 59"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve show several peaks
swith a total duration of about 30 sec.  The peak count rate
was ~1600 counts/sec (15-350 keV), at ~4 sec after the trigger. 

The XRT began observing the field at 23:11:30.3 UT, 88.0 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 39.2275,
-33.1485 which is equivalent to:
   RA(J2000)  = 02h 36m 54.61s
   Dec(J2000) = -33d 08' 54.5"
with an uncertainty of 2.1 arcseconds (radius, 90% containment). This
location is 26 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. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (2.54 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.3
(+1.96/-1.74) x 10^21 cm^-2 (90% confidence). 

  UVOT took a finding chart exposure of 250 seconds with the U filter
starting  304 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 19.2 mag. Data  from the list of sources
generated on-board are not available at this time. No  correction has
been made for the expected extinction corresponding to E(B-V) of 
0.02. 

Burst Advocate for this burst is H. A. Krimm (hans.krimm 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.)