Tidal Evolution of the Planetary System around HD 83443

Two planets with orbital period ratio approximately 10:1 have been discoveredaround the star HD 83443. The inner and more massive planet, HD 83443b, has thesmallest semi-major axis among all currently known exoplanets. Unlike othershort period exoplanets, it maintains a substantial orbital eccentricity,e_1=0.079+/- 0.008, in spite of efficient tidal damping. This is a consequenceof its secular interactions with HD 83443c whose orbital eccentricitye_2=0.42+/-0.06. Dissipation, associated with tides the star raises in theinner planet, removes energy but not angular momentum from its orbit, whilesecular interactions transfer angular momentum but not energy from the inner tothe outer planet's orbit. The outward transfer of angular momentum decreasesthe tidal decay rate of the inner planet's orbital eccentricity whileincreasing that of the outer planet. The alignment of the apsides of theplanets' orbits is another consequence of tidal and secular interactions. Inthis state the ratio of their orbital eccentricities, e_1/e_2, depends upon thesecular perturbations the planets exert on each other and on additionalperturbations that enhance the inner planet's precession rate. Tidal androtational distortions of the inner planet along with general relativityprovide the most important of these extra precessional perturbations, each ofwhich acts to reduce e_1/e_2. Provided the planets' orbits are coplanar, theobserved eccentricity ratio uniquely relates sin i andC=(k_2/k_{2J})(R_1/R_J)^5, where the tidal Love number, k_2, and radius, R_1,of the inner planet are scaled by their Jovian equivalents.Comment: 4 pages, accepted to ApJ main journa