# Binary star systems

## Homework Statement

Angular separation of stars 1.5 arcsecs
Parallax 0.0050 arcsecs
Apparent vis magnitude 2.5 (star a) and 7.5 (star b)

The two stars may be in orbit about each other in a binary system, or may be separate stars viewed by chance in almost the same direction in the sky.

(i) What are the radial velocities of Stars A and B?

(ii) Give two examples of further observational results that would demonstrate that the stars are definitely not in abinary system.

(iii) Give two examples of further observational results that would
demonstrate that the stars are definitely in a binary system.

(iv) If the stars appeared to be so close together that they were unresolved (i.e. appeared as one star), give a further example of an observational result that would demonstrate that they are in a binary system.

None

## The Attempt at a Solution

(i) I've got 15000ms-1 and 21000ms-1

(ii)

(iii)

(iv) Eclipsing binaries if the plane of the orbit is perpendicular to the plane of the sky?

I know it has something to do with visual binaries and spectroscopic binaries but can't think how to apply it :-(

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I know it has something to do with visual binaries and spectroscopic binaries but can't think how to apply it :-(
Well, you can measure the radial velocities even if you cannot separate them in a telescope.

(iv) multiple eclipses are a good idea.

What about a simple observation of 1-2 orbits, if the period is not too long?

What about a determination of the 3D motion of both stars, or differences in their parallax?