GCN Circular 14748
A. Cucchiara (UCSC/UCO Lick), D. Perley (Caltech), and S. B. Cenko (GSFC) report on behalf of a larger collaboration: On June 3.97 UT we start observing the optical afterglow of the Short GRB 130603B (Melandri et al. GCN 14735, Evans et al., GCN 14739, Levan et al. GCN 14742, and de Ugarte Postigo et al. GCN 14743) with the Gemini-South telescope equipped with the GMOS camera. The observation sequence consists of a series of 8x3min exposures in the g',r' and i' filters. The OT is clearly detected in individual exposures. Using the coadded frames and a 0.7" aperture, we estimate the following magnitudes: g = 21.7 +/- 0.2 r = 21.2 +/- 0.1 i = 20.7 +/- 0.2 These are not corrected for Galactic extinction or for contribution of the host galaxy, which is likely significant. An RGB image of the field showing the optical transient has been posted to: http://www.astro.caltech.edu/~dperley/gcn/130603b/130603b_gmos.png Also, a spectroscopic sequence was obtained: based on CaHK lines and several emission lines we confirm the redshift of GRB 130603B to be z=0.356 (as also reported by Thoene et al. GCN. 14744, Foley et al. 14745). We thank the Gemini South Staff, in particular A. Cardwell, J. Turner and Mischa Schirmer, for the excellent support.