[vsnet-grb-info 23186] Konus-Wind observation of GRB 190805B

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25285
SUBJECT: Konus-Wind observation of GRB 190805B
DATE:    19/08/08 05:42:10 GMT
FROM:    Anna Kozlova at Ioffe Institute  <ann_kozlova at mail.ioffe.ru>

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

The long-duration GRB 190805B
(MAXI/GSC detection: Sato et al., GCN Circ. 25271;
Fermi/GBM detection: Hamburg & Meegan, GCN Circ. 25277)
triggered Konus-Wind at T0=17159.354 s UT (04:45:59.354).

The burst light curve shows a multipeaked structure
which starts at ~T0-6.1 s and has a total duration of ~27.9 s.
The emission is seen up to ~6 MeV.

As observed by Konus-Wind, the burst
had a fluence of 1.46(-0.16,+0.24)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+14.832 s,
of 4.76(-1.60,+8.56)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+24.832 s)
is best fit in the 20 keV - 6 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -1.07(-0.23,+0.26)
and Ep = 315(-73,+148) keV (chi2 = 66/79 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.0
(chi2 = 65/78 dof).

The spectrum near the maximum count rate
(measured from T0+8.448 to T0+16.640 s)
is best fit in the 20 keV - 6 MeV range
by a power law with exponential cutoff model
with  alpha = -1.28(-0.44,+0.55)
and Ep = 281(-118,-281) keV (chi2 = 45/78 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -1.7
(chi2 = 44/77 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB190805_T17159/

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