The well-aligned orbit of Wasp-84b: evidence for disk migration of a hot Jupiter

D. R. Anderson; A. H. M. J. Triaud; O. D. Turner; D. J. A. Brown; B. J. M. Clark; B. Smalley; A. Collier Cameron; A. P. Doyle; M. Gillon; C. Hellier; C. Lovis; P. F. L. Maxted; D. Pollacco; D. Queloz; A. M. S. Smith

doi:10.1088/2041-8205/800/1/L9

The well-aligned orbit of Wasp-84b: evidence for disk migration of a hot Jupiter

D. R. Anderson^*, A. H. M. J. Triaud, O. D. Turner, D. J. A. Brown, B. J. M. Clark, B. Smalley, A. Collier Cameron, A. P. Doyle, M. Gillon, C. Hellier, C. Lovis, P. F. L. Maxted, D. Pollacco, D. Queloz, A. M. S. Smith

^*Corresponding author for this work

School of Physics and Astronomy

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Abstract

We report the sky-projected orbital obliquity (spin–orbit angle) of WASP-84 b, a 0.69 planet in an 8.52 day orbit around a G9V/K0V star, to be λ = −0.3 ± 1.7°. We obtain a true obliquity of ψ = 17.3 ± 7.7° from a measurement of the inclination of the stellar spin axis with respect to the sky plane. Due to the young age and the weak tidal forcing of the system, we suggest that the orbit of WASP-84b is unlikely to have both realigned and circularized from the misaligned and/or eccentric orbit likely to have arisen from high-eccentricity migration. Therefore we conclude that the planet probably migrated via interaction with the protoplanetary disk. This would make it the first "hot Jupiter" () to have been shown to have migrated via this pathway. Further, we argue that the distribution of obliquities for planets orbiting cool stars (T_eff < 6250 K) suggests that high-eccentricity migration is an important pathway for the formation of short-orbit, giant planets.

Original language	English
Article number	L9
Number of pages	6
Journal	Astrophysical Journal Letters
Volume	800
Issue number	1
DOIs	https://doi.org/10.1088/2041-8205/800/1/L9
Publication status	Published - 10 Feb 2015

Keywords

Planets and satellites: dynamical evolution and stability
Planet-disk interactions
Planets and satellites: individual (WASP-84b)
Planet-star interactions
Stars: individual (WASP-84)
Exoplanet HD 80606B
Tidal dissipation
Stellar obliquity
Giant planet
Long-period
Transit
Spin
System
Misalignment
Evolution

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Cameron_2015_APL_WellAligned
© 2015. The American Astronomical Society. All rights reserved. Reproduced in accordance with the AAS copyright policy. The final version can be found at: http://dx.doi.org/10.1088/2041-8205/800/1/L9
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Astronomy at St Andrews 2015-2018: Astronomy at St Andrews 2015-2018
Jardine, M. M. (PI), Cameron, A. C. (CoI), Cyganowski, C. J. (CoI), Horne, K. D. (CoI) & Wood, K. (CoI)
Science & Technology Facilities Council
1/04/15 → 31/03/18
Project: Standard
AGN Echo mapping: AGN Echo Mapping and Mineral Clouds in Alien Atmospheres
Horne, K. D. (PI)
Science & Technology Facilities Council
1/04/12 → 31/08/12
Project: Standard
Astrophysics at St Andrews:2012 - 2014: Astrophysics at St Andrews: 2012 - 2014
Horne, K. D. (PI)
Science & Technology Facilities Council
1/10/11 → 31/03/12
Project: Standard

Cite this

Anderson, D. R., Triaud, A. H. M. J., Turner, O. D., Brown, D. J. A., Clark, B. J. M., Smalley, B., Cameron, A. C., Doyle, A. P., Gillon, M., Hellier, C., Lovis, C., Maxted, P. F. L., Pollacco, D., Queloz, D., & Smith, A. M. S. (2015). The well-aligned orbit of Wasp-84b: evidence for disk migration of a hot Jupiter. Astrophysical Journal Letters, 800(1), Article L9. https://doi.org/10.1088/2041-8205/800/1/L9

