A search for Galactic runaway stars using Gaia Data Release 1 and Hipparcos proper motions

TL;DR

This study uses Gaia DR1 and Hipparcos proper motions to identify 76 runaway stars, including new discoveries, revealing insights into their ages, spectral types, and origins, especially the role of supernova explosions.

Contribution

First to utilize Gaia DR1 proper motions to detect runaway stars, identifying new candidates and analyzing their properties in comparison with previous surveys.

Findings

Detected 76 runaway stars, 17 possibly new.

Older runaways tend to have traveled longer distances.

High fraction of fast rotators among O star runaways.

Abstract

CONTEXT.The first Gaia Data Release (DR1) significantly improved the previously available proper motions for the majority of the Tycho-2 stars. AIMS. We want to detect runaway stars using Gaia DR1 proper motions and compare our results with previous searches. METHODS. Runaway O stars and BA supergiants are detected using a 2-D proper-motion method. The sample is selected using Simbad, spectra from our GOSSS project, literature spectral types, and photometry processed using CHORIZOS. RESULTS. We detect 76 runaway stars, 17 (possibly 19) of them with no prior identification as such, with an estimated detection rate of approximately one half of the real runaway fraction. An age effect appears to be present, with objects of spectral subtype B1 and later having travelled for longer distances than runaways of earlier subtypes. We also tentatively propose that the fraction of runaways is lower among BA supergiants that among O stars but further studies using future Gaia data releases are needed to confirm this. The frequency of fast rotators is high among runaway O stars, which indicates that a significant fraction of them (and possibly a majority) is produced in supernova explosions.