On the M_V -- Inclination Relationship for Nova-like Variables

TL;DR

This study investigates the relationship between absolute magnitude and inclination in nova-like stars, confirming Webbink et al.'s model and showing that mass transfer rate primarily causes observed spread in brightness.

Contribution

It validates Webbink et al.'s inclination-magnitude relation using Gaia data and clarifies the dominant role of mass transfer rate in brightness variation.

Findings

Mass transfer rate dominates the spread in M_V at given inclination.

The relation aligns with theoretical population models and observational data.

White dwarf mass has a minor effect on the M_V-inclination relationship.

Abstract

Using a sample of Nova-like stars from the Ritter and Kolb catalog, we examine the relationship between their Gaia determined absolute magnitude and the inclination of the binary system. Webbink et al. (1987) derived a relationship between these two variables that provides a good fit and allows differentiation between $\dot{M}$ (and possibly M_{WD}) as a function of inclination. We show that the spread in M_V, at a given i, is dominated by the mass transfer rate with only a small dependence on the white dwarf mass. The validated relation shows that present-day theoretical population studies of cataclysmic variables as well as model fits to observational data yield mass transfer rates and white dwarf masses consistent with the Gaia derived M_V for the nova-like stars.