{
  "bibcode": "2022GCN.32752....1B",
  "body": "Ilfan Bikmaev (KFU, AST, Kazan), Irek Khamitov (TUG, Antalya, KFU, Kazan),\nEldar Irtuganov (KFU, AST, Kazan), Mark Gorbachev (KFU, AST, Kazan),\nNail Sakhibullin (KFU, AST, Kazan), Rodion Burenin (IKI, Moscow)\n\nreport:\n\nWe have performed additional optical observations of the OT GRB221009A\n(Dichiara et al., GCN 32632, GCNs 32635, 32636,32636, 32641, 32657,\n32658, 32660, 32666, 32668, 32670, 32671, 32676, 32677, 32678, 32679,\n32680, 32683, 32684, 32685, 32686, 32691, 32692, 32693, 32694, 32695,\n32700, 32705, 32707, 32709, 32727, 32729, 32730, 32736, 32738, 32739,\n32740, 32743, 32746, 32749, 32750) by using 1.5-meter joint\nRussian-Turkish telescope (RTT-150, TUBITAK National Observatory,\nAntalya, Turkey) and TFOSC instrument in October 13, 2022. We made\nseries of images in riz filters with 600 sec exposures each.\n\nWe clearly see the OT in all frames. Photometric data were calibrated\nusing nearby PS1 star. Results of our photometry are given in the\nTable:\n\nJD                T-T0    Filter  mag   merr\n                 (hours)   \n2459866.2034967   99.601  r      20.53  0.09\n2459866.2115203   99.793  i      19.51  0.06\n2459866.2189183   99.971  z      18.63  0.05\n2459866.2263488  100.149  r      20.63  0.09\n2459866.2339414  100.332  i      19.41  0.05\n2459866.2413937  100.510  z      18.76  0.05\n2459866.2488331  100.689  r      20.71  0.15\n2459866.2562889  100.868  i      19.52  0.05\n2459866.2636921  101.046  z      18.69  0.04\n2459866.2711805  101.225  r      20.54  0.10\n2459866.2786139  101.404  i      19.44  0.04\n2459866.2862528  101.587  z      18.75  0.04\n2459866.2937201  101.766  r      20.55  0.12\n2459866.3010995  101.943  i      19.45  0.05\n2459866.3088004  102.128  z      18.74  0.05\n2459866.3162909  102.308  r      20.74  0.16\n2459866.3238331  102.489  i      19.43  0.05\n2459866.3314625  102.672  z      18.83  0.05\n2459866.3389523  102.852  r      20.90  0.23\n2459866.3464004  103.031  i      19.48  0.06\n2459866.3558217  103.257  z      18.74  0.05\n2459866.3633150  103.437  r      20.86  0.27\n2459866.3707428  103.615  i      19.50  0.07\n2459866.3798291  103.833  z      18.71  0.06\n\nRTT-150 light curves for 4 nights observations are shown in the Figure:\n\nhttps://www.srg.cosmos.ru/static/images/grb/lc_grb221009A_RTT150.jpg\n\n\nPower law decay indexes based on RTT-150 griz observations, taking in\naccount our data obtained earlier (Bikmaev et al., GCN 32743) are as\nfollows:\n\ng:   -1.42 +- 0.20\nr:   -1.47 +- 0.07\ni:   -1.40 +- 0.04\nz:   -1.38 +- 0.04\n\nOur measurements of the OT power law decay agree well with that\nmeasured in infrared bands (O'Connor et al., GCN 32750, Brivio et al.,\nGCN 32652, Durbak et al. GCN 32654), obtained during nearly the same\nperiods of OT observations.\n\nThe mean value of (r - z) color indicates no any significant changes\nin the optical spectrum slope during four nights of our observations.",
  "circularId": 32752,
  "createdOn": 1665745397000,
  "email": "rodion@hea.iki.rssi.ru",
  "subject": "GRB221009A: RTT-150 optical observations",
  "submitter": "Rodion Burenin at IKI, Moscow  <rodion@hea.iki.rssi.ru>",
  "eventId": "GRB 221009A"
}