Pre-Explosive Observational Properties of Type Ia Supernovae
  The evolutionary path of rotating CO WDs directly accreting CO-rich matter is
followed up to few seconds before the explosive breakout in the framework of
the Double Degenerate rotationally-driven accretion scenario.
  We find that the evolutionary properties depend only on the actual mass of
the accreting WD and not on the previous history. We determine the expected
frequency and amplitude of the gravitational wave emission, which occurs during
the mass transfer process and acts as a self-tuning mechanism of the accretion
process itself. The gravitational signal related to Galactic sources can be
easily detected with the next generation of space-born interferometers and can
provide notable constraints to the progenitor model. The expected statistical
distribution of pre-explosive objects in the Galaxy is provided also in the
effective temperature-apparent bolometric magnitude diagrams which can be used
to identify merged DD systems via UV surveys.
  We emphasize that the thermonuclear explosion occurs owing to the decay of
physical conditions keeping over-stable the structure above the classical
Chandrasekhar limit and not by a steady increase of the WD mass up to this
limit. This conclusion is independent of the evolutionary scenario for the
progenitors, but it is a direct consequence of the stabilizing effect of
rotation. Such an occurrence is epistemological change of the perspective in
defining the ignition process in accreting WDs. Moreover, this requires a long
evolutionary period (several million years) to attain the explosion after the
above mentioned conditions cease to keep stable the WD. Therefore it is
practically impossible to detect the trace of the exploding WD companion in
recent pre-explosion frames of even very near SN Ia.
