We extend earlier efforts to determine whether the late ( t \geq 60d ) light-curves of type Ia SNe are better explained by the escape of positrons from the ejecta or by the complete deposition of positron kinetic energy in a trapping magnetic field .
We refine our selection of Ia SNe , using those that have extensive BVRI photometry 35 days or more after maximum light .
Assuming all SNe within a given \Delta m _ { 15 } ( B ) range form a distinct sub-class , we fit a combined light-curve for all class members with a variety of models .
We improve our previous calculations of energy deposition rates by including the transport of the comptonized electrons .
Their non-local and time-dependent energy deposition produces a correction of as much as \leq 0.10 ^ { m } for Chandrasekhar models and \leq 0.18 ^ { m } for sub-Chandrasekhar models .

We find that applying a filter efficiency correction , derived from measured spectra , to B , V , R , and I light-curves after day 50 can produce a consistent bolometric light-curve .
The V band is an accurate indicator of total emission in the 3500 \AA - 9700 \AA range , with a constant fraction ( \sim 25 % ) appearing in the V band after day 50 .
This suggests that the V band scales with the bolometric luminosity , and that the deposited energy is instantaneously recycled into optical emission during this epoch .
Varying bolometric corrections for the other bands are derived .
We see significant evolution of the colors of SNe Ia between day 50 and day 170 .
We suggest that this may be due to the transition from spectra dominated by emission lines from the radioactive nucleus , ^ { 56 } Co , to those from the stable daughter nucleus , ^ { 56 } Fe .
We show that the B , V , R , and I band light-curves of SNe Ia after t \geq 60d can be completely explained with energy deposition from ^ { 56 } Co decay photons and positrons if substantial positron escape occurs .