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 yr, 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 (≳30 yr) are consistent with a massive white dwarf model of ~1.2 M⊙. 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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- October 2023
- DOI:
- 10.1093/mnrasl/slad096
- arXiv:
- arXiv:2307.05278
- Bibcode:
- 2023MNRAS.525L..56K
- Keywords:
-
- stars: individual(LMC [HP99]159);
- novae;
- cataclysmic variables;
- white dwarfs;
- X-rays: stars;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 4 pages, 4 figures, accepted in MNRAS (Letters)