Time evolution of magnetic activity cycles in young suns: The curious case of kappa Ceti

S. Boro Saikia (1) , T. Lueftinger (2) , C. P. Folsom (3, 4) , A. Antonova (5) , Evelyne Alecian (6) , J. -F. Donati (7) , M. Guedel (1) , J. C. Hall (8) , S. V. Jeffers (9) , O. Kochukhov (10) , S. C. Marsden (11) , Y. T. Metodieva (1) , M. Mittag (12) , Julien Morin (13) , V. Perdelwitz (12, 14) , P. Petit (7) , M. Schmid (1) , A. A. Vidotto (15, 16)

1 University of Vienna [Vienna]
2 ESTEC - European Space Research and Technology Centre
3 RMCC - Royal Military College of Canada
4 University of Tartu
5 Institute of Astronomy of the Bulgarian Academy of Sciences
6 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
7 IRAP - Institut de recherche en astrophysique et planétologie
8 Lowell Observatory [Flagstaff]
9 MPS - Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research
10 Uppsala University
11 USQ - University of Southern Queensland
12 UHH - Universität Hamburg
13 LUPM - Laboratoire Univers et Particules de Montpellier
14 Ariel University
15 Trinity College Dublin
16 Universiteit Leiden = Leiden University

A detailed investigation of the magnetic properties of young Sun-like stars can provide valuable information on our Sun's magnetic past and its impact on the early Earth. We determine the properties of the moderately rotating young Sun-like star kappa Ceti's magnetic and activity cycles using 50 years of chromospheric activity data and six epochs of spectropolarimetric observations. The chromospheric activity was determined by measuring the flux in the Ca II H and K lines. A generalised Lomb-Scargle periodogram and a wavelet decomposition were used on the chromospheric activity data to establish the associated periodicities. The vector magnetic field of the star was reconstructed using the technique of Zeeman Doppler imaging on the spectropolarimetric observations. Our period analysis algorithms detect a 3.1 year chromospheric cycle in addition to the star's well-known ~6 year cycle period. Although the two cycle periods have an approximate 1:2 ratio, they exhibit an unusual temporal evolution. Additionally, the spectropolarimetric data analysis shows polarity reversals of the star's large-scale magnetic field, suggesting a ~10 year magnetic or Hale cycle. The unusual evolution of the star's chromospheric cycles and their lack of a direct correlation with the magnetic cycle establishes kappa Ceti as a curious young Sun. Such complex evolution of magnetic activity could be synonymous with moderately active young Suns, which is an evolutionary path that our own Sun could have taken.

Domaines: Astrophysique [astro-ph]; Astrophysique stellaire et solaire [astro-ph.SR]

S. Boro Saikia, T. Lueftinger, C. P. Folsom, A. Antonova, Evelyne Alecian, et al.. Time evolution of magnetic activity cycles in young suns: The curious case of kappa Ceti. Astronomy and Astrophysics - A&A, 2022, 658, pp.A16. ⟨10.1051/0004-6361/202141525⟩. ⟨hal-03428844⟩