# A UV and optical study of 18 old novae with Gaia DR2 distances: mass accretion rates, physical parameters, and MMRD

## TL;DR

This study combines UV, optical, and Gaia data to analyze 18 old novae, deriving physical parameters, accretion rates, and a new MMRD relation, revealing correlations and challenging previous assumptions about nova evolution.

## Contribution

It provides a homogeneous set of accretion rates for old novae using Gaia distances, introduces a new MMRD relation, and uncovers novel correlations among nova physical parameters.

## Key findings

- All novae were super-Eddington during outburst.
- Average maximum magnitude at outburst is -7.5±1.0.
- Median accretion rate is around 10^-8.5 M_sun/year.

## Abstract

{We combine the results of our earlier study of the UV characteristics of 18 classical novae (CNe) with data from the literature and with the recent precise distance determinations from the Gaia satellite to investigate the statistical properties of old novae. All final parameters for the sample include a detailed treatment of the errors and their propagation. The physical properties reported here include the absolute magnitudes at maximum and minimum, a new maximum magnitude versus rate of decline (MMRD) relation, and the inclination-corrected 1100--6000-\AA\ accretion disk luminosity. Most importantly, these data have allowed us to derive a homogenous set of accretion rates in quiescence for the 18 novae. All novae in the sample were super-Eddington during outburst, with an average absolute magnitude at maximum of $-7.5\pm1.0$. The average absolute magnitude at minimum corrected for inclination is $3.9\pm1.0$. The median mass accretion rate is $\log\dot{M}_{1M\odot}=-8.52$ (using $1M\odot$ as WD mass for all novae) or $\log\dot{M}_{M_{WD}}=-8.48$ (using the individual WD masses). These values are lower than those assumed in studies of CNe evolution and appear to attenuate the need for a hibernation hypothesis to interpret the nova phenomenon. We identified a number of correlations among the physical parameters of the quiescent and eruptive phases, some already known but others new and even surprising. Several quantities correlate with the speed class $t_3$ including, unexpectedly, the mass accretion rate ($\dot{M)}$. This rate correlates also with the absolute magnitude at minimum corrected for inclination, and with the outburst amplitude, providing new and simple ways to estimate $\dot{M}$ through its functional dependence on (more) easily observed quantities. There is no correlation between $\dot{M}$ and the orbital period.}