Radial velocities of giant stars: an investigation of line profile variations

TL;DR

This study analyzes radial velocity variations in 179 red giant stars to understand their causes, examining correlations with stellar parameters and line profile changes, to distinguish between planetary companions and stellar activity.

Contribution

It provides a detailed investigation of line profile variations and their relation to radial velocity changes in giant stars, advancing understanding of stellar activity versus planetary signals.

Findings

80% of monitored stars show RV variations >20 m/s

43 stars exhibit significant periodicities

Correlation between RV amplitude and surface gravity investigated

Abstract

Since 1999, a radial velocity survey of 179 red giant stars is ongoing at Lick Observatory with a one month cadence. At present ~20-100 measurements have been collected per star with an accuracy of 5 to 8 m/s. Of the stars monitored, 145 (80%) show radial velocity (RV) variations at a level >20 m/s, of which 43 exhibit significant periodicities. Here, we investigate the mechanism causing the observed radial velocity variations. Firstly, we search for a correlation between the radial velocity amplitude and an intrinsic parameter of the star, in this case surface gravity (log g). Secondly, we investigate line profile variations and compare these with theoretical predictions.