GRB 120918A

B. N. Barlow (PSU), W. H. Baumgartner (GSFC/UMBC), C. Gronwall (PSU),
D. M. Palmer (LANL), M. Stamatikos (OSU/NASA/GSFC) and
B.-B. Zhang (PSU) report on behalf of the Swift Team:

At 11:16:10 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 120918A (trigger=534015).  Swift could not slew to the
burst because of the Sun constraint. 
The BAT on-board calculated location is 
RA, Dec 181.054, -32.758 which is 
   RA(J2000) = 12h 04m 13s
   Dec(J2000) = -32d 45' 26"
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 50 sec.  The peak count rate
was ~2500 counts/sec (15-350 keV), at ~0 sec after the trigger. 

Due to a Sun observing constraint, Swift cannot slew to the BAT
position until 17:37 UT on 2012 November 15. There will thus be no XRT
or UVOT data for this trigger before this time. 

Burst Advocate for this burst is B. N. Barlow (bnb2 AT 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.)

S. D. Barthelmy (GSFC), B. N. Barlow (PSU), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (OSU),
J. Tueller (GSFC), T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):
 
Using the data set from T-239 to T+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 120918A (trigger #534015)
(Barlow, et al., GCN Circ. 13799
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 ).  The BAT ground-calculated position is
RA, Dec = 181.042, -32.762 deg, which is 
   RA(J2000)  =  12h 04m 10.1s 
   Dec(J2000) = -32d 45' 43.5" 
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 15%.
 
The mask-weighted light curve shows several overlapping peaks starting
at ~T-5 sec, the main peak at ~T+1 sec, and ending at ~T+40 sec.
T90 (15-350 keV) is 25.1 +- 2.5 sec (estimated error including systematics).
 
The time-averaged spectrum from T-2.86 to T+23.90 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.00 +- 0.39, 
and Epeak of 85.5 +- 36.3 keV (chi squared 55.6 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 3.7 +- 0.6 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T-0.28 sec in the 15-150 keV band is
4.5 +- 0.5 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.60 +- 0.09 (chi squared 63.5 for 57 d.o.f.).  All the quoted errors
are at the 90% confidence level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/534015/BA/