Observations of active-chromosphere stars – I. Spectroscopic study of AB Dor and PZ Tel

We present high-resolution spectroscopic data on the rapidly rotating late-type stars AB Dor (HD 36705) and PZ Tel (HD 174429). Both stars show chromospheric activity, with strong Ca II K emission and a filled-in Hα line, as noted previously by other workers. No apparent relationship holds between the level of Hα filling and rotation phase for either star. In one observing run of a few days there was a clear anticorrelation between the strength of Ca II K emission and the photometric wave for AB Dor. There is some indication, although the data are sparse, that this also occurred in an earlier observing run. For PZ Tel, lack of data prevents any conclusion about a possible relationship between the strength of Ca II K emission and the photometric wave. The radial velocity data strongly suggest that both stars are single. We find that the radial velocity of AB Dor is +28.0±4.6 km s−1 (39 measurements), in very good agreement with earlier work, while for PZ Tel, from 26 measurements, we find $\upsilon_\text r=-3.2\pm3.7 \enspace \text {km s}^{-1}$. These are the first radial velocity measurements for PZ Tel.