GRB 130504B

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

"At 07:32:03.39 UT on 04 May 2013, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 130504B (trigger 389345526/ 130504314).

The on-ground calculated location, using the GBM trigger
data, is RA = 353.5, DEC = -5.6 (J2000 degrees, equivalent to 23 h 34 m, -05
d 34'),
with an uncertainty of 1 degree (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 57 degrees. Moreover, this 
burst was bright enough to result in a Fermi spacecraft autonomous 
rapid repoint (ARR) maneuver. 

This burst was also independently detected by INTEGRAL SPI-ACS.

The GBM light curve consists of a single spike with a duration (T90) 
of about 0.4 s (50-300 keV). The time-averaged spectrum from T0-0.064 s 
to T0+0.448 s is best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.42 +/- 0.04  and the 
cutoff energy, parameterized as Epeak, is 1300 (+80/-70)keV.

The event fluence (10-1000 keV) in this time interval is
(6.01 +/- 0.14)E-06 erg/cm^2. The 0.064-sec peak photon flux measured
starting from T0+0.32 s in the 10-1000 keV band
is 40 +/- 2 ph/s/cm^2.

A Band function fits the spectrum equally well with 
Epeak= 1300 +/-80 keV, alpha = -0.42 +/-0.04 
and beta = -3.4 (+0.4/-0.9).

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

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

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

S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer, on
behalf of the Swift-BAT team, report:

The short-duration, hard spectrum, intense GRB 130504B (von Kienlin et 
al., GCN Circ. 14560
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 ) has been observed by Fermi GBM, INTEGRAL 
(SPI-ACS), Konus-Wind, Swift (BAT), and MESSENGER (GRNS), so far, at 
about 27123 s UT (07:32:03). The burst was outside the coded field of 
view of the BAT.

We have triangulated it to a preliminary, 3 sigma error box whose 
coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   347.952 (23h 11m 49s)  -5.739 ( -5d 44' 20")
  Corners:
   347.658 (23h 10m 38s)  -5.056 ( -5d 03' 20")
   348.087 (23h 12m 21s)  -6.133 ( -6d 07' 58")
   348.256 (23h 13m 01s)  -6.420 ( -6d 25' 10")
   347.821 (23h 11m 17s)  -5.345 ( -5d 20' 41")
  ---------------------------------------------
The error box area is 196 sq. arcmin, and its maximum
dimension is 1.5 deg (the minimum one is 2.9 arcmin). The Sun distance 
was 57 deg.

This box can be improved.

The center of the GBM location (von Kienlin, GCN Circ. 14560
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 ) is 5.6
deg from the center of the IPN box.

A triangulation map will be posted at
http://www.ioffe.ru/LEA/GRBs/GRB130504_T27119/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 short-duration hard GRB 130504B
(Fermi-GBM detection: von Kienlin, GCN 14560
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 ;
IPN triangulation: Golenetskii et al., GCN 14561
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 )
triggered Konus-Wind at T0=27119.723s UT (07:31:59.723)

The light curve shows a double-peaked structure
from ~T0-0.064 s to ~T0+0.368s.
The total duration of the burst is ~0.430 s
The emission is seen up to ~8 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB130504_T27119/

As observed by Konus-Wind, the burst
had a fluence of (9.3 � 0.9)x10-6 erg/cm2,
and a 16-ms peak flux, measured from T0+0.320s,
of (5.0 � 0.9)x10-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The spectrum of the burst (measured from T0 to T0+0.256 s)
is best fit in the 20 keV - 15 MeV range
by the cutoff power law with the following model parameters:
the photon index alpha = -0.50 � 0.13,
the peak energy Ep = 980 � 125 keV,
chi2 = 40/36 dof.

All the quoted results are preliminary.

T. Yasuda, M. Tashiro, Y. Terada, Y. Ishida, H. Ueno, S. Sugimoto
(Saitama U.), M. Ohno, K. Takaki, T. Kawano, R. Nakamura, S. Furui,
Y. Fukazawa (Hiroshima U.), M. Yamauchi, N. Ohmori, M. Akiyama
(Univ. of Miyazaki), 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 bright, short, IPN localized GRB 130504B (GCN 14560
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 ;  von Kienlin et
al., GCN 14561
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 ; Golenetskii et al.) triggered the Suzaku Wide-band
All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV
at 07:32:03.063 UT (=T0).

The observed light curve shows a double-peaked structure starting at
T0+0.25 s, ending at T0+0.75 s with a duration (T90) of about
0.38 seconds.
The fluence in 100 - 1000 keV was 4.97(+0.15/-0.30) x10^-6 erg/cm^2.
The 1-s peak flux measured was 7.60 (+0.28/-0.54) photons/cm^2/s
in the same  energy range.

Preliminary result shows that the time-averaged spectrum from T0 to T0+1
s is well fitted by a power-law with exponential cutoff model:
dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
alpha       0.41 (+0.20/-0.22), and
Epeak      1321 (+139/-129) keV (chi^2/d.o.f. = 35.1/24).

All the quoted errors are at statistical 90% confidence level.

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