The evolutionary status of Cataclysmic Variables: Eclipse modelling of 15 systems

TL;DR

This study measures component masses in 15 Cataclysmic Variables, revises the orbital period minimum, and evaluates CV evolution models, providing new calibrations and insights into donor star properties.

Contribution

It offers new mass measurements, calibrates superhump period excess relations, and revises the CV orbital period minimum, enhancing understanding of CV evolution.

Findings

White dwarf masses are high with no trend with orbital period.

Orbital period minimum is revised to approximately 79.6 minutes.

Standard evolutionary tracks fit some data but not the period minimum or donor radii below 0.1 M$_{ ext{sun}}$.

Abstract

We present measurements of the component masses in 15 Cataclysmic Variables (CVs) - 6 new estimates and 9 improved estimates. We provide new calibrations of the relationship between superhump period excess and mass ratio, and use this relation to estimate donor star masses for 225 superhumping CVs. With an increased sample of donor masses we revisit the implications for CV evolution. We confirm the high mass of white dwarfs in CVs, but find no trend in white dwarf mass with orbital period. We argue for a revision in the location of the orbital period minimum of CVs to $79.6 \pm 0.2$ min, significantly shorter than previous estimates. We find that CV donors below the gap have an intrinsic scatter of only 0.005 R$_{\odot}$ around a common evolutionary track, implying a correspondingly small variation in angular momentum loss rates. In contrast to prior studies, we find that standard CV evolutionary tracks - without additional angular momentum loss - are a reasonable fit to the donor masses just below the period gap, but that they do not reproduce the observed period minimum, or fit the donor radii below 0.1 M$_{\odot}$.