GCN Circular 6568

J. S. Bloom (UC Berkeley), H.-W. Chen (U Chicago), D. A. Perley (UC 
Berkeley), and L. Pollack (UC Santa Cruz) report:

"The receipt of the BAT_POSITION notice for GRB 070621 (Sbarufatti et 
al. GCN #6560) triggered our automated imaging program on Gemini South 
at 23:18:26 UT and the first images were obtained at 22 June 2007 
04:54:57 UT by Byran Miller and the Gemini staff once the conditions 
cleared. Images in griz-bands were obtained, with a total of 5x180 
second exposures in each band.

A number of faint sources are detected near the UVOT-enhanced XRT 
position (Sbarufatti et al., GCN #6567), including the source (s1 = 
21:35:10.14, -24:49:06.9) to the South of the XRT position which may be 
the same source noted by Malesani et al. (GCN #6565). There is an 
apparent galaxy (s4: 21:35:10.34, -24:49:02.2, PA ~ -45 deg) to the east 
of the GRB but outside the current XRT position. A color image of the 
field has been posted (*) along with a ds9 region file (**) giving the 
J2000 locations of the sources near the GRB.

We note the presence of an asteroid, not found in the Minor Planet 
Checker (***), moving near the GRB at the time of the Gemini 
observations. The quickly derived parameters for this asteroid are:

  apparent motion: 10.4 S "/hr, 4.69 W "/hr
  position (ecliptic): lambda = +318:07:27.207, beta = -09:53:28.791  @ 
  22 June 2007 05:22:37.4 UTC

(*)   http://lyra.berkeley.edu/~jbloom/grb070621-gemini.png
(**)  http://lyra.berkeley.edu/~jbloom/grb070621-gemini.reg
(***) http://scully.harvard.edu/~cgi/CheckSN

We thank Bryan Miller and the Gemini Staff for observing this ToO."