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Magnetic activity variations of epsilon Eridani
Gray, David F.; Baliunas, Sallie L.
AA(University of Western Ontario, London, Ontario, Canada), AB(University of Western Ontario, London, Ontario, Canada)
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 441, no. 1, p. 436-442 (ApJ Homepage)
Publication Date:
NASA/STI Keywords:
K Stars, Magnetic Variations, Periodic Variations, Solar Granulation, Stellar Magnetic Fields, Stellar Rotation, Stellar Temperature, Astronomical Photometry, Astronomical Spectroscopy, Calcium, H Lines, K Lines, Spectral Emission
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The variations in magnetic activity, temperature and granulation of epsilon Eri (HR 1084, HD 22049, K2 V, B-V = 0.88) in the interval from 1986 to 1992 are discussed in this paper. We monitored the magnetic activity with the Ca II H and K-line emission, the temperature with the ratio of depths of two spectral lines, and the granulation with spectral-line asymmetries. Rotational modulation is seen only in the H and K emission, and it shows a period of 11.10 +/- 0.03 days, in agreement with earlier published values. The star has one dominant activity longitude. The magnetic activity of epsilon Eri is strong and shows irregular excursions that may be superposed on a cyclic variation having a period approximately equal to 5 yr. During the 1986-1992 interval the magnetic activity went through a broad relative minimum. Temperature and granulation changes mimic the variation in H and K emission, with excursions approximately equal to 15 K and approximately equal to 35 m/s, repectively. No long-term photometric observations are available for epsilon Eri, but we calculate a 1.2% variation in luminosity and 0.014 mag in V to have occurred, assuming the radius of the star is constant.

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