A Light Curve Analysis of 32 Recent Galactic Novae --- Distances and White Dwarf Masses

TL;DR

This study analyzes 32 recent galactic novae using a time-stretching method to determine their distances, reddening, and white dwarf masses, revealing classifications and the applicability of a universal decline law.

Contribution

Introduces a novel time-stretching method for nova light curves to uniformly determine distances and white dwarf masses from a single approach.

Findings

32 galactic novae distances and WD masses determined

Novas classified into LV Vul and V1500 Cyg types

Method applicable to novae following the universal decline law

Abstract

We obtained the absolute magnitudes, distances, and white dwarf (WD) masses of 32 recent galactic novae based on the time-stretching method for nova light curves. A large part of the light/color curves of two classical novae often overlap each other if we properly squeeze/stretch their timescales. Then, a target nova brightness is related to the other template nova brightness by $(M_V[t])_{\rm template} = (M_V[t/f_{\rm s}] - 2.5 \log f_{\rm s})_{\rm target}$, where $t$ is the time, $M_V[t]$ is the absolute $V$ magnitude, and $f_{\rm s}$ is their timescaling ratio. Moreover, when these two time-stretched light curves, $(t/f_{\rm s})$-$(M_V-2.5 \log f_{\rm s})$, overlap each other, $(t/f_{\rm s})$-$(B-V)_0$ do too, where $(B-V)_0$ is the intrinsic $B-V$ color. Thus, the two nova tracks overlap each other in the $(B-V)_0$-$(M_V-2.5 \log f_{\rm s})$ diagram. Inversely using these properties, we obtain/confirm the distance and reddening by comparing each nova light/color curves with the well calibrated template novae. We classify the 32 novae into two types, LV Vul and V1500 Cyg types, in the time-stretched $(B-V)_0$-$(M_V-2.5 \log f_{\rm s})$ color-magnitude diagram. The WD mass is obtained by direct comparison of the model $V$ light curves with the observation. Thus, we obtain a uniform set of 32 galactic classical novae that provides the distances and WD masses from a single method. Many novae broadly follow the universal decline law and the present method can be applied to them, while some novae largely deviate from the universal decline law and so the method cannot be directly applied to them. We discuss such examples.