GCN Circular 14804

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

We imaged the field of GRB 130606A (Ukwatta et al., GCN 14781
Not found
 
 
) with the 
robotic Palomar 60-inch telescope throughout the night of 2013-06-07 UT, 
beginning at 04:01 UT and continuing until morning twilight at 11:39 UT. 
  Initial observations consisted of a series of r, i, and z-band frames; 
later in the night we switched to exclusively z-band observations. 
Transparency and seeing conditions were good throughout.

The GRB afterglow (Jelinek et al., GCN 14782
Not found
 
 
; Xu et al., GCN 14783
Not found
 
 
; 
Nagayama et al., GCN 14784
Not found
 
 
) is well-detected in the z-band exposures and 
marginally detected in the other filters.  Preliminary (not 
fringe-corrected) aperture photometry of a few select points yields:

t_start(d)  t_exp(s) filter  magnitude
  0.30679     180     z = 18.62 +/- 0.08
  0.42224     180     z = 19.22 +/- 0.09
  0.50888     180     z = 19.59 +/- 0.11
  0.58040     180     z = 19.73 +/- 0.22

The afterglow decays as a power-law with an index of approximately 
alpha=1.6-1.7 over the course of the observations.

Given the redshift (Castro-Tirado et al., GCN 14796
Not found
 
 
; Lunnan et al., GCN 
14798
Not found
 
 
) these relatively bright fluxes indicate an extremely luminous 
afterglow, especially at early times; similar to the luminous 
high-redshift GRB 050904 (e.g. Kann, Masetti, & Klose 2007; AJ 133:1187).