The impact of unresolved magnetic spots on high precision radial velocity measurements

TL;DR

This paper models how unresolved magnetic spots on stars can create noise in radial velocity measurements, affecting exoplanet detection, especially for Earth-like planets, and highlights the importance of understanding stellar magnetic activity.

Contribution

It introduces a star model based on Epsilon Eridani to simulate magnetic spot effects on radial velocities, revealing their impact on exoplanet detection.

Findings

Magnetic spots can induce radial velocity signals up to 10 m/s.

Spot distribution significantly influences radial velocity measurements.

Understanding stellar magnetic activity is crucial for detecting Earth-like exoplanets.

Abstract

The Doppler method of exoplanet detection has been extremely successful, but suffers from contaminating noise from stellar activity. In this work a model of a rotating star with a magnetic field based on the geometry of the K2 star Epsilon Eridani is presented and used to estimate its effect on simulated radial velocity measurements. A number of different distributions of unresolved magnetic spots were simulated on top of the observed large-scale magnetic maps obtained from eight years of spectropolarimetric observations. The radial velocity signals due to the magnetic spots have amplitudes of up to 10 m s$^{-1}$, high enough to prevent the detection of planets under 20 Earth masses in temperate zones of solar type stars. We show that the radial velocity depends heavily on spot distribution. Our results emphasize that understanding stellar magnetic activity and spot distribution is crucial for detection of Earth analogues.