TITLE: GCN CIRCULAR NUMBER: 18282 SUBJECT: GRB150911A MITSuME Okayama Ks-band upper-limit DATE: 15/09/11 20:40:22 GMT FROM: Kenshi Yanagisawa at OAO/NAOJ Kenshi Yanagisawa, Daisuke Kuroda, Yasuhiro Shimizu, Hideyuki Izumiura (OAO/NAOJ), Michitoshi Yoshida (Hiroshima-U), Kouji Ohta(Kyoto-U) and Nobuyuki Kawai(Tokyo Tech.) report on behalf of the MITSuME collaboration: We observed the field of GRB150911A (Starling et al, GCN18280) in Ks-band with a wide-field near infrared imager at Okayama Astrophysical Observatory (Japan). The imager has effective aperture of 0.91 m. Observations started from 18:56 UT on 11th September, just 16 min after the BAT trigger, to 19:10 UT. The total exposure of 6 min was successfully obtained. In our co-add image, we did not find any new point source within the enhanced XRT error circle (Starling et al, GCN18280) down to limiting magnitude of Ks=14.3 (Vega, S/N=10) . The photometric calibration was made against 2MASS field stars. T0+[s] MID-UT T-EXP[sec] Ks --------------------------------------------------- +1380 19:03 375 >14.3 --------------------------------------------------- T0+ : Elapsed time after the burt [sec] T-EXP: Total Exposure time [sec]