TITLE:   GCN CIRCULAR
NUMBER:  44053
SUBJECT: GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
DATE:    26/03/20 01:38:39 GMT
FROM:    Alexei Pozanenko at IKI, Moscow <grb.alex@gmail.com>

P. Minaev (IKI) , A. Pozanenko (IKI) on behalf of GRB follow-up team

We analyzed GRB 260310A (Hamburg et al., GCN 43975; Salunke et al.,
GCN 43958; Atteia et al., GCN 43981) using publicly available data of
GBM/Fermi. The burst consists of several emission episodes with a
total duration of T_90 = 86 s. Time integrated energy spectrum,
constructed in the time interval (-4, 70) s since GBM trigger, is best
described by Band model with E_p = 175 keV and fluence F = 1.74e-5 erg
cm^-2 in 1 keV - 10 MeV range. Using z = 0.153 (Hinds et al., GCN
43977; de Ugarte Postigo et al., GCN 43984) we obtain E_iso = 9.8e50
erg. GRB 260310A is placed above the correlation fit for type II
(long) bursts on Ep,i – Eiso diagram, as mentioned in (Atteia et al.,
GCN 43981), but it is inside 2 sigma correlation regions for both type
I (short) and type II (long) bursts, therefore we cannot consider it
as a clear outlier. Indeed, at the EH – T_90,i diagram (see [1-2] for
details) GRB 260310A is well classified as type II (long) burst. The
Ep,i – Eiso and EH - T90,i diagrams can be found at
https://heaiki.ru/lvc/GRB260310A/

[1] - Minaev et al., MNRAS, 492, 1919, 2020
[2] - Minaev et al., Astronomy Letters, 46, 9, 573, 2020