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GCN Circular 6528

Subject
GRB 070611: Watcher Observations
Date
2007-06-13T17:57:50Z (17 years ago)
From
Gary Melady at UCD <gmelady@bermuda.ucd.ie>
Gary Melady, John French, (University College Dublin), Petr Kubanek, 
Martin Jelinek (IAA CSIC Granada, Spain)

on behalf of the Watcher collaboration report:

The Watcher 40cm robotic telescope, located at Boyden Observatory, South
Africa, began imaging the field of GRB 070611 (Stroh et al., GCN
6494) at 01:58:33 UT, 1m 17s after the Swift trigger (40s after receipt of 
the GCN notice).

We combined our initial series of 10s exposures to create a 440s unfiltered 
image with an exposure mid-time of 2:05:21 (501s after the burst). This shows 
no new source in the XRT error box (Stroh et al., GCN 6496) down to an R-band 
limiting magnitude of approx. 19.2 (in comparison to USNO-B1). Later images show 
a faint, uncatalogued source within the XRT error box coincident with the ROTSE 
detection (Rykoff et al., GCN 6497).

These observations are summarised below:

mean time UT      t-t0(s) 	exp(s) 	      Rmag
-------------------------------------------------------- 
 02:18:56          1316		 900	  19.08 +/- 0.24
 02:32:48	   2148		 210	  18.53 +/- 0.24
 02:37:11	   2411		 180	  19.12 +/- 0.30
 02:42:46	   2746		 240	  18.99 +/- 0.26
 02:48:54	   3144		 330	  19.19 +/- 0.24

The source is not detected in subsequent observations down to an R-band limiting 
magnitude of approx 19.2.

The field was no longer observed after 02:54 due to the system's
incorrect handling of the retracted XRT position.

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