TITLE: GCN CIRCULAR NUMBER: 18402 SUBJECT: GRB 151006A: MITSuME Okayama upper limits DATE: 15/10/06 11:52:48 GMT FROM: Daisuke Kuroda at OAO/NAOJ D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ), S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto) and N. Kawai(Tokyo Tech) report on behalf of MITSuME and OISTER collaboration: We observed the field of GRB 151006A (Kocevski et al., GCNC 18398) with the optical three color (g', Rc and Ic) CCD camera attached to the MITSuME 50cm telescope of Okayama Astrophysical Observatory. The observation started on 2015-10-06 09:56:35 UT (~93 sec after the burst). We did not find any new point source within the enhanced XRT error circle (Evans, GCNC 18399) in all the three bands. Three sigma upper limits of the OT are listed below. We used GSC2.3 catalog for flux calibration. #T0+[day] MID-UT T-EXP[sec] g' Rc Ic ----------------------------------------------------- 0.00707 10:05:12 540.0 >18.6 >18.6 >18.0 ----------------------------------------------------- T0+ : Elapsed time after the burst [day] T-EXP: Total Exposure time [sec]