DD Systems as Supernovae Ia Progenitors

L.Piersanti, A.Tornambé, O.StranieroINAF – Osservatorio Astronomico di Teramo

Inmaculada DominguezUniversitad de Granada

LII Congresso SAIt4- 8 May 2008, Teramo - Italy

The Evolutionary Scenario

Type Ia Supernovae are produced by the thermonuclear disruption of CO WDs which approach MCh due to mass accretion from their companions in binary systems

(Hoyle & Fowler 1960)

Explosion Mechanism:

Delayed Detonation Model (Khakhlov 1991)

We don’t know the mechanism triggering the transition!

Progenitor System

The companion is a normal star with an H-rich envelope

The companion is a CO White Dwarf

SD Scenario DD Scenario

Synchronization of the orbits!

Merging WDs

Shrinkage of the orbits due to GWR

Emission

Dynamical mass transfer from M2 to

M1

M2 disruption and Accretion Disk

formation

Angular Momentum deposition

Accreting WD becomes very fast rotator

Final Outcomes DD Systems

Rotation tunes the accretion rate!

Mfin=1.49 M0!

Observational Evidence

(Gallagher et a. 2005)

No very Bright event in early type galaxies

Dimmer events could be undetected

Differences in the total mass of DD

Systems!

Ingredients of our cooking

1) Large database of stellar evolutionary tracks (1-11 M0 – M=0.1)

2) Salpeter mass function (=-2.35) for the binary system total mass

3) Flat distribution for log(A)

4) q distribution according to a sample of local spectroscopic binaries

5) CE efficiency according to Zwart & Verbunt (1995)

Results: I

For a single SF burst Cumulative number of events

Results: II

Distribution of the mean mass as a function of time

High mass DD Systems

Low mass DD Systems

Age=5 107

yr

Age=13 Gyr

Results: III

Single Star Formation Episode Continuous Stars Formation

Mass Distribution at various Age

ConclusionsDD systems can be regarded as SNe Ia progenitor systems

IFthe effects of rotation are taken into account

In fact …

1. Rotation triggers the accretion process, acting as a fine-tuning mechanism

2. Due to rotation, Mtot of the exploding object can vary in the range 1.4-2.2 M0

3. High mass merging DD systems occurs only at short time after SF

4. Long term evolution is dominated by low mass DD systems

Models of differentially rotating WD are needed!!!