Spin-orbit evolution of short-period planets

Ian Dobbs-Dixon, D. N C Lin, Rosemary A. Mardling

Research output: Contribution to journalArticle

Abstract

The negligible eccentricity of all extrasolar planets with periods less than 6 days can be accounted for by dissipation of tidal disturbances within their envelopes that are induced by their host stars. In the period range of 7-21 days, planets with circular orbits coexist with planets with eccentric orbits. These are referred to as the borderline planets. We propose that this discrepancy can be attributed to the variation in spin-down rates of young stars. In particular, prior to spin-down, dissipation of a planet's tidal disturbance within the envelope of a sufficiently rapidly spinning star can excite eccentricity growth and, for a more slowly spinning star, at least reduce the eccentricity-damping rate. In contrast, tidal dissipation within the envelope of a slowly spinning low-mass mature star can enhance the eccentricity-damping process. On the basis of these results, we suggest that short-period planets around relatively young stars may have a much larger dispersion in eccentricity than those around mature stars. We also suggest that because the rate of angular momentum loss from G and K dwarfs via stellar winds is much faster than the tidal transfer of angular momentum between themselves and their very short (3-4 days) period planets, they cannot establish a dynamical configuration in which the stellar and planetary spins are approximately parallel and synchronous with the orbital frequency. In principle, however, such configurations may be established for planets (around G and K dwarfs) with orbital periods of up to several weeks. In contrast to G and K dwarfs, the angular momentum loss due to stellar winds is much weaker in F dwarfs. It is therefore possible for synchronized short-period planets to exist around such stars. The planet around Tau Boo is one such example.

Original languageEnglish (US)
Pages (from-to)464-476
Number of pages13
JournalAstrophysical Journal
Volume610
Issue number1 I
DOIs
StatePublished - Jul 20 2004

Fingerprint

planets
planet
orbits
stars
eccentricity
metal spinning
angular momentum
envelopes
dissipation
stellar winds
damping
disturbances
orbitals
eccentric orbits
disturbance
circular orbits
extrasolar planets
configurations
rate

Keywords

  • Planetary systems

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Spin-orbit evolution of short-period planets. / Dobbs-Dixon, Ian; Lin, D. N C; Mardling, Rosemary A.

In: Astrophysical Journal, Vol. 610, No. 1 I, 20.07.2004, p. 464-476.

Research output: Contribution to journalArticle

Dobbs-Dixon, Ian ; Lin, D. N C ; Mardling, Rosemary A. / Spin-orbit evolution of short-period planets. In: Astrophysical Journal. 2004 ; Vol. 610, No. 1 I. pp. 464-476.
@article{c732989dca0a4b12af1ad09fb7d69bde,
title = "Spin-orbit evolution of short-period planets",
abstract = "The negligible eccentricity of all extrasolar planets with periods less than 6 days can be accounted for by dissipation of tidal disturbances within their envelopes that are induced by their host stars. In the period range of 7-21 days, planets with circular orbits coexist with planets with eccentric orbits. These are referred to as the borderline planets. We propose that this discrepancy can be attributed to the variation in spin-down rates of young stars. In particular, prior to spin-down, dissipation of a planet's tidal disturbance within the envelope of a sufficiently rapidly spinning star can excite eccentricity growth and, for a more slowly spinning star, at least reduce the eccentricity-damping rate. In contrast, tidal dissipation within the envelope of a slowly spinning low-mass mature star can enhance the eccentricity-damping process. On the basis of these results, we suggest that short-period planets around relatively young stars may have a much larger dispersion in eccentricity than those around mature stars. We also suggest that because the rate of angular momentum loss from G and K dwarfs via stellar winds is much faster than the tidal transfer of angular momentum between themselves and their very short (3-4 days) period planets, they cannot establish a dynamical configuration in which the stellar and planetary spins are approximately parallel and synchronous with the orbital frequency. In principle, however, such configurations may be established for planets (around G and K dwarfs) with orbital periods of up to several weeks. In contrast to G and K dwarfs, the angular momentum loss due to stellar winds is much weaker in F dwarfs. It is therefore possible for synchronized short-period planets to exist around such stars. The planet around Tau Boo is one such example.",
keywords = "Planetary systems",
author = "Ian Dobbs-Dixon and Lin, {D. N C} and Mardling, {Rosemary A.}",
year = "2004",
month = "7",
day = "20",
doi = "10.1086/421510",
language = "English (US)",
volume = "610",
pages = "464--476",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "1 I",

