GCN Circular 9878
S. B. Pandey, W. Zheng, F. Yuan and C. Akerlof (U Mich), report on behalf of the ROTSE collaboration: ROTSE-IIIa, located at the Siding Spring Observatory Australia, responded ~ 283 sec after the GBM trigger 273582310 (Bissaldi E. & Connaughton V. GCNC 9866). The Set of images starting ~ 1.4 hours after the trigger covered the GRB 090902B location. The OT (Perley et al. GCNC 9870, Kennea & Stratta GCNC 9868) was detected at 15.9+-0.2 mag in the sum of 30x60 sec exposures. The images taken by ROTSE-IIIc (located naer the H.E.S.S. site at Mt. Gamsberg, Namibia) around 6.6 hours after the burst marginally detect the OT, indicating a decay of ~ 2 magnitudes. The unfiltered images were calibrated relative to USNO B1.0. Further analysis is in progress.