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General magnetic field on the weakly‐active yellow giant Pollux and on the old dwarf star 61 Cyg A
Author(s) -
Baklanova D.,
Plachinda S.,
Mkrtichian D.,
Han I.,
Kim K.M.
Publication year - 2011
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.201111590
Subject(s) - physics , astrophysics , dipole , light curve , astronomy , magnetic dipole , rotation period , radius , magnetic field , equator , observatory , stars , latitude , computer security , quantum mechanics , computer science
Pollux is yellow giant with known regular surface magnetic field about 1 Gauss. An analysis of the periodic behavior of the magnetic field of Pollux was performed. For this purpose, we used literature data together with spectropolarimetric observations, which were carried out during 10 nights in 2010 at the Crimean Astrophysical Observatory, and spectropolarimetric observations, which were obtained at Bohyunsan Optical Astronomy Observatory during 4 nights in 2007. The radial velocity measurements of Pollux show variations with a period of 592.9 days due to the planetary companion. The rotational period of the Pollux equals to 491.5 days. Improved dipole parameters are presented. The centered dipole gives the angle between spin axis and line of sight, i ∼ 45°, and the angle between the spin and dipole axes, β ∼ 135°. We suppose that a few points that lie outside of the dipole magnetic field curve by more than three errors are the result of the emergence of magnetic unipolar spots on the stellar surface. We discuss the possibility of these events in comparison with solar‐like star 61 Cyg A and the Sun. Numerical simulations of the magnetic geometry lead us to the conclusion that the spots may have an angular radius of ∼1.5° with the magnetic intensity ∼3000 G. Such active regions can be formed at the same latitudes as on the Sun near the 40° from the equator (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)