%0 Journal Article
%T ɛ Eridani: an active K dwarf and a planet hosting star?. The variability of its large-scale magnetic field topology
%+ Institut für Astrophysik [Göttingen]
%+ Institut de recherche en astrophysique et planétologie (IRAP)
%+ University of Southern Queensland (USQ)
%+ Laboratoire Univers et Particules de Montpellier (LUPM)
%A Jeffers, Sandra, V.
%A Petit, Pascal
%A Marsden, Stephen, C.
%A Morin, Julien
%A Donati, Jean-François
%A Folsom, Colin, P.
%Z Based on observations made with Telescope Bernard Lyot (TBL, Pic du Midi, France) of the Observatoire Midi-Pyrenees, which is operated by the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France.
%< avec comité de lecture
%Z LUPM:14-032
%@ 0035-8711
%J Monthly Notices of the Royal Astronomical Society
%I Oxford University Press (OUP): Policy P - Oxford Open Option A
%V 569
%P A79
%8 2014
%D 2014
%Z 2014A&A...569A..79J
%R 10.1051/0004-6361/201423725
%K stars: activity
%K stars: magnetic field
%K starspots
%K magnetic fields
%Z Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR]Journal articles
%X The young K-dwarf ɛ Eridani is an example of a young active planet hosting star that has shown over long-term monitoring of its chromospheric emission to exhibit cyclic magnetic activity. In this paper, we investigate how ɛ Eridani's large-scale magnetic field geometry evolves over the timescale of its S-index cycle using spectropolarimetric observations and the technique of Zeeman-Doppler imaging. Our observations comprise six epochs secured over a time period of nearly seven years, with each almost yearly observational epoch showing a dramatic change in the large-scale magnetic field topology, with no stable regions. The poloidal field varies from strongly dipolar to mono-polar and the toroidal field is non-existent to begin with and then emerges to dominate the magnetic field energy before disappearing and re-emerging again. A potential cycle is detected in the poloidal field, but further observations are needed to confirm this.
%G English
%Z Bcool
%2 https://hal.science/hal-01770030/document
%2 https://hal.science/hal-01770030/file/2014A%26A...569A..79J.pdf
%L hal-01770030
%U https://hal.science/hal-01770030
%~ IN2P3
%~ IRD
%~ INSU
%~ METEO
%~ UNIV-TLSE3
%~ CNRS
%~ UNIV-MONTP2
%~ CNES
%~ OMP
%~ OMP-IRAP
%~ LUPM
%~ MIPS
%~ UNIV-MONTPELLIER
%~ LUPM_AS
%~ UNIV-UT3
%~ UT3-INP
%~ UT3-TOULOUSEINP
%~ UM1-UM2