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

¹ Institut für Physik und Astronomie, Universität Potsdam, Haus 28, Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany
² Department of Physics, University of Warwick, Coventry CV4 7AL, UK
³ Dr. Karl Remeis-Observatory & ECAP, Astronomical Institute, Friedrich-Alexander University Erlangen-Nuremberg, Sternwartstr. 7, 96049 Bamberg, Germany
⁴ Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, Leibnizstraße 15, 24118 Kiel, Germany
⁵ Max Planck Institut für Astrophysik, Karl-Schwarzschild-Straße 1, 85748 Garching bei München, Germany
⁶ Department of Astronomy and Theoretical Astrophysics Center, University of California, Berkeley, CA 94720-3411, USA

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 15 December 2025
Accepted: 27 February 2026

Abstract

Over the past decade, runaway stars believed to originate either as surviving donors of Type Ia supernovae or as partially deflagrated accretors producing Type Iax supernovae, have been identified. 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 six such objects are known and one more is suspected. In this paper we report the discovery of a new LP 40−365 type runaway star that is 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 disc approximately 2.8 Myr ago with an ejection velocity exceeding 600 km s⁻¹. 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.