Rotation periods of late-type dwarf stars from time-series high-resolution spectroscopy of chromospheric indicators

TL;DR

This study measures rotation periods of 48 late-type dwarf stars using high-resolution spectroscopy of chromospheric activity indicators, establishing a new empirical relation to predict stellar rotation from activity levels.

Contribution

It introduces an activity-based empirical relation for predicting rotation periods of late K to mid-M dwarfs, largely independent of spectral type and metallicity.

Findings

Good agreement between Ca II H&K and H-alpha indicators.

Established a reliable activity-rotation relation.

Some stars' rotation periods match planetary orbital periods.

Abstract

We determine rotation periods of a sample of 48 late F-type to mid-M dwarf stars using time-series high-resolution spectroscopy of the Ca II H&K and H-alpha chromospheric activity indicators. We find good agreement between the rotation periods obtained from each of these two indicators. An empirical relationship between the level of chromospheric emission measured by log (R'HK) and the spectroscopic rotation periods is reported. This relation is largely independent of the spectral type and the metallicity of the stars and can be used to make a reliable prediction of rotation periods for late K to mid-M dwarfs with low levels of activity. For some stars in the sample, the measured spectroscopic rotation periods coincide, or are very close, to the orbital periods of postulated planets. In such cases, further studies are needed to clarify whether the associated periodic radial velocity signals reveal the existence of planets or are due to magnetic activity.