Radial Velocity Planet Detection Biases at the Stellar Rotational Period

TL;DR

This paper investigates how stellar activity, especially rotational modulation, biases the detection of Earth-like planets via radial velocity methods, emphasizing the need for simultaneous photometry and multi-wavelength spectroscopy.

Contribution

It provides data-driven models quantifying stellar activity noise and its impact on exoplanet detection, highlighting the challenge of distinguishing planetary signals from stellar rotation effects.

Findings

Stellar activity noise timescales match habitable zone orbital periods around early M-dwarfs.

Monitoring stellar rotation via photometry is crucial for RV planet detection.

Activity signals can be mitigated using spectroscopic indicators and multi-wavelength RV measurements.

Abstract

Future generations of precise radial velocity (RV) surveys aim to achieve sensitivity sufficient to detect Earth mass planets orbiting in their stars' habitable zones. A major obstacle to this goal is astrophysical radial velocity noise caused by active areas moving across the stellar limb as a star rotates. In this paper, we quantify how stellar activity impacts exoplanet detection with radial velocities as a function of orbital and stellar rotational periods. We perform data-driven simulations of how stellar rotation affects planet detectability and compile and present relations for the typical timescale and amplitude of stellar radial velocity noise as a function of stellar mass. We show that the characteristic timescales of quasi-periodic radial velocity jitter from stellar rotational modulations coincides with the orbital period of habitable zone exoplanets around early M-dwarfs. These coincident periods underscore the importance of monitoring the targets of RV habitable zone planet surveys through simultaneous photometric measurements for determining rotation periods and activity signals, and mitigating activity signals using spectroscopic indicators and/or RV measurements at different wavelengths.