GCN Circular 31566

P. Minaev (IKI), A. Pozanenko (IKI) report on behalf of GRB IKI FuN:

We investigated SPI-ACS/INTEGRAL data of GRB 210919A detected by Swift 
(Tohuvavohu et al. GCN 30846
Not found
 
 
).  GRB 210919A was not triggered by IBAS at 
INTEGRAL observatory. We find the burst in SPI-ACS/INTEGRAL data with a 
significance of 5 sigma and duration of 0.15 s. The total count fluence 
of the burst is 900 �� 185 counts, which corresponds to the fluence of 
2.4e-7 erg/cm^2 in 10-1000 keV energy band (the 95% confidence region is 
7.2e-8 -- 8.4e-7 erg/cm^2, incl. systematics). We do not find both 
precursor and extended emission components for the burst. Light curve of 
GRB 210919A can be found in

http://grb.rssi.ru/GRB210919A/GRB210919A_SPI-ACS_light_curve.png

Using spectral data of BAT/Swift (Barthelmy et al. GCN 30863
Not found
 
 
) and 
possible redshift of z = 0.2411 (Rossi et al. GCN 31453
Not found
 
 
) we estimated 
Eiso = (1.3 �� 0.3)e49 erg in 15-150 keV energy band. Although spectral 
parameter Ep was not constrained yet, we can estimate Ep using T90,i - 
EH diagram [1] by constructing a trajectory depending on the Ep,i 
parameter, where Ep,i is Ep in a rest frame. The most probable value is 
found to be Ep,i = 90 keV with 95% confidence region of (14 ��� 640) keV 
which is converted into observable Ep = 73 (11 --  516) keV. Since GRB 
210919A was detected by SPI-ACS with a nominal lower threshold of >80 
keV, Ep can be further limited to the energy range of 80 - 516 keV.

The T90,i - EH diagram can be found in

http://grb.rssi.ru/GRB210919A/GRB210919A_EHD.png

[1] - Minaev et al., MNRAS, 492, 1919, 2020