Simulating starspot activity jitter for spectral types F--M: realistic estimates for a representative sample of known exoplanet hosts

TL;DR

This study models starspot activity to estimate the typical radial velocity jitter caused by starspots on stars from spectral types F to M, aiding in exoplanet detection efforts.

Contribution

It provides realistic simulations of starspot-induced RV jitter for a representative sample of known exoplanet host stars across spectral types F to M.

Findings

Estimated peak-to-peak RV jitter for different stellar types.

Characterized starspot activity levels across a sample of 15 stars.

Provided a reference for activity-induced RV variability in exoplanet surveys.

Abstract

Dark spots on the surface of active stars produce changes in the shapes of the spectral lines that mimic spurious Doppler shifts, compromising the detection of small planets by means of the radial velocity (RV) technique. Modelling the spot-driven RV variability (known as ``jitter'') and how it affects the RV data sets is therefore crucial to design efficient activity-filtering techniques and inform observing strategies. Here, we characterise starspots and simulate the radial velocity curves induced by them to determine typical jitter amplitudes for a representative sample of 15 known host stars spanning between F and M spectral type. We collect information on the $\log R'_{\mathrm{HK}}$ activity index from the literature for 205 stars and, due to a lack of data in the temperature range 4000-4500 K, we measure it for ten stars using archival data. Additional stellar parameters required for the simulations are collected from the literature or constrained by observational data, in order to derive realistic estimates. Our results can be used as reference to determine typical peak-to-peak spot-induced RV jitter in the visible domain that can be expected when targeting host stars with different properties.