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## Main Question or Discussion Point

I have this problem:

Given is period of an eclipsing binary star system is 34 days, rest wavelength is 6563 angstroms while max doppler shift of 2.34 angstroms

I used the doppler equation to figure out the orbital speed of the star; now the question says to use the simplistic model of being in a circular orbit about the other star , calculate the sum of the masses of the stars in solar units.

I know I have to use the modified kepler 3rd law to find the combined mass but how do i get 'a' or semi major axis? Do I just multiply the orbital speed by the period in seconds to get this?

thanks

Given is period of an eclipsing binary star system is 34 days, rest wavelength is 6563 angstroms while max doppler shift of 2.34 angstroms

I used the doppler equation to figure out the orbital speed of the star; now the question says to use the simplistic model of being in a circular orbit about the other star , calculate the sum of the masses of the stars in solar units.

I know I have to use the modified kepler 3rd law to find the combined mass but how do i get 'a' or semi major axis? Do I just multiply the orbital speed by the period in seconds to get this?

thanks