GRB 081215A

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 very bright GRB 081215A (Fermi/GBM trigger 251059717 / 081215784: 
Preece, GCN 8678
Loading...
 
 , 8679
Loading...
 
 ) localized by IPN (Golenetskii et al., GCN 8702
Loading...
 
 ) 
triggered Konus-Wind at T0=67721.281 s UT (18:48:41.281).

As observed by Konus-Wind the burst
had a fluence of (7.99 +/- 0.68)x10^-5 erg/cm2,
and a 16-ms peak flux measured from T0+0.448 s
of (1.24 +/- 0.17)x10^-4 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst
(from T0 to T0+12.544 s) is well be fitted (in the 20 keV - 5 MeV
range) by GRB (Band) model for which:
the low-energy photon index is alpha = -0.870(-0.064, +0.070),
the high energy photon index beta = -2.20(-0.19, +0.13),
the peak energy Ep = 447(-52, +60) keV (chi2 = 72.2/76 dof).
The spectrum of the most intense peak
(from T0+0.256 s to T0+0.512 s) is well fitted (in the 20 keV-10 MeV
range) by GRB (Band) model for which:
the low-energy photon index is alpha = -0.49(-0.10, +0.12),
the high energy photon index beta = -2.38(-0.37, +0.23),
the peak energy Ep = 1001(-174, +193) keV (chi2 = 57.5/58 dof).
In this spectrum a statistically significant emission is clearly seen up 
to 10 MeV.

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

[GCN OPS NOTE(23dec08): Per author's request, "2.38(-0.37, +0.23)"
was changed to "-2.38(-0.37, +0.23)".]

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

M. Marisaldi, F. Fuschino, I. Donnarumma, E. Del Monte and M. Feroci on
behalf of the AGILE Team,

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

AGILE-MCAL and Konus-Wind observed the very bright GRB 081215A at about 
18:48:38 UT (corresponds to the Fermi/GBM
trigger 251059717 / 081215784: Preece, GCN 8678
Loading...
 
 , 8679
Loading...
 
 ). The burst was 
outside the coded field of view of the SuperAGILE. The burst light curve 
shows a multipeaked structure with a total duration of ~10 sec.
The Swift-BAT saw nothing at this time. Hence, taking in account the 
high intensity of this GRB, that means the source of the burst was below 
the horizon for Swift.

Triangulation gives an annulus centered at RA(2000)=78.201 (05h 12m 48s)
  Dec(2000)=+17.575 (+17d 34' 32"), whose radius is 51.547 � 0.508 deg
(3sigma). The Fermi/GBM ground position (Preece, GCN 8678
Loading...
 
 ) is 5 deg away 
from the center line of the annulus. The Konus ecliptic latitude 
response constrains the arrival direction to a band between ecliptic 
latitudes +30 and +53 degrees.

Combining all these data, we have triangulated
this burst to a single error box, whose corners are:
-----------------------------------------------------
     RA(2000), deg              Dec(2000), deg
-----------------------------------------------------
1: 129.016 (08h 36m 04s)   +50.756 (+50d 45' 22")
2: 122.577 (08h 10m 18s)   +58.308 (+58d 18' 28")
3: 121.670 (08h 06m 41s)   +57.174 (+57d 10' 27")
4: 127.051 (08h 28m 12s)   +51.125 (+51d 07' 32")
-----------------------------------------------------

Preliminary analysis of the Konus-Wind data yields
a burst fluence of ~7x10^-5 erg/cm2 (in the 20 keV - 5 MeV range),
and an Epeak of the time-integrated spectrum of ~450 keV.

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/GRB081215_T67721/

Julie McEnery (NASA/GSFC) reports on behalf of the Fermi LAT team

We report a detection by the Fermi Large Area Telescope (LAT) of 
emission from GRB081215A (Preece et al, GCN8678
Loading...
 
 ).

