GCN Circular 28872

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

The long-duration GRB 201103B
(AGILE detection: Ursi et al., GCN Circ. 28831
Not found
 
 
;
ZTF afterglow discovery: Coughlin et al., GCN Circ. 28841
Not found
 
 
;
IPN triangulation: Svinkin et al., GCN Circ. 28844
Not found
 
 
)
triggered Konus-Wind at T0=65207.923 s UT (18:06:47.923).

The burst light curve shows a multi-peaked structure
which starts at ~T0-14 s, peaks at ~T0+1.5, and ends at ~T0+20 s,
followed by a weaker emission seen up to ~T0+91 s.
The total burst duration is ~105 s.
The emission is seen up to ~5 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB201103_T65207/

As observed by Konus-Wind, the burst
had a fluence of 5.26(-0.77,+0.82)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+1.536 s,
of 1.49(-0.24,+0.25)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+16.640 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.72(-0.16,+0.19),
the high energy photon index beta = -2.54(-1.13,+0.33),
the peak energy Ep = 403(-60,+74) keV
(chi2 = 102/97 dof).

The spectrum near the maximum count rate
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.71(-0.12,+0.13)
and Ep = 466(-47,+58) keV (chi2 = 104/98 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.4
(chi2 = 102/97 dof).

Assuming the redshift z=1.105 (Xu et al., GCN Circ. 28847
Not found
 
 
)
and a standard cosmology model with H_0 = 67.3 km/s/Mpc,
Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is ~1.8x10^53 erg,
the peak luminosity L_iso is ~1.1x10^53 erg/s,
and the rest-frame peak energy of the time-integrated spectrum,
Ep,z,i is ~850 keV.

With these values, GRB 201103B is consistent with the 'Amati'
and 'Yonetoku' relations built for 316 KW GRBs with known z
classified as Type II (Tsvetkova et al., ApJ 2020 submitted).
The 68% and 90% prediction bands for Type II are show with
dark and light shaded regions, respectively, see
http://www.ioffe.ru/LEA/GRBs/GRB201103_T65207/GRB201103B.pdf

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