Stellar activity as noise in exoplanet detection II. Application to M dwarfs

TL;DR

This study examines how starspot activity on M dwarf stars affects the detection and characterization of exoplanets via radial velocity measurements, highlighting the challenges posed by stellar activity.

Contribution

It introduces a method to simulate starspot-induced RV jitter and assesses its impact on exoplanet detection around active M dwarfs.

Findings

Starspot activity can cause significant deviations in RV measurements.

Even low spot coverage can affect planet detection within the habitable zone.

Higher activity levels increase the difficulty of accurate planetary parameter recovery.

Abstract

The ubiquity of M dwarf stars combined with their low masses and luminosities make them prime targets in the search for nearby, habitable exoplanets. We investigate the effects of starspot-induced radial velocity (RV) jitter on detection and characterization of planets orbiting M dwarfs. We create surface spot configurations with both random spot coverage and active regions. Synthetic stellar spectra are calculated from a given spot map, and RV measurements are obtained using cross-correlation technique. We add the RV signal of an orbiting planet to these jitter measurements, and reduce the data to "measure" the planetary parameters. We investigate the detectability of planets around M dwarfs of different activity levels, and the recovery of input planetary parameters. When studying the recovery of the planetary period we note that while our original orbital radius places the planet inside the HZ of its star, even at a filling factor of 2% a few of our measurements fall outside the "conservative Habitable Zone". Higher spot filling factors result in more and higher deviations. Our investigations suggest that caution should be used when characterizing planets discovered with the RV method around stars that are (or are potentially) active.