The Activity Cycle of tau Ceti
Abstract
The temperature, granulation, and chromospehric emission of tau Ceti (HR 509, HD 10700, G8 V, B-V = 0.72) in the 1984-1992 interval are studied for magnetic-cycle type variations. Yearly-mean temperature measurements are determined to +/- 3-4 K using ratios of spectral line depths, and show no systematic variations over the 9 yr interval. Granulation is monitored using the asymmetries of spectral lines. There is some indication of systematic variation in velocity span, but this variation is not well established. The Ca II H and K line emission, although weak by stellar standards, may show two cycles of variability in the 1970-1992 time span with a period of approximately = 11 yr. No rotation modulation is seen in any of the parameters, but the very narrow spectral lines of tau Cet points to a nearly pole-on orientation so that none would be expected.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 1994
- DOI:
- 10.1086/174210
- Bibcode:
- 1994ApJ...427.1042G
- Keywords:
-
- Astronomical Spectroscopy;
- Chromosphere;
- Dwarf Stars;
- Stellar Activity;
- Stellar Magnetic Fields;
- Stellar Spectra;
- Stellar Temperature;
- H Lines;
- K Lines;
- Line Spectra;
- Spectral Emission;
- Stellar Rotation;
- Variations;
- Velocity Distribution;
- Astrophysics;
- STARS: ACTIVITY;
- STARS: INDIVIDUAL CONSTELLATION NAME: TAU CETI;
- TECHNIQUES: SPECTROSCOPIC