Photospheric and chromospheric magnetic activity of seismic solar analogs

Observational inputs on the solar-stellar connection from Kepler and Hermes ^⋆

¹ Laboratoire AIM, CEA/DRF-CNRS, Université Paris 7 Diderot, IRFU/SAp, Centre de Saclay, 91191 Gif-sur-Yvette, France
e-mail: david.salabert@cea.fr
² High Altitude Observatory, National Center for Atmospheric Research, PO Box 3000, Boulder, CO 80307-3000, USA
³ Department of Physics, Montana State University, Bozeman, MT 59717-3840, USA
⁴ Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
⁵ Departamento de Astrofísica, Universidad de La Laguna, 38205 La Laguna, Tenerife, Spain
⁶ Space Science Institute, 4750 Walnut street Suite#205, Boulder, CO 80301, USA
⁷ Visiting Scientist, National Solar Observatory, 3665 Discovery Dr., Boulder, CO 80303, USA
⁸ Universidade Federal do Rio Grande do Norte, UFRN, Dep. de Física, DFTE, CP1641, 59072-970 Natal, RN, Brazil
⁹ Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA
¹⁰ Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark

Received: 23 March 2016
Accepted: 3 August 2016

Abstract

We identify a set of 18 solar analogs among the seismic sample of solar-like stars observed by the Kepler satellite rotating between 10 and 40 days. This set is constructed using the asteroseismic stellar properties derived using either the global oscillation properties or the individual acoustic frequencies. We measure the magnetic activity properties of these stars using observations collected by the photometric Kepler satellite and by the ground-based, high-resolution Hermes spectrograph mounted on the Mercator telescope. The photospheric (S_ph) and chromospheric ( index) magnetic activity levels of these seismic solar analogs are estimated and compared in relation to the solar activity. We show that the activity of the Sun is comparable to the activity of the seismic solar analogs, within the maximum-to-minimum temporal variations of the 11-yr solar activity cycle 23. In agreement with previous studies, the youngest stars and fastest rotators in our sample are actually the most active. The activity of stars older than the Sun seems to not evolve much with age. Furthermore, the comparison of the photospheric, S_ph, with the well-established chromospheric, index, indicates that the S_ph index can be used to provide a suitable magnetic activity proxy which can be easily estimated for a large number of stars from space photometric observations.