PY 228: STELLAR ASTROPHYSICS
HOMEWORK #2: DUE FEB. 9
This homework involves the use of the program binaries on a
REALM workstation. To execute this program follow these simple steps:
- Log on to a REALM (Unity, EOS, PAMS...) workstation
- Type add py228_info
- Type cp /ncsu/py228_info/ucla/Binaries ~/Binaries (This copies
the X application defaults file to your root directory.)
- Run the program by typing binaries
- Verify Kepler's three laws.
- Increase the eccentricity to view an elliptical orbit.
- For a highly elliptical orbit, in what part of the orbit is the star
moving the fastest?
- Keeping the masses of the two stars constant, vary the binary separation
and record the period. Does the orbit satisfy Kepler's Third Law?
- Set up the program to simulate the binary star Algol using the following
parameters.
- Primary Mass = 3.7 solar masses
- Primary Radius = 2.9 solar radii
- Primary Temperature = 13,000 K
- Secondary Mass = 0.8 solar masses
- Secondary Radius = 3.5 solar radii
- Secondary Temperature = 4,500 K
- Orbital Separation = 13.96 solar radii
- Orbital Eccentricity = 0.015
- Orbital Inclination = 81.4 degrees
What is the orbital period? Watch the light curve and the "View from Earth".
Is there a bug in this program? (Which star is more luminous?)
Forgetting that you know the answers, begin from
the observations (radial velocity curves and orbital period) and derive the
masses of the two stars.
- Adjust the orbital inclination to 0 degrees. Why is such a binary system much
less useful in obtaining stellar parameters?
- Set up a close binary system with a primary star of spectral type B0V,
a secondary star of spectral type G0V, and a separation of 60 solar radii.
What is the orbital period? Notice the slight wobble of the primary star.
Now change the luminosity class of the primary
to a supergiant, choosing a spectral type that gives roughly the same mass
as the star had when it was on the main sequence. What will happen to this
system when the primary star evolves into a supergiant?