Discovery of a Thorne-Zytkow object candidate in the Small Magellanic Cloud

TL;DR

This paper reports the discovery of a Thorne-Zytkow object candidate in the Small Magellanic Cloud, providing potential direct evidence for a new class of star with unique chemical signatures, and offering insights into stellar interiors and nucleosynthesis.

Contribution

First identification of a TZO candidate exhibiting distinctive chemical features, supporting the existence of this theoretical stellar class.

Findings

Detection of anomalous heavy-element and Li lines in the candidate's spectrum

First observational evidence supporting the existence of TZOs

Implications for new stellar evolution models and nucleosynthesis pathways

Abstract

Thorne-Zytkow objects (TZOs) are a theoretical class of star in which a compact neutron star is surrounded by a large, diffuse envelope. Supergiant TZOs are predicted to be almost identical in appearance to red supergiants (RSGs). The best features that can be used at present to distinguish TZOs from the general RSG population are the unusually strong heavy-element and Li lines present in their spectra, products of the star's fully convective envelope linking the photosphere with the extraordinarily hot burning region in the vicinity of the neutron star core. Here we present our discovery of a TZO candidate in the Small Magellanic Cloud. It is the first star to display the distinctive chemical profile of anomalous element enhancements thought to be unique to TZOs. The positive detection of a TZO will provide the first direct evidence for a completely new model of stellar interiors, a theoretically predicted fate for massive binary systems, and never-before-seen nucleosynthesis processes that would offer a new channel for Li and heavy-element production in our universe.