TITLE: GCN CIRCULAR NUMBER: 19147 SUBJECT: GRB 160303A: MMT Optical Detection DATE: 16/03/04 19:45:16 GMT FROM: Wen-fai Fong at U of Arizona W. Fong (University of Arizona) reports on behalf of a larger collaboration: "We observed the location of the possibly short-duration GRB 160303A (Beardmore et al., GCN 19126) with MMTCam mounted on the 6.5-m MMT at a mid-time of 2016 Mar 4.232 UT (18.64 hr post-burst). We obtained 9x200-sec of r-band observations in 1.0" seeing at a mean airmass of 1.2. We detect the optical afterglow (Butler et al., GCN 19131) with a magnitude of r(AB)~23.90 +/- 0.15 (calibrated to SDSS) at a position consistent with the NOT position (de Ugarte Postigo et al., GCN 19136). Our measured afterglow brightness is consistent with the VLT value at a similar epoch (Klose et al., GCN 19142)."