XO-3b: A Massive Planet in an Eccentric Orbit Transiting an F5V Star Christopher M. Johns–Krull1,2, Peter R. McCullough3, Christopher J. Burke3, Jeff A. Valenti3, K. A. Janes4, J. N. Heasley5, L. Prato6, R. Bissinger7, M. Fleenor8, C. N. Foote9, E. Garcia–Melendo10, B. L. Gary11, P. J. Howell4, F. Mallia12, G. Masi13, T. Vanmunster14
[email protected] ABSTRACT We report the discovery of a massive (Mpsini= 13.02 0.64 MJ; total mass 13.25 0.64 MJ), ± ± th large (1.95 0.16 RJ) planet in a transiting, eccentric orbit (e = 0.260 0.017) around a 10 magnitude F5V± star in the constellation Camelopardalis. We designate the± planet XO-3b, and the star XO-3, also known as GSC 03727-01064. The orbital period of XO-3b is 3.1915426 0.00014 days. XO-3 lacks a trigonometric distance; we estimate its distance to be 260 23 pc. The± radius ± −1 of XO-3 is 2.13 0.21 R⊙, its mass is 1.41 0.08 M⊙, its vsini = 18.54 0.17 km s , and its metallicity is [Fe/H]± = 0.177 0.027. This± system is unusual for a number± of reasons. XO-3b is one of the most massive− planets± discovered around any star for which the orbital period is less than 10 days. The mass is near the deuterium burning limit of 13 MJ, which is a proposed boundary between planets and brown dwarfs. Although Burrows et al. (2001) propose that formation in a disk or formation in the interstellar medium in a manner similar to stars is a more logical way to differentiate planets and brown dwarfs, our current observations are not adequate to address this distinction.