A VIMOS spectroscopy of photometric variables and straggler candidates in omega Centauri

TL;DR

This study uses VIMOS spectroscopy to analyze photometric variables and straggler candidates in omega Centauri, confirming cluster membership and revealing a high binary fraction among blue stragglers.

Contribution

It provides the first spectroscopic confirmation of membership and binary status for a significant sample of variables and stragglers in omega Centauri.

Findings

Velocity variations detected in 22 objects

54 out of 74 candidates confirmed as cluster members

Blue straggler binary fraction may be as high as 69%

Abstract

We report a spectroscopic study of 19 photometric variables and 55 blue, yellow and red straggler candidates in the field of omega Centauri. We confirm the cluster membership of 18 variables and 54 straggler candidates. Velocity variations are detected in 22 objects, and another 17 objects are classified as suspected of being velocity-variable. Velocity data of 11 photometric variables phase with their photometric periods, however none of these objects has a mass function indicating the presence of a massive degenerate component. Based on both photometric and spectroscopic data we find that the fraction of binaries among blue stragglers may be as high as 69 per cent.