}

TY - JOUR

T1 - Spin-orbit evolution of short-period planets

AU - Dobbs-Dixon, Ian

AU - Lin, D. N C

AU - Mardling, Rosemary A.

PY - 2004/7/20

Y1 - 2004/7/20

N2 - The negligible eccentricity of all extrasolar planets with periods less than 6 days can be accounted for by dissipation of tidal disturbances within their envelopes that are induced by their host stars. In the period range of 7-21 days, planets with circular orbits coexist with planets with eccentric orbits. These are referred to as the borderline planets. We propose that this discrepancy can be attributed to the variation in spin-down rates of young stars. In particular, prior to spin-down, dissipation of a planet's tidal disturbance within the envelope of a sufficiently rapidly spinning star can excite eccentricity growth and, for a more slowly spinning star, at least reduce the eccentricity-damping rate. In contrast, tidal dissipation within the envelope of a slowly spinning low-mass mature star can enhance the eccentricity-damping process. On the basis of these results, we suggest that short-period planets around relatively young stars may have a much larger dispersion in eccentricity than those around mature stars. We also suggest that because the rate of angular momentum loss from G and K dwarfs via stellar winds is much faster than the tidal transfer of angular momentum between themselves and their very short (3-4 days) period planets, they cannot establish a dynamical configuration in which the stellar and planetary spins are approximately parallel and synchronous with the orbital frequency. In principle, however, such configurations may be established for planets (around G and K dwarfs) with orbital periods of up to several weeks. In contrast to G and K dwarfs, the angular momentum loss due to stellar winds is much weaker in F dwarfs. It is therefore possible for synchronized short-period planets to exist around such stars. The planet around Tau Boo is one such example.

AB - The negligible eccentricity of all extrasolar planets with periods less than 6 days can be accounted for by dissipation of tidal disturbances within their envelopes that are induced by their host stars. In the period range of 7-21 days, planets with circular orbits coexist with planets with eccentric orbits. These are referred to as the borderline planets. We propose that this discrepancy can be attributed to the variation in spin-down rates of young stars. In particular, prior to spin-down, dissipation of a planet's tidal disturbance within the envelope of a sufficiently rapidly spinning star can excite eccentricity growth and, for a more slowly spinning star, at least reduce the eccentricity-damping rate. In contrast, tidal dissipation within the envelope of a slowly spinning low-mass mature star can enhance the eccentricity-damping process. On the basis of these results, we suggest that short-period planets around relatively young stars may have a much larger dispersion in eccentricity than those around mature stars. We also suggest that because the rate of angular momentum loss from G and K dwarfs via stellar winds is much faster than the tidal transfer of angular momentum between themselves and their very short (3-4 days) period planets, they cannot establish a dynamical configuration in which the stellar and planetary spins are approximately parallel and synchronous with the orbital frequency. In principle, however, such configurations may be established for planets (around G and K dwarfs) with orbital periods of up to several weeks. In contrast to G and K dwarfs, the angular momentum loss due to stellar winds is much weaker in F dwarfs. It is therefore possible for synchronized short-period planets to exist around such stars. The planet around Tau Boo is one such example.

KW - Planetary systems

UR - http://www.scopus.com/inward/record.url?scp=4444379988&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=4444379988&partnerID=8YFLogxK

U2 - 10.1086/421510

DO - 10.1086/421510

M3 - Article

AN - SCOPUS:4444379988

VL - 610

SP - 464

EP - 476

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1 I

ER -