Stellar Evolution Challenge

γ Persei: a challenge for stellar evolution models

From the published visual and spectroscopic observations together with some unpublished radial velocities kindly provided by R.F. Griffin, we determine an orbit which accurately reproduces the time of the primary eclipse observed by Griffin et al. (1994) and also recompute Hipparcos astrometric parameters. The orbital parallax is slightly off with respect to Hipparcos whereas the agreement of t...

Stellar Structure and Evolution

Stellar Evolution Presenting

Stars “evolve” with time in a predicable manner. Our theory of stellar evolution is one of the foundations of astrophysics, is well tested and verified, and has enabled great advances in many fields of astrophysics. As such, stellar evolution is a cornerstone of any astronomy course, from the 100 level up through graduate levels. One of the leading software to model a star’s evolution in detail...

Horizontal Branch Stellar Evolution

I review aspects of the evolution of horizontal branch (HB) stars. The defining characteristic of this, the core He-burning phase of evolution for M < Mflash ∼ 2.2M⊙, is a spread in observed colour amongst HB stars within the (almost) chemically homogeneous, isochronous populations found in Galactic globular clusters. The inference is that the stars within a given cluster must have undergone va...

Hot DQ White Dwarf Stars: A New Challenge to Stellar Evolution

We report the discovery of a new class of hydrogen-deficient stars: white dwarfs with an atmosphere primarily composed of carbon, with little or no trace of hydrogen or helium. Our analysis shows that the atmospheric parameters found for these stars do not fit satisfactorily in any of the currently known theories of post-asymptotic giant branch (AGB) evolution, although these objects might be t...