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We report on a V ¼ 11:2 early K dwarf, , that hosts a R p ¼ 0:98AE 0:03 0:01 R J , M p ¼ 0:57 AE 0:06 M J transiting extrasolar planet, XO-2b, with an orbital period of 2:615857 AE 0:000005 days. XO-2 has high metallicity, ½Fe/H ¼ 0:45 AE 0:02, high proper motion, tot ¼ 157 mas yr À1 , and a common proper motion stellar companion with 31 00 separation. The two stars are nearly identical twins, with very similar spectra and apparent magnitudes. Due to the high metallicity, these early K dwarf stars have a mass and radius close to solar, M ? ¼ 0:98 AE 0:02 M and R ? ¼ 0:97AE 0:02 0:01 R . The high proper motion of XO-2 results from an eccentric orbit (Galactic pericenter, R per < 4 kpc) well confined to the Galactic disk (Z max $ 100 pc). In addition, the phase-space position of XO-2 is near the Hercules dynamical stream, which points to an origin of XO-2 in the metal-rich, inner thin disk and subsequent dynamical scattering into the solar neighborhood. We describe an efficient Markov chain Monte Carlo algorithm for calculating the Bayesian posterior probability of the system parameters from a transit light curve.

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We report the discovery of a massive (M p sini= 13.02 ± 0.64 M J ; total mass 13.25 ± 0.64 M J ), large (1.95 ± 0.16 R J ) planet in a transiting, eccentric orbit (e = 0.260 ± 0.017) around a 10 th 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 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 −1 , 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 M J , 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. XO-3b is also unusual in that its eccentricity is large given its relatively short orbital period. Both the planetary radius and the inclination are functions of the spectroscopically determined stellar radius. Analysis of the transit light curve of XO-3b suggests that the spectroscopically derived parameters may be over estimated. Though relatively noisy, the light curves favor a smaller radius in order to better match the steepness of the ingress and egress. The light curve fits imply a planetary radius of 1.25±0.15 R J , which would correspond to a mass of 12.03 ± 0.46 M J . A precise trigonometric parallax measurement or a very accurate light curve is needed to resolve the uncertainty in the planetary mass and radius.

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We investigate the long-term motion of Saturn's north pole hexagon and the structure of its associated eastward jet, using Cassini imaging science system and ground-based images from 2008 to 2014. We show that both are persistent features that have survived the long polar night, the jet profile remaining essentially unchanged. During those years, the hexagon vertices showed a steady rotation period of 10 h 39 min 23.01 ± 0.01 s. The analysis of Voyager 1 and 2 (1980)(1981) and Hubble Space Telescope and ground-based (1990-1991) images shows a period shorter by 3.5 s due to the presence at the time of a large anticyclone. We interpret the hexagon as a manifestation of a vertically trapped Rossby wave on the polar jet and, because of their survival and unchanged properties under the strong seasonal variations in insolation, we propose that both hexagon and jet are deep-rooted atmospheric features that could reveal the true rotation of the planet Saturn.