GRB 081209

S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and K. 
Hurley on behalf of the Konus-Wind team,

J. Cummings, S. Barthelmy, N. Gehrels, and H. Krimm, on behalf of
the Swift-BAT team,

M. Marisaldi, F. Fuschino, E. Del Monte, Y. Evangelista, I. Lapshov, M. 
Rapisarda, and A. Giuliani, on behalf of the AGILE Team,
report:

AGILE-MCAL, Swift-BAT, and Konus-Wind observed the short-duration hard 
spectrum GRB 081209 at about 23:31:56 UT (corresponds to the Fermi/GBM 
trigger 250558317). The burst was outside the coded field of view of the 
BAT and SuperAGILE. The burst light curve shows a single peak with a 
duration of ~0.2 sec.

Triangulation gives an annulus centered at RA(2000)=77.269 (05h 09m 05s) 
  Dec(2000)=+17.346 (+17d 20' 47"), whose radius is 48.435 +/- 0.181 deg 
(3sigma).  This intersects the GBM error circle (the Fermi-GBM ground 
position is RA(2000), Dec(2000) = 88.980d (+05h 55m 55s), +71.450d (+71d 
27' 00")) assuming its 3sigma uncertainty of 11.8 deg (7.8deg stat + 
3deg syst)) to form a long 3sigma error box whose corners are at
-------------------------------------------------
        RA(2000)                 Dec(2000)
-------------------------------------------------
  104.995 (06h 59m 59s)   +61.438 (+61d 26' 16")
  105.760 (07h 03m 02s)   +61.616 (+61d 36' 58")
   62.128 (04h 08m 31s)   +64.879 (+64d 52' 43")
   62.813 (04h 11m 15s)   +64.597 (+64d 35' 47") 
--------------------------------------------------

This error box may be improved.

Preliminary analysis of the Konus-Wind data yields
a burst fluence of ~2x10^-6 erg/cm2 (in the 20 keV - 3 MeV range),
and an Epeak of the time-integrated spectrum of ~1 MeV.

Detailed spectral parameters will be reported later.

The K-W light curve of this GRB and IPN triangulation map is
available at http://www.ioffe.ru/LEA/GRBs/GRB081209_T84720/

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 short hard GRB 081209 (Golenetskii et al., GCN 8646
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 ; Fermi GBM 
trigger 250558317) triggered Konus-Wind at T0=84720.033 s UT (23:32:00.033).

As observed by Konus-Wind the burst
had a fluence of 2.39(-0.52, +0.58)x10^-6 erg/cm2,
and a 16-ms peak flux measured from T0-0.012 s
of 2.68(-0.83, +0.87)x10^-5 erg/cm2/s
(both in the 20 keV - 3 MeV energy range).

The spectrum accumulated from T0 to T0+0.128 s is well fitted (in the 20 
keV - 3 MeV range) by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.33(-0.31, +0.41),
and Ep = 961(-257, +432) keV (chi2 = 11.2/17 dof).
Fitting by GRB (Band) model yields the same alpha and Ep,
and only an upper limit on the high energy
photon index: beta < -1.7 (chi2 = 11.2/16 dof).

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

Colleen A. Wilson-Hodge (NASA/MSFC) and Valerie Connaughton (UAH)
report on behalf of the Fermi GBM Team:

"At 23:41:56.39 UT on 9 December 2008, the Fermi Gamma-Ray Burst Monitor
(GBM) triggered and located GRB 081209 (trigger 250558317 / 081209981).

The on-ground calculated location, using the GBM trigger data, is
RA = 45.3, DEC = 63.5 (J2000 degrees, equivalent to 02 h 20 m, 68 d 52'),
with an uncertainty of 4.9 degrees (radius, 1-sigma containment,
statistical only; there is additionally a systematic error which is
currently estimated to be 2 to 3 degrees). This location overlaps the IPN
arc reported in Golenetskii et al. 2008 (GCN Circular #8646
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 ).
 
The angle from the Fermi LAT boresight is 109 degrees.

The GBM light curve consists of a single peak with a duration (T90) of
about 0.4 s (8-1000 keV). The time-averaged spectrum from T0-0.110 s to
T0+0.210 s is best fit by a Band function with Epeak = 808 +/- 163 keV,
alpha = -0.5 +/- 0.1, and beta = -2.0 +/- 0.1. (chi squared 321.85 for
360 d.o.f.).

The event fluence (8-1000 keV) in this time interval is
(5.9 +/- 0.3)E-07 erg/cm^2. The 1-sec photon flux measured starting from
T0-0.110 s in the 8-1000 keV band is 7.8 +/- 0.4 ph/s/cm^2.

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