GCN Circular 32105
Subject
GRB 220521A: classification and detection by SPI-ACS/INTEGRAL
Event
Date
2022-05-24T14:55:52Z (4 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
P. Minaev (IKI), A. Pozanenko (IKI), G. Mozgunov (MIPT, IKI) report on
behalf of GRB IKI FuN:
We analyzed GRB 220521A till now detected by Swift and GBM/Fermi (Fermi
GBM Team, GCN 32075; Dichiara et al., GCN 32076; Poolakkil and Meegan,
GCN 32089) using publicly available data of GBM/Fermi and
SPI-ACS/INTEGRAL. Using GBM/Fermi data we estimated the duration of T_90
= 12.0 +/- 0.5 s in 7 - 100 keV energy band and performed spectral
analysis in the time interval of (-1, 12) s. The best fit is obtained
for CPL model with following parameters: E_p = 62 (-15, +68) keV, alpha
= -1.5 +/- 0.4. The fluence of F = (9.8 +/- 1.2)E-7 erg/cm**2 is
obtained in 10 - 1000 keV energy band. The parameters are close to those
reported in (Poolakkil and Meegan, GCN 32089).
Using redshift of z = 5.6 (Fynbo et al., GCN 32079; Cucchiara et al.,
GCN 32099) we obtain E_iso = (6.2 �� 0.8)E52 erg in 1-10000 keV energy
range. Using T_90,i - EH diagram [1,2] we classify the burst as type II
(long burst) for any possible redshift greater than z = 0.07. T_90,i -
EH diagram can be found in
http://grb.rssi.ru/GRB220521A/GRB220521A_EHD.png
The burst was also detected by SPI-ACS/INTEGRAL with total statistical
significance of 5.8 sigma. The angle to the SPI-ACS axis is 47 degrees.
Comparing fluences of long-duration GRBs registered by both SPI-ACS and
GBM/Fermi (Chelovekov et al., in preparation) we estimated the GRB
220521A fluence to be 1.1E-6 erg/cm**2 in the 10-1000 keV energy band
(the 95% confidence region 3.4E-7 ��� 4.1E-6 erg/cm**2, incl.
systematics). Light curves based on GBM/Fermi and SPI-ACS/INTEGRAL data
can be found in
http://grb.rssi.ru/GRB220521A/GRB220521A_light_curves.png
[1] - Minaev et al., MNRAS, 492, 1919, 2020
[2] - Minaev et al., Astronomy Letters, 46, 9, 573, 2020