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GCN Circular 15246

Subject
GRB 130925A: Swift detection of a burst
Date
2013-09-25T04:26:41Z (10 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
A. Y. Lien (NASA/GSFC/ORAU), C. B. Markwardt (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL),
J. L. Racusin (NASA/GSFC), M. H. Siegel (PSU) and T. N. Ukwatta (MSU)
report on behalf of the Swift Team:

At 04:11:24 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 130925A (trigger=571830).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 41.183, -26.134 which is 
   RA(J2000) = 02h 44m 44s
   Dec(J2000) = -26d 08' 03"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed that the burst
was active during the pre-planned slew before the nominal trigger
with an additional peak extending at least to T+170. The peak count
rate was ~2700 counts/sec (15-350 keV), at ~110 sec after the trigger. 

The XRT began observing the field at 04:13:52.3 UT, 147.4 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 41.1766, -26.1544 which is equivalent to:
   RA(J2000)  = +02h 44m 42.38s
   Dec(J2000) = -26d 09' 15.8"
with an uncertainty of 5.1 arcseconds (radius, 90% containment). This
location is 76 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy. 

UVOT took a finding chart exposure of 150 seconds with the White 
filter starting 156 seconds after the BAT trigger. No credible 
afterglow candidate has been found in the initial data products. The 
2.7'x2.7' covers 100% of the XRT error circle. The typical 3-sigma
upper limit has been about 19.6 mag. Results 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 A. Y. Lien (yarleen AT gmail.com). 
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.)
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