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Title: Hydrodynamics and Survivability during Post-main-sequence Planetary Engulfment
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 1Mstar 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 ≈10Rand up to a few decades at the tip of the red giant branch (RGB). No SBs can eject the envelope of a 1Mstar before it evolves to ≈10Rif the orbit of the SB is the only energy source contributing to the ejection. In contrast, SBs as small as ≈10MJupcan 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.

 
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PAR ID:
10456912
Author(s) / Creator(s):
; ; ; ; ; ; ; ;
Publisher / Repository:
DOI PREFIX: 10.3847
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
954
Issue:
2
ISSN:
0004-637X
Format(s):
Medium: X Size: Article No. 176
Size(s):
Article No. 176
Sponsoring Org:
National Science Foundation
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