Premium
Changing stellar activity cycles
Author(s) -
Oláh K.,
Strassmeier K.G.,
Granzer T.,
Soon W.,
Baliunas S.L.
Publication year - 2007
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.200710839
Subject(s) - stars , physics , astrophysics , star (game theory) , fourier analysis , rotation period , fourier transform , stellar rotation , quantum mechanics
We investigated continuous long‐term photometric datasets of thirteen active stars, Ca II variability of one single mainsequence star, and 10.7 cm radio data of the Sun, with simple Fourier‐ and time‐frequency analysis. The data reflect the strength of the activity manifested in magnetic spots. All studied stars show multiple (2 to 4) cycles of different lengths. The time‐frequency analysis reveals, that in several cases of the sample one or two of the cycles exhibit continuous changes (increase or decrease). For four stars (V711 Tau, IL Hya, HK Lac, HD 100180) and for the Sun we find that the cycle length changes are strong, amounting to 10–50% during the observed time intervals. The cycle lengths are generally longer for stars with longer rotational periods. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)