Extreme Helium Stars

Most stars evolve from the main sequence to become red giants. As red giants, their atmospheres are generally rich in hydrogen. Subsequently they contract to become white dwarfs. During this process, they lose nearly all their outermost layers. Apparently, some lose all of their hydrogen, revealing layers of helium and carbon. These are the hydrogen-deficient stars...

At least, that's the simple picture. In practice, stars don't lose their outer layers that easily. The question is: How did the hydrogen-deficient stars lose their hydrogen ?

Did they suffer some massive mixing due to thermonnuclear detonation in the atmosphere of a white dwarf or did they form from the merger of two white dwarfs?

My study of hydrogen-deficient stars includes their Galactic distribution, surface composition, pulsations, ejecta and real-time evolutionary changes.

Studies of the atmospheres of B-type H-deficient stars
to measure temperature, gravity and surface composition
Studies of pulsations in variable H-deficient stars.
Click here for a simulation of pulsating helium star V652 Her
Studies of the evolution of extreme helium stars

This page is maintained by:
Simon Jeffery (csj@star.arm.ac.uk)
Last modified: 08/06/00

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