Observations of active-chromosphere stars - IV. Photometry and spectroscopy of CF Octantis (HD 196818)

Details Observations of active-chromosphere stars - IV. Photometry and spectroscopy of CF Octantis (HD 196818) Observations of active-chromosphere stars - IV. Photometry and spectroscopy of CF Octantis (HD 196818)

Aug 1997

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997mnras.289..515i&link_type=abstract

Monthly Notices of the Royal Astronomical Society, Volume 289, Issue 3, pp. 515-524.

Astronomy and Astrophysics

Astronomy

4

Stars: Activity, Stars: Chromospheres, Stars: Individual: Cf Oct (Hd 196818)

Scientific paper

We present photometry and spectroscopy of the single, K-type, active-chromosphere star CF Octantis (=HD 196818), from 1982 to 1986. The photometric data show the 20-d rotation period seen previously, and also demonstrate that the light curve is variable on time-scales of a few months, which we ascribe to variations in the properties of starspots. We postulate that a temporary dimming of minimum light seen in mid-1983 was a result of the appearance and later disappearance of a relatively small spot or spot group, which had a lifetime between 10 and 24 months. The main spot appeared relatively stable during the interval of our observations, with a lifetime of at least 3 years. Our radial velocity data are consistent with the results of other work in that no variations above observational scatter are seen. Both the Ca K and Hα emission are variable, with tentative evidence for the latter that a lower emission level occurred near the phase of photometric maximum, although the spectroscopic and photometric data were not contemporaneous. The lithium abundance is found to be log N(Li)=0.45+/-0.15. The star may have evolved from a rapidly rotating A-F main-sequence star.

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