GRB 090401A, GRB 090401

M. Suzuki, M. Ohno, M. Kokubun, T. Takahashi (ISAS/JAXA),
N. Kodaka, W. Iwakiri, M. Tashiro, Y. Terada, Y. Urata, A. Endo,
K. Onda, K. Morigami, T. Sugasahara (Saitama U.), T. Enoto,
K. Nakazawa, K. Makishima (Univ. of Tokyo), S. Sugita, K. Yamaoka
(Aoyama Gakuin U.), Y. E. Nakagawa, T. Tamagawa (RIKEN), T. Uehara,
T. Takahashi, Y. Fukazawa, C. Kira, Y. Hanabata (Hiroshima U.),
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 GRB090401A (Swift/BAT trigger #348128; Schady et al., 
GCN 9062
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 ; Sato et al., GCN 9064
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 ) was detected by the the Suzaku Wide-band 
All-sky Monitor (WAM) which covers an energy range of 50 keV - 5 MeV 
at 00:02:34.509 UT (=T0).

The observed light curve shows a multi-peaked structure lasting from 
T0-5s to T0+38s.  There is also a weak precursor starting at ~T0-103s, 
 resulting in the total duration (T90) of about 112 seconds.
The fluence in 100 - 1000 keV was 1.37(-0.10,+0.08) x10^-5 erg/cm^2.
The 1-s peak flux measured from T0+27s was 5.1(-0.4,+0.5) photons/cm^2/s
in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-5s to
T0+38s is fitted by a single power-law with a photon index
of 2.14 (-0.13,+0.14) (chi^2/d.o.f = 21.4/24).
3 % systematic errors were included in low energy channels. 
All the quoted errors are at 90% confidence level. 

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

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 most intense part of the long GRB 090401A (Swift-BAT trigger 
#348128: Schady et al., GCN 9062
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 ; Sato et al., GCN 9064
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 ) triggered 
Konus-Wind at T0=170.845 s UT (00:02:50.845).

The burst light curve shows a weak emission starting at ~T0-120s 
followed by the main multipeaked part at ~T0-24s, which had a duration 
of ~40s. There is a hint of an earlier emission.

As observed by Konus-Wind the burst
had a fluence of 2.14(-0.17, +0.19)x10^-5 erg/cm2,
and a 256-ms peak flux measured from T0+7.648 s
of 2.79(-0.42, +0.44)x10^-6 erg/cm2/s
(both in the 20 keV - 1 MeV energy range).

The spectrum of the most intense part
(from T0 to T0+16.640 s) can be fitted (in the 20 keV - 1 MeV
range) by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -1.26(-0.14, +0.15),
and Ep = 218(-34, +51) keV (chi2 = 87.9/60 dof).
Fitting by GRB (Band) model yields the same alpha and Ep,
and only an upper limit on the high energy
photon index: beta < -2.3 (chi2 = 87.9/59 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/GRB090401_T00170/

G. Sato (ISAS), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), 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), P. Schady (MSSL-UCL),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-239 to T+713 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 090401 (trigger #348128)
(Schady, et al., GCN Circ. 9062
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 ).  The BAT ground-calculated position is
RA, Dec = 350.920, 29.762 deg, which is 
   RA(J2000)  =  23h 23m 40.8s 
   Dec(J2000) = +29d 45' 44.1" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 38%.
 
The mask-weighted light curve starts out at T-20 sec when the burst location
first came into the BAT FOV during a planned-target slew maneuver.  There is
evidence for emission starting prior to burst coming to the FOV.  There are
two small peaks at T+0 and T+30 sec. Then comes the main emission
with a series of at least 7 overlapping peaks starting at ~T+95 sec and
returning to background at ~T+190 sec.  T90 (15-350 keV) is 112 +- 15 sec
(estimated error including systematics).
 
The time-averaged spectrum from T-9.4 to T+160.0 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.70 +- 0.05.  The fluence in the 15-150 keV band is 1.1 +- 0.0 x 10^-5 erg/cm2.
The 1-sec peak photon flux measured from T+122.05 sec in the 15-150 keV band
is 10.9 +- 0.5 ph/cm2/sec.  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/348128/BA/

P. Schady (MSSL-UCL), S. D. Barthelmy (GSFC), N. Gehrels (NASA/GSFC),
S. T. Holland (CRESST/USRA/GSFC), H. A. Krimm (CRESST/GSFC/USRA),
C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL), A. M. Parsons (GSFC),
B. A. Rowlinson (U Leicester) and L. Vetere (PSU) report on behalf of
the Swift Team:

At 00:00:59 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 090401 (trigger=348128).  The BAT on-board calculated 
location is RA, Dec 350.909, +29.767 which is 
   RA(J2000)  =  23h 23m 38s
   Dec(J2000) = +29d 46' 00"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a small peak at
~T+30 sec and then two large peaks at ~T+100 and ~T+120 sec. 
The peak count rate was ~4000 counts/sec (15-350 keV), at ~120 sec
after the trigger. 

Due to an observing constraint, Swift cannot slew to
the BAT position. It will not be possible to observe
until 2nd May due to a sun constraint. There will thus 
be no XRT or UVOT data for this trigger. 

Burst Advocate for this burst is P. Schady (ps AT mssl.ucl.ac.uk). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)