MAGNETIC ACTIVITY VARIATIONS OF EPSILON-ERIDANI

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 almost-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 almost-equal-to 15 K and almost-equal-to 35 m s-1, respectively. 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.