Abstract
We briefly review the current theoretical understanding of the light curves of novae. These curves exhibit a homologous nature, dubbed the universal decline law, and when time-normalized, they almost follow a single curve independently of the white dwarf (WD) mass or chemical composition of the envelope. The optical and near-infrared light curves of novae are reproduced mainly by free-free emission from their optically thick winds. We can estimate the WD mass from multiwavelength observations because the optical, UV, and soft X-ray light curves evolve differently and we can easily resolve the degeneracy of the optical light curves. Recurrent novae and classical novae are a testbed of type Ia supernova scenarios. In the orbital period versus secondary mass diagram, recurrent novae are located in different regions from classical novae and the positions of recurrent novae are consistent with the single degenerate scenario.
Highlights
A nova outburst is a thermonuclear runaway event on a white dwarf (WD)
For a more massive WD, its light curve decays more quickly mainly because of its smaller envelope mass, so the evolution time scale is shorter. These light curves follow a common shape, known as the universal decline law. If we plot these light curves on logarithmic time since the outburst, and shift them in the vertical and horizontal directions, all the light curves essentially converge into a single curve (Hachisu & Kato 2010) independently
We note that (1) high Ne/O line ratios could be an indication of a massincreasing WD and (2) strong Ne lines are detected even in the slow nova V723 Cas (Iijima 2006), which harbors a low-mass WD (0.5–0.6 M )
Summary
After unstable hydrogen shellburning sets in, the envelope greatly expands and the WD becomes very bright and reaches its optical maximum. V838 Her is a very fast nova, one of the fastest novae except for the superbright novae It exhibits a normal super-Eddington luminosity in the early phase. Many classical novae exhibit super-Eddington luminosity, i.e., the peak luminosity exceeds the Eddington luminosity at the photosphere. Hachisu fer to a brief summary of super-Eddington luminosity and a theoretical explanation of maximum magnitude versus rate of decline of novae (the MMRD relation) by Kato (2012), the common path in the color-color diagram by Hachisu and Kato (2014), and information on instability of the shell flash by Kato & Hachisu (2012)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
