TITLE:   GCN CIRCULAR
NUMBER:  11411
SUBJECT: GRB 101117B: Swift detection of a burst
DATE:    10/11/17 19:27:41 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

C. W. Wolf (PSU), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),
S. Campana (INAF-OAB), N. Gehrels (NASA/GSFC), D. Grupe (PSU),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), W.B Landsman (GSFC),
V. Mangano (INAF-IASFPA), C. B. Markwardt (NASA/GSFC) and
P. T. O'Brien (U Leicester) report on behalf of the Swift Team:

At 19:13:23 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 101117B (trigger=438675).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is RA, Dec 172.909, -72.662 which is 
   RA(J2000) = 11h 31m 38s
   Dec(J2000) = -72d 39' 41"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a two-spike
structure with a duration of about 6 sec.  The peak count rate
was ~7000 counts/sec (15-350 keV), at ~3 sec after the trigger. 

The XRT began observing the field at 19:14:40.9 UT, 77.0 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source located at RA, Dec 173.00251, -72.66317 which
is equivalent to:
   RA(J2000)  = 11h 32m 0.60s
   Dec(J2000) = -72d 39' 47.4"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 100 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 (1.33 x
10^21 cm^-2, Kalberla et al. 2005), with an excess column of 2.2
(+2.09/-1.81) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the white
filter  starting  82 seconds after the BAT trigger.  No credible
afterglow candidate  has been found in the initial data products.  The
2.7' x 2.7' sub-image covers 100%  of the XRT error circle.  The
estimated 3-sigma upper limit is white > 20.4 mag.  No correction has
been made for the expected Galactic extinction corresponding to a 
reddening of E_{B-V} =  0.38 mag.  Photometry is on the UVOT
photometry system of Poole et al. (2008). 

Burst Advocate for this burst is C. W. Wolf (cwolf AT astro.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.)