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GCN Circular 36584

Subject
Konus-Wind detection of GRB 240529A
Date
2024-05-31T22:37:34Z (13 days ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
Via
legacy email
D. Svinkin, 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 240529A
(Swift-BAT detection: Eyles-Ferris et al., GCN 36556;
AstroSat-CZTI detection: Joshi et al., GCN 36560;
Insight-HXMT/HE detection: Tan et al., GCN 36578;
IPN triangulation: Kozyrev et al., GCN 36583)
triggered Konus-Wind at T0=10304.829 s UT (02:51:44.829).

The burst light curve shows two separated multipeaked emission episodes.
The first episode starts at ~T0-14.1 s and has a total duration of ~150 s,
the second (detected by Swift-BAT) starts at ~T0+344 s and lasts up to ~T0+520 s.
The emission is seen up to ~3 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB240529_T10304/

As observed by Konus-Wind, the burst
had a fluence of 1.3(-0.5,+0.4)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+6.960 s,
of 3.40(-0.93,+1.10)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+491.264 s)
is best fit in the 20 keV - 3 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.11(-0.36,+1.61),
the high energy photon index beta = -2.02(-7.98,+0.22),
the peak energy Ep = 161(-100,+203) keV
(chi2 = 56/66 dof).

The spectrum near the maximum count rate
(measured from T0 to T0+7.936 s)
is best fit in the 20 keV - 3 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.00(-0.10,+0.15),
the high energy photon index beta = -2.85(-1.37,+0.50),
the peak energy Ep = 210(-33,+26) keV
(chi2 = 61/66 dof).

Assuming the redshift z=2.695 (Ugarte Postigo et al., GCN 36574)
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 2.2(-0.8,+0.7)x10^54 erg,
the peak luminosity L_iso is 2.1(-0.6,+0.7)x10^53 erg/s,
the rest-frame peak energy of the time-integrated spectrum Ep,i,z is 595(-370,+750) keV,
and the rest-frame peak energy at the peak of the emission Ep,p,z is 776(-122,+96) keV.
With the obtained estimates, GRB 240529A is inside 90% prediction band
for the 'Amati' relation and inside 68% prediction band
for the 'Yonetoku' relation 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/GRB240529_T10304/GRB240529A_rest_frame.pdf

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


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