{
  "bibcode": "2022GCN.32818....1B",
  "body": "S. Belkin (IKI, HSE), A. Moskvitin (SAO RAS), V. Kim (FAI), A. Pozanenko \n(IKI),  M. Krugov (FAI), R. Uklein (SAO RAS), N. Pankov (HSE) report on \nbehalf of GRB IKI FuN:\n\nWe continue observations of GRB 221009A (Swift J1913.1+1946) (Dichiara \net al., GCN 32632; Kennea and Williams, GCN  32635; Veres et al., GCN \n32636; Bissaldi et al., GCN  32636; Svinkin et al., GCN 32641; Piano et \nal., GCN 32657; Pillera et al., GCN 32658;  Gotz et al., GCN 32660; Xiao \net al., GCN 32661; Frederiks et al., GCN 32668; GCN 32668; Ripa\net al., GCN 32685; Kozyrev et al., GCN 32805).  Observations  with \nAZT-20 telescope of Assy-Turgen observatory obtained on  October 20, 21 \nand TOO photometry with BTA SAO RAS telescope equipped with SCORPIO-2 \nwas obtained on  October 16 and 18.  The optical afterglow (GCNs 32632, \n  32635, 32636, 32641, 32657, 32658, 32660, 32666, 32668, 32670, 32671, \n32676, 32677, 32678, 32679, 32680, 32683, 32684, 32685, 32686, 32691, \n32692, 32693, 32694, 32695, 32700, 32705, 32707, 32709, 32727, 32729, \n32730, 32736, 32738, 32739, 32740, 32743, 32746, 32749, 32750; 32752; \n32753; 32755; 32758; 32765; 32769; 32771; 32795; 32799; 32803; 32804; \n32809; 32811) is detected in combined images of g',r',i' filters.\n\nPreliminary photometry of the afterglow on 2022-10-20/21 obtained in \nAssy observatory with  AZT-20 telescope is following\n\nDate       UT start  t-T0       Exp.   Filter  OT    Err.   UL(3sigma)\n                     (mid, days)  (s)           (AB)\n2022-10-20/21 n/d   11.55024    59*60  g'      23.7   0.2   24.5\n2022-10-21 14:18:18 12.05299    30*60  r'      21.94  0.07  23.9\n2022-10-21 14:49:37 12.08516    30*60  i'      20.72  0.11  23.3\n\nThe photometry is based on nearby PS1 stars.\n\nThe light curve based on our observations can be found in \nhttp://grb.rssi.ru/GRB221009A/GRB221009A_lc_cc_15_cut.png\n\nWe observe a bump in the light curve starting on 6th days since trigger. \nThe light curve is clearly chromatic at the bump. We  can assume that \nthe chromatic bump is a supernova over an afterglow of GRB 221009A \n(Belkin et al., GCN 32769).",
  "circularId": 32818,
  "createdOn": 1666478836000,
  "email": "apozanen@iki.rssi.ru",
  "subject": "GRB 221009A: optical observations, SN photometric evidence",
  "submitter": "Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>",
  "eventId": "GRB 221009A"
}