TITLE:   GCN CIRCULAR
NUMBER:  14846
SUBJECT: GRB 130610A: P60 Observations
DATE:    13/06/10 05:19:12 GMT
FROM:    S. Bradley Cenko at Caltech  <cenko@srl.caltech.edu>

S. B. Cenko (NASA/GSFC) and D. A. Perley (Caltech) report on behalf of a
larger collaboration:

We have imaged the optical afterglow of the Swift GRB 130610A (Cummings et
al., GCN 14842) with the robotic Palomar 60 inch telescope.  A series of
90 s exposures in the g', r', i', and z' filters were begun starting at
04:23 UT on 2013 Jun 10 (1.18 hr after the Swift trigger).  We detect the
afterglow in individual exposures in all 4 filters.  Using nearby point
sources from SDSS for calibration, we measure a magnitude of r' = 19.8 in
our initial images.  Compared with earlier observations with the Liverpool
telescope (Melandri et al., GCN 14843), this suggests a power-law decay
index of ~ 1.2.