GCN Circular 4483

Klotz, A. (CESR-OMP), Boer M. (OHP), Atteia J.L. (LATT-OMP) report:

We imaged the field of GRB 060511 detected by SWIFT
(trigger 176818) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.

First image was acquired 20s after the GCN trigger
(7s after the notice). The field elevation increased
from 23 degrees above horizon and weather conditions
were good. Moon was just rising (23 deg from the field)
at the begining of observations. Due to a technical
problem, there was no image between 261 and 510s
after the trigger.

We detected no new source comparing our individual
unfiltered images with the USNO-B1 catalog within
the error circle at the XRT position (Goad et al.
GCNC 4481).

 From individual frames we give early limits:

Day : 2006-01-11
UT-start      UT-end      (sec since GRB)  Exp(s)  R-mag
04:23:25.7  - 04:24.25.7    20 -   80        60   >16.2 (one frame trailed)
04:24:32.4  - 04:25.02.4    86 -  116        30   >17.0 (one frame)
04:25:08.7  - 04:25.38.7   122 -  152        30   >17.0 (one frame)
04:31:36.2  - 04:33:06.2   510 -  600        90   >17.7 (one frame)

To increase the signal to noise, we co-added series frames.
The source at the XRT position (Goad et al. GCNC 4481) is
marginaly detected on the first co-addition:

Day : 2006-01-11
UT-start      UT-end      (sec since GRB)  R-mag
04:24:32   - 04:27.27      86 -   261      ~18.3 (sum of 5 frames of 30s)
04:31:36   - 04:40.13     510 -  1027      >18.7 (sum of 6 frames of 90s)

Magnitudes were estimated with the nearby USNO-B1 stars.

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