Transcript TU Muscae and the Early-type Overcontact Binaries

Binary Stars
Dirk Terrell
Southwest Research Institute
[email protected]
Why Bother with Binaries?
•
Provide accurate data that are very difficult to determine
for single stars such as masses and radii.
•
Are very common- the majority of stellar systems are
binaries.
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They are interesting objects in and of themselves. Still
many puzzles to solve about their structure and
evolution.
Visual Binaries
The two stars are resolved, so we see the orbital motion
directly. Interferometric techniques give the same kind of
data.
Spectroscopic Binaries
Single-lined spectroscopic binary: spectral lines of one star are visible.
Double-lined spectroscopic binary: spectral lines of both stars are visible.
Dan Durda
http://www.boulder.swri.edu/~durda/
X-ray Binaries
Pulses from the neutron star act as a clock and can be used to
measure the orbit.
Mark Garlick - http://space-art.co.uk/
Eclipsing Binaries
Binary orbital plane is oriented so that the two stars pass in front of
one another as seen from Earth. The light curve is rich in information
about the two stars.
Wide Variety of Light Curves
Algols
High-mass stars evolve faster than low mass stars
But in Algols the less massive star is evolved. How is that
possible?
Mass transfer! The low mass star was once the more massive
star, evolved, and dumped matter onto the other star, eventually
reversing the mass ratio.