Accounting for Convective Blue-Shifts in the Determination of Absolute Stellar Radial Velocities

TL;DR

This paper shows how 3D hydrodynamical simulations and stellar models can correct for convective blue-shifts and gravitational redshifts, enabling precise absolute stellar radial velocity measurements with uncertainties below 0.1 km/s.

Contribution

It introduces a method combining simulations and stellar data to accurately account for convective and gravitational effects in radial velocity determinations.

Findings

Convective blue-shifts can be predicted to within ~0.070 km/s using 3D simulations.

Gravitational redshifts can be constrained with similar precision using stellar models.

Absolute radial velocities can be measured with uncertainties better than ~0.1 km/s.

Abstract

For late-type non-active stars, gravitational redshifts and convective blueshifts are the main source of biases in the determination of radial velocities. If ignored, these effects can introduce systematic errors of the order of ~ 0.5 km/s. We demonstrate that three-dimensional hydrodynamical simulations of solar surface convection can be used to predict the convective blue-shifts of weak spectral lines in solar-like stars to ~ 0.070 km/s. Using accurate trigonometric parallaxes and stellar evolution models, the gravitational redshifts can be constrained with a similar uncertainty, leading to absolute radial velocities accurate to better than ~ 0.1 km/s.