Abstract
Abstract
The engulfment of substellar bodies (SBs), such as brown dwarfs and planets, by giant stars is a possible explanation for rapidly rotating giants, lithium-rich giants, and the presence of SBs in close orbits around subdwarfs and white dwarfs. We perform three-dimensional hydrodynamical simulations of the flow in the vicinity of an engulfed SB. We model the SB as a rigid body with a reflective surface because it cannot accrete. This reflective boundary changes the flow morphology to resemble that of engulfed compact objects with outflows. We measure the drag coefficients for the ram-pressure and gravitational drag forces acting on the SB, and use them to integrate its trajectory inside the star. We find that engulfment can increase the luminosity of a 1 M
⊙ star by up to a few orders of magnitude. The time for the star to return to its original luminosity is up to a few thousand years when the star has evolved to ≈10 R
⊙ and up to a few decades at the tip of the red giant branch (RGB). No SBs can eject the envelope of a 1 M
⊙ star before it evolves to ≈10 R
⊙ if the orbit of the SB is the only energy source contributing to the ejection. In contrast, SBs as small as ≈10 M
Jup can eject the envelope at the tip of the RGB. The numerical framework we introduce here can be used to study planetary engulfment in a simplified setting that captures the physics of the flow at the scale of the SB.
Funder
University of California Institute for Mexico and the United States
Consejo Nacional de Ciencia y Tecnología
National Aeronautics and Space Administration
National Science Foundation
Heising-Simons Foundation
University of California, Santa Cruz
Texas Advanced Computing Center
University of Texas, Austin
Gordon and Betty Moore Foundation
Publisher
American Astronomical Society
Subject
Space and Planetary Science,Astronomy and Astrophysics
Cited by
1 articles.
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1. Flow morphology of a supersonic gravitating sphere;Monthly Notices of the Royal Astronomical Society;2023-11-09