Recurrent novae and long-term evolution of mass-accreting white dwarfs -- toward the accurate mass retention efficiency

The mass growth rate of mass-accreting white dwarfs (WDs) is a key factor in binary evolution scenarios toward Type Ia supernovae. Many authors have reported very different WD mass increasing rates. In this review, we clarify the reasons for such divergence, some of which come from a lack of numerical techniques, usage of old opacities, different assumptions for binary configurations, inadequate initial conditions, and unrealistic mass-loss mechanisms. We emphasize that these assumptions should be carefully chosen in calculating the long-term evolution of accreting WDs. Importantly, the mass-loss mechanism is the key process determining the mass retention efficiency: the best approach involves correctly incorporating the optically thick wind because it is supported by the multiwavelength light curves of novae.Comment: 23 pages, 8 figures. Figure 7 is replaced. Several points of discussion are added. Submitted versio

Towards the Super Yang-Mills Theory on the Lattice

We present an entirely new approach towards a realization of the supersymmetric Yang-Mills theory on the lattice. The action consists of the staggered fermion and the plaquette variables distributed in the Euclidean space with a particular pattern. The system is shown to have fermionic symmetries relating the fermion and the link variables.Comment: 12 pages, 3 figure

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

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.Comment: 4 pages, 4 figures, accepted in MNRAS (Letters