Suppose you have just discovered a new X--ray binary, which contains a B2 main sequence star orbiting an unseen companion. The separation of stars is estimated to be 40 million km, and the orbital period of the visible star is 12 days.
(a) Calculate the masses of the two stars in the system (watch your units, keep star masses in Msun units, put P into years and A into AU. OR use the full equation of Newton's version of Kepler's 3rd law with G and everything else in the same units as G).
(b) Estimate the mass of the unseen companion-- is it a neutron star or a black hole? Explain.