TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  2710
SUBJECT: GRB 040912: Optical Observations
DATE:    04/09/15 04:36:26 GMT
FROM:    James Rhoads at STScI  <rhoads@stsci.edu>

Armin Rest (CTIO), James Rhoads (STScI), and Peter Weilbacher (Durham)
report on behalf of a larger collaboration:
 
We have observed the field of GRB 040912 using the 4m Blanco telescope
and CCD Mosaic-2 camera at CTIO.  We obtained two epochs during the
first night following the burst, at UT September 13.033 and 13.205.
Each epoch consisted of four R band exposures of 300 seconds, for a
total of 20 minutes' integration per epoch.  Conditions were
photometric but seeing was mediocre, at 1.35" in the first epoch 
and 1.01" in the second epoch.

Preliminary image subtraction analysis reveals no compelling afterglow
candidates.  Our search is sensitive to a change in flux density of 
1.9 microJansky, which corresponds to the complete disappearance 
of an object with magnitude R=23.0