GRB 140428B

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

K. Hurley, on behalf of the Interplanetary Network,

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

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

The short-duration, hard spectrum GRB 140428B has been observed by
Fermi (GBM: trigger 420414281), INTEGRAL (SPI-ACS), Konus-Wind, and Mars 
Odyssey (HEND), so far, at about 78278 s UT (21:44:38).

We have triangulated it to a preliminary, 3 sigma error box whose
coordinates are:
   ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
     2.006 (00h 08m 01s) +68.172 (+68d 10' 20")
  Corners:
     6.132 (00h 24m 32s) +68.636 (+68d 38' 09")
     2.619 (00h 10m 29s) +68.455 (+68d 27' 18")
   358.176 (23h 52m 42s) +67.601 (+67d 36' 04")
     1.415 (00h 05m 40s) +67.887 (+67d 53' 13")
  ---------------------------------------------
The error box area is 0.608 sq. deg, and its maximum dimension is 3.14
deg (the minimum one is 18 arcmin).

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB140428_T78275/IPN/

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

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

The short-duration GRB 140428B (IPN triangulation: Golenetskii et al., 
GCN 16184
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 ) triggered Konus-Wind at T0=78275.456 s UT (21:44:35.456).

The burst light curve shows a single pulse with a total
duration of ~0.15 s.

As observed by Konus-Wind, the burst
had a fluence of 9.23(-0.95,+0.88)x10^-7 erg/cm2,
and a 16-ms peak flux, measured from T0-0.014 s,
of (1.43 +/- 0.38)x10^-5 erg/cm2/s
(both in the 20 keV - 1.2 MeV energy range).

Modeling the K-W 3-channel time-integrated spectrum
(from T0-0.064 s to T0+0.80 s)
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) yields
alpha = -0.75(-0.24, +0.26), and
Ep = 1050(-343,+1750) keV

All the quoted errors are estimated at the 1 sigma confidence level.
All the quoted results are preliminary.

The K-W light curve of this burst is available at
http://www.ioffe.rssi.ru/LEA/GRBs/GRB140428_T78275/

George Younes (USRA/MSFC)
report on behalf of the Fermi GBM Team:

"At 21:44:38.60 UT on 28 April 2014, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 140428B (trigger 420414281 / 140428906, IPN
triangulation: Golenetskii et al., GCN 16184
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 ).

The angle from the Fermi LAT boresight is 111 degrees.

This burst also triggered Konus-Wind (Pal'shin et al. GCN #16188
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 ).

The GBM light curve consists of a single pulse
with a duration (T90) of about 0.5 s (50-300 keV).
The time-averaged spectrum from T0-0.32 s to T0+19 s is well fit by
a power law function with an exponential
high-energy cutoff.  The power law index is -0.6 +/- 0.2 and
the cutoff energy, parameterized as Epeak, is 410 (-80, +134) keV.

The event fluence (10-1000 keV) in this time interval is
(9.0 +/- 1.0)E-07 erg/cm^2. The 0.064-sec peak photon flux measured
starting from T0-0.064 s in the 10-1000 keV band
is 17 +/- 2 ph/s/cm^2.

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