GCN Circular 14330

GRB 130315A: Zadko observatory - Gingin optical observations
------------------------------**------------------------------**----------
H. Dereli (UNS-CNRS-OCA), A. Klotz (IRAP-CNRS-OMP),
D. Macpherson (UWA/ICRAR), D. Coward (UWA),
B. Gendre (IRAP-CNRS-OMP), M. Boer, K. Siellez, O. Bardho (UNS-CNRS-OCA),
A. Williams (PO-UWA), R. Martin (PO-UWA)
report:

We imaged the field of GRB 130315A detected by SWIFT
(trigger 551126) with the Zadko robotic telescope (D=100cm)
located at the observatory - Gingin, Australia.

The observations started 1.22h after the GRB trigger.
The elevation of the field increased from
65 degrees above horizon and weather conditions
were good.

We co-added a series of unfiltered exposures and we
substracted images taken with the same telescope
4h to 8h later to eliminate contaminations by
foreground stars. We did not detect any optical
transient at the position provided by Schmidl
et al. (GCNC 14325):

t0+1.22h to t0+1.54h : Rlim = 20.4

This limiting magnitude and the detection
of Schmidl et al. (GCNC 14325) implies a
decay with alpha < 0.67. As Schmidl et al.
(GCNC 14325) announced alpha > 0.75 after 12h
we suspect a late rising of a faint afterglow
or a break of the decay.

Magnitudes were estimated with the nearby NOMAD1
stars and are not corrected for galactic
dust extinction.