[vsnet-grb-info 4655] GRB 070512: IPN localization and Konus spectrum of a bright burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6408
SUBJECT: GRB 070512: IPN localization and Konus spectrum of a bright burst
DATE:    07/05/14 19:01:07 GMT
FROM:    Valentin Pal'shin at Ioffe Inst  <val at mail.ioffe.ru>

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

K. Hurley and T. Cline, on behalf of the Mars Odyssey GRB team,

I. Mitrofanov, A. Kozyrev, M. Litvak, A. Sanin, V. Tret'yakov and A.
Parshukov, on behalf of the HEND-Odyssey GRB team,

W. Boynton, C. Fellows, K. Harshman, C. Shinohara and R. Starr, on
behalf of the GRS-Odyssey GRB team,

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

A bright GRB triggered Konus-Wind at 2007-05-12 T0=21972.572 s UT 
(06:06:12.572). It was also observed by Mars Odyssey (HEND and GRS), and 
Swift-BAT. The burst was outside of the field of view of Swift-BAT, so 
it was not imaged.

The burst light curve shows a single smooth pulse with a duration
of ~2 sec, followed by a weak tail seen up to T-T0 ~10 sec.
There is substantial time lag between light curve in different 
Konus-Wind bands.

It was triangulated to the MO-Wind annulus centered at
RA=357.861 (23h 51m 27s) Dec=-2.565 (-2d 33' 55"),
whose radius is 87.897 +/- 0.035  deg (3 sigma).
The Wind-Swift annulus constrains the arrival direction
to the long 3-sigma error box (portion of the annulus) with corners:

  ---------------------------------------------------
    RA, deg                 Dec, deg     (J2000)
  ---------------------------------------------------
   269.113 (17h 56m 27s)   -20.440 (-20d 26' 25")
   269.181 (17h 56m 43s)   -20.642 (-20d 38' 31")
   268.735 (17h 54m 56s)   -30.959 (-30d 57' 32")
   268.823 (17h 55m 18s)   -30.761 (-30d 45' 41")
  ---------------------------------------------------

The area of the box is 0.361 sq. deg.

We note that this error box is consistent with the direction of
the Galactic bulge.  We are waiting for MESSENGER data to reduce
the size of the error box.

Preliminary analysis of the Konus-Wind data yields a burst fluence of
2.86(-0.12, +0.10)x10^-5 erg/cm2 (in the 20 keV - 1 MeV range).
The time-integrated spectrum of the burst (from T0 to T0+9.472 s)
can be fitted (in the 20 keV - 1 MeV range)
by GRBM (Band) model for which:
the low-energy photon index is alpha = -0.68(-0.18, +0.19),
the high energy photon index beta = -2.65 (-0.46, +0.20),
the peak energy Ep = 191(-18, +23) keV (chi2 = 68/59 dof).

So the burst cannot definitely be placed in either the short
or long GRB class.

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

The Konus-Wind light curve of this GRB is available
at http://www.ioffe.rssi.ru/LEA/GRBs/GRB070512_T21972/