GCN Circular 15952

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 140311A detected by SWIFT
(trigger 591390) with the Zadko robotic telescope (D=100cm)
located at the observatory - Gingin, Australia.

The observations started 119.5s after the GRB trigger
(46.9s after the notice). The elevation of the field was at
45 degrees above horizon and weather conditions
were good.

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 the OT discovered by Xu et al. GCNC 15947
with a limiting magnitude of:

t0+119.5s to t0+179.5s : Rlim = 19.5

The second image is 30.0s exposure in tracking mode
We detect the OT discovered by Xu et al. GCNC 15947:
t0+208s to t0+238s : R = 19.6 +/- 0.5

Follow-up was performed until the dawn which arrived
18 minutes after the trigger.

We co-added a series of exposures:
t0+208s to t0+325s : R = 19.9 +/- 0.3
t0+338s to t0+515s : R = 19.2 +/- 0.3
t0+530s to t0+1111s : R = 18.5 +/- 0.3

Conclusions, the afterglow brightness increases
slowly during the first 18 minutes after the trigger.

Magnitudes were estimated with the nearby star
NOMAD1 0906-0229793 (R=16.44) and are not corrected
for galactic dust extinction.