HD 147506b: A Supermassive Planet in an Eccentric Orbit Transiting a Bright Star

Abstract

We report the discovery of a massive ( M p 9:04 AE 0:50 M J ) planet transiting the bright (V 8:7) F8 star HD 147506, with an orbital period of 5:63341 AE 0:00013 days and an eccentricity of e 0:520 AE 0:010. From the transit light curve we determine that the radius of the planet is R p 0:982 0:038 0:105 R J . HD 147506b (also coined HAT-P-2b) has a mass about 9 times the average mass of previously known transiting exoplanets and a density of p % 12 g cm 3 , greater than that of rocky planets like the Earth. Its mass and radius are marginally consistent with theories of structure of massive giant planets composed of pure H and He, and accounting for them may require a large (k100 M ) core. The high eccentricity causes a ninefold variation of insolation of the planet between peri-and apastron. Using follow-up photometry, we find that the center of transit is T mid 2;454;212:8559 AE 0:0007 ( HJD) and the transit duration is 0:177 AE 0:002 days.