Physics of nova outbursts: Theoretical models of classical nova outbursts with optically thick winds on $1.2M_{\odot }$ and $1.3M_{\odot }$ 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 $\log T_{\mathrm{ph}}$ (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 $t_{\mathrm{peak}}$ and the expansion timescale ${\tau }_{\exp }$ at $t=0$. With this relation, we are able to predict the time to optical maximum $t_{\mathrm{peak}}$ from the ignition model (at $t=0$) without following a time-consuming nova wind evolution.

arXiv comment10 pages, 8 figures, accepted for publication in PASJ