# Turbulence and Rotation in Solar-Type Stars

## TL;DR

This study analyzes turbulence velocities and their depth distribution in the photospheres of solar-type stars using high-resolution spectra, revealing how turbulence varies with stellar parameters and rotation.

## Contribution

It provides new estimates of micro- and macroturbulence velocities and their depth profiles in 13 stars, using Fourier analysis of spectral lines, and explores their relation to stellar temperature, gravity, and rotation.

## Key findings

- Macroturbulence increases with depth in stellar atmospheres.
- Higher temperature and faster rotation correlate with higher turbulence velocities.
- The ratio of macroturbulence to rotation velocity varies from 1 to 1.7 among stars.

## Abstract

Stellar spectra with a high resolution of 115000 obtained with the HARPS spectrograph provide an opportunity to examine turbulence velocities and their depth distributions in the photosphere of stars. Fourier analysis was performed for 17 iron lines in the spectra of 13 stars with an effective temperature of 4900--6200 K and a logarithm of surface gravity of 3.9--5.0 as well as in the spectrum of the Sun as a star. Models of stellar atmospheres were taken from the MARCS database. The standard concept of isotropic Gaussian microturbulence was assumed in this study. A satisfactory fit between the synthesized profiles of spectral lines and observational data verified the reliability of the Fourier method. The most likely estimates of turbulence velocities, the rotation velocity, and the iron abundance and their photospheric depth distribution profiles were obtained as a result. Microturbulence does not vary to any significant degree with depth, while macroturbulence has a marked depth dependence. The macroturbulence velocity increases with depth in the stellar atmosphere. The higher the effective temperature of a star and the stronger the surface gravity, the steeper the expected macroturbulence gradient. The mean macroturbulence velocity increases for stars with higher temperatures, weaker gravity, and faster rotation. The mean macro- and microturbulence velocities are correlated with each other and with the rotation velocity in the examined stars. The ratio between the macroturbulence velocity and the rotation velocity in solar-type stars varies from 1 (the hottest stars) to 1.7 (the coolest stars). The age dependence of the rotation velocity is more pronounced than that of the velocity of macroturbulent motions.