GCN Circular 31081
Subject
GRB 211023A: classification and SPI-ACS/INTEGRAL registration
Event
Date
2021-11-13T19:43:24Z (4 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
P. Minaev (IKI), A. Pozanenko (IKI), S. Grebenev (IKI), I. Chelovekov
(IKI) report on behalf of GRB IKI FuN
We analyzed GRB 211023A (Di Lalla et al. GCN 30961; Lesage et al. GCN
30965; Ursi et al. GCN 30969; Ridnaia et al. GCN 31022) using publicly
available data of GBM/Fermi and SPI-ACS/INTEGRAL.
Using GBM/Fermi we clearly detect early emission, starting about 80 s
before the GBM trigger. The extended emission (possibly associated with
the activity detected by LAT, Di Lalla et al. GCN 30961, and/or its
extremely bright afterglow, Zhirkov et al. GCN 30977; Kann et al. GCN
30982) was also found, becoming dominant since approximately 150 s the
trigger. Thus, a time profile consists of three episodes with a total
burst duration of more than 300 s in GBM/Fermi (7 - 850 keV), while T90
= 117 +/- 0.5 s. GRB 211023A was also registered by SPI-ACS/INTEGRAL
with marginal detection of the early and the extended emission (T90 =
120 +/- 9 s). Time profiles of GBM and SPI-ACS are presented at
http://grb.rssi.ru/GRB211023A/GRB211023A_GBM_ACS_light_curve.png
We performed spectral analysis of the burst using GBM/Fermi data in the
time interval of (-20, 160) s after the GBM trigger, covering the main
part of GRB activity. The best parameters of Band model are following:
Ep = 96 +/- 5 keV, alpha = -1.67 +/- 0.03, beta = -2.21 +/- 0.05 and
fluence F = (1.341 +/- 0.004)*10^-4 erg/cm^2 in 10 - 1000 keV range.
Assuming a redshift z = 0.390 (Pozanenko et al., GCN 31053) we estimated
Eiso = (7.45 +/- 0.05)*10^52 erg in the 1 keV - 10 MeV energy band.
The position of the burst at Ep,i - Eiso and T90,i - EH diagram [1,2] is
shown by black annuli at
http://grb.rssi.ru/GRB211023A/GRB211023A_Ep-Eiso_two_episodes_SN.png
and
http://grb.rssi.ru/GRB211023A/GRB211023A_EHD_two_episoses_SN.png
The position is typical for type II (long) GRBs, although it is in the
lower bound of their 2 sigma correlation region. This is because of its
relatively low value of the Ep,i parameter. Note that low values of Ep,i
are typical for the nearby bursts (z < 0.5), associated with supernovae
(shown by red annuli at
http://grb.rssi.ru/GRB211023A/GRB211023A_Ep-Eiso_two_episodes_SN.png
and
http://grb.rssi.ru/GRB211023A/GRB211023A_EHD_two_episoses_SN.png )
[1] - Minaev et al., MNRAS, 492, 1919, 2020
[2] - Minaev et al., Astronomy Letters, 46, 9, 573, 2020