This burst was at an angle of 86 degrees to the LAT boresight, which 
means that neither directional nor energy information can be obtained 
with the standard analysis procedures.

Using a non-standard data selection, over 100 counts above background 
were detected within a 0.5 s interval in coincidence with the main GBM 
peak. The significance of this excess was greater than 8 sigma. A 
preliminary study of the instrument performance at such a large 
inclination suggests that these events are likely to be low energy 
gamma-rays, with energies less than 200 MeV.

Further analysis is ongoing.

The Fermi LAT point of contact for this burst is Julie McEnery 
(julie.mcenery@nasa.gov).

The Fermi LAT is a pair conversion telescope designed to cover the 
energy band from 20 MeV to greater than 300 GeV. It is the product of an 
international collaboration between NASA and DOE in the U.S. and many 
scientific institutions across France, Italy, Japan and Sweden.
This message can be cited.

Robert Preece (UAH) reports on behalf of the Fermi GBM Team:

"The correct event fluence for the GRB detection reported
in Circular Number 8678 should be:
(5.44 +/- 0.07)E-5 erg/cm^2 in the energy interval 8-1000 kev
for times -T0-1.79 s to T0+13.57 s. Thanks to Alexander Kann
at TLS Tautenburg for spotting the error."

Robert Preece (UAH) reports on behalf of the Fermi GBM Team:

"At 18:48:36.85 UT on 15 December 2008, the Fermi Gamma-Ray Burst  
Monitor
triggered and located GRB 081215 (trigger 251059717 / 081215784).

The on-ground calculated location, using the GBM trigger
data, is RA = 135.0, DEC = +53.8 (J2000 degrees,
equivalent to 09 h 00 m 00.00, 53 d 48 '), 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 86 degrees.

The on-board GBM Flight Software localization for this very bright
burst, as reported in the GCN Notices, was consistent
with a position on the Earth's surface, likely due to a large scattered
flux from the Earth. This resulted in an autonomous and erroneous
"100%  Below horizon" classification for this event which prevented an
automated ground localization from being sent through the GCN notice
system.

The GBM light curve consists of a very hard narrow pulse on
top of a broader emission episode,
with a duration (T90) of about 7.7 s (8-1000 keV).
The time-averaged spectrum from T0-1.79 s to T0+13.57 s is
best fit by a Band function with Epeak = 304 +/- 11 keV,
alpha = -0.585 +/- 0.022, and beta = -2.066 +/- 0.038.

The event fluence (8-1000 keV) in this time interval is
(3.54 +/- 0.05)E-6 erg/cm^2. The 1-sec photon flux measured
starting from T0+1.28 s in the 8-1000 keV band
is 68.9 +/- 1.0 ph/s/cm^2.

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

V. Lipunov, E. Gorbovskoy,

If the GRB 081215A really connected with M31 (Gorbovskoy et al, GCN 
Circ 8671
Loading...
 
 ,  8672
Loading...
 
 ) it must be Soft Gamma Repeater or Andromeda X-ray 
binary source.

The message may be cited.

mailto: lipunov@sai.msu.ru

E. Gorbovskoy, V. Lipunov, V.Kornilov, A.Belinski, N.Shatskiy, N.Tyurina, 
D.Kuvshinov, P.Balanutsa
Sternberg Astronomical Institute, Moscow State University

A. Tlatov, A.V. Parhomenko Kislovodsk Solar Station of the Pulkovo Observatory

V.Krushinski, I.Zalognikh
Ural State University, Kourovka


S.Yazev, K.Ivanov
Irkutsk State University

One of the four  MASTER Very Wide Field Cameras located at Kislovodsk
(http://apollo.sai.msu.ru/, D=50 mm, 4x1000 square degrees, 35'' per pix)
has observed  Fermi  error box  (Trig Num 251059717) with 5s exposures during 
all night without time gap between images.
The M31 (ANdromeda) is inside Fermi error box.

The message may be cited.

mailto: lipunov@sai.msu.ru