P. D'Avanzo (INAF-OAB), S. D. Barthelmy (GSFC), D. N. Burrows (PSU),
J. A. Kennea (PSU), H. A. Krimm (CRESST/NSF/USRA),
A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL),
B. Sbarufatti (INAF-OAB/PSU) and M. H. Siegel (PSU) report on behalf
of the Swift Team:
At 17:30:26 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 161113A (trigger=722063). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 179.834, -5.347, which is
RA(J2000) = 11h 59m 20s
Dec(J2000) = -05d 20' 49"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows two overlapping peaks
with a total duration of about 45 sec. The peak count rate
was ~2400 counts/sec (15-350 keV), at ~15 sec after the trigger.
The XRT began observing the field at 17:31:18.5 UT, 51.8 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 179.79351,
-5.30848 which is equivalent to:
RA(J2000) = 11h 59m 10.44s
Dec(J2000) = -05d 18' 30.5"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 200 arcseconds from the BAT onboard position. 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 (2.11 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 6.5
(+6.17/-4.70) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 1.07e-08 erg cm^-2 s^-1 (0.2-10
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 78 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 expected extinction corresponding to E(B-V) of
Burst Advocate for this burst is P. D'Avanzo (paolo.davanzo AT brera.inaf.it).
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.)