Discovery of a runaway star likely ejected by a Type Iax Supernova

TL;DR

This paper reports the discovery of a new neon- and oxygen-rich runaway star, likely ejected by a Type Iax supernova, providing insights into supernova progenitors and stellar ejection mechanisms.

Contribution

It presents the identification and analysis of a new LP 40-365 type star, expanding understanding of their origins and properties compared to previous known objects.

Findings

Star is hotter than previous LP 40-365 stars.

Star likely ejected from Galactic disk 2.8 million years ago.

Ejection velocity exceeds 600 km/s, unbound from the Galaxy.

Abstract

Over the past decade, runaway stars have been identified, believed to originate either as surviving donors of Type Ia supernovae or as partially deflagrated accretors producing Type Iax supernovae. While the former have been extensively studied recently, the origins of the latter (also called LP 40-365 type stars) remain under-explored and therefore less well understood. So far seven such objects are known. In this paper, we report the discovery of a new LP 40-365 type runaway star, notably hotter than previously studied members of this class. Spectral analysis confirms that its atmosphere is neon- and oxygen-dominated, consistent with earlier analyses of other LP 40-365 type stars. Kinematic analysis indicates that the star has a high probability of being unbound from the Galaxy and was most likely ejected from the Galactic disk approximately 2.8 Myr ago with an ejection velocity exceeding 600 km/s. This result further emphasizes the discrepancy between the abundance yields and kick velocities predicted by white dwarf deflagration models and those observed in stars of LP 40-365 type, underscoring the need for a reassessment of such systems.