GRB 140828A

A. Melandri (INAF-OAB), M. G. Bernardini (INAF-OAB),
P. D'Avanzo (INAF-OAB), P. A. Evans (U Leicester),
A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester), T. Sakamoto (AGU)
and M. H. Siegel (PSU) report on behalf of the Swift Team:

At 06:54:14 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 140828A (trigger=610953). 
The BAT on-board calculated location is 
RA, Dec 142.011, +14.590 which is 
   RA(J2000) = 09h 28m 03s
   Dec(J2000) = +14d 35' 24"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single-peaked
structure with a duration of about 20 sec.  The peak count rate
was ~1200 counts/sec (15-350 keV), at ~1 sec after the trigger. 

Due to a Sun observing constraint, Swift cannot slew to the BAT
position until 22:33 UT on 2014 September 29. There will thus be no XRT
or UVOT data for this trigger before this time. 

Burst Advocate for this burst is A. Melandri (andrea.melandri 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.)

A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team:

"At 06:54:12.18 UT on 28 August 2014, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 140828A (trigger 430901655 / 140828288), which
was also detected by the Swift/BAT (Melandri et al. 2014, GCN 16751
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 )
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight is 57 degrees.

The GBM light curve consists of a single pulse
with a duration (T90) of about 24 s (50-300 keV).
The time-averaged spectrum from T0-6.1 s to T0+16.4 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -1.5 +/- 0.1  and
the cutoff energy, parameterized as Epeak, is 140 +/- 30 keV.

The event fluence (10-1000 keV) in this time interval is
(3.5 +/- 0.2)E-06 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0+2.43 s in the 10-1000 keV band
is 3.5 +/- 0.2  ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."

C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
A. Y. Lien (GSFC/UMBC), A. Melandri (INAF-OAB), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 140828A (trigger #610953)
(Melandri, et al., GCN Circ. 16751
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 ).  The BAT ground-calculated position is
RA, Dec = 142.029, 14.569 deg which is 
  RA(J2000)  =  09h 28m 07.0s 
  Dec(J2000) = +14d 34' 09.2" 
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 26%.

The mask-weighted light curve shows a single peak starting at T-7 sec, peaking 
at T+1 sec and ending at T+10 sec.  There is a hint of an emission peaking 
at T+14 sec.  T90 (15-350 keV) is 18.8 +- 4.0 sec (estimated error including 
systematics).

The time-averaged spectrum from T-5.8 to T+18.4 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 0.6 +- 0.7, 
and Epeak of 54 +- 11 keV (chi squared 70.26 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 1.3 +- 0.1 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+0.51 sec in the 15-150 keV band is
2.2 +- 0.3 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.78 +- 0.13 (chi squared 81.57 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/610953/BA/