THE WELL-ALIGNED ORBIT OF WASP-84b: EVIDENCE FOR DISK MIGRATION OF A HOT JUPITER

Journal Article · Tue Feb 10 04:00:00 EST 2015 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/800/1/L9· OSTI ID:22364202

Anderson, D. R.; Turner, O. D.; Brown, D. J. A.; Clark, B. J. M.; Smalley, B.; Cameron, A. Collier; Doyle, A. P.; Gillon, M.; Hellier, C.; Lovis, C.; Maxted, P. F. L.; Pollacco, D.; Queloz, D.; Smith, A. M. S., ^[1]

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1. N. Copernicus Astronomical Centre, Polish Academy of Sciences, Bartycka 18, 00-716, Warsaw (Poland)

We report the sky-projected orbital obliquity (spin–orbit angle) of WASP-84 b, a 0.69M{sub Jup} 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” (P<10 d) to have been shown to have migrated via this pathway. Further, we argue that the distribution of obliquities for planets orbiting cool stars (T{sub eff} < 6250 K) suggests that high-eccentricity migration is an important pathway for the formation of short-orbit, giant planets.

• OSTI ID: 22364202
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 800; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
INCLINATION
JUPITER PLANET
ORBITS
PROTOPLANETS
SATELLITES
STABILITY
STAR EVOLUTION
STARS