Microturbulence in A/F Am/Fm stars

TL;DR

This study measures microturbulent velocities in A and F type stars across different environments, revealing a maximum in mid-A spectral types and decreasing velocities in cooler and hotter stars, using high-resolution spectroscopy.

Contribution

It provides a comprehensive dataset of microturbulence in A/F stars across various clusters and field stars, and compares results with recent models and surveys.

Findings

Microturbulent velocities peak around A5V to A9V stars.

Velocities decrease to about 1 km/s in cooler and hotter stars.

Results agree with recent analytical formulations and Gaia-ESO survey data.

Abstract

A programme to observe all A dwarfs in open clusters brighter than V=6.5 mag of various ages and in the field was initiated several years ago. In this work we present the current status of microturbulent velocity for A and F dwarfs. We have performed high resolution high signal-to-noise spectroscopy of stars well distributed in mass along the Main Sequence. Microturbulent velocities are derived iteratively by fitting grids of synthetic spectra calculated in LTE to observed spectra of 61 A field stars, 55 A and 58 F in open clusters (Pleiades, Coma Berenices, Hyades and the Ursa Major moving group). We compared our results to recent works and found a good agreement with their analytical formulation for the standard microturbulence. Our results show a broad maximum for microturbulent velocities in the range A5V to about A9V and a decrease (to $\sim 1$ km/s) for cooler and hotter stars as indicated in Smalley (2004).We also present a comparison to preliminary science results of Lobel et al. (2013) for the Gaia-ESO Public Spectroscopic Survey.