Accretion-induced Collapse from Helium Star + White Dwarf Binaries

Jared Brooks, Josiah Schwab, Lars Bildsten, Eliot Quataert, Bill Paxton

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

Accretion-induced collapse (AIC) occurs when an O/Ne white dwarf (WD) grows to nearly the Chandrasekhar mass (), reaching central densities that trigger electron captures in the core. Using Modules for Experiments in Stellar Astrophysics (MESA), we present the first true binary simulations of He star + O/Ne WD binaries, focusing on a He star in a 3 hr orbital period with 1.1-1.3 M.O/Ne WDs. The helium star fills its Roche lobe after core helium burning is completed and donates helium on its thermal timescale to the WD,M ≈ 3 × 10-3M. yr-1, which is a rate high enough that the accreting helium burns stably on the WD. The accumulated carbon/oxygen ashes from the helium burning undergo an unstable shell flash that initiates an inwardly moving, carbon burning flame. This flame is only quenched when it runs out of carbon at the surface of the original O/Ne core. Subsequent accumulation of fresh carbon/oxygen layers also undergo thermal instabilities, but no mass loss is triggered, which allows MWD → Mch, and then triggers the onset of AIC. We also discuss the scenario of accreting C/O WDs that experience shell carbon ignitions to become O/Ne WDs, and then, under continuing mass transfer, lead to AIC. Studies of the AIC event rate using binary population synthesis should include all of these channels, especially this latter channel, which has been previously neglected but might dominate the rate.

Original languageEnglish (US)
Article number151
JournalAstrophysical Journal
Volume843
Issue number2
DOIs
StatePublished - Jul 10 2017
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • binaries: close
  • novae cataclysmic variables
  • supernovae: general
  • white dwarfs

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