A star is transited by a planet. From the measured period T and the transit duration t alone, show that one can obtain an upper bound on the density of the transited star : rhomax= 3T/(G(pi2)(t3)). Hint: Combine Kepler's Law [(omega2)(a3)=GMstar and the equation t=((rstarT)/(pi*a))*(1-b2)1/2 to eliminate a, and then extract the density of the spherical star. The upper bound is obtained by assuming an impact parameter b=0.

A star is transited by a planet. From the measured period T and the transit duration t alone, show that one can obtain an upper bound on the density of the transited star : rhomax= 3T/(G(pi2)(t3)). Hint: Combine Kepler's Law [(omega2)(a3)=GMstar and the equation t=((rstarT)/(pia))(1-b2)1/2 to eliminate a, and then extract the density of the spherical star. The upper bound is obtained by assuming an impact parameter b=0.