GRB 120728B

K. Hurley on behalf of the Mars Odyssey and MESSENGER GRB teams,

I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin,
on behalf of the HEND-Odyssey GRB team,

S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks,
D. Svinkin, and T. Cline on behalf of the Konus-Wind team,

V. Connaughton, M. Briggs, and C. Meegan, on behalf of the Fermi
GBM team,

W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr, on
behalf of the GRS-Odyssey GRB team,

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C.
Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, and

D. M. Smith, J. McTiernan, and W. Hajdas, on behalf of the
RHESSI team,  report:

The long-duration, intense GRB 120728B was observed by Konus-Wind, Fermi 
(GBM: trigger 365163927), INTEGRAL (SPI-ACS), Mars Odyssey (HEND), and 
RHESSI at about 37524 s UT (10:25:24).

We have triangulated it to a preliminary, 3 sigma error box whose
coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   103.772 (06h 55m 05s) -45.893 (-45d 53' 36")
  Corners:
   103.695 (06h 54m 47s) -44.477 (-44d 28' 37")
   103.463 (06h 53m 51s) -47.210 (-47d 12' 37")
   103.857 (06h 55m 26s) -47.308 (-47d 18' 29")
   104.069 (06h 56m 17s) -44.576 (-44d 34' 33")
  ---------------------------------------------
The error box area is 0.745 sq. deg, and its maximum
dimension is 2.8 deg.

This box can be improved.

The time history and spectrum will be given in a forthcoming GCN Circular.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB120728_T37534/IPN/

S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin,
P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf
of the Konus-Wind team, report:

The long-duration intense GRB 120728B
(IPN detection and localization: Hurley at al., GCN 13549
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 )
triggered Konus-Wind at T0=37534.985s UT (10:25:34.985)

The light curve shows multiple pulses in at least
three main bursting episodes.
The total duration of the burst is ~250 s,
the emission is seen up to 5 Mev.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB120728_T37534/

As observed by Konus-Wind, the burst
had a fluence of 1.20(-0.15,+0.15)x10-4 erg/cm2,
and a 64-ms peak flux, measured from T0+57.472 s,
of 3.8(-0.4,+0.4)x10-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the main emission episode
(measured from T0 to T0+192.256 s)
is best fit in the 20 keV - 5 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.3 (-0.1, +0.1),
the high energy photon index beta = -2.9 (-1.0, +0.3),
the peak energy Ep = 77(-5, +4) keV,
chi2 = 86.9/75 dof.

The spectrum at the maximum count rate
(measured from T0+55.552 to T0+64.256 s) is best fitted
is best fit in the 20 keV - 2 MeV range
by a power law with exponential cutoff model, for which:
alpha = -1.0 (-0.1, +0.1),
and Ep = 95(-4, +4) keV,
chi2 = 67.8/57 dof.


All the quoted results are preliminary.
All the quoted errors are at the 90% confidence level.

S. Foley (UCD/MPE)
reports on behalf of the Fermi GBM Team:

"At 10:25:24.24 UT on 28 July 2012, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 120728B (trigger 365163927 / 120728434)
which was also detected by Konus-Wind
(Golenetskii et al., GCN 13552
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 ).
This burst was localized by the IPN (Hurley et al., GCN 13549
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 ).
The GBM on-ground calculated location is consistent with the
IPN location.

The angle from the Fermi LAT boresight is 117 degrees.
Moreover, this burst was bright enough to result in a Fermi spacecraft
autonomous repoint request (ARR) maneuver.

The GBM light curve consists of multiple pulses
with a duration (T90) of about 105 s (50-300 keV).
The time-averaged spectrum from T0+8.7 s to T0+113.2 s is
well fit by a power law function with an exponential
high-energy cutoff.  The power law index is -1.31 +/-0.01 and
the cutoff energy, parameterized as Epeak, is
94.86 (+1.04/-1.01) keV.

The event fluence (10-1000 keV) in this time interval is
(1.27 +/- 0.02)E-4 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+69.6 s in the 10-1000 keV band
is 42.8 +/- 0.6 ph/s/cm^2.


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