Observations of the extreme runaway HD271791: nucleosynthesis in a core-collapse supernova

TL;DR

This study investigates the extreme runaway star HD271791, suggesting it originated from a core-collapse supernova, and aims to analyze its elemental abundances to understand nucleosynthesis processes, including potential r-process element production.

Contribution

The paper presents a detailed spectral analysis of HD271791 to explore its supernova origin and nucleosynthesis, including non-LTE calculations for element abundance determination.

Findings

HD271791 has a velocity exceeding the Galactic escape velocity.

Spectral analysis indicates enrichment of alpha-process elements.

The star likely originated from a type Ibc supernova in a binary system.

Abstract

Some young, massive stars can be found in the Galactic halo. As star formation is unlikely to occur in the halo, they must have been formed in the disk and been ejected shortly afterwards. One explanation is a supernova in a tight binary system. The companion is ejected and becomes a runaway star. HD\,271791 is the kinematically most extreme runaway star known (Galactic restframe velocity $725 \pm 195\, \rm km\,s^{-1}$, which is even larger than the Galactic escape velocity). Moreover, an analysis of the optical spectrum showed an enhancement of the $\alpha$-process elements. This indicates the capture of supernova ejecta, and therefore an origin in a core-collapse supernova. As such high space velocities are not reached by the runaway stars in classical binary supernova ejection scenarios, a very massive but compact primary, probably of Wolf-Rayet type is required. HD\,271791 is therefore a perfect candidate for studying nucleosynthesis in a supernova of probably type Ibc. The goal of this project is to determine the abundances of a large number of elements from the $\alpha$-process, the iron group, and heavier elements by a quantitative analysis of the optical and UV spectral range. Detailed line-formation calculations are employed that account for deviations from local thermodynamic equilibrium (non-LTE). We intend to verify whether core-collapse supernova are a site of r-process element production. Here, we state the current status of the project.