title: Precise stellar surface gravities from the time scales of convectively driven brightness variations.
abstract: A significant part of the intrinsic brightness variations in cool stars of low and intermediate mass arises from surface convection (seen as granulation) and acoustic oscillations (p-mode pulsations). The characteristics of these phenomena are largely determined by the stars' surface gravity (g). Detailed photometric measurements of either signal can yield an accurate value of g. However, even with ultraprecise photometry from NASA's Kepler mission, many stars are too faint for current methods or only moderate accuracy can be achieved in a limited range of stellar evolutionary stages. This means that many of the stars in the Kepler sample, including exoplanet hosts, are not sufficiently characterized to fully describe the sample and exoplanet properties. We present a novel way to measure surface gravities with accuracies of about 4%. Our technique exploits the tight relation between g and the characteristic time scale of the combined granulation and p-mode oscillation signal. It is applicable to all stars with a convective envelope, including active stars. It can measure g in stars for which no other analysis is now possible. Because it depends on the time scale (and no other properties) of the signal, our technique is largely independent of the type of measurement (for example, photometry or radial velocity measurements) and the calibration of the instrumentation used. However, the oscillation signal must be temporally resolved; thus, it cannot be applied to dwarf stars observed by Kepler in its long-cadence mode.
authors.affiliation: Institute of Astrophysics, University of Vienna, Türkenschanzstrasse 17, Vienna 1180, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Kallinger
authors.affiliation: Max-Planck-Institute für Sonnensystemforschung, Justus-von-Liebig-Weg 3, Göttingen 37077, Germany.; Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, Aarhus C 8000, Denmark.
authors.forename: Saskia
authors.identifier: 0000-0002-1463-726X
authors.initials: S
authors.lastname: Hekker
authors.affiliation: Laboratoire AIM, CEA/DSM-CNRS, Université Paris Diderot-IRFU/SAp, Centre de Saclay, Gif-sur-Yvette Cedex 91191, France.
authors.forename: Rafael A
authors.identifier: 0000-0002-8854-3776
authors.initials: RA
authors.lastname: García
authors.affiliation: Sydney Institute for Astronomy, School of Physics, University of Sydney, Sydney, New South Wales 2006, Australia.; SETI Institute, 189 Bernardo Avenue, Mountain View, CA 94043, USA.; Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, Aarhus C 8000, Denmark.
authors.forename: Daniel
authors.initials: D
authors.lastname: Huber
authors.affiliation: Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia V6T 1Z1, Canada.
authors.forename: Jaymie M
authors.initials: JM
authors.lastname: Matthews
mesh_terms: D001256:Astronomy / Q000379:methods*; D005118:Extraterrestrial Environment; D006112:Gravitation; D055609:Stars, Celestial
keywords: Stars; convection; granulation; stellar fundamental parameters; stellar oscillations