Incorrect binary star statements?

Question

I need a bit of help here. Which 2 of these statements are incorrect and why ?

1) The orbital speeds of neutron stars in binary systems can be determined using the changing frequency of pulses over the orbital cycle if they are pulsars.

2) In general , the masses of stars in spectroscopic binaries binaries will be underestimated because the angle between the plane of the orbit and the plane of the sky is unknown

3) Type 1a supernovae are believed to arise as a result of mass transfer onto a white dwarf in a binary system

4) The deepest minimum in the light curve of an eclipsing binary star occurs when the largest star is eclipsed.

Thanks.

Answer 1

Let's start with the easy one. Number 3 is true.

Number 4 is incorrect because when the smaller star eclipses the larger one, you are still getting light from both of them.  When the smaller star goes behind the larger one, it is completely obscured and we see no light from it.  Note: this is true regardless of which star is brighter.

Number 2 seems to be incorrect because we get information about the masses of stars from their orbital *period*.  We can see the length of a period regardless of the inclination of an eclipsing binary.  I'm also having some difficulty with the term "plane of the sky," which tends to prejudice me against the statement.

For number 1, the pulse frequency is useful in determining red and blue shifts and therefore, the speed.  You need more information, though, because of what was mentioned in number 2: the degree of orbital tilt is going to affect the apparent speed.  I think this one is correct, although it is worded in such a way as to make it a somewhat incomplete ststement.