GRB 121122A

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, C. Meegan, and V. Pelassa, 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,

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,

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

A long-duration, intense GRB 121122A with strong spectral evolution was 
observed by Konus-Wind, Fermi (GBM: trigger 375311695), INTEGRAL 
(SPI-ACS), MESSENGER (GRNS), Swift (BAT), and Suzaku (WAM), at about 
76493 s UT (21:14:53). 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:
     35.262 (02h 21m 03s) +45.139 (+45d 08' 21")
   Corners:
     50.638 (03h 22m 33s) +46.661 (+46d 39' 39")
     46.318 (03h 05m 16s) +47.134 (+47d 08' 01")
     25.058 (01h 40m 14s) +40.194 (+40d 11' 39")
     27.431 (01h 49m 44s) +41.325 (+41d 19' 31")
   ---------------------------------------------
The error box area is 6.9 sq. deg, and its maximum dimension is 19.6 deg 
(the minimum one is 2.1 deg, the minimum annulus width is 0.2 deg).

This box can be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB121122_T76497/IPN/

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

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 121122A
(IPN detection and localization: Hurley et al., GCN 14001
Loading...
 
 )
triggered Konus-Wind at T0=76497.048s UT (21:14:57.048)

The burst light curve is formed by three overlapped FRED-like pulses;
a total duration of the burst is ~12 s.
A behavior of hardness ratios between the instrument's light curves
in different energy bands suggests a strong hard-to-soft spectral evolution.
The emission is seen up to 7 MeV.

As observed by Konus-Wind, the burst
had a fluence of (4.1 � 0.1)x10-5 erg/cm2,
and a 64-ms peak flux, measured from T0+1.728 s,
of (1.0 � 0.1)x10-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst (measured T0 to T0+15.616 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.53 � 0.05,
the high energy photon index beta = -3.3 � 0.2,
the peak energy Ep = 183 � 4 keV,
chi2 = 106/91 dof.

The spectrum at the maximum count rate (measured T0 to T0+1.792 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = +0.58 � 0.12,
the high energy photon index beta = -3.0 � 0.2,
the peak energy Ep = 308 � 13 keV,
chi2 = 69.4/60 dof.

The time-resolved spectral analysis reveals
a steady decrease of Ep from ~700 keV to ~100 keV
during the first 8 seconds of the burst,
which can be described by a power law with
the temporal decay index of ~0.6 .

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB121122_T76497/

All the quoted results are preliminary.

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

"At 21:14:52.55 UT on 22 Nov 2012, the Fermi Gamma-Ray Burst Monitor
triggered and located the intense GRB 121122A (trigger 375311695/121122885,
IPN detection and localization: Hurley et al., GCN 14001
Loading...
 
 ).

The angle from the Fermi LAT boresight is 159 degrees.

The GBM light curve consists of two overlapping peaks with FRED-like pulses
with a duration (T90) of about 8.2 s (50-300 keV).
The time-averaged spectrum from T0-1.0 s to T0+17.4 s is
well fit by a Band function with Epeak = 178 +/- 4 keV,
alpha = -0.68 +/- 0.06 , and beta = -3.1 +/- 0.1.

The event fluence (10-1000 keV) in this time interval is
(5.46 +/- 0.07)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+4.7 s in the 10-1000 keV band
is 56 +/- 3 ph/s/cm^2.

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

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

The long, IPN localized GRB 121122A (Hurley et al., GCN 14001
Loading...
 
 )
was detected by the the Suzaku Wide-band All-sky Monitor (WAM) which
covers an energy range of 50 keV - 5 MeV at 21:14:53 UT (=T0).

The observed light curve shows double-peaked FRED-like structure
lasting from T0 to T0+7 s with a duration (T90) of about 7 seconds.
The fluence in 100 - 1000 keV was 1.98 (+0.11/-0.16) x 10^-5 erg/cm^2.
The 1-s peak flux measured from T0 was 12.7 (+10.1/-1.25) photons/cm^2/s
in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0 to
T0+7 s is well fitted by a single power-law with a photon index
of 3.08 (+0.17/-0.15) (chi2/d.o.f = 9.6/14).

The light curves with 1-sec time resolution for this burst will be
appeared at:
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/untrig/grb_table.html