Constraining the Physics of AM Canum Venaticorum Systems with the Accretion Disk Instability Model

TL;DR

This paper uses the accretion disk instability model to analyze AM CVn systems, constraining their mass transfer rates based on observed outburst behaviors and orbital periods, and predicting future observational trends.

Contribution

It provides a new constraint on mass transfer rates in AM CVn systems as a function of orbital period using observational data and the disk instability model.

Findings

Mass transfer rate scales as (P/1000 s)^{-5.2}

The functional form aligns with recurrence time relations

Outburst duration dependence will flatten with more data

Abstract

Recent work by Levitan et al has expanded the long-term photometric database for AM CVn stars. In particular, their outburst properties are well-correlated with orbital period, and allow constraints to be placed on the secular mass transfer rate between secondary and primary if one adopts the disk instability model for the outbursts. We use the observed range of outbursting behavior for AM CVn systems as a function of orbital period to place a constraint on mass transfer rate versus orbital period P. We infer a rate ~5 x 10^{-9} Msun/yr (P/1000 s)^{-5.2}. We show the functional form so obtained is consistent with the recurrence time-orbital period relation found by Levitan et al using a simple theory for the recurrence time. Also, we predict their steep dependence of outburst duration on orbital period will flatten considerably once the longer orbital period systems have more complete observations.