GCN Circular 4898
Malcolm Hicken (CFA), Maryam Modjaz (CFA), Peter Challis (CFA), Robert Kirshner (CFA), Jose Luis Prieto (OSU), Krzystof Stanek (OSU) and Richard Cool (Arizona) report: The CFA Supernova Group obtained UBVRr'i' photometry of 9 comparison stars in the field of GRB060218/SN2006aj on March 4, 2006 UT. Data was taken using the FLWO 1.2m telescope at Mt. Hopkins, Arizona. We present our V-band light curve in Modjaz, et. al. (2006), astro-ph/0603377, submitted to ApJL. A finding chart, coordinates and photometry can be found at the following website: http://cfa-www.harvard.edu/oir/Research/supernova/sn2006aj_compstars.html It should be noted that our V magnitudes are approximately 0.27 mag fainter than those derived in GCN 4777 by Cool, et. al. at http://mizar.as.arizona.edu/~grb/public/GRB060218. There is also an offset in the other bands. In investigating this photometric offset, Richard Cool has discovered calibration offsets between the two SDSS photometric reductions of this field indicating possible non-photometric conditions or other calibration problems in the SDSS photometry. The problem is being investigated to ensure data with suspicious photometric quality will be flagged as such in future SDSS GRB releases.