[vsnet-grb-info 25783] Konus-Wind observation of GRB200528A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  27883
SUBJECT: Konus-Wind observation of GRB200528A
DATE:    20/06/02 09:06:41 GMT
FROM:    Anastasia Tsvetkova at Ioffe Institute  <tsvetkova at mail.ioffe.ru>

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

The long-duration, soft-spectrum GRB200528A
(Swift detection: Ambrosi et al., GCN 27832;
Barthelmy et al., GCN 27839;
Fermi GBM Observation: Fletcher, von Kienlin & Meegan, GCN 27841;
CALET Gamma-Ray Burst Monitor detection: Pal'shin et al., GCN 27855)
triggered Konus-Wind at T0=37675.256 s UT (10:27:55.256).

The burst light curve shows a complex structure
which starts at ~T0-33.8 s, with a total duration of~60.0 s,
and comprises two double-peaked emission episodes.
The emission is seen up to ~1 MeV.

As observed by Konus-Wind, the burst
had a fluence of 2.12(-0.07,+0.07)x10^-5 erg/cm2,
and a 64-ms peak energy flux, measured from T0+1.696 s,
of 2.38(-0.35,+0.35)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst
(measured from T0 to T0+33.024 s)
is best fit in the 20 keV - 1 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -1.41(-0.14,+0.14),
and Ep = 64(-5,+5) keV (chi2 = 50/60 dof).
Fitting by the GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index:
beta < -2.89 (chi2 = 49/59 dof).

The spectrum near the peak count rate
(measured from T0+0.256 to T0+8.448 s)
is best fit in the 20 keV - 1 MeV range
by the power law with exponential cutoff model
with  alpha = -1.14(-0.15,+0.16),
and Ep = 75(-4,+5) keV (chi2 = 52/60 dof).
Fitting by the GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index:
beta < -3.03 (chi2 = 51/59 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB200528_T37675/

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