TITLE:   GCN CIRCULAR
NUMBER:  8997
SUBJECT: GRB 090313: Gemini-S photometry
DATE:    09/03/14 10:38:18 GMT
FROM:    Daniel Perley at U.C. Berkeley  <dperley@astro.berkeley.edu>

D. A. Perley (UC Berkeley) reports on behalf of a larger collaboration:

Following our spectroscopic integration on the optical afterglow of GRB
090313 (GCN 8994), we acquired one 60s frame in each of g, r, i, and z
filters using Gemini-S (GMOS) in imaging mode between 05:11 and 05:18 UT
(20.07 hours after the burst).  We report the following magnitudes:

g = 21.62 +/- 0.08
r = 20.12 +/- 0.03
i = 19.50 +/- 0.05
z = 19.03 +/- 0.05

The optical SED is well-fit assuming a moderate (A_V ~< 0.4) amount of
SMC-like dust extinction.  The presence of a 2175 A dust feature is
strongly ruled out by the z-band measurement.