GCN Circular 37982

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

The long-duration GRB 241030A
(Fermi-GBM detection: Fermi GBM Team, GCN 37955
Not found
 
 
;
Swift-BAT detection: Klingler et al., GCN 37956
Not found
 
 
;
SVOM/GRM observation: Wang et al., GCN 37972
Not found
 
 
;
Fermi-LAT detection: Pillera et al., GCN 37979
Not found
 
 
)
triggered Konus-Wind at T0=20996.591 s UT (05:49:56.591).

The burst light curve shows a multipeaked structure
which starts at ~T0-112.7 s and has a total duration of ~210.4 s.
The emission is seen up to ~10 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB241030_T20996/

As observed by Konus-Wind, the burst
had a fluence of 5.48(-1.28,+1.95)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+26.448 s,
of 3.45(-0.82,+0.89)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+103.168 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 = -0.99(-0.19,+0.40),
the high energy photon index beta = -2.26(-0.61,+0.30),
the peak energy Ep = 140(-43,+35) keV
(chi2 = 123/87 dof).

The spectrum near the maximum count rate
(measured from T0+22.016 to T0+28.160 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 = -0.91(-0.21,+0.23)
and Ep = 196(-35,+55) keV (chi2 = 91/88 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.2
(chi2 = 91/87 dof).

Assuming the redshift z=1.411 (Zheng et al., (GCN 37959
Not found
 
 
))
and a standard cosmology 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 2.84(-0.68,+1.04)x10^53 erg,
the peak luminosity L_iso is 4.47(-1.07,+1.15)x10^52 erg/s,
the rest-frame peak energy of the time-averaged spectrum
Ep,i,z is 339(-103,+84) keV and the spectrum near the maximum count rate
Ep,p,z is 473(-84,+133) keV.

With the obtained estimates, GRB 241030A is inside 68% prediction bands for
both 'Amati' and 'Yonetoku' relations derived for the sample of >300 long
KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021),
see http://www.ioffe.ru/LEA/GRBs/GRB241030_T20996/GRB241030A_rest_frame.pdf

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