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GCN Circular 32105

Subject
GRB 220521A: classification and detection by SPI-ACS/INTEGRAL
Date
2022-05-24T14:55:52Z (2 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
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