GCN Circular 16064

A. Klotz, D. Turpin (IRAP-CNRS-OMP), D. Macpherson (UWA/ICRAR), D. 
Coward (UWA),
M. Boer, B. Gendre, K. Siellez, H. Dereli, O. Bardho (UNS-CNRS-OCA),
A. Williams (PO-UWA), R. Martin (PO-UWA)
report:

We imaged the field of GRB 140301A detected by SWIFT
(trigger 589590) with the Zadko robotic telescope (D=100cm)
located at the observatory - Gingin, Australia.

The observations started 70.7s after the GRB trigger
(40.5s after the notice). The elevation of the field was at
26 degrees above horizon and weather conditions
were good. Images were retrieved 30 days after their
acquisitions due to a storage software problem.

The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
We do not detect any OT with a limiting magnitude of:
t0+70.7s to t0+130.7s : Rlim = 18.4

The second image is 30.0s exposure in tracking mode:
t0+159s to t0+189s : Rlim = 19.7

We co-added series of unfiltered exposures.
The OT discovered by Kruehler et al. (GCNC 15899)
is marginally detected 841 s (+/-255 s) after
the trigger. More precisely the photometry is:

=start= =end=
  159 s   275 s  CRlim = 21.8
  289 s   465 s  CRlim = 21.8
  586 s  1096 s  CR = 21.7 +/- 0.4
1217 s  1727 s  CRlim = 21.9

This suggests this faint afterglow had culminated in
brightness R=21.7 at t0+841s. Then it had declined
to R=23.1 at t0+4.97h (Kruehler et al. GCN 15899
Not found
 
 
)
and to r'=23.8 at t0+11h (Elliott et al. GCNC 15904).
This is compatible with a temporal decay of ~0.5.

A photometry follow-up was performed with the Zadko
telescope :

=start= =end=
20.4 h  20.8 h  CRlim = 22.2

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