GCN Circular 32663

I. Lapshov, S. Molkov, I. Mereminsky, A. Semena, V. Arefiev,
A. Tkachenko, A.Lutovinov (IKI RAS)
on behalf of the SRG/ART-XC team:

At 13:19:55 UT on 09 October 2022, the Mikhail Pavlinsky ART-XC
telescope on board the SRG observatory detected a strong burst
lasting few hundred seconds. Further analysis showed that the
source of emission was out of the field
of view of the instrument and the signal passed through the
telescope structure. We associate this event with a gamma-ray burst
GRB 221009A which was detected by Swift (Kennea et al. GCN #32635),
Fermi-GBM (Veres et al. GCN #32636, Lesage et al. GCN #32642),
Fermi-LAT (Bissaldi et al. GCN #32637, Pillera et al. GCN #32658),
the IPN (Svinkin et al. GCN #32641), SPI/ACS (Gotz et al. GCN #32660).

The ART-XC event corresponds to the second (brightest) burst episode
(see e.g. GCN #32642).
Since the radiation came out of the FoV, a prompt spectral analysis
of the event is impossible, however, due to the strong attenuation of
the signal passed through the surrounding matter, we register a
light curve shape that is practically not distorted by instrumental
effects such as deadtime, pile-up or telemetry problems. The light curve
in the full ART-XC energy range has a complex multi-peak structure
with two main maxima on 60th and 340th seconds from the start. The
event duration is near of 550 seconds.