TITLE: GCN CIRCULAR NUMBER: 5977 SUBJECT: GRB 061222B: MITSuME Akeno optical upper limits DATE: 06/12/24 15:32:47 GMT FROM: Nobuyuki Kawai at Tokyo Tech T. Ishimura, Y. Yatsu, T. Shimokawabe, N. Vasquez, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We observed the error box of GRB061222B (Racusin et al., GCN 5957) with the 3-color 50cm MITSuME Telescope at Akeno, Japan starting at 12:52:28 UT, 8.7 hours after the trigger. In the co-added images of Ic, Rc, and g' bands, we did not detect the afterglow (Berger, GCN 5956). The 3-sigma limiting magnitudes based on USNO-B1.0 (I-band) and NOMAD (R-band,g'-band) stars are following. Filter start time end time Exp(s) Mag (3-sigma upper limit) ----------------------------------------------------------------- Ic 12:52:28 13:29:50 60s * 29 18.3 Rc 12:52:28 13:29:50 60s * 29 19.7 g' 12:52:28 13:29:50 60s * 29 19.4 -----------------------------------------------------------------