TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4861
SUBJECT: GRB060306: APO Ks-band Imaging Observations
DATE:    06/03/12 04:41:38 GMT
FROM:    Hsiao-Wen Chen at U Chicago  <hchen@oddjob.uchicago.edu>

H.-W. Chen (U Chicago), X. Fan (U Arizona), F. Hearty (Colorado), M. Bayliss 
(Chicago), D. Q. Lamb (U Chicago), R. McMillan (APO), B. Ketzeback (APO), J. 
Barentine (APO), J. Dembicky (APO), and D. York (U Chicago) report:

"We obtained a 3x300 sec dithered exposures in Ks of the field of
GRB060306 (Angelini et al., GCN 4848), using the NIC-FPS near-infrared camera 
on the 3.5 m telescope at the Apache Point Observatory.  The
observations started at 20060306.10 UT (~ 2 hrs after the initial
Swift trigger) through variable clouds and under a mean seeing
condition of 1 arcsec.  Calibrating the final stacked image to 2MASS
stars in the field gives a 5 sigma depth of Ks=20.4 over a 1 arcsec diameter 
aperture.  Within the XRT error circle (Page et al., GCN 4850), we locate a 
single source at

 		RA(J2000)  = 02:44:23.0
 		Dec(J2000) = -02:08:51.2,

which is also present in the DSS red plate (see also Price et al.,
GCN 4854, and Nysewander et al., GCN 4857).  Based on the 2MASS photometry, 
we estimate the source brightness to be Ks=18.3 +/- 0.1 mag.  Comarison with 
the Ks image taken a day later by Nysewander et al. (GCN4857) shows no 
variability of this source.

The stacked image is available at 
http://lambda.uchicago.edu/public/grb/grb060306/grb060306K.fits.

NIC-FPS is currently in its commissioning phase."