GRB 090301A

E. E. Fenimore (LANL), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC),
T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. N. Ukwatta (GWU), L. Vetere (PSU)
(i.e. the Swift-BAT team):
 
Using the data set from T-61 to T+242 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 090301A (trigger #344582)
(Vetere, et al., GCN Circ. 8920
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 ).  The BAT ground-calculated position is
RA, Dec = 338.142, 26.639 deg, which is 
   RA(J2000)  =  22h 32m 34.2s 
   Dec(J2000) = +26d 38' 19.0" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 35%.
 
The mask-weighted light curve shows a complex of overlapping and separated
peaks starting at ~T-20 sec and ending some time after T+86 sec
at which time the burst location went ouf out the BAT FOV when Swift slewed
to the next planned target.  Given that the burst location will not come out
of the Sun observing consrtaint until after April 15,  we will not have 
any further data on this burst.  T90 (15-350 keV) is 41.0 +- 2.2 sec
(estimated error including systematics).
 
The time-averaged spectrum from T-17.0 to T+72.2 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.08 +- 0.12, 
and Epeak of 343.3 +- 328.8 keV (chi squared 37.39 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 2.3 +- 0.03 x 10^-5 erg/cm2
and the 1-sec peak flux measured from T+23.07 sec in the 15-150 keV band is
18.7 +- 0.6 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.25 +- 0.03 (chi squared 43.70 for 57 d.o.f.).  All the quoted errors
are at the 90% confidence level.
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/344582/BA/

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

The bright long GRB 090301A (Swift-BAT trigger #344582: Vetere et al., 
GCN 8920
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 ; Fenimore et al., GCN 8923
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 ) triggered Konus-Wind at 
T0=24949.694 s UT (06:55:49.694).

The burst light curve shows a multipeaked structure with a duration of
~50 s, followed by a weak tail marginally seen up to ~T0+200 s.

As observed by Konus-Wind the burst
had a fluence of (1.13 +/- 0.08)x10^-4 erg/cm2,
and a 64-ms peak flux measured from T0+25.408 s
of (1.51 +/- 0.23)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+44.032 s) is well fitted (in the 20 keV - 5 MeV
range) by GRB (Band) model for which:
the low-energy photon index alpha = -0.87 +/- 0.05,
the high energy photon index beta = -2.65(-0.47, +0.25),
the peak energy Ep = 429(-32, +34) keV (chi2 = 77.5/76 dof).

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

The Konus-Wind light curve of this GRB is available
at http://www.ioffe.ru/LEA/GRBs/GRB090301_T24949/

T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo),
Y. Hanabata, Y. Fukazawa, T. Takahashi, T. Uehara, C. Kira (Hiroshima U.),
Y. Terada, M. Tashiro, Y. Urata, A. Endo, K. Onda, N. Kodaka,
K. Morigami, T. Sugasahara, W. Iwakiri (Saitama U.), M. Ohno,
M. Kokubun, M. Suzuki, T. Takahashi (ISAS/JAXA), K. Yamaoka,
S. Sugita (Aoyama Gakuin U.), Y.E. Nakagawa, T. Tamagawa (RIKEN),
E. Sonoda, M. Yamauchi, H. Tanaka, R. Hara, N. Ohmori, K. Kono,
H. Hayashi (Univ. of Miyazaki), S. Hong (Nihon U.),
N. Vasquez (Tokyo Tech), on behalf of the Suzaku WAM team, report:

The bright long GRB 090301A (Swift/BAT trigger #344582; Fenimore et al., GCN 8923
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 ) 
triggered the Suzaku Wide-band All-sky Monitor (WAM) which covers 
an energy range of 50 keV - 5 MeV at 06:55:50.862 UT (=T0).

The observed light curve shows a multi-peaked structure lasting from T0-2s 
to T0+48s with a duration (T90) of about 35 seconds. The fluence in 100 - 
1000 keV was 6.9(-0.5, +0.1) x 10^-5 erg/cm^2.  The 1-s peak flux measured 
from T0+27 was 14.8(+/-0.9) photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from 
T0-2s to T0+48s is fitted by a GRB Band model as follows.
the low-energy photon index alpha: -0.93 (-0.16, +0.18),
the high-energy photon index beta: -2.82 (-0.74, +0.29),
the break energy E0:       536 (-101, +131) keV,
and the peak energy Epeak: 574 +/- 170 keV (chi^2/d.o.f = 68/56).

Due to the high counting rate of this GRB, a 1% systematic error 
 was added for low energy channels. 
All the quoted errors are at the 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