  Although Type Ia supernovae (SNe Ia) play very important roles in many
astrophysical fields, the exact nature of the progenitors of SNe Ia is still
unclear. At present, the single degenerate (SD) model is a very likely one.
Following the comprehensive SD model developed by Meng & Yang (2010), we show
the properties of SNe Ia companions at the moment of the supernova explosion.
The results may provide help in searching for companion stars in supernova
remnants. We compared our results with the companion candidate Tycho G of
Tycho's supernova and found that integral properties of the star (mass, space
velocity, radius, luminosity and effective temperature) are all consistent with
those predicted from our SD model with the exception of the rotational
velocity. If Tycho G was the companion star of Tycho's supernova, an
interaction between supernova ejecta and the rotational companion might be a
key factor to solve the confliction, and then it could be encouraged to do a
detailed numerical simulation about the interaction.
