GRB221009A: RTT-150 optical observations

We have performed optical observations of the OT GRB221009A (Dichiara et al., GCN 32632, GCNs 32635, 32636,32636, 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) by using 1.5-meter joint Russian-Turkish telescope (RTT-150, TUBTAK National Observatory, Antalya, Turkey) in October 10-12, 2022. We used TFOSC instrument for photometry in griz filters and low resolution spectroscopy in the 3800 - 8870 A range. During 3 consecutive nights starting 27.6 hours since the trigger we make series of images in griz with 600 sec exposures each. We clearly see the OT in all frames. Photometric data were calibrated using nearby PS1 star. Results of our photometry are given in the Table. JD T-T0 Filter mag merr (hours) 2459863.2056537 27.653 g 20.13 0.08 2459863.2131298 27.832 r 18.65 0.02 2459863.2205018 28.009 i 17.52 0.01 2459863.2278493 28.185 z 16.81 0.01 2459863.3452805 31.004 g 20.44 0.25 2459863.3681597 31.553 r 18.81 0.05 2459863.3760363 31.742 i 17.69 0.02 2459863.3840870 31.935 z 16.99 0.01 2459864.1923863 51.334 r 19.53 0.04 2459864.2002009 51.522 i 18.40 0.02 2459864.2076914 51.702 z 17.69 0.02 2459864.2153146 51.884 g 21.15 0.21 2459864.3645166 55.465 r 19.67 0.11 2459864.3728065 55.664 i 18.49 0.04 2459864.3804310 55.847 z 17.72 0.03 2459865.2047148 75.630 i 18.82 0.03 2459865.2122502 75.811 r 20.03 0.06 2459865.2198393 75.993 z 18.20 0.04 2459865.2273203 76.173 i 19.02 0.07 2459865.2347618 76.351 r 19.97 0.08 2459865.2422699 76.531 z 18.19 0.05 2459865.2497386 76.711 i 19.09 0.10 2459865.2571590 76.889 r 20.07 0.19 2459865.2646685 77.069 z 18.40 0.08 2459865.2720521 77.246 i 18.95 0.07 2459865.2795044 77.425 r 20.32 0.17 2459865.2869724 77.604 z 18.26 0.03 2459865.2943683 77.782 i 18.93 0.04 2459865.3092743 78.140 z 18.23 0.03 2459865.3167266 78.318 i 18.93 0.04 2459865.3241129 78.496 r 20.17 0.12 2459865.3315775 78.675 z 18.23 0.04 2459865.3389639 78.852 i 18.92 0.04 2459865.3507442 79.135 r 20.26 0.16 2459865.3583217 79.317 z 18.30 0.04 2459865.3733491 79.677 r 20.24 0.19 2459865.3809028 79.859 z 18.18 0.04 Two series of low resolution (12 A) spectra were obtained in October 10, UT = 17:43 - 19:54 and in October 11, UT = 17:24 - 20:32. Their analysis is underway.