A new Hyper-Runaway star discovered from LAMOST and GAIA: ejected almost in the galactic rotation direction

TL;DR

This paper reports the discovery of a new hyper-runaway star from LAMOST and GAIA data, analyzing its properties and possible ejection mechanisms, suggesting it was ejected from the Galactic disk likely due to supernova or stellar interactions.

Contribution

The paper presents the first identification and detailed analysis of a new hyper-runaway star, including its trajectory and potential ejection origin, based on combined LAMOST and GAIA data.

Findings

Star is either a B-type main sequence or blue horizontal branch star.

Star's trajectory intersects with the Galactic disk, excluding the Galactic center as origin.

Likely ejected from the Galactic disk by supernova or stellar interactions.

Abstract

In this paper, we report the discovery of a new late-B type unbound hyper-runaway star (LAMOST-HVS4) from the LAMOST spectroscopic surveys. According to its atmospheric parameters, it is either a B-type main sequence (MS) star or a blue horizontal branch (BHB) star. Its Galactocentric distance and velocity are 30.3 +/- 1.6 kpc and 586 +/- 7 km/s if it is an MS star, and they are 13.2 +/- 3.7 kpc and 590 +/- 7 km/s if a BHB star. We track its trajectories back, and find that the trajectories intersect with the Galactic disk and the Galactic center lies outside of the intersection region at the 3 sigma confidence level. We investigate a number of mechanisms that could be responsible for the ejection of the star, and find that it is probably ejected from the Galactic disk by supernova explosion or multiple-body interactions in dense young stellar clusters.