TITLE:   GCN CIRCULAR
NUMBER:  45945
SUBJECT: GRB 261010A: initial pulse rest-frame energetics from Konus-Wind detection
DATE:    26/10/13 18:34:08 GMT
FROM:    Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>

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

Using the Konus-Wind spectrum of the short initial pulse of GRB 261010A
(Ep = 847(-194,+299) keV; GCN 45925) and the KW-measured fluence of this
pulse (5.91+/-1.06)E-6 erg/cm2, we estimate the pulse's rest-frame energetics
at two possible redshifts:

- assuming the redshift z= 0.070 (Corcoran et al., GCN 45912),
the isotropic energy release E_iso to (7.1 ± 1.3)x10^49 erg,
the isotropic peak luminosity L_iso to (7.8 ± 1.4)x10^49 erg/s,
and the rest-frame peak energy Ep,z to 906(-208,+320) keV.

- at the redshift z=0.785 (Castro-Tirado et al., GCN 45928),
E_iso is (1.02 ± 0.18)x10^52 erg, L_iso is (1.85 ± 0.3)x10^52 erg/s,
and Ep,z is 1512(-346,+534) keV.

With the obtained estimates, GRB 261010A is an outlier (outside 90% prediction bands)
of 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),
however is consistent with Type I (short/hard) GRB initial pulse energetics,
plotted in the same rest-frame planes.
See http://www.ioffe.ru/LEA/GRBs/GRB261010_T69424/GRB261010A_rest_frame.pdf

This supports the hypothesis that the burst represents a merger-driven event
(Zhu and Tam, GCN 45932; Maccary et al., GCN 45944), a scenario proposed
taking into account other  properties of the burst prompt emission.

All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.