evolution for various WD masses (from $0.5~M_\sun$ to $1.38~M_\sun$) and showed that the main parameter which determines the speed class of novae is the WD mass. A nova on a more massive WD evolves faster because the ignition mass (envelope mass at the epoch when hydrogen ignites) is much smaller and is blown off in the wind in a much shorter time.

The acceleration mechanism of the wind is the so-called continuum radiation-driven [@fri66]. The matter in the envelope is accelerated deep inside the photosphere, in other words, at/near the iron peak of the radiative opacity ($\log T$ (K) $\sim 5.2$). So, it is called the optically thick winds. This mechanism is common among all the WD masses ranging from $\sim0.5~M_\sun$ to $1.38~M_\sun$ [@kat94h].

Nova spectra in the decay phase are dominated by free-free emission [@gal76; @enn77; @kra84; @nai09] until the nova entered the nebular phase where strong emission lines such as \[\] are dominant. Free-free emission of novae is originating from the expanding hot and optically thin gaseous plasma, that is, outside the photosphere of the optically thick winds. Free-free emission light curves of novae are theoretically calculated from the wind-mass loss rate $\dot M_{\rm wind}$, photospheric velocity $v_{\rm 