Unformatted text preview: Here the right hand sides are completely known, so we infer the lefthand sides. These data only give masses if we know the inclination of the
orbit, i. But, in general, we will not know this, so our data only measure a
combination of masses and i.
For one special group of stars, we do get M1 and M2 directly | from
\eclipsing" binaries, where the light curve shows an eclipse (see gure). light flux, F/(F1 +F2 ) 1.2 τ 1
0 0 .5 1
time, t /τ 1.5 Here, the stars are eclipsing one another . This scenario is only possible
if i 90 (provided that the stellar radii separation, which we can check
in the above equations; if this is not true, the stars are so distorted that we
cannot use this method anyway). Thus, sin i 1. Errors in i have little
eect on the masses derived, because sin i changes slowly at i 90.
In fact, the best data on masses of stars comes from eclipsing spectroscopic
double-lined binaries, even though these are hard to nd.
An alternative approach is to measure many noneclipsing binaries, assume
i to be selected at random, and use statistics to derive the distribution of
masses, M1 and M2.
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- Fall '09
- Planet, Left-handedness, The Masses, Right-hand rule, right hand sides