GCN Circular 31865
Subject
GRB 220408A: redshift lower limit estimating
Date
2022-04-09T15:51:10Z (2 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
P. Minaev (IKI), A. Pozanenko (IKI) report on behalf of GRB IKI FuN:
We analysed GRB 220408A detected by Fermi (Fermi GBM team, GCN 31847;
Bissaldi et al., GCN 31856), by Swift (GCN Caputo et al., GCN 31848).
Using publicly available data of GBM/Fermi we estimate the duration
T_90 = 32.3 +/- 2.5 s in (7 - 150) keV energy band. We performed
spectral analysis in a time interval of (-1, 22) s since GBM trigger,
the best fit is obtained for Band model with following parameters: E_p =
36.5 +/- 5.0 keV, alpha = -0.50 +/- 0.35, beta = -2.5 +/- 0.2. The
fluence of F = (2.0 +/- 0.2)E-6 erg/cm**2 is obtained in 10 - 1000 keV
energy band. Using T_90,i - EH diagram [1,2] we can classify the burst
as type II (long) and find the minimal possible redshift value of z =
0.03, which is excluding possible association with M51 galaxy and
confirming larger distance of GRB 220408A (Zhu et., GCN 31864).
The T_90,i - EH diagram can be found in
http://grb.rssi.ru/GRB220408A/GRB220408A_EHD.png
[1] - Minaev et al., MNRAS, 492, 1919, 2020
[2] - Minaev et al., Astronomy Letters, 46, 9, 573, 2020
