The Carnegie Supernova Project: Intrinsic Colors of Type Ia Supernovae
  We present an updated analysis of the intrinsic colors of SNe Ia using the
latest data release of the Carnegie Supernova Project. We introduce a new
light-curve parameter very similar to stretch that is better suited for
fast-declining events, and find that these peculiar types can be seen as
extensions to the population of "normal" SNe Ia. With a larger number of
objects, an updated fit to the Lira relation is presented along with evidence
for a dependence on the late-time slope of the B-V color-curves with stretch
and color. Using the full wavelength range from u to H band, we place
constraints on the reddening law for the sample as a whole and also for
individual events/hosts based solely on the observed colors. The photometric
data continue to favor low values of Rv, though with large variations from
event to event, indicating an intrinsic distribution. We confirm the findings
of other groups that there appears to be a correlation between the derived
reddening law, Rv, and the color excess, E(B-V), such that larger E(B-V) tends
to favor lower Rv. The intrinsic u-band colors show a relatively large scatter
that cannot be explained by variations in Rv or by the Goobar (2008) power-law
for circumstellar dust, but rather is correlated with spectroscopic features of
the supernova and is therefore likely due to metallicity effects.
