Starspot Jitter in Photometry, Astrometry and Radial Velocity Measurements

TL;DR

This paper derives analytical relations for starspot-induced jitter in photometry, astrometry, and radial velocity measurements, compares these with observations and simulations, and assesses implications for exoplanet detection sensitivity.

Contribution

It introduces new analytical formulas for starspot jitter effects and evaluates their impact on high-precision exoplanet detection methods.

Findings

Starspot jitter amplitude estimated for specific stars.

Comparison of jitter with observational data and simulations.

Implication that stellar activity limits planet detection sensitivity.

Abstract

Analytical relations are derived for the amplitude of astrometric, photometric and radial velocity perturbations caused by a single rotating spot. The relative power of the star spot jitter is estimated and compared with the available data for $\kappa^1$ Ceti and HD 166435, as well as with numerical simulations for $\kappa^1$ Ceti and the Sun. A Sun-like star inclined at $i=90\degr$ at 10 pc is predicted to have a RMS jitter of 0.087 \uas in its astrometric position along the equator, and 0.38 m s$^{-1}$ in radial velocities. If the presence of spots due to stellar activity is the ultimate limiting factor for planet detection, the sensitivity of SIM Lite to Earth-like planets in habitable zones is about an order of magnitude higher that the sensitivity of prospective ultra-precise radial velocity observations of nearby stars.