TITLE: GCN CIRCULAR NUMBER: 6175 SUBJECT: GRB 070306: ART-3 early optical and near infrared constraints DATE: 07/03/07 04:25:57 GMT FROM: Ken ichi Torii at Osaka U The error region of GRB 070306 (Pandey et al. GCN 6169; Page et al. GCN 6172; Barthelmy et al. 6173) was observed with the ART-3a and ART-3b under the partly cloudy condition. The imaging started at 2007 March 6, 16:43:00 UT (92 s after the trigger) in Ic band (ART-3a), and at 16:43:24 UT (116 s after the trigger) in J band (ART-3b). We do not detect neither optical nor near infrared counterpart for the IR afterglow candidate (Rol et al. GCN 6174). From the useful data sets, we derive the following 3 sigma upper limits for any new source within the XRT error region (GCN 6172), relative to USNO-B1.0 I2 or 2MASS J magnitudes. ----------------------------------------- StartUT Filter Limit Exposure ========================================= 16:52:28 Ic 17.3 60s x 7 16:48:28 J 13.3 20s x 121 =========================================