GRB 090715A

S. Sugita, K. Yamaoka (Aoyama Gakuin U.), M. Ohno, M. Suzuki, 
M. Kokubun, T. Takahashi (ISAS/JAXA), M. Tashiro, Y. Terada, 
A. Endo, K. Onda, W. Iwakiri, T. Sugasahara (Saitama U.), 
Y. E. Nakagawa, T. Tamagawa (RIKEN), N. Ohmori, A. Daikyuji, 
E. Sonoda, K. Kono, H. Hayashi, K. Noda, Y. Nishioka, M. Yamauchi 
(Univ. of Miyazaki), N. Vasquez (Tokyo Tech.), Y. Urata (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 short hard GRB 090715A (Swift/BAT trigger #357498; 
Racusin et al., GCN 9666
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 ; Baumgartner et al., GCN 9680
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 ) 
triggered the Suzaku Wide-band  All-sky Monitor (WAM) which covers an 
energy range of 50 keV - 5 MeV at 2009-07-15 17:25:39.033 UT (=T0). 

The observed light curve shows a multi-peaked structure, starting at 
T0+0.05 s and ending at T0+0.70 s, with a total duration (T90) of about 0.5 s. 
The fluence in 100 - 1000 keV was 1.13(-0.20, +0.08) x10^-6 erg/cm^2.  
The 1-s peak flux measured from T0 s was 2.25(-0.29, +0.12) photons/cm^2/s 
in the same energy range.

Preliminary result shows that the time-averaged spectrum from
T0 s to T0+1 s is well fitted by a power-law with exponential cutoff model:
  dN/dE ~  E^{-alpha} * exp(-(2-alpha)*E/Epeak) with
  alpha:     0.76(-0.46, +0.37), and
  Epeak:     588(-118, +216) keV (chi^2/d.o.f. = 18.1/30).

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

The light curves for this burst will be available at:
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html

E. Berger and W.-f. Fong (Harvard) report:

"We observed the field centered on the BAT error circle of the short GRB 
090715A (GCNs #9666
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 ,9680
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 ) with the VLA at a frequency of 8.46 GHz 
starting on 2009 July 16.98 UT (30.1 hours post burst).  We detect a
single bright source within the BAT error circle which is cataloged in
the VLA FIRST survey and is moreover extended.  No other sources are
detected within the BAT error circle above a 4-sigma level of 85
microJy.  In addition, we do not detect any point source in coincidence
with the nearby galaxy NGC3130."

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 090715A (Swift trigger=357498:
Racusin et al., GCN 9666
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 ; Baumgartner et al., 9680)
triggered Konus-Wind at T0=62736.657 s UT (17:25:36.657).

The burst had a duration of ~0.32 s.
The Konus-Wind light curves of this GRB are available at
http://www.ioffe.ru/LEA/GRBs/GRB090715_T62736/

As observed by Konus-Wind the burst had
a fluence of 3.5(-1.5,+2.1)x10-6 erg/cm2, and
a 16-ms peak flux measured from T0+0.016 s
of 2.0(-0.8,+1.2)x10-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst
(from T0 to T0+0.128 s) is well fitted (in the 20 keV - 10 MeV range)
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -1.13(-0.25,+0.42),
and Ep = 1658(-1010,+3957)keV (chi2 = 8.9/13 dof).

Fitting by GRB (Band) model yields:
the low-energy photon index alpha = -0.90(-0.45,+1.2),
the high energy photon index beta < -1.5,
the peak energy Ep = 738(-614,+3775) keV (chi2 = 8.2/12 dof).

The emission is clearly seen up to 7 MeV.

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

W. H. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC), 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),
J. L. Racusin (PSU), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
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+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 090715A (trigger #357498)
(Racusin, et al., GCN Circ. 9666
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 ).  The BAT ground-calculated position is
RA, Dec = 152.102, 10.006 deg, which is 
   RA(J2000)  =  10h 08m 24.5s 
   Dec(J2000) = +10d 00' 22.4" 
with an uncertainty of 2.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 22%.
 
The mask-weighted light curve shows a single spike starting at ~T-0.1 sec,
peaking at ~T+0.1 sec, and ending at ~T+0.7 sec.  Following the intial spike,
there is extended emission from ~T+20 to ~T+55 sec at a flux level ~50 times
lower than the peak flux of the spike.  T90 (15-350 keV) is 63 +- 18 sec
(estimated error including systematics).
 
The time-averaged spectrum from T-0.1 to T+67.8 sec is best fit by a simple
power-law model.  We note that this spectral analysis includes both
the spike and the extended emission.  Qualitatively, the spike is harder
than the extended emission. The power law index of the time-averaged spectrum is
1.28 +- 0.42.  The fluence in the 15-150 keV band is 9.8 +- 2.2 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.11 sec in the 15-150 keV band
is 3.9 +- 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/357498/BA/

S. B. Pandey (U Mich), S.A. Yost (College of St. Benedict), W. Zheng,
F. Yuan (U Mich), report on behalf of the ROTSE collaboration:

ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia,
responded to the short-hard GRB 090715A (Swift trigger 357498,  Racusin J. L., GCN 9666
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 ), producing images
beginning 7.1 s after the GCN notice time. An automated response took
the first image at 17:26:05.1 UT, 25.9 s after the burst, under fair
conditions.
We took 10 5-sec and 10 20-sec exposures and imaging is ongoing.
These unfiltered images are calibrated relative to USNO A2.0 (R). 

Comparison to the DSS (second epoch) reveals no new sources
within the 3-sigma Swift/BAT error circle, for both single images and
coadding into sets of 10.
Individual images have limiting magnitudes ranging from 15.4-16.6; we
set the following specific limits.
start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
17:26:05.1   17:27:21.5        76     16.8           25.9       Y
17:27:36.4   17:32:18.5       282     17.4          117.2       Y