Astrometric effects of solar-like magnetic activity in late-type stars and their relevance for the detection of extrasolar planets

Abstract

Using a simple model based on the characteristics of sunspots and faculae in solar active regions, the effects of surface brightness inhomogeneities on the position of the photocentre of the disk of a solar-like, magnetically active star, are studied. A general law is introduced, giving the maximum amplitude of the photocentre excursion produced by a distribution of active regions with a given surface filling factor. The consequences for the detection of extrasolar planets by means of the astrometric method are investigated with some applications to forthcoming space missions, such as GAIA and SIM, as well as to ground-based interferometric measurements. Spurious detections of extrasolar planets can indeed be caused by activity-induced photocentre oscillations, requiring a simultaneous monitoring of the optical flux and a determination of the rotation period and of the level of activity of the target stars for an appropriate discrimination.

17 pages, 6 figures, accepted by New Astronomy

References in corpus (2)

• The Extrasolar Planet epsilon Eridani b - Orbit and Mass
• Comparing different approaches to model the rotational modulation of the Sun as a star

Cited by in corpus (6)

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• A new estimation of astrometric exoplanet detection limits in the habitable zone around nearby stars
• Predictions of astrometric jitter for Sun-like stars. I. The model and its application to the Sun as seen from the ecliptic
• Multiwavelength Mitigation of Stellar Activity in Astrometric Planet Detection