[vsnet-grb-info 16488] GRB 150428A: P60 observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17769
SUBJECT: GRB 150428A: P60 observations
DATE:    15/04/28 06:00:44 GMT
FROM:    Daniel Perley at Caltech  <dperley at astro.caltech.edu>

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

We observed the field of GRB 150428A (Page et al., GCN 17765) using the 
Palomar 60-inch robotic telescope starting at UT 03:40:50 on the night 
of 2015-04-28, acquiring a sequence of r, i, and z-band exposures under 
excellent seeing conditions.

Stacking a series of 9x180s i-band images between 03:44 and 04:25 UT, we 
detect no sources within the enhanced XRT error circle (Osborne et al., 
GCN 17768) down to a limiting magnitude of i > 22.7 mag at a median time 
of 2.65 hours after the trigger.  We note that the source reported by 
GROND (Knust et al., GCN 17767) is not within the enhanced error circle, 
but we marginally detect this source at a similar magnitude (i = 22.8 
+/- 0.3 mag).