We present early photometric and spectroscopic data on the afterglow of GRB
060218 and report the evolution of the underlying supernova 2006aj. Our data
span a time-range of 4 days to 22 days after the GRB and clearly establish that
SN 2006aj is a fast-evolving broad-lined Type Ic SN with an extremely short
rise-time (~ 10 days) and a large optical luminosity (M_V = -18.7 mag). The SN
properties are deduced well since the GRB afterglow does not contribute a
significant amount to the total light output. The spectra show broad lines
indicative of large expansion velocities, but are better matched by those of SN
2002ap and SN 1997ef (that are not associated with a GRB) than those of the
proto-typical GRB-related SN 1998bw. We refine the redshift estimate to z =
0.0335 +/- 0.00007. The host-galaxy is a low-metallicity dwarf galaxy (with M_V
\~ -16.0 mag), similar to host-galaxies of other GRB-associated SNe.Comment: 7 pages using emulateapj, 3 figures, accepted by ApJL, minor changes
compared to v