[vsnet-grb-info 4755] GRB 070611: ROTSE-III Detection of Late Rising Optical Counterpart

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6497
SUBJECT: GRB 070611: ROTSE-III Detection of Late Rising Optical Counterpart
DATE:    07/06/11 04:26:49 GMT
FROM:    Eli Rykoff at U of Michigan/ROTSE  <erykoff at umich.edu>

Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit

E. S. Rykoff, F. Yuan, S. A. Yost (U. Mich), report on behalf of the 
ROTSE collaboration:

ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia,
responded to GRB 070611 (Swift trigger 282003; Stroh et al.,
GCN 6494), producing images beginning 7.6 s after the GCN notice time, 
as reported in GCN 6495 (Schaefer, et al.).  These unfiltered images are 
calibrated relative to USNO-B1.0 (R).

Further analysis reveals a faint, late-rising counterpart at a position 
consistent with the XRT position reported in GCN 6496 (Stroh, et al.). 
At a midpoint of 2157 s after the burst (in a 600 s stacked image), the 
counterpart was at a peak magnitude of 18.4+/-0.1 at a position:

    00:07:58.0 -29:45:19.4 (J2000) [uncertainty < 1"]

The counterpart then faded below 19th magnitude by 6000 s post-burst.

A jpeg image is available at 
http://www.rotse.net/images/gsb282003_3c041-050_key.jpg
Note that the object marked 156 is the candidate in question.