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A decade ago, the detection of the first transiting extrasolar planet provided a direct constraint on its composition and opened the door to spectroscopic investigations of extrasolar planetary atmospheres. Because such characterization studies are feasible only for transiting systems that are both nearby and for which the planet-to-star radius ratio is(More)
The GJ 581 planetary system was already known to harbour three planets, including two super-Earths planets which straddle its habitable zone. We report here the detection of an additional planet – GJ 581e – with a minimum mass of 1.9 M ⊕. With a period of 3.15 days, it is the innermost planet of the system and has a ∼5% transit probability. We also correct(More)
We report the discovery of a Neptune-mass planet around Gl 581 (M3V, M = 0.31 M ⊙), based on precise Doppler measurements with the HARPS spectrograph at La Silla Observatory. The radial velocities reveal a circular orbit of period P = 5.366 days and semi-amplitude K 1 = 13.2 m s −1. The resulting minimum mass of the planet (m 2 sin i) is only 0.052 M Jup =(More)
We present Spitzer Space T elescope infrared photometry of a primary transit of the hot Neptune GJ 436b. The observations were obtained using the 8 µm band of the InfraRed Array Camera (IRAC). The high accuracy of the transit data and the weak limb-darkening in the 8 µm IRAC band allow us to derive (assuming M = 0.44 ± 0.04 M⊙ for the primary) a precise(More)
This Letter reports on the detection of two super-Earth planets in the Gl 581 system, already known to harbour a hot Neptune. One of the planets has a mass of 5 M ⊕ and resides at the " warm " edge of the habitable zone of the star. It is thus the known exoplanet which most resembles our own Earth. The other planet has a 7.7 M ⊕ mass and orbits at 0.25 AU(More)
We present Spitzer Space Telescope infrared photometry of a secondary eclipse of the hot Neptune GJ 436 b. The observations were obtained using the 8-µm band of the InfraRed Array Camera (IRAC). The data spanning the predicted time of secondary eclipse show a clear flux decrement with the expected shape and duration. The observed eclipse depth of slightly(More)
The transiting extrasolar planet XO-3b is remarkable, with a high mass and eccentric orbit. These unusual characteristics make it interesting to test whether its orbital plane is parallel to the equator of its host star, as it is observed for other transiting planets. We performed radial velocity measurements of XO-3 with the SOPHIE spectrograph at the(More)
Exoplanets orbiting close to their parent stars may lose some fraction of their atmospheres because of the extreme irradiation. Atmospheric mass loss primarily affects low-mass exoplanets, leading to the suggestion that hot rocky planets might have begun as Neptune-like, but subsequently lost all of their atmospheres; however, no confident measurements have(More)