TITLE: GCN CIRCULAR NUMBER: 19152 SUBJECT: GRB 160303A: Continued optical monitoring from NOT DATE: 16/03/05 20:35:02 GMT FROM: Antonio de Ugarte Postigo at IAA-CSIC A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), T. Kruehler (MPE Garching) D. Xu (NAOC/CAS), D. Malesani (DARK/NBI), Z. Cano (U. Iceland), N.R. Tanvir (U. Leicester),M. Messa (Stockholm Univ., Oskar Klein Centre), E. Gafton (NOT, Stockholm Univ. and Oskar Klein Centre) and I. R. Losada (Nordita and Stockholm Univ.) report on behalf of a larger collaboration: We continued the monitoring of GRB 160303A (Beardmore et al., GCN 19126) with MOSCA at the 2.5m Nordic Optical Telescope (La Palma, Spain). On a 9x300s observation with mean epoch 2:10 UT of 5 March 2016 (37.27 hr after the burst) we detect the afterglow (Butler et al GCN19131) at a magnitude of r = 25.2 +/- 0.2, as compared to the SDSS field stars. This is consistent with the magnitude reported by GROND (Bolmer et al. GCN 19150) at a similar epoch. Gathering the r-band data from the different GCNs (Butler et al. GCN19131; de Ugarte Postigo et al. GCN 19136; Jeong et al. GCN 19140; Im et al. GCN 19141; Klose et al. GCN 19142; de Ugarte Postigo et al. GCN 19143; Graham et al. GCN 19144; Bolmer et al. GCN 19150) the light curve seems to have been flat, or even increasing in brightness during the first 4-8 hrs after the burst. After this, the light curve begins a steep decay with alpha = 1.23 +/- 0.14 (F_nu ~ t^-alpha). This is not unlike the behaviour of other short GRBs, f.ex. GRB 130603B (de Ugarte Postigo et al. 2014 A&A 563, 62), which was interpreted as being a magnetar powered event.