Physics of nova outbursts: Theoretical models of classical nova outbursts with optically thick winds on $1.2~M_\odot$ and $1.3~M_\odot$ white dwarfs

Abstract

We present time-dependent nova outburst models with optically thick winds for a 1.2 and 1.35 $M_\odot$ white dwarfs (WDs) with a mass accretion rate of $5 \times 10^{-9}~M_\odot$ yr$^{-1}$ and for a 1.3 $M_\odot$ WD with $2 \times 10^{-9}~M_\odot$ yr$^{-1}$. The X-ray flash occurs 11 days before the optical peak of the 1.2 $M_\odot$ WD and 2.5 days before the peak of the 1.3 $M_\odot$ WD. The wind mass loss rate of the 1.2 $M_\odot$ WD (1.3 $M_\odot$ WD) reaches a peak of $6.4 \times 10^{-5}~M_\odot$ yr$^{-1}$ ($7.4 \times 10^{-5}~M_\odot$ yr$^{-1}$) at the epoch of the maximum photospheric expansion with the lowest photospheric temperature of $\log T_{\rm ph}$ (K)=4.33 (4.35). The nuclear energy generated during the outburst is lost in a form of radiation (61% for the 1.2 $M_\odot$ WD; 47% for the 1.3 $M_\odot$ WD), gravitational energy of ejecta (39%; 52%), and kinetic energy of the wind (0.28%; 0.29%). We found an empirical relation for fast novae between the time to optical maximum from the outburst $t_{\rm peak}$ and the expansion timescale $\tau_{\rm exp}$ at $t=0$. With this relation, we are able to predict the time to optical maximum $t_{\rm peak}$ from the ignition model (at $t=0$) without following a time-consuming nova wind evolution.