How drag force evolves in global common envelope simulations

Journal Article · Mon Oct 07 00:00:00 EDT 2019 · Monthly Notices of the Royal Astronomical Society

DOI:https://doi.org/10.1093/mnras/stz2813· OSTI ID:1638892

Chamandy, Luke  ^[1]; Blackman, Eric G. ^[1]; Frank, Adam ^[1]; Carroll-Nellenback, Jonathan ^[1]; Zou, Yangyuxin ^[1]; Tu, Yisheng ^[1]

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1. Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA

ABSTRACT We compute the forces, torque, and rate of work on the companion-core binary due to drag in global simulations of common envelope (CE) evolution for three different companion masses. Our simulations help to delineate regimes when conventional analytic drag force approximations are applicable. During and just prior to the first periastron passage of the in-spiral phase, the drag force is reasonably approximated by conventional analytic theory and peaks at values proportional to the companion mass. Good agreement between global and local 3D ‘wind tunnel’ simulations, including similar net drag force and flow pattern, is obtained for comparable regions of parameter space. However, subsequent to the first periastron passage, the drag force is up to an order of magnitude smaller than theoretical predictions, quasi-steady, and depends only weakly on companion mass. The discrepancy is exacerbated for larger companion mass and when the inter-particle separation reduces to the Bondi–Hoyle–Lyttleton accretion radius, creating a turbulent thermalized region. Greater flow symmetry during this phase leads to near balance of opposing gravitational forces in front of and behind the companion, hence a small net drag. The reduced drag force at late times helps explain why companion-core separations necessary for envelope ejection are not reached by the end of limited duration CE simulations.

• Research Organization: Univ. of Rochester, NY (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: SC0001063
• OSTI ID: 1638892
• Alternate ID(s): OSTI ID: 1801424
• Journal Information: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Vol. 490 Journal Issue: 3; ISSN 0035-8711
• Publisher: Oxford University Press
• Country of Publication: United Kingdom
• Language: English

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