TITLE: GCN CIRCULAR NUMBER: 15290 SUBJECT: GRB 131002A: ISON-NM optical observations DATE: 13/10/02 19:06:52 GMT FROM: Alexei Pozanenko at IKI, Moscow L. Elenin (KIAM), A. Volnova (IKI), I. Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed optical transient(Guidorzi et al., GCN 15282) of the Swift GRB 131002A (Barlow et al., GCN 15283) with 0.4-m SANTEL-400AN telescope of ISON-NM observatory starting on Oct., 2 (UT) 06:55:23 (i.e. 58 s after burst trigger) in robotic mode. Series of 30 s exposures were obtained in clear filter. After PSF subtraction of a nearby bright star we clearly detect the optical transient in each single frames of initial series. Coordinates of the optical transient are (J2000) 16 52 53.29 +82 03 15.6 with uncertainty of 0.25" in both coordinates. Preliminary photometry is based on USNO-B1.0 (R2) stars. The maximum brightness of the OT (15.2 +/- 0.05) was detected in the second frame at 0.00141 days after trigger. Light curve of the initial stage of the OT can be found at http://grb.rssi.ru/GRB131002A/GRB131002A_ISON-NM_lc.png