GCN Circular 32769
Subject
GRB 221009A: continued Assy optical afterglow observations, possible SN evidence
Event
Date
2022-10-16T15:33:29Z (3 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Belkin (IKI, HSE), V. Kim (FAI), A. Pozanenko (IKI), M. Krugov
(FAI), Y. Aimuratov (FAI), N. Pankov (HSE) report on behalf of GRB IKI FuN:
We continue observations of GRB 221009A (Swift J1913.1+1946) (Dichiara
et al., GCN 32632; Kennea and Williams, GCN 32635; Veres et al., GCN
32636; Bissaldi et al., GCN 32636; Svinkin et al., GCN 32641; Piano et
al., GCN 32657; Pillera et al., GCN 32658; Gotz et al., GCN 32660;
Frederiks et al., GCN 32668) with AZT-20 telescope of Assy-Turgen
observatory. The observations were carried out on 2022-10-11 --
2022-10-15. The optical afterglow ( GCNs 32632, 32635, 32636, 32641,
32657, 32658, 32660, 32666, 32668, 32670, 32671, 32676, 32677, 32678,
32679, 32680, 32683, 32684, 32685, 32686, 32691, 32692, 32693, 32694,
32695, 32700, 32705, 32707, 32709, 32727, 32729, 32730, 32736, 32738,
32739, 32740, 32743, 32746, 32749, 32750; 32752; 32753; 32755; 32758;
32765).
Preliminary photometry of the afterglow on 2022-10-15 is following
Date UT start t-T0 Exp. Filter OT Err. UL(3sigma)
(mid, days) (s)
2022-10-15 15:29:43 6,10259 30*60 g' 22.60 0.12 23.4
2022-10-15 14:25:00 6,05765 30*60 r' 20.96 0.05 22.9
2022-10-15 14:56:19 6,07939 30*60 i' 20.00 0.04 23.2
2022-10-15 16:01:07 6,11918 15*60 z' 19.31 0.08 21.0
The photometry is based on the nearby PS1 stars.
The light curve based in our photometry can be found in
http://grb.rssi.ru/GRB221009A/GRB221009A_lc_cc_7_cut.png
The power law (PL) fit parameters are also shown in the figure and do
not include photometry on 2022-10-15. It can be seen that the color
change g-i and photometry g, r on October 15, 2022 deviate significantly
from the PL approximation. We hypothesize that this behaviour may
indicate a supernova rise.