טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentMarjan Ilkov
SubjectCommon Envelope WD-core Merger as Type Ia Supernova
Progenitors
DepartmentDepartment of Physics
Supervisor Full Professor Soker Noam
Full Thesis textFull thesis text - English Version


Abstract

First, we study the spinning down time scale of rapidly rotating white dwarfs (WDs) in the frame of the core-degenerate (CD) scenario for type Ia supernovae (SNe Ia). In the CD scenario the Chandrasekhar or super-Chandrasekhar mass WD is formed at the termination of the common envelope phase or during the planetary nebula phase, from a merger of a WD companion with the hot core of a massive asymptotic giant branch star. In the CD scenario the rapidly rotating WD is formed shortly after the stellar formation episode, and the delay from stellar

formation to explosion is basically determined by the spin-down time of the rapidly rotating merger remnant. We find that gravitational radiation is inefficient in spinning down WDs, while the magneto-dipole radiation torque can lead to delay times that are required to explain SNe Ia.

Next, we calculate the expected number of type Ia supernovae in the (CD) scenario and find it to match observations within the uncertainties of the code. We use a simple population synthesis code that avoids the large uncertainties involved in estimating the final orbital separation of the common envelope evolution. Instead, we assume that systems where the core of the secondary asymptotic giant branch (AGB) star is more massive than the WD remnant of the primary star merge at the termination of the common envelope phase. We also use a simple prescription to

count systems that have strong interaction during the AGB phase, but not during the earlier red giant branch (RGB) phase. That a very simple population synthesis code that uses the basics of stellar evolution ingredients can match the observed rate of SN Ia might suggest that the CD-scenario plays a major role in forming SN Ia.