The orbital motion, absolute mass, and high-altitude winds of exoplanet HD209458b

For extrasolar planets discovered using the radial velocity method, the spectral characterization of the host star leads to a mass-estimate of the star and subsequently of the orbiting planet. In contrast, if also the orbital velocity of the planet would be known, the masses of both star and planet could be determined directly using Newtons law of gravity, just as in the case of stellar double-line eclipsing binaries. Here we report on the detection of the orbital velocity of extrasolar planet HD209458b. High dispersion ground-based spectroscopy during a transit of this planet reveals absorption lines from carbon monoxide produced in the planet atmosphere, which shift significantly in wavelength due to the change in the radial component of the planet orbital velocity. These observations result in a mass determination of the star and planet of 1.00+-0.22 Msun and 0.64+-0.09 Mjup respectively. A ~2 km/sec blueshift of the carbon monoxide signal with respect to the systemic velocity of the host star suggests the presence of a strong wind flowing from the irradiated dayside to the non-irradiated nightside of the planet within the 0.01-0.1 mbar atmospheric pressure range probed by these observations. The strength of the carbon monoxide signal suggests a CO mixing ratio of 1-3x10-3 in this planets upper atmosphere.

The changing phases of extrasolar planet CoRoT-1b

Hot Jupiters are a class of extrasolar planet that orbit their parent stars at very short distances. Due to their close proximity, they are expected to be tidally locked, which can lead to a large temperature difference between their day and nightsides. Infrared observations of eclipsing systems have yielded dayside temperatures for a number of transiting planets. Furthermore the day-night contrast of the transiting extrasolar planet HD 189733b was mapped using infrared observations. It is expected that the contrast between the dayside and nightside of hot Jupiters is much higher at visual wavelengths as we move shortward of the peak emission, and could be further enhanced by reflected stellar light. Here we report on the analysis of optical photometric data of the transiting hot Jupiter CoRoT-1b, which cover 36 planetary orbits. The nightside hemisphere of the planet is consistent with being entirely black, with the dayside flux dominating the optical phase curve. This means that at optical wavelengths the planets phase variation is just as we see it for the interior planets in our own solar system. The data allow only for a small fraction of reflected light, corresponding to a geometric albedo <0.20.