GRB 090720B

J. M. Burgess (UAH), A. Goldstein (UAH) and A. J. van der Horst
(NASA/MSFC/ORAU) report on behalf of the Fermi GBM Team:

"At 17:02:56.91 UT on 20 July 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090720B (trigger 269802178 / 090720710).
The on-ground calculated location, using the GBM trigger
data, is RA = 203.0, DEC = -54.8 (J2000 degrees,
equivalent to 13h 32m, -54d 48'), with an uncertainty
of 2.9 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 is 56 degrees.

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

The GBM light curve consists of two bright peaks with a
duration (T90) of about 20 s (8-1000 keV).
The time-averaged spectrum from T0+0.0 s to T0+20.1 s is well
fit by a power law function with an exponential high energy cutoff.
The power law index is -1.01 +/- 0.05 and the cutoff energy,  
parameterized
as Epeak, is 982 +/- 186 keV (chi squared 484 for 483 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(1.06 +/- 0.03)E-5 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+5.8 s in the 8-1000 keV band
is 10.9 +/- 0.4 ph/s/cm^2.

A Band function fits the spectrum equally well (chi squared 482 for
482 d.o.f.) with Epeak= 924 +/- 201 keV, alpha = -1.00 +/- 0.05
and beta = -2.43 +/- 0.47.

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

S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and T.
Cline on behalf of the Konus-Wind team,

A. von Kienlin, A. Rau, and K. Hurley on behalf of the
INTEGRAL SPI-ACS GRB team,

M. Marisaldi, F. Fuschino, C. Labanti, M. Galli, G. Di Cocco
on behalf of the AGILE team,

K. Yamaoka, M. Ohno, Y. Fukazawa, T. Takahashi, M. Tashiro, Y. Terada,
T. Murakami, K. Makishima, and Y. Hanabata on behalf of the Suzaku-WAM 
team, and

V. Connaughton, M. Briggs, and C. Meegan, on behalf of the Fermi GBM
team, report:

Suzaku-WAM, Konus-Wind, AGILE-MCAL, and INTEGRAL (SPI-ACS) observed the 
bright GRB 090720B at about 17:02:57 UT (the Fermi/GBM trigger 
269802178/090720710: Burgess et al. GCN 9698
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 ).
We have triangulated this burst to a Konus-GBM annulus centered at 
RA(2000)=274.434 (18h 17m 44s)  Dec(2000)=-23.965 (-23d 57' 54"), whose 
radius is  60.824 +/- 0.031 (3 sigma).
Triangulation of the Konus-SPI-ACS gives an annulus centered
at RA(2000)=274.426 (18h 17m 42s)  Dec(2000)=-18.772 (-18d 46' 19"), 
whose radius is  64.910 +/- 0.252 (3 sigma).

Together, these 2 annuli yield a 3-sigma error box whose center and 
corners are:
-----------------------------------------------
      RA(2000), deg              Dec(2000), deg
-----------------------------------------------
Center:
   201.609 (13h 26m 26s)   -55.000 (-55d 00' 01")
Corners:
   201.763 (13h 27m 03s)   -59.798 (-59d 47' 54")
   201.580 (13h 26m 19s)   -58.693 (-58d 41' 36")
   201.793 (13h 27m 10s)   -50.725 (-50d 43' 29")
   201.823 (13h 27m 17s)   -51.627 (-51d 37' 36")
-----------------------------------------------

The error box area is 0.500 sq. deg and may be refined.

The GBM on-ground location (Burgess et al. GCN 9698
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 ) is consistent with 
the IPN box.

A map is posted at http://www.ioffe.ru/LEA/GRBs/GRB090720_T61379/IPN/
showing GBM contours (statistical) and best-fit position (star),
and the IPN annuli (solid lines with centers dot-dashed).

This map will also be posted at http://ssl.berkeley.edu/ipn3/090720B .

The IPN localization may be improved.

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:


GRB 090720B (Fermi/GBM trigger 269802178/090720710: Burgess et al., GCN 9698
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 ;
IPN localization box: Golenetskii et al., GCN 9700
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 )
triggered Konus-Wind at T0=61379.486 s UT (17:02:59.486).

This bright hard GRB started with a series of several short spikes,
followed by a smoother structure. The emission is seen above 10 MeV
for the whole duration of the event (~16 s).
The Konus-Wind light curves of this GRB are available at
http://www.ioffe.ru/LEA/GRBs/GRB090720_T61379/

As observed by Konus-Wind the burst had a fluence
of 1.8(-0.5,+0.7)x10-5 erg/cm2, and
a 2-ms peak flux, measured from T0+0.186 s,
of 8.3(-2.8,+4.1)x10-5 erg/cm2/s
(both in the 20 keV - 15 MeV energy range).

The time-integrated spectrum of the burst, measured from T0 to T0+16.640 s,
is well fit (in the 20 keV - 15 MeV range)
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep), with
alpha = -1.16(-0.13,+0.17), and
Ep = 1370(-580,+1190)keV (chi2 = 99/98 dof).

The spectrum at the maximum count rate, measured from T0+0.128 to T0+0.192 s,
is also well fit (in the 20 keV - 15 MeV range) by a power law with
exponential cutoff model, for which:
alpha = -0.47(-0.42,+0.71), and
Ep = 710(-280,+590)keV (chi2 = 7.3/8 dof).

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