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Free keywords:
Stellar activity; Solar activity; Astrometric exoplanet detection; Stellar atmospheres
Abstract:
The advent of Gaia, capable of measuring stellar wobbles caused by orbiting planets, raised interest in the astrometric detection of exoplanets. Another source of such wobbles (often also called jitter) is stellar magnetic activity. A quantitative assessment of the stellar astrometric jitter is important for a more reliable astrometric detection and characterization of exoplanets. We calculate the displacement of the solar photocenter due to the magnetic activity for an almost 16 yr period (1999 February 2-2014 August 1). We also investigate how the displacement depends on the spectral passband chosen for observations, including the wavelength range to be covered by the upcoming Small-JASMINE mission of JAXA. This is done by extending the SATIRE-S model for solar irradiance variability to calculating the displacement of the solar photocenter caused by the magnetic features on the surface of the Sun. We found that the peak-to-peak amplitude of the solar photocenter displacement would reach 0.5 mu as if the Sun were located 10 pc away from the observer and observed in the Gaia G filter. This is by far too small to be detected by the Gaia mission. However, the Sun is a relatively inactive star so one can expect significantly larger signals for younger, and, consequently, more active stars. The model developed in this study can be combined with the simulations of emergence and surface transport of magnetic flux which have recently become available to model the astrometric jitter over the broad range of magnetic activities.
