GRB 090910

V.Chaplin (UAH) reports on behalf of the Fermi GBM Team:

"At 19:29:48.81 UT on 10 SEP 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090910 (trigger 274303790 / 090910812).

The on-ground calculated location, using the GBM trigger
data, is RA = 296.2, DEC = 72.3 (J2000 degrees,
equivalent to 19h 44m, 72 d 18'), with an uncertainty
of 1.0 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 107 degrees.

The on-board GBM Flight Software localization for this event,
as reported in the GCN notice, was consistent with a position
near the Earth's limb.  Furthermore, the trigger occurred as
the spacecraft was at a high magnetic latitude.  The resulting
autonomous classification for the event was "Distant Particles",
which is erroneous.

The GBM light curve consists of three distinct pulses
close in time from T0-5s to about T0+45s, with a smaller pulse
visible in several detectors at about T0+70s.  The duration (T90)
of this event is approximately 62s (8-1000 keV).
The time-averaged spectrum from T0-7.2 s to T0+44 s is
best fit by a Band function with Epeak = 274.8 +/- 56.1 keV,
alpha = -0.9 +/- 0.1, and beta = -2.0 +/- 0.2 (chi squared 397.41
for 360 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(9.2 +/- 0.7)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+2 s in the 8-1000 keV band
is 2.3 +/- 0.6 ph/s/cm^2.

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

I. Donnarumma, Y. Evangelista, E. Del Monte, M. Feroci, F. Lazzarotto,
L. Pacciani, P. Soffitta, E. Costa, I. Lapshov, M. Rapisarda
(INAF/IASF Rome), A. Giuliani, A. Chen, S. Mereghetti, F. Perotti,
P. Caraveo (INAF/IASF Milan), A. Pellizzoni, M. Pilia (INAF/OA Cagliari),
S. Vercellone (INAF/IASF Palermo), A. Bulgarelli, F. Gianotti,
M. Trifoglio, G. Di Cocco, C. Labanti, F. Fuschino, M. Marisaldi,
M. Galli, (INAF/IASF Bologna), M. Tavani, G. Pucella, F. D'Ammando,
E. Striani, V. Vittorini, A. Argan, A. Trois, G. Piano, S. Sabatini
(INAF/IASF Rome), G. Barbiellini, F. Longo, E. Moretti (INFN Trieste),
P. Picozza, A. Morselli (INFN Roma-2), M. Prest, E. Vallazza (Universita`
dell'Insubria), P. Lipari, D. Zanello (INFN Roma-1), and  P. Giommi,
C. Pittori, P. Santolamazza, F. Verrecchia (ASDC) and L. Salotti (ASI),
on behalf of the AGILE Team, report:

"SuperAGILE detected a long gamma ray burst on 10 October 2009,
at 02:43:09 UT. The event had a duration of about 10 s in the 17-60 keV
energy range, with a highly structured shape. Assuming a Crab-like energy
spectrum, the peak flux on 1-s timescale was about 6.2E-07 erg/cm2/s.
The burst position was reconstructed  as (RA, Dec)
(298.669, -22.538) deg, which is:

RA(J2000)  = 19h 54m 40.51s
Dec(J2000) = -22d 32' 17.36"

with an uncertainty of 3' radius. The given uncertainty accounts
for both the statistical and systematic errors.

An analysis of the AGILE Gamma Ray Imager (GRID) data is in progress."