TITLE:   GCN CIRCULAR
NUMBER:  16057
SUBJECT: GRB 140331A: Zadko observatory - Gingin optical observations
DATE:    14/03/31 17:22:24 GMT
FROM:    Alain Klotz at IRAP-CNRS-OMP  <Alain.Klotz@free.fr>

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 140331A detected by SWIFT
(trigger 594081) with the Zadko robotic telescope (D=100cm)
located at the observatory - Gingin, Australia.

The observations started 8.26h after the GRB trigger.
The elevation of the field was at 50 degrees above
horizon and weather conditions were good.

We co-added two series of unfiltered
exposures. They show clearly the presence of the object
reported by Littlejohns  et al. (GCNC 16050) that
coincides with SDSS J085927.51+024304.0:

=start=  =end=  Rmag
  8.26h   8.68h  20.1 +/- 0.3
  9.74h  10.43h  20.1 +/- 0.3

The magnitude remains constant during our observation
and is compatible with the magnitude found in visible
bands by Littlejohns  et al. (GCNC 16050) with RATIR
less than two hours after the trigger.
This suggests that the optical object is probably not
the afterglow of GRB 130331A.

Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.