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title = "The well-aligned orbit of Wasp-84b: evidence for disk migration of a hot Jupiter",

abstract = "We report the sky-projected orbital obliquity (spin–orbit angle) of WASP-84 b, a 0.69 planet in an 8.52 day orbit around a G9V/K0V star, to be λ = −0.3 ± 1.7°. We obtain a true obliquity of ψ = 17.3 ± 7.7° from a measurement of the inclination of the stellar spin axis with respect to the sky plane. Due to the young age and the weak tidal forcing of the system, we suggest that the orbit of WASP-84b is unlikely to have both realigned and circularized from the misaligned and/or eccentric orbit likely to have arisen from high-eccentricity migration. Therefore we conclude that the planet probably migrated via interaction with the protoplanetary disk. This would make it the first {"}hot Jupiter{"} () to have been shown to have migrated via this pathway. Further, we argue that the distribution of obliquities for planets orbiting cool stars (Teff < 6250 K) suggests that high-eccentricity migration is an important pathway for the formation of short-orbit, giant planets.",

keywords = "Planets and satellites: dynamical evolution and stability, Planet-disk interactions, Planets and satellites: individual (WASP-84b), Planet-star interactions, Stars: individual (WASP-84), Exoplanet HD 80606B, Tidal dissipation, Stellar obliquity, Giant planet, Long-period, Transit, Spin, System, Misalignment, Evolution",

author = "Anderson, {D. R.} and Triaud, {A. H. M. J.} and Turner, {O. D.} and Brown, {D. J. A.} and Clark, {B. J. M.} and B. Smalley and Cameron, {A. Collier} and Doyle, {A. P.} and M. Gillon and C. Hellier and C. Lovis and Maxted, {P. F. L.} and D. Pollacco and D. Queloz and Smith, {A. M. S.}",

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doi = "10.1088/2041-8205/800/1/L9",

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T2 - evidence for disk migration of a hot Jupiter

AU - Anderson, D. R.

AU - Triaud, A. H. M. J.

AU - Turner, O. D.

AU - Brown, D. J. A.

AU - Clark, B. J. M.

AU - Smalley, B.

AU - Cameron, A. Collier

AU - Doyle, A. P.

AU - Gillon, M.

AU - Hellier, C.

AU - Lovis, C.

AU - Maxted, P. F. L.

AU - Pollacco, D.

AU - Queloz, D.

AU - Smith, A. M. S.

PY - 2015/2/10

Y1 - 2015/2/10

N2 - We report the sky-projected orbital obliquity (spin–orbit angle) of WASP-84 b, a 0.69 planet in an 8.52 day orbit around a G9V/K0V star, to be λ = −0.3 ± 1.7°. We obtain a true obliquity of ψ = 17.3 ± 7.7° from a measurement of the inclination of the stellar spin axis with respect to the sky plane. Due to the young age and the weak tidal forcing of the system, we suggest that the orbit of WASP-84b is unlikely to have both realigned and circularized from the misaligned and/or eccentric orbit likely to have arisen from high-eccentricity migration. Therefore we conclude that the planet probably migrated via interaction with the protoplanetary disk. This would make it the first "hot Jupiter" () to have been shown to have migrated via this pathway. Further, we argue that the distribution of obliquities for planets orbiting cool stars (Teff < 6250 K) suggests that high-eccentricity migration is an important pathway for the formation of short-orbit, giant planets.

AB - We report the sky-projected orbital obliquity (spin–orbit angle) of WASP-84 b, a 0.69 planet in an 8.52 day orbit around a G9V/K0V star, to be λ = −0.3 ± 1.7°. We obtain a true obliquity of ψ = 17.3 ± 7.7° from a measurement of the inclination of the stellar spin axis with respect to the sky plane. Due to the young age and the weak tidal forcing of the system, we suggest that the orbit of WASP-84b is unlikely to have both realigned and circularized from the misaligned and/or eccentric orbit likely to have arisen from high-eccentricity migration. Therefore we conclude that the planet probably migrated via interaction with the protoplanetary disk. This would make it the first "hot Jupiter" () to have been shown to have migrated via this pathway. Further, we argue that the distribution of obliquities for planets orbiting cool stars (Teff < 6250 K) suggests that high-eccentricity migration is an important pathway for the formation of short-orbit, giant planets.

KW - Planets and satellites: dynamical evolution and stability

KW - Planet-disk interactions

KW - Planets and satellites: individual (WASP-84b)

KW - Planet-star interactions

KW - Stars: individual (WASP-84)

KW - Exoplanet HD 80606B

KW - Tidal dissipation

KW - Stellar obliquity

KW - Giant planet

KW - Long-period

KW - Transit

KW - Spin

KW - System

KW - Misalignment

KW - Evolution

U2 - 10.1088/2041-8205/800/1/L9

DO - 10.1088/2041-8205/800/1/L9

M3 - Article

SN - 2041-8205

VL - 800

JO - Astrophysical Journal Letters

JF - Astrophysical Journal Letters

IS - 1

M1 - L9

ER -

The well-aligned orbit of Wasp-84b: evidence for disk migration of a hot Jupiter

Abstract

Keywords

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Projects

Astronomy at St Andrews 2015-2018: Astronomy at St Andrews 2015-2018

AGN Echo mapping: AGN Echo Mapping and Mineral Clouds in Alien Atmospheres

Astrophysics at St Andrews:2012 - 2014: Astrophysics at St Andrews: 2012 - 2014

Cite this