[vsnet-grb-info 18011] GRB 160525B: Swift detection of a burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19459
SUBJECT: GRB 160525B: Swift detection of a burst
DATE:    16/05/25 09:34:47 GMT
FROM:    David Palmer at LANL  <palmer at lanl.gov>

H. A. Krimm (CRESST/GSFC/USRA), S. D. Barthelmy (GSFC),
A. D'Ai (INAF-IASFPA), P.A. Evans (U Leicester), C. Gronwall (PSU),
F. E. Marshall (NASA/GSFC), A. Maselli (INAF-IASFPA),
K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of
the Swift Team:

At 09:25:07 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160525B (trigger=687522).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 149.443, +51.180 which is 
   RA(J2000)  =  09h 57m 46s
   Dec(J2000) = +51d 10' 49"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a single peak
structure with a duration of about 10 sec.  The peak count rate
was ~1500 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 09:26:31.0 UT, 83.4 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 149.38688, 51.20658 which is equivalent
to:
   RA(J2000)  = 09h 57m 32.85s
   Dec(J2000) = +51d 12' 23.7"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 158 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. No spectrum from the promptly downlinked
event data is yet available to determine the column density. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 88 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 none of
the XRT error circle. 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 0.01. 

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.)