Finding Exoplanets Orbiting Young Active Stars. I. Technique

TL;DR

This paper introduces a new technique to remove starspot signatures from stellar line-profiles, significantly reducing stellar jitter and enabling the detection of hot-Jupiter exoplanets around young, active stars with high rotational velocities.

Contribution

The paper presents a novel method for cleaning starspot signals from stellar line-profiles, improving radial velocity measurements for active stars.

Findings

Starspot signals can be reduced by over 80% in stellar line-profiles.

The method successfully recovers Jupiter-mass planets in simulated and real data.

It enables planet detection around stars previously too active for RV surveys.

Abstract

Stellar activity, such as starspots, can induce radial velocity (RV) variations that can mask or even mimic the RV signature of orbiting exoplanets. For this reason RV exoplanet surveys have been unsuccessful when searching for planets around young, active stars and are therefore failing to explore an important regime which can help to reveal how planets form and migrate. This paper describes a new technique to remove spot signatures from the stellar line-profiles of moderately rotating, active stars (vsini ranging from 10 to 50 km/s). By doing so it allows planetary RV signals to be uncovered. We used simulated models of a G5V type star with differing dark spots on its surface along with archive data of the known active star HD49933 to validate our method. The results showed that starspots could be effectively cleaned from the line-profiles so that the stellar RV jitter was reduced by more than 80%. Applying this procedure to the same models and HD49933 data, but with fake planets injected, enabled the effective removal of starspots so that Jupiter mass planets on short orbital periods were successfully recovered. These results show that this approach can be useful in the search for hot-Jupiter planets that orbit around young, active stars with a vsini of 10 - 50 km/s.