Linking chromospheric activity and magnetic field properties for late-type dwarf stars

Monthly Notices of the Royal Astronomical Society, vol. 514, pp. 4300–4319

Abstract

ABSTRACT Spectropolarimetric data allow for simultaneous monitoring of stellar chromospheric $\log {R^{\prime }_{\rm {HK}}}$ activity and the surface-averaged longitudinal magnetic field, Bl, giving the opportunity to probe the relationship between large-scale stellar magnetic fields and chromospheric manifestations of magnetism. We present $\log {R^{\prime }_{\rm {HK}}}$ and/or Bl measurements for 954 mid-F to mid-M stars derived from spectropolarimetric observations contained within the PolarBase database. Our magnetically active sample complements previous stellar activity surveys that focus on inactive planet-search targets. We find a positive correlation between mean $\log {R^{\prime }_{\rm {HK}}}$ and mean log |Bl|, but for G stars the relationship may undergo a change between $\log {R^{\prime }_{\rm {HK}}}\sim -4.4$ and −4.8. The mean $\log {R^{\prime }_{\rm {HK}}}$ shows a similar change with respect to the $\log {R^{\prime }_{\rm {HK}}}$ variability amplitude for intermediately active G stars. We also combine our results with archival chromospheric activity data and published observations of large-scale magnetic field geometries derived using Zeeman–Doppler Imaging. The chromospheric activity data indicate a slight under-density of late-F to early-K stars with $-4.75\le \log {R^{\prime }_{\rm HK}}\le -4.5$. This is not as prominent as the original Vaughan–Preston gap, and we do not detect similar under-populated regions in the distributions of the mean |Bl|, or the Bl and $\log {R^{\prime }_{\rm HK}}$ variability amplitudes. Chromospheric activity, activity variability, and toroidal field strength decrease on the main sequence as rotation slows. For G stars, the disappearance of dominant toroidal fields occurs at a similar chromospheric activity level as the change in the relationships between chromospheric activity, activity variability, and mean field strength.

Authors 11

1. E. L. Brown

   University of Southern Queensland

   Affiliation as printed

   University of Southern Queensland, Centre for Astrophysics , Toowoomba, QLD 4350, Australia

2. S. V. Jeffers

   Max Planck Institute for Solar System Research

   Affiliation as printed

   Solar and Stellar Interiors Department, Max Planck Institut for Solar System Research , Justus-von-Liebig-Weg 3, D-37077 Göttingen, Germany

3. S. C. Marsden

   University of Southern Queensland

   Affiliation as printed

   University of Southern Queensland, Centre for Astrophysics , Toowoomba, QLD 4350, Australia

4. J. Morin

   Centre National de la Recherche Scientifique · Université de Montpellier · Laboratoire Univers et Particules de Montpellier

   Affiliation as printed

   LUPM, Université de Montpellier , CNRS, Place Eugéne Bataillon, F-34095 Montpellier, France

5. S. Boro Saikia

   University of Vienna

   Affiliation as printed

   University of Vienna, Department of Astrophysics , Turkenschanzstrasse 17, A-1180 Vienna, Austria

6. Pascal M. Petit

   Centre National de la Recherche Scientifique · Institut de Recherche en Astrophysique et Planétologie · Université de Toulouse

   Affiliation as printed

   Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse , CNRS, CNES, F-31400 Toulouse, France

7. M. Jardine

   University of St Andrews

   Affiliation as printed

   SUPA, School of Physics and Astronomy, University of St Andrews , North Haugh, St Andrews KY16 9SS, UK

8. Victor See

   University of Exeter · European Space Agency · European Space Research and Technology Centre

   Affiliation as printed

   European Space Agency (ESA), European Space Research and Technology Centre (ESTEC) , Keplerlaan 1, NL-2201 AZ Noordwijk, the Netherlands

   University of Exeter, Department of Physics & Astronomy , Stoker Road, Devon, Exeter EX4 4QL, UK

9. A. A. Vidotto Aachen Leiden Observatory

   Leiden University · Trinity College Dublin · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden, the Netherlands

   School of Physics, Trinity College Dublin, The University of Dublin , College Green, Dublin-2, Ireland

10. Matthew W. Mengel

    University of Southern Queensland

    Affiliation as printed

    University of Southern Queensland, Centre for Astrophysics , Toowoomba, QLD 4350, Australia

11. Merten Nikolay Dahlkemper

    European Organization for Nuclear Research · University of Göttingen

    Affiliation as printed

    CERN, Teacher and Student Programmes , Esplanade de Particules 1, CH-1211 Genève 23, Switzerland

    University of Göttingen, Physics Education Research , Friedrich Hund Platz 1, D-37077 Göttingen, Germany