GRB 100131A

V.Yurkov, S.Sergienko Blagoveschensk Educational State University, 
Blagoveschensk


E. Gorbovskoy, V. Lipunov, V.Kornilov, A.Belinski, N.Shatskiy, N.Tyurina, 
D.Kuvshinov, P.Balanutsa, V.V.Chazov, P.V.Kortunov, A.Kuznetsov, D.Zemnukhov, 
M. Kornilov
Sternberg Astronomical Institute, Moscow State University

A. Tlatov, A.V. Parhomenko, D. Dormidontov
Kislovodsk Solar Station of the Pulkovo Observatory


V.Krushinski, I.Zalozhnih, T.Kopytova, A. Popov Ural State University, Kourovka


K.Ivanov, S.Yazev, N.M.Budnev, E.Konstantinov, V.Lenok
Irkutsk State University


MASTER  robotic telescope (MASTER-Net: http://observ.pereplet.ru, 200
mm, FOV=8 square degrees (testing mode)) and  Very Wide Field Camera (D=50 mm, 
1000 square  degrees, 11 Mpx, 36" per pix, mounted on telescope) located at 
Blagoveschensk   was responted to the  GRB 100131A (Fermi GBM  alert,
  Goldstein et al, GCN CIRC 10358
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 ) 76 sec after first Notice 
time and 93 s after the GRB time.
The center FOV of the main telescope correspond to first alert 
imformation:

  RA=107.420+-3         DEC=+3.730+-3

The limit of the main telescope images is aboute 15 mag (unfiltered).


We have a number images with 5 s exposition from Very Wide Field Camera.
The image limit from Very Wide Filed Camera ~10 mag.
There is now OT in our images inside Fermi error box (A. Goldstein, GCN 
CIRC 10358
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 ) brighter 10 mag.

The imege  is available  at 
http://observ.pereplet.ru/images/GRB100131A/grb100131A.jpg .
The circles correspond to  1sigma + systematic Fermi error box, and
  3sigma+systematic error box.
The message may be cited.

mailto: lipunov@sai.msu.ru

Y. Nishioka, H. Hayashi, N. Ohmori, A. Daikyuji, E. Sonoda, K. Kono,
 K. Noda, M. Yamauchi (Univ. of Miyazaki), T. Sugasahara, M. Tashiro, 
 Y. Terada, A. Endo, K. Onda, W. Iwakiri (Saitama U.), S. Sugita
 (Nagoya U.), K. Yamaoka (Aoyama  Gakuin U.), M. Ohno, M. Suzuki, 
 M. Kokubun, T. Takahashi (ISAS/JAXA), Y. E. Nakagawa, T. Tamagawa 
 (RIKEN), N. Vasquez (Tokyo Tech.), Y. Urata, H.M  Lin (NCU), 
 Y. Hanabata, T. Uehara, T. Takahashi, Y. Fukazawa (Hiroshima U.), 
 T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo), S. Hong (Nihon U.), 
 on behalf of the Suzaku WAM team, report
 
 The long GRB 100131A (Fermi/GBM trigger #286651859 ; A. Goldstein et al., GCN 10358
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 ) 
 triggered the Suzaku Wide-band  All-sky Monitor (WAM) which covers an 
 energy range of 50 keV - 5 MeV on 2010-01-31 17:30:58.052 UT (=T0). 
 
 The observed light curve shows a multi-peaked structure lasting from T0-0.5s to T0+2s,
 followed by a weaker emission seen up to T0+4s with a duration (T90) of 
 about 3.2 seconds. The fluence in 100 - 1000 keV was 2.72(-0.41, +0.30) x10^-6 erg/cm^2. 
 The 1-s peak flux measured from T0 s was 4.52(-0.80, +0.57) photons/cm^2/s in the same 
 energy range.

 Preliminary result shows that the time-averaged spectrum from T0-0.5s to 
 T0+5.5s is well fitted by a single power-law with a photon index 
 of 2.62 (-0.37, +0.44) (chi^2/d.o.f = 11.8/13).

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

 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

A. Goldstein (UAH) reports on behalf of the Fermi GBM Team: 

"At 17:30:57.67 UT on 31 January 2010, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 100131A (trigger 286651859 / 100131730).
The Fermi Observatory executed a maneuver following this trigger and 
tracked the burst location for the next 5 hours, subject to 
Earth-angle constraints.

The on-ground calculated location, using the GBM trigger 
data, is RA = 120.4, DEC = +16.5 (J2000 degrees, 
equivalent to 08h 02m, 16d 29'), with an uncertainty 
of 1.2 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 was 27 degrees.

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

The GBM light curve consists of a single bright spike with substructure
with a duration (T90) of about 6.2 s (8-1000 keV). 
The time-averaged spectrum from T0 to T0+4.5 s is 
best fit by a Band function with Epeak = 132.10 +/- 6.28 keV, 
alpha = -0.63 +/- 0.05, and beta = -2.21 +/- 0.05
(Castor C statistic of 413 for 360 d.o.f.).

The event fluence (8-1000 keV) in this time interval is 
(7.723 +/- 0.130)E-06 erg/cm^2. The 0.128-sec peak photon flux measured 
starting from T0 in the 8-1000 keV band is 33.8 +/- 1.5 ph/s/cm^2.

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