Population synthesis for double white dwarfs. II. Semi-detached systems: AM CVn stars

By G. Nelemans, S. P. Portegies Zwart, F. Verbunt, Lev Yungelson. 2001

260 citations recorded by the source corpus.

We study two models for AM CVn stars: white dwarfs accreting (i) from a helium white dwarf companion and (ii) from a helium-star donor. We show that in the first model possibly no accretion disk forms at the onset of the mass transfer. The stability and the rate of mass transfer then depend on the tidal coupling between the accretor and the orbital motion. In the second model the formation of AM CVn stars may be prevented by detonation of the CO white dwarf accretor and the disruption of the system. With the most favourable conditions for the formation of AM CVn stars we find a current Galactic birth rate of $6.8 10^{-3} {\rm yr^{-1}}$. Unfavourable conditions give $1.1 10^{-3} {\rm yr^{-1}}$. The expected total number of the systems in the Galaxy is 9.4 10 7 and 1.6 10 7 , respectively. We model very simple selection effects to get some idea about the currently expected observable population and discuss the (quite good) agreement with the observed systems.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/c4d91503676140922dc4aa8d00e5c0c369d8b5ba

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Citations in the corpus

The gravitational wave background from cosmological compact binaries (2003, methodology): “…not attempt to compare to distributions in mass, mass ratio or period in detail: the observed distributions are subject to complex selection effects, and turn out often to be most constraining for WD cooling models (e.g. Nelemans et al. 2001b), whose development is beyond the scope of this paper.”
White Dwarf Donors in Ultracompact Binaries: The Stellar Structure of Finite-Entropy Objects (2003, background): “In the scenario of coolingWDs reaching contact via in-spiral (e.g., Nelemans et al. 2001), the relative number of He versus C/O WDs that come into contact and stably reach longer orbital periods is difficult to know.”
COSMIC Variance in Binary Population Synthesis (2019, unknown): “As a fiducial CE model, we use the variable binding energy parameter in conjunction with a constant CE efficiency parameter α=1.0 following previous results (e.g., Nelemans et al. 2001a; Dominik et al. 2012).”
ACCELERATING COMPACT OBJECT MERGERS IN TRIPLE SYSTEMS WITH THE KOZAI RESONANCE: A MECHANISM FOR “PROMPT” TYPE Ia SUPERNOVAE, GAMMA-RAY BURSTS, AND OTHER EXOTICA (2010, background): “Similar scenarios with different mass components may produce AM CVn or R CrB stars, depending on the stability of mass transfer as the WDs interact (Webbink 1984, Nelemans et al. 2001), or millisecond pulsars (Saio & Nomoto 1985).”
Reconstructing the evolution of white dwarf binaries: further evidence for an alternative algorithm for the outcome of the common-envelope phase in close binaries (2004, methodology): “Another situation where a large fraction of the total mass is lost is in the case of mass transfer from a giant to another giant leading to a double spiral-in (e.g. Brown 1995; Nelemans et al. 2001b).”
Short-period AM CVn systems as optical, X-ray and gravitational-wave sources (2003, methodology): “One has to keep in mind that a lot of these assumptions are badly constrained, which means that the number of progenitor systems is rather uncertain (e.g. Nelemans et al. 2001a).”
Probing ultralight bosons with binary black holes (2018, background): “Indeed, population synthesis codes [142 – 144] suggest that there are presently of the order of 10 5 to 10 6 galactic BH-BH and BH-NS binaries of comparable masses with orbital frequencies distributed in the mHz region.”
The gravitational wave signal from the Galactic disk population of binaries containing two compact objects. (2001, methodology): “The fact that the numbers here are different from the numbers given in Portegies Zwart & Yungelson (1998, 1999)2, Nelemans et al. (2001b) and Brown et al. (2001) is caused by the differences in the assumed IMF, initial binary fraction and star formation history.”
Cataclysmic variables with evolved secondaries and the progenitors of AM CVn stars (2001, background): “First, while NPVY assume a similar star-formation rate (by mass) at the present epoch (3.6 versus 3.5M⊙ yr −1), their star-formation rate was much higher in the past, starting with a star-formation rate of 15M⊙ yr −1 and decaying with an exponential decay time of 7Gyr (Nelemans et al. 2001b).”
The evolution of hierarchical triple star-systems (2016, background): “When both stars have loosely bound envelopes, such as for giants, both envelopes can be lost simultaneously (hereafter double-CE, see Brown, 1995; Nelemans et al., 2001).”
Predicting the LISA white dwarf binary population in the Milky Way with cosmological simulations (2019, methodology): “16 shows the spatial distri- bution of the systems detected by LISA with the Galactic model used in Nelemans et al. (2001b).”
Mass transfer between double white dwarfs (2003, methodology): “To add to this, Nelemans et al. (2001) estimate that while 99% of AM CVns have periods P > 2000 sec, they will only form ∼ 10% of the observed sample, an estimate that itself depends upon highly uncertain assumptions about selection.”