MOCCA-SURVEY database I. Accreting white dwarf binary systems in globular clusters -- II. Cataclysmic variables -- progenitors and population at birth

TL;DR

This study uses simulations to analyze the formation, properties, and evolution of cataclysmic variables in globular clusters, revealing dynamic influences on their progenitors and implications for comparing cluster and field CV populations.

Contribution

It demonstrates how cluster dynamics influence CV formation and properties, providing insights into their birth rates, age differences, and potential origins of field CVs from clusters.

Findings

CV formation occurs in two regimes: an initial burst and a steady rate.

Cluster CVs can be significantly older than field CVs.

Some field CVs may originate from globular clusters.

Abstract

This is the second in a series of papers associated with cataclysmic variables (CVs) and related objects, formed in a suite of simulations for globular cluster evolution performed with the MOCCA Monte Carlo code. We study the properties of our simulated CV populations throughout the entire cluster evolution. We find that dynamics extends the range of binary CV progenitor properties, causing CV formation from binary progenitors that would otherwise not become CVs. The CV formation rate in our simulations can be separated into two regimes: an initial burst ($\lesssim$ 1 Gyr) connected with the formation of the most massive white dwarfs, followed by a nearly constant formation rate. This result holds for all models regardless of the adopted initial conditions, even when most CVs form dynamically. Given the cluster age-dependence of CV properties, we argue that direct comparisons to observed Galactic field CVs could be misleading, since cluster CVs can be up to 4 times older than their field counterparts. Our results also illustrate that, due mainly to unstable mass transfer, some CVs that form in our simulations are destroyed before the present-day. Finally, some field CVs might have originated from globular clusters, as found in our simulations, although the fraction of such escapers should be small relative to the entire Galactic field CV population.