GCN Circular 2594

GRB 040511: Second Epoch Optical Observations

Nidia Morrell (Las Campanas Observatory), Hsiao-Wen Chen (MIT), Joshua S.
Bloom (Harvard/CfA), Jason X. Prochaska (UCO/Lick), A. Dullighan, G.
Ricker, N. Butler, and R. Vanderspek (MIT):

"We have obtained a second epoch of R-band images of the field around GRB
040511 (Dullinghan et al., GCN #2588) using the SITe#3 CCD imager on the
40 inch Swope telescope at the Las Campanas Observatory.  The observations
were carried out starting at 01:30 UT 13 May 2004 (~36 hours after the
burst).  Three exposures of 600 sec duration were taken under photometric
and sub-arcsec seeing conditions.  The 5-sigma depth of the stacked image
is R~23.6 mag over a 2"-diameter aperture.

A comparison of the stacked image with the first-epoch images obtained at
~11 hr after the burst (Chen et al., GCN #2591) shows that none of the
~7100 sources of Rc <~ 23 in the 14.8' x 20' region have variability by
more than 0.25 mag. The few larger-amplitude outliers in the magnitude
(epoch1) vs. magnitude (epoch2) plot are due to detector artifacts."

The magnitude-magnitude plot that shows the comparison of object
photometry obtained from two epochs and all the imaging data are publicly
available at http://www.graasp.org/. Click the "Data" link.

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