TITLE:   GCN CIRCULAR
NUMBER:  30308
SUBJECT: GRB 210619B: Mini-MegaTORTORA early optical observations
DATE:    21/06/23 11:18:23 GMT
FROM:    Sergey Karpov at SAO RAS  <karpov@sao.ru>

S.Karpov (FZU CAS, Czech Republic; SAO RAS and Kazan Federal University,
Russia)
G.Beskin (SAO RAS and Kazan Federal University, Russia),
N. Lyapsina (SAO RAS, Russia),
E.Ivanov, E.Katkova, A.Perkov (OJS RPC PSI, Russia),
A.Biryukov (SAI MSU and Kazan Federal University, Russia),
V.Sasyuk (Kazan Federal University, Russia)

Mini-MegaTORTORA nine-channel wide-field monitoring system  with high
temporal resolution responded to the BAT trigger and observed the position
of GRB 210619B (D'Avanzo et al., GCN 30261) since 2021-06-20 00:00:20 UT
(T+55 s, during the ongoing gamma-ray emission) and until 2021-06-20
00:10:28 UT (T + 663 s). The system simultaneously acquired series of
frames with 1 s exposures, 5 s exposures and 30 s exposures in white light,
10 s exposures in B filter, and 10 s exposures in V filter.

The transient was clearly detectable in all acquired sequences except B
filter ones. Overall behaviour of the early light curve is consistent with
the smooth decay reported by Jelinek et al. (GCN 30263), with no
large-amplitude variability apparent in high temporal resolution data.

Mini-MegaTORTORA belongs to Kazan Federal University and is located at
Special Astrophysical Observatory near Russian 6-m telescope.

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