Space Supernova

Masters Thesis

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Department of Physics & Astronomy

A new channel for the formation and evolution of subdwarf stars

Subdwarfs are fascinating and important objects in astronomy. There are two primary types of subdwarfs including sdBs and sdOs. They are very hot with surface temperatures between 20000 and 100000K which makes them very blue because of their strong ultraviolet emission. It is thought that they can explain the UV excess seen in old elliptical galaxies that do not have young, massive, and thus hot stars.

The main objective of this thesis work is to investigate the formation of hot subdwarfs in binary systems for the widest range of initial conditions describing the properties of progenitor binaries. We ignored possible observational constraints so as not to influence our choice of the progenitor grid. We were thus able to develop an unbiased picture of the ‘ensemble evolution’. With this goal in mind we evolved nearly 4000 progenitor binaries with primary (donor) masses between 1.2M to 8M and secondary (companion) masses that were 25%, 50%, 80% and 90%of the donor’s mass. A large number of initial orbital periods were also investigated implying different states of chemical evolution of the primary at the onset of mass transfer.

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