[vsnet-grb-info 23769] Konus-Wind observation of GRB 190928A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25868
SUBJECT: Konus-Wind observation of GRB 190928A
DATE:    19/09/30 11:29:55 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred at mail.ioffe.ru>

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

The long, very bright GRB 190928A
(AGILE/MCAL detection: Ursi et al., GCN 25859;
IPN triangulation: Hurley et al., GCN 25864;
CALET Gamma-Ray Burst Monitor detection: Pal'shin et al., GCN 25865)
triggered Konus-Wind (KW) at T0=47536.665 s UT (13:12:16.665).

The burst light curve starts with a smooth pulse, which was followed,
after a period of low-level emission, by a much more intense,
multi-peaked emission complex. The total duration of the burst is ~195 s.
The emission is seen up to ~15 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB190928_T47536/

As observed by Konus-Wind, the burst had
a fluence of (4.9 ± 0.3)x10^-4 erg/cm^2 and
a 256-ms peak energy flux, measured from T0+103.168,
of (9.0 ± 0.2)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+185.334 s)
is best fit in the 20 keV - 20 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.98 (-0.07,+0.07),
the high energy photon index beta = -1.97 (-0.13,+0.07),
the peak energy Ep = 591 (-88,+108) keV,
chi2 = 89/97 dof.

The spectrum near the peak count rate (measured from T0+103.168 s
to T0+103.424 s) is best fit in the 20 keV - 20 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.72 (-0.25,+0.26),
the high energy photon index beta = -1.73 (-0.24,+0.09),
the peak energy Ep = 636 (-232,+754) keV,
chi2 = 72/57 dof.

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