Evolution of Cataclysmic Variables and Related Binaries Containing a White Dwarf

Abstract

We present a binary evolution study of cataclysmic variables (CVs) and related systems with white dwarf accretors, including for example, AM CVn systems, classical novae, supersoft X-ray sources, and systems with giant donor stars. Our approach intentionally avoids the complications associated with population synthesis algorithms thereby allowing us to present the first truly comprehensive exploration of all of the subsequent binary evolution pathways that ZACVs might follow (assuming fully non-conservative, Roche-lobe overflow onto an accreting WD) using the sophisticated binary stellar evolution code MESA. The grid consists of 56,000 initial models, including 14 white dwarf accretor masses, 43 donor-star masses (0.1 − 4.7 M ), and 100 orbital periods. We explore evolution tracks in the orbital period and donor-mass (P orb − M don ) plane in terms of evolution dwell times, masses of the white dwarf accretor, accretion rate, and chemical composition of the center and surface of the donor star. We report on the differences among the standard CV tracks, those with giant donor stars, and ultrashort period systems. We show where in parameter space one can expect to find supersoft X-ray sources, present a diagnostic to distinguish among different evolutionary paths to forming AM CVn binaries, quantify how the minimum orbital period in CVs depends on the chemical composition of the donor star, and update the P orb (M wd ) relation for binaries containing white dwarfs whose progenitors lost their envelopes via stable Roche-lobe overflow. Finally, we indicate where in the P orb − M don the accretion disks will tend to be stable against the thermal-viscous instability, and where gravitational radiation signatures may be found with LISA.

A 9-h CV with one outburst in 4 yr of Kepler data

“…The canonical model for the formation and evolution of cataclysmic variables has been discussed extensively in the literature (see, e.g., Rappaport et al 1983;Patterson 1984;Warner 1995;Howell, Nelson, & Rappaport 2001;Knigge et al 2011;Goliasch & Nelson 2015;Kalomeni et al 2016, and references therein). While the more massive primary is evolving up the red giant or asymptotic giant branch it overflows its Roche lobe (i.e., RLOF) leading to dynamically unstable mass transfer.…”

“…This evolutionary channel is thought to contribute to the formation of the ultrashort period AM CVn stars (Podsiadlowski, Han & Rappaport 2003), which are strong low-frequency gravitational wave sources that are expected to be detectable by LISA. For a review of these and related CV evolutionary channels see Goliasch & Nelson (2015) and Kalomeni et al (2016).…”

Cataclysmic variable evolution and the white dwarf mass problem: A Review

“…Cataclysmic variables (CVs) are semi-detached short period binaries in which a white dwarf (WD) primary stably accretes mass from a low-mass companion, hereafter the donor or secondary star (see Warner, 1995, for a comprehensive review). The donor is typically an unevolved low-mass main-sequence (MS) star, although systems at orbital periods below ∼ 1 h or above ∼ 5 − 6 h can have a degenerate companion or a slightly evolved donor, respectively (e.g., Goliasch & Nelson, 2015;Kalomeni et al, 2016).…”

V1082-Sgr: A magnetic cataclysmic variable with a lobe-filling companion star

“…We assume that magnetic braking works in stars less massive than 1.4 M⊙ which have a convective envelope (Verbunt & Zwaan 1981;Rappaport et al 1983;Lin et al 2011;Kalomeni et al 2016). All other parameters are set to take their default values in the code.…”

“…All other parameters are set to take their default values in the code. Since the retention efficiencies for both hydrogen and helium burning are still highly uncertain, for simplicity, we assume the WD does not accumulate the accreted matter, and the lost matter carries the specific angular momentum of the WD (Kalomeni et al 2016). We set the initial WD mass MWD to be 0.77M⊙ and 0.88M⊙, the initial companion mass 0.9M⊙ M2 2.6M⊙ (with a step of 0.1M⊙), and the initial orbital period 0.5 P orb 5 days (with a step of 0.05 day).…”