GRB 110529A

Julie McEnery (NASA/GSFC), Johan Bregeon (INFN Pisa) and
Dan Kocevski (SLAC)  report on behalf of the Fermi-LAT collaboration.

The Fermi Large Area Telescope (LAT) detected emission from GRB
110529A also detected by GBM (trigger 328322924) at 00:48:42.87 UT
on May 29, 2011.

The GBM location was inside the LAT field of view at an angle of
~30 degrees to the LAT boresight; no significant excess is seen
using standard analysis procedures.

Using a non-standard data selection, over 30 counts above background
were detected within a 0.1 s interval coinciding with the time of the
GBM emission. This data selection has insufficient spatial resolution
to provide a reliable LAT localization.

Since an excess of events were not seen using the standard analysis
selection, this detection is likely due to low energy gamma-rays
(below 100 MeV).

Further analysis is ongoing.

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 hard GRB 110529A (GBM trigger 328322924, GCN 12044
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triggered Konus-Wind at T0=2920.249s UT (00:48:40.249)

The burst light curve consists of a single sharp pulse
with a total duration of ~0.57 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/GRB110529_T02920/

As observed by Konus-Wind the burst
had a fluence of (5.1 � 1.1)x10-6 erg/cm2,
and a 16-ms peak flux, measured from T0,
of 7.0(-3.0,+2.2)x10-5 erg/cm2/s
(both in the 20 keV - 5 MeV energy range).

The time-integrated spectrum of the burst
(from T0 to T0+0.256 s) is best fitted
in the 20 keV - 5 MeV range by the GRB (Band)
model, for which:
the low-energy photon index alpha = -0.43 (-0.36, +0.89),
the high energy photon index beta = -1.7 (-0.3, +0.2),
the peak energy Ep = 428(-226, +363) keV,
chi2 = 14.3/26 dof.

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

J. Michael Burgess (UAH) and Sylvain Guiriec (UAH)
report on behalf of the Fermi GBM Team:

"At 00:48:42.87 UT on 29 May 2011, the Fermi Gamma-Ray Burst Monitor
triggered and located the very bright and short
GRB 110529A (trigger 110529034 / 110529034).

The on-ground calculated location, using the GBM trigger
data, is RA = 118.33, DEC = 67.91 (J2000 degrees,
equivalent to 7h 53m, +67d 54'), with an uncertainty
of 1.5 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 30 degrees.

This GRB was also observed by Konus-Wind (GCN 12045
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The GBM light curve consists of two short bright peaks
with a duration (T90) of about 0.41s (50-300 keV).
The time-averaged spectrum from T0-0.0 s to T0+.44s is
adequately fit by a Band function with
Epeak = 1161 +/- 265 keV, alpha = -0.88 +/- 0.06,
and beta = -2.05+/- 0.15

The event fluence (10-1000 keV) in this time interval is
(2.32 +/- 0.01)E-6 erg/cm^2. The 0.256-sec peak photon flux
measured starting from T0+0.00 s in the 10-1000 keV band
is 23.6826 +/- 0.68 ph/s/cm^2.

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

S. Sugita (Nagoya U.), Y. E. Nakagawa (Waseda U.),
W. Iwakiri, Y. Terada, M. Tashiro,  K. Takahara, T. Yasuda (Saitama U.),
T. Uehara, Y. Hanabata, T. Takahashi, Y. Fukazawa (Hiroshima U.),
K. Yamaoka (Aoyama Gakuin U.), M. Ohno, M. Kokubun, T. Takahashi (ISAS/JAXA),
N. Ohmori, M. Akiyama, M. Yamauchi (Univ. of Miyazaki),
Y. Urata, P. Tsai, C-J. Chuang (NCU), K. Nakazawa, K. Makishima (Univ.
of Tokyo),
on behalf of the Suzaku WAM team, report:

The bright short GRB 110529A  (McEnery et al., GCN 112044
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triggered the Suzaku Wide-band  All-sky Monitor (WAM) which covers an
energy range of 50 keV - 5 MeV at 2011-05-29 00:48:42.855 UT (=T0).

The observed light curve shows a single FRED-like peak
starting at T0s, ending  at T0+0.438s, with a duration
(T90) of 0.344 +/- 0.049 seconds.
The fluence in 100 - 1000 keV was 1.93 (+/- 0.12) x 10^-6 erg/cm^2.
 The 1-s peak flux measured from T0s was 7.16 (+/- 0.45) photons/cm^2/s
in the same  energy range.

Preliminary result shows that the time-averaged spectrum from
T0s to T0+0.5s is well fitted by a power-law with exponential cutoff model:
  dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
  alpha       1.02 (-0.20, 0.16)), and
  Epeak       1052 (-196, +254) keV (chi^2/d.o.f. = 55.9/52).

We also shows the results with the same spectrum
fitted by a GRB Band model fixing beta of -2.5
the low-energy photon index alpha: -0.80 (-0.26, 0.34),
the high-energy photon index beta: -2.5 (fixed),
and the peak energy Epeak: 791 (-161, 242) keV (chi^2/d.o.f = 53.6/52).

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