  Published B and V fluxes from nearby Type Ia supernovae are fitted to
light-curve templates with 4-6 adjustable parameters. Separately, B magnitudes
from the same sample are fitted to a linear dependence on B-V color within a
post-maximum time window prescribed by the CMAGIC method. These fits yield two
independent SN magnitude estimates B_max and B_BV. Their difference varies
systematically with decline rate Delta m_15 in a form that is compatible with a
bilinear but not a linear dependence; a nonlinear form likely describes the
decline-rate dependence of B_max itself. A Hubble fit to the average of B_max
and B_BV requires a systematic correction for observed B-V color that can be
described by a linear coefficient R = 2.59 +- 0.24, well below the coefficient
R_B ~ 4.1 commonly used to characterize the effects of Milky Way dust. At 99.9%
confidence the data reject a simple model in which no color correction is
required for SNe that are clustered at the blue end of their observed color
distribution. After systematic corrections are performed, B_max and B_BV
exhibit mutual rms intrinsic variation equal to 0.074 +- 0.019 mag, of which at
least an equal share likely belongs to B_BV. SN magnitudes measured using
maximum-luminosity or CMAGIC methods show comparable rms deviations of order ~
0.14 mag from the Hubble line. The same fit also establishes a 95% confidence
upper limit of 486 km/s on the rms peculiar velocity of nearby SNe relative to
the Hubble flow.

Astrophysics