A helium nova in the Large Magellanic Cloud -- the faint supersoft X-ray source [HP99]159

Abstract

We propose a helium nova model for the Large Magellanic Cloud (LMC) supersoft X-ray source (SSS) [HP99]159. This object has long been detected as a faint and persistent SSS for about 30 years, and recently been interpreted to be a source of steady helium-shell burning, because no hydrogen lines are observed. We find that the object can also be interpreted as in a decaying phase of a helium nova. The helium nova is slowly decaying toward the quiescent phase, during which the observed temperature, luminosity, and SSS lifetime ($\gtrsim 30$ years) are consistent with a massive white dwarf model of $\sim$ 1.2 $M_{\odot }$. If it is the case, this is the second discovery of a helium nova outburst after V445 Pup in our Galaxy and also the first identified helium nova in the LMC. We also discuss the nature of the companion helium star in relation to Type Ia supernova progenitors.

4 pages, 4 figures, accepted in MNRAS (Letters)

References in corpus (5)

• He-accreting carbon-oxygen white dwarfs and type Ia supernovae
• Helium Nova on a Very Massive White Dwarf -- A Light Curve Model of V445 Puppis (2000) Revised
• A radio-detected Type Ia supernova with helium-rich circumstellar material
• A comparative study of the strength of flickering in cataclysmic variables
• A helium-burning white dwarf binary as a supersoft X-ray source

Cited by in corpus (1)

• [HP99] 159 -- Properties of the first Supersoft X-ray Source with a Helium star donor