Showing papers by "François Bouchy published in 2004"

The HARPS survey for southern extra-solar planets. II. A 14 Earth-masses exoplanet around μ Arae

Abstract: In this letter we present the discovery of a very light planetary companion to the star mu Ara (HD160691). The planet orbits its host once every 9.5days, and induces a sinusoidal radial velocity signal with a semi-amplitude of 4.1 m/s, the smallest Doppler amplitude detected so far. These values imply a mass of m2 sini = 14 earth-masses. This detection represents the discovery of a planet with a mass slightly smaller than that of Uranus, the smallest ``ice giant" in our Solar System. Whether this planet can be considered an ice giant or a super-earth planet is discussed in the context of the core-accretion and migration models.

The HARPS survey for southern extra-solar planets II. A 14 Earth-masses exoplanet around mu Arae

Abstract: In this letter we present the discovery of a very light planetary companion to the star mu Ara (HD160691). The planet orbits its host once every 9.5days, and induces a sinusoidal radial velocity signal with a semi-amplitude of 4.1 m/s, the smallest Doppler amplitude detected so far. These values imply a mass of m2 sini = 14 earth-masses. This detection represents the discovery of a planet with a mass slightly smaller than that of Uranus, the smallest ``ice giant" in our Solar System. Whether this planet can be considered an ice giant or a super-earth planet is discussed in the context of the core-accretion and migration models.

The HARPS search for southern extra-solar planets. I. HD 330075 b: A new "hot Jupiter"

Abstract: We report on the first extra-solar planet discovered with the brand new HARPS instrument. The planet is a typical "hot Jupiter" with m2 sini = 0.62 MJup and an orbital period of 3.39 days, but from the photometric follow-up of its parent star HD 330075 we can exclude the presence of a transit. The induced radial-velocity variations exceed 100 m s −1 in semi-amplitude and are easily detected by state-of-the-art spectro-velocimeters. Nevertheless, the faint magnitude of the parent star (V = 9.36) benefits from the efficient instrument: with HARPS less than 10 observing nights and 3 h of total integration time were needed to discover the planet and characterize its orbit. The orbital parameters determined from the observations made during the first HARPS run in July 2003 have been confirmed by 7 additional observations carried out in February 2004. The bisector analysis and a photometric follow-up give no hint for activity-induced radial-velocity variations, indicating that the velocity curve is best explained by the presence of a low-mass companion to the star. In this paper we present a set of 21 measurements of excellent quality with weighted rms as low as 2.0 m s −1 . These measurements lead to a well defined orbit and consequently to the precise orbital parameters determination of the extra-solar planet HD 330075 b.

The HARPS search for southern extra-solar planets I. HD330075 b: a new 'hot Jupiter'

Abstract: We report on the first extra-solar planet discovered with the brand new HARPS instrument. The planet is a typical 'hot Jupiter' with m2sini = 0.62 MJup and an orbital period of 3.39 days, but from the photometric follow-up of its parent star HD330075 we can exclude the presence of a transit. The induced radial-velocity variations exceed 100 m/s in semi-amplitude and are easily detected by state-of-the-art spectro-velocimeters. Nevertheless, the faint magnitude of the parent star (V = 9.36) benefits from the efficient instrument: With HARPS less than 10 observing nights and 3 hours of total integration time were needed to discover the planet and characterize its orbit. The orbital parameters determined from the observations made during the first HARPS run in July 2003 have been confirmed by 7 additional observations carried out in February 2004. The bisector analysis and a photometric follow-up give no hint for activity-induced radial-velocity variations, indicating that the velocity curve is best explained by the presence of a low-mass companion to the star. In this paper we present a set of 21 measurements of excellent quality with weighted rms as low as 2.0 m/s. These measurements lead to a well defined orbit and consequently to the precise orbital parameters determination of the extra-solar planet HD330075b.

The exoplanet hunter HARPS: performance and first results

Abstract: HARPS is a new high resolution “bre-fed spectrograph dedicated to the extremely precise measurement ofstellar radial velocities. After being used for about one year including the commissioning runs we report avery successful implementation of the measures taken to maximise stability, eciency and spectral performance.Using the Simultaneous ThAr Reference Method a short term precision of 0.2 ms Š 1 during one night and a longterm precision of the order of 1 ms Š 1 have been achieved. Equipped with a fully automated data reductionpipeline that produces solar system barycentric radial velocities in near real-time, HARPS promises to deliverdata of unequalled quality. HARPS will primarily be used for the search for exoplanets and in the “eld ofasteroseismology. First exciting scienti“c results con“rm these expectations.Keywords: spectroscopy, exoplanet, asteroseismology, radial velocity 1. INTRODUCTION HARPS, the High Accuracy Radial velocity Planet Searcher saw its First Light at the 3.6m telescope of ESOsLa Silla Observatory in February 2003, exactly 3 years after the project was formally launched as a cooperativeeort between the HARPS Consortium and the European Southern Observatory ESO. The former consists ofPhysikalisches Institut der Universit¨ at Bern, Observatoire de Haute Provence (OHP) and Service dA´ eronomiedu CNRS under the leadership of Observatoire de de Gen` eve, on ESOs side substantial contributions camefrom La Silla Observatory and the Instrumentation Division at the Garching Headquarters. More details of thehistory can be found in Mayor.

Asteroseismology: oscillations on the star Procyon.

Abstract: Arising from: J. M. Matthews et al. Nature 430, 51–53 (2004) Stars are spheres of hot gas whose interiors transmit acoustic waves very efficiently. Geologists learn about the interior structure of Earth by monitoring how seismic waves propagate through it and, in a similar way, the interior of a star can be probed using the periodic motions on the surface that arise from such waves. Matthews et al. claim that the star Procyon does not have acoustic surface oscillations of the strength predicted1. However, we show here, using ground-based spectroscopy, that Procyon is oscillating, albeit with an amplitude that is only slightly greater than the noise level observed by Matthews et al. using spaced-based photometry.