# Variable stars luminosity

1. Jan 11, 2013

### Gregg

1. The problem statement, all variables and given/known data

Given pulsation period in days, (surface temperature) and mass of an RR Lyra variable star. How do you find luminosity?

2. Relevant equations

The relevant equations seem to be for finding the luminosity of Cepheids... there are no equations for Lyrae... Other than, absolute magnitude is 49 solar masses luminosities, for all RRs.

Should I use

$$\Pi \approx \sqrt{\frac{3\pi}{2 \gamma G \rho}}$$ to get L from

$$\frac{L}{L_{\odot}} = {\left ( \frac{R}{R_{\odot}} \right )}^2 {\left ( \frac{T}{T_{\odot}} \right )}^4$$ ?