Rotation and magnetism of Kepler pulsating solar-like stars

Towards asteroseismically calibrated age-rotation relations^⋆

¹ Laboratoire AIM, CEA/DSM – CNRS – Univ. Paris Diderot – IRFU/SAp, Centre de Saclay, 91191 Gif-sur-Yvette Cedex, France
e-mail: rgarcia@cea.fr
² Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
³ Department of Astronomy, The Ohio State University, Columbus, Ohio 43210, USA
⁴ CNRS, Institut de Recherche en Astrophysique et Planétologie, 14 avenue Édouard Belin, 31400 Toulouse, France
⁵ Université de Toulouse, UPS-OMP, IRAP, 31400 Toulouse, France
⁶ Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
⁷ Department of Astrophysics, IMAPP, Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands
⁸ School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
⁹ Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA
¹⁰ U. Federal do Rio Grande do Norte, UFRN, Dep. de Física Teórica e Experimental, DFTE, CP 1641, 59072-970 Natal, RN, Brazil
¹¹ Stellar Astrophysics Centre, Dept. of Physics and Astronomy, Aarhus Univ., Ny Munkegade 120, 8000 Aarhus C, Denmark
¹² Institut für Astrophysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
¹³ Max-Planck Institute for Solar System Research Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
¹⁴ Instituto de Astrofísica de Andalucía (CSIC), 3004 Granada, Spain
¹⁵ Universidad de La Laguna, Dpto de Astrofísica, 38206 Tenerife, Spain
¹⁶ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain

Received: 26 March 2014
Accepted: 24 September 2014

Abstract

Kepler ultra-high precision photometry of long and continuous observations provides a unique dataset in which surface rotation and variability can be studied for thousands of stars. Because many of these old field stars also have independently measured asteroseismic ages, measurements of rotation and activity are particularly interesting in the context of age-rotation-activity relations. In particular, age-rotation relations generally lack good calibrators at old ages, a problem that this Kepler sample of old-field stars is uniquely suited to address. We study the surface rotation and photometric magnetic activity of a subset of 540 solar-like stars on the main-sequence and the subgiant branch for which stellar pulsations have been measured. The rotation period was determined by comparing the results from two different analysis methods: i) the projection onto the frequency domain of the time-period analysis, and ii) the autocorrelation function of the light curves. Reliable surface rotation rates were then extracted by comparing the results from two different sets of calibrated data and from the two complementary analyses. General photometric levels of magnetic activity in this sample of stars were also extracted by using a photometric activity index, which takes into account the rotation period of the stars. We report rotation periods for 310 out of 540 targets (excluding known binaries and candidate planet-host stars); our measurements span a range of 1 to 100 days. The photometric magnetic activity levels of these stars were computed, and for 61.5% of the dwarfs, this level is similar to the range, from minimum to maximum, of the solar magnetic activity. We demonstrate that hot dwarfs, cool dwarfs, and subgiants have very different rotation-age relationships, highlighting the importance of separating out distinct populations when interpreting stellar rotation periods. Our sample of cool dwarf stars with age and metallicity data of the highest quality is consistent with gyrochronology relations reported in the literature.