TITLE: GCN CIRCULAR NUMBER: 14475 SUBJECT: GRB 130427A: T100 observations DATE: 13/04/27 22:39:19 GMT FROM: Eda Sonbas at NASA/GSFC E. Sonbas (Adiyaman Univ.), T. Guver (Sabanci Univ.), E. Gogus (Sabanci Univ.), H. Kirbiyik (TUG) report on behalf of a larger collaboration We observed the field of Swift GRB 130427A (Maselli et al. GCN#14448) with the 1.0 meter T100 telescope (TUBITAK National Observatory, Antalya - Turkey), starting April, 27, 20:39:28 UT (~ 13 hours after the trigger). Observations were carried out in the R filter under good weather conditions. The afterglow is clearly detected in 60 s R band images at a position that is consistent with Elenin et al. GCN#14450 Using USNO-B1 star USNO-B1 1177-0254824 (RA= 11:32:31.23, Dec= +27:42:23.02 ) in the field, the magnitudes of the OT were estimated as follows; t-t0 (hr) exp.(s) filt mag err (+/-) 12.850 60 R 16.2 0.05 12.871 60 R 16.6 0.03 12.874 60 R 16.3 0.03 12.877 60 R 16.5 0.01 Further observations using the same filter are ongoing. We are grateful to the TUBITAK National Observatory staff for promptly scheduling the observations and their technical support.