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Foretellings of Ragnarök: World-engulfing Asymptotic Giants and the Inheritance of White Dwarfs

Mustill, Alexander LU and Villaver, Eva (2012) In The Astrophysical Journal 761(2).
Abstract
The search for planets around white dwarf stars, and evidence for dynamical instability around them in the form of atmospheric pollution and circumstellar disks, raises questions about the nature of planetary systems that can survive the vicissitudes of the asymptotic giant branch (AGB). We study the competing effects, on planets at several AU from the star, of strong tidal forces arising from the star's large convective envelope, and of the planets' orbital expansion due to stellar mass loss. We study, for the first time, the evolution of planets while following each thermal pulse on the AGB. For Jovian planets, tidal forces are strong, and can pull into the envelope planets initially at ~3 AU for a 1 M ☉ star and ~5 AU for a 5 M ☉ star.... (More)
The search for planets around white dwarf stars, and evidence for dynamical instability around them in the form of atmospheric pollution and circumstellar disks, raises questions about the nature of planetary systems that can survive the vicissitudes of the asymptotic giant branch (AGB). We study the competing effects, on planets at several AU from the star, of strong tidal forces arising from the star's large convective envelope, and of the planets' orbital expansion due to stellar mass loss. We study, for the first time, the evolution of planets while following each thermal pulse on the AGB. For Jovian planets, tidal forces are strong, and can pull into the envelope planets initially at ~3 AU for a 1 M ☉ star and ~5 AU for a 5 M ☉ star. Lower-mass planets feel weaker tidal forces, and terrestrial planets initially within 1.5-3 AU enter the stellar envelope. Thus, low-mass planets that begin inside the maximum stellar radius can survive, as their orbits expand due to mass loss. The inclusion of a moderate planetary eccentricity slightly strengthens the tidal forces experienced by Jovian planets. Eccentric terrestrial planets are more at risk, since their eccentricity does not decay and their small pericenter takes them inside the stellar envelope. We also find the closest radii at which planets will be found around white dwarfs, assuming that any planet entering the stellar envelope is destroyed. Planets are in that case unlikely to be found inside ~1.5 AU of a white dwarf with a 1 M ☉ progenitor and ~10 AU of a white dwarf with a 5 M ☉ progenitor. (Less)
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author
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Solar and Stellar Astrophysics, planets and satellites: dynamical evolution and stability, stars: AGB and post-AGB, stars: evolution
in
The Astrophysical Journal
volume
761
issue
2
publisher
University of Chicago Press
external identifiers
  • scopus:84870776119
DOI
10.1088/0004-637X/761/2/121
language
English
LU publication?
no
id
7d5eb478-c926-4dfe-89ab-e60be048b322 (old id 4500267)
date added to LUP
2014-06-25 15:11:16
date last changed
2017-04-09 04:37:03
@article{7d5eb478-c926-4dfe-89ab-e60be048b322,
  abstract     = {The search for planets around white dwarf stars, and evidence for dynamical instability around them in the form of atmospheric pollution and circumstellar disks, raises questions about the nature of planetary systems that can survive the vicissitudes of the asymptotic giant branch (AGB). We study the competing effects, on planets at several AU from the star, of strong tidal forces arising from the star's large convective envelope, and of the planets' orbital expansion due to stellar mass loss. We study, for the first time, the evolution of planets while following each thermal pulse on the AGB. For Jovian planets, tidal forces are strong, and can pull into the envelope planets initially at ~3 AU for a 1 M ☉ star and ~5 AU for a 5 M ☉ star. Lower-mass planets feel weaker tidal forces, and terrestrial planets initially within 1.5-3 AU enter the stellar envelope. Thus, low-mass planets that begin inside the maximum stellar radius can survive, as their orbits expand due to mass loss. The inclusion of a moderate planetary eccentricity slightly strengthens the tidal forces experienced by Jovian planets. Eccentric terrestrial planets are more at risk, since their eccentricity does not decay and their small pericenter takes them inside the stellar envelope. We also find the closest radii at which planets will be found around white dwarfs, assuming that any planet entering the stellar envelope is destroyed. Planets are in that case unlikely to be found inside ~1.5 AU of a white dwarf with a 1 M ☉ progenitor and ~10 AU of a white dwarf with a 5 M ☉ progenitor.},
  articleno    = {121},
  author       = {Mustill, Alexander and Villaver, Eva},
  keyword      = {Astrophysics - Earth and Planetary Astrophysics,Astrophysics - Solar and Stellar Astrophysics,planets and satellites: dynamical evolution and stability,stars: AGB and post-AGB,stars: evolution},
  language     = {eng},
  number       = {2},
  publisher    = {University of Chicago Press},
  series       = {The Astrophysical Journal},
  title        = {Foretellings of Ragnarök: World-engulfing Asymptotic Giants and the Inheritance of White Dwarfs},
  url          = {http://dx.doi.org/10.1088/0004-637X/761/2/121},
  volume       = {761},
  year         = {2012},
}