Stellar Parameters Flashcards
What is the orbital period of the mood?
28d
What is the equation for the angular radius of something in the sky?
α = R/d, where R is the radius of the star and d is its distance from Earth
What is the lunar occultation method to examine stars and what is its problem?
Moon passes in front of the star. Problem is the Moon does not pass in front of many stars.
How can we use a binary system to look at stellar parameters?
Look at where the orbiting star is over time, and this tells us something about the stars.
In a binary system, what do both the stars orbit?
The centre of mass of the system.
What is the equation for the combined mass of the binary system?
M1+M2 = 4π^2/G * (r1+r2)^3/P^2, where P is the period and r1 and r2 are the maximum distances the stars can have from the centre of mass.
How can we use absorption spectra to study binary systems?
Notice that lines are blue shifted when a star is moving towards us and red shifted when going away from us.
What is the equation of the mass function?
M1+M2 = P/2πG * (v1 + v2)^3/sin^3(i), where i is the orbital inclination (90 degress for an edge on view and 0 degrees for a face on view of the binary system.
What are the two types of eclipsing binary systems?
Total eclipse and partial eclipse.
What can use total eclipses for?
Get the radii of the stars.
What are the two equations to measure the radii of the stars in a binary system?
t(e)-t(t)/P = 4R(A)/(2π(r(A)+r(B)) and t(e)+t(t)/P = 4R(B)/(2π(r(A)+r(B)), where R is the stellar radius, r is the distance from centre of mass and e and t represent the full and total eclipses.
What is the equation for the effective temperature of the star in binary system?
Teff = (f/σα^2)^1/4, where f is the flux detected at Earth and α is the radius of star.
What is the equation for the relative velocity of the binary stars?
v = vA + vB = 2πrA/P + 2πrB/P = 2π/P (rA + rB)
What are the equations for the distances d(e) and d(t) for a full eclipse and a total eclipse?
d(e) = 2R(A) + 2R(B), d(t) = 2R(A) - 2R(B)
What do we do with the distance equations?
Use v=d/t, and set them equal to the relative velocity equations, then do one plus the other and one minus the other to get the final equations.
