[vsnet-grb-info 20450] Konus-Wind observation of GRB 180325A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22546
SUBJECT: Konus-Wind observation of GRB 180325A
DATE:    18/03/26 09:41:07 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred at mail.ioffe.ru>

D. Frederiks, S. Golenetskii, R.Aptekar, M. Ulanov, D. Svinkin,
A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline,
on behalf of the Konus-Wind team, report:

The long GRB 180325A (Swift-BAT trigger 817564:
Troja et al., GCN 22532; Lien et al., GCN 22545)
triggered Konus-Wind at T0=6866.876 s UT (01:54:26.876)

The burst light curve shows a single pulse,
which started at ~T0-1 s and peaked at ~T0+1.7 s.
The total duration of the burst is ~10 s.
The emission is seen up to ~7 MeV.

As observed by Konus-Wind, the burst had a fluence of
(1.9 ± 0.3)x10^-5 erg/cm2 and a 64-ms peak energy flux,
measured from T0+1.728, of (8.2 ± 1.3)x10^-6 erg/cm2
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+7.424 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.50 (-0.19,+0.21),
the high energy photon index beta = -2.65 (-1.06,+0.31),
the peak energy Ep = 306 (-39,+50) keV,
chi2 = 99/92 dof.

Assuming the redshift z=2.25 (Heintz et al., GCN 22535)
and a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.3, and Omega_Lambda = 0.7,
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is ~2.3x10^53 erg,
the peak luminosity L_iso is ~3.2x10^53 erg/s,
and the rest-frame peak energy of the time-integrated spectrum,
Ep,z, is ~995 keV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB180325_T06866/

All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.