Some properties of Massive Stars derived analytically

TYPEAstrophysics Seminar
Speaker:Giora Shaviv
Time:14:30 - 15:30
Location:Lidow 620

We apply isentropic, homogeneous stellar models to investigate properties of very massive stars. These simplified models are a natural generalization of polytropic models to cases of complex equations of state. 

A limiting total mass-entropy density relation is discovered and discussed. This relation is a direct generalization of Chandrasekhar's limiting mass for white dwarfs, and is useful for obtaining a general picture of the evolutionary tracks. Tracks of central conditions on the pressure-temperature plane are calculated for these models and the occurrence of a non existence domain is discovered. 

We find that models with mass M < MChand evolve to vanishing entropy density and temperature. On the other hand, model with mass M > MChand tend to a limiting entropy density and infinite density and temperature. For every mass there exists a limiting entropy density slim(M) below which a star cannot reach. Actually there are no hydrostatic states for isentropes with entropy density below the limit slim(M).

We derive the limiting mass of a star that forms from an interstellar cloud.
We investigate the fate of an accreting star immersed in an interstellar cloud.

We show that a merger between two isentropic stars can yield a collapse to a black hole.