GRB 130425A

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

"At 07:51:16.23 UT on 25 April 2013, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 130425A (trigger 388569079 / 130425327).

The on-ground calculated location, using the GBM trigger data, 
is RA = 19.0, DEC = -72.2 (J2000 degrees, equivalent 
to 01 h 16 m, -72 d 12 '), with an uncertainty of 2.9 degrees 
(radius, 1-sigma containment, statistical only; there is additionally 
a systematic error which is currently estimated to be 2 to 3 degrees).

The angle from the Fermi LAT boresight is 150 degrees.

The GBM light curve shows two peaks  with a duration (T90) 
of about 66 s (50-300 keV). The time-averaged spectrum from 
T0-2.880 s to T0+69.825 s is best fit by a power law function 
with an exponential high-energy cutoff.  The power law index
 is -1.28 +/- 0.03  and the cutoff energy, parameterized as Epeak, is 254
(+14/-13) keV.

The event fluence (10-1000 keV) in this time interval is
(5.2 +/- 0.1)E-05 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0+43.5207 s in the 10-1000 keV band
is 21.8 +/- 1.1 ph/s/cm^2.

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

K. Hurley, and J. Goldsten, on behalf of the MESSENGER GRNS 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,

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

K. Yamaoka, M. Ohno, Y. Hanabata, Y. Fukazawa, T. Takahashi, M. Tashiro,
Y. Terada, T. Murakami, and K. Makishima, on behalf of the Suzaku WAM
team, report:

The long-duration, intense GRB 130425A (Fermi/GBM detection: von 
Kienlin, GCN Circ. 14442
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 ) has been observed by Konus-Wind, MESSENGER 
(GRNS), INTEGRAL (SPI-ACS), and Suzaku (WAM), so far, at about 28280 s 
UT (07:51:20).

We have triangulated it to a preliminary, 3 sigma error box whose 
coordinates are:
---------------------------------------------
  RA(2000), deg                 Dec(2000), deg
---------------------------------------------
  Center:
     6.211 (00h 24m 51s) -70.183 (-70d 11' 00")
  Corners:
    14.165 (00h 56m 40s) -70.601 (-70d 36' 05")
    11.987 (00h 47m 57s) -70.402 (-70d 24' 09")
   358.255 (23h 53m 01s) -69.341 (-69d 20' 28")
     0.370 (00h 01m 29s) -69.740 (-69d 44' 24")
---------------------------------------------
The error box area is 0.683 sq. deg, and its maximum
dimension is 5.58 deg (the minimum one is 45 arcmin).

This box may be improved.

The center of the GBM location (von Kienlin, GCN Circ. 14442
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 ) is 4.6
deg from the center of the IPN box.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB130425_T28280/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 130425A
(Fermi-GBM detection: von Kienlin, GCN 14442
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 ;
IPN triangulation: Hurley et al., GCN 14446
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 )
triggered Konus-Wind at T0=28280.029s UT (07:51:20.029)

The light curve shows an initial pulse, from ~T0-9 s to
~T0+15 s, followed by a bright multi-peaked structure
from ~T0+30 s to ~T0+68 s.
A total duration of the burst is ~80 s.
The emission is seen up to 10 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB130425_T28280/

As observed by Konus-Wind, the burst
had a fluence of (5.9 � 0.7)x10-5 erg/cm2,
and a 64-ms peak flux, measured from T0+39.808s,
of (7.1 � 0.6)x10-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+73.216 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.29 � 0.08,
the high energy photon index beta = -2.46 � 0.23,
the peak energy Ep = 167 � 17 keV,
chi2 = 107/97 dof.

The spectrum at the maximum count rate (measured from T0+33.024
to T0+40.448 s) is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.10 � 0.12,
the high energy photon index beta = -2.40 � 0.36,
the peak energy Ep = 237 � 45 keV,
chi2 = 91/97 dof.

All the quoted results are preliminary.

M. Akiyama, M. Yamauchi, N. Ohmori (Univ. of Miyazaki),
M. Ohno, K. Takaki, T. Kawano, R. Nakamura, S. Furui, Y. Fukazawa
(Hiroshima U.),
M. Tashiro, Y. Terada, T. Yasuda, Y. Ishida, H. Ueno, S. Sugimoto (Saitama U.),
K. Yamaoka (Nagoya U.),  S. Sugita (Ehime U.), Y. E. Nakagawa, M. Kokubun,
T. Takahashi (ISAS/JAXA), W. Iwakiri(RIKEN), Y. Hanabata (ICRR), Y. Urata
(NCU), K. Nakazawa, K. Makishima (Univ. of Tokyo) on behalf of the Suzaku
WAM team, report:

The long GRB 130425A (Fermi-GBM detection: von Kienlin, GCN 14442
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 ;
IPN localization: Hurley et al., GCN14446
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 ) triggered by the 
Suzaku Wide-band All-sky Monitor (WAM) which covers an energy range of
50 keV - 5 MeV at 07:51:22.243 UT (=T0).

The observed light curve shows a weak initial single peak from T0-2s to 
T0-1s and multi-peaked structure starting from T0+30s from T0+61s,
with a duration (T90) of about 61 seconds.
The fluence in 100 - 1000 keV was 2.74(+0.12/-0.18) x 10^-5^  erg/cm^2^ .
The 1-s peak flux measured from T0+37s was 6.51(+0.96/-1.26) photons/cm^2/s
in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-2s to
T0+61s is well fitted by a single power-law with a photon index of
2.41 (+0.19/-0.17) (chi^2/d.o.f = 14.7/14).

All the quoted errors are at statistical 90% confidence level,
in which the systematic uncertainties are not included.

The light curves for this burst will be available at:
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html