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GCN Circular 16938

Subject
GRB 141022A: Swift detection of a burst
Date
2014-10-22T01:48:24Z (10 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
A. Vargas (PSU), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), J. A. Kennea (PSU), V. Mangano (PSU),
D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/PSU) and
T. N. Ukwatta (LANL) report on behalf of the Swift Team:

At 01:27:42 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 141022A (trigger=616061).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 241.901, -72.129 which is 
   RA(J2000) = 16h 07m 36s
   Dec(J2000) = -72d 07' 44"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of about 30 sec.  The peak count rate
was ~1000 counts/sec (15-350 keV), at ~8 sec after the trigger. 

The XRT began observing the field at 01:29:57.6 UT, 134.9 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 241.8698, -72.1255
which is equivalent to:
   RA(J2000)  = 16h 07m 28.75s
   Dec(J2000) = -72d 07' 31.7"
with an uncertainty of 2.2 arcseconds (radius, 90% containment). This
location is 36 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 in excess of the Galactic value (1.04 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 7.9
(+6.17/-4.49) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 250 seconds with the U filter starting
135 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. The
8'x8' region for the list of sources generated on-board covers 100% of the XRT
error circle. Because of the density of catalogued stars, further analysis is
required to report an upper limit for any afterglow in the region. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.10. 

Burst Advocate for this burst is A. Vargas (avargas AT swift.psu.edu). 
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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