Precise radial velocities of giant stars. IV. A correlation between surface gravity and radial velocity variation and a statistical investigation of companion properties

Abstract

Since 1999, we have been conducting a radial velocity survey of 179 K giants using the CAT at UCO/Lick observatory. At present ~20-100 measurements have been collected per star with a precision of 5 to 8 m/s. Of the stars monitored, 145 (80%) show radial velocity (RV) variations at a level >20 m/s, of which 43 exhibit significant periodicities. Our aim is to investigate possible mechanism(s) that cause these observed RV variations. We intend to test whether these variations are intrinsic in nature, or possibly induced by companions, or both. In addition, we aim to characterise the parameters of these companions. A relation between log g and the amplitude of the RV variations is investigated for all stars in the sample. Furthermore, the hypothesis that all periodic RV variations are caused by companions is investigated by comparing their inferred orbital statistics with the statistics of companions around main sequence stars. A strong relation is found between the amplitude of the RV variations and log g in K giant stars, as suggested earlier by Hatzes & Cochran (1998). However, most of the stars exhibiting periodic variations are located above this relation. These RV variations can be split in a periodic component which is not correlated with log g and a random residual part which does correlate with log g. Compared to main-sequence stars, K giants frequently exhibit periodic RV variations. Interpreting these RV variations as being caused by companions, the orbital param eters are different from the companions orbiting dwarfs. Intrinsic mechanisms play an important role in producing RV variations in K giants stars, as suggested by their dependence on log g. However, it appears that periodic RV variations are additional to these intrinsic variations, consistent with them being caused by companions.

10 pages, accepted by A&A

References in corpus (21)

• Catalog of Nearby Exoplanets
• Towards a deterministic model of planetary formation. III. Mass distribution of short-period planets around stars of various masses
• Core-Accretion Model Predicts Few Jovian-Mass Planets Orbiting Red Dwarfs
• Observed Properties of Exoplanets: Masses, Orbits, and Metallicities
• The Lick Planet Search: Detectability and Mass Thresholds
• Spectroscopic metallicities for planet-host stars: extending the samples
• Retired A Stars and Their Companions: Exoplanets Orbiting Three Intermediate-Mass Subgiants
• Precise radial velocities of giant stars. III. Spectroscopic stellar parameters
• Evolved stars hint to an external origin of enhanced metallicity in planet-hosting stars
• Confirmation of the Planet Hypothesis for the Long-period Radial Velocity Variations of Beta Geminorum
• An Eccentric Hot Jupiter Orbiting the Subgiant HD 185269
• A Planetary Mass Companion to the K0 Giant HD 17092
• A substellar companion around the intermediate-mass giant star HD 11977
• Precise Radial Velocities of Giant Stars II. Pollux and its Planetary Companion
• The brown dwarf desert as a consequence of orbital migration
• Precise radial velocities of giant stars: I. Stable stars
• A Strategy for Identifying the Grid Stars for the Space Interferometry Mission (SIM)
• Discovery of a planet around the K giant star 4 UMa
• Solar-like oscillations in Procyon A
• p-mode frequencies in solar-like stars : I. Procyon A
• Solar-like oscillations in the metal-poor subgiant nu Indi: constraining the mass and age using asteroseismology

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