Searching for Rapid Orbital Decay of WASP-18b

Journal Article · Mon Feb 20 04:00:00 EST 2017 · Astrophysical Journal Letters

DOI:https://doi.org/10.3847/2041-8213/AA5D9F· OSTI ID:22654536

Wilkins, Ashlee N.; Deming, Drake; Hamilton, Douglas ^[1]; Delrez, Laetitia ^[2]; Barker, Adrian J. ^[3]; Gillon, Michael; Jehin, Emmanuel ^[4]

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1. Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States)
2. Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE (United Kingdom)
3. Department of Applied Mathematics, School of Mathematics, University of Leeds, Leeds LS2 9JT (United Kingdom)
4. Space Sciences, Technologies and Astrophysics Research (STAR) Institute, Université de Liège, allée du 6 Août 19C, B-4000 Lige (Belgium)

The WASP-18 system, with its massive and extremely close-in planet, WASP-18b ( M{sub p} = 10.3 M{sub J}, a = 0.02 au, P = 22.6 hr), is one of the best-known exoplanet laboratories to directly measure Q ′, the modified tidal quality factor and proxy for efficiency of tidal dissipation, of the host star. Previous analysis predicted a rapid orbital decay of the planet toward its host star that should be measurable on the timescale of a few years, if the star is as dissipative as is inferred from the circularization of close-in solar-type binary stars. We have compiled published transit and secondary eclipse timing (as observed by WASP, TRAPPIST, and Spitzer ) with more recent unpublished light curves (as observed by TRAPPIST and Hubble Space Telescope ) with coverage spanning nine years. We find no signature of a rapid decay. We conclude that the absence of rapid orbital decay most likely derives from Q ′ being larger than was inferred from solar-type stars and find that Q ′ ≥ 1 × 10{sup 6}, at 95% confidence; this supports previous work suggesting that F stars, with their convective cores and thin convective envelopes, are significantly less tidally dissipative than solar-type stars, with radiative cores and large convective envelopes.

• OSTI ID: 22654536
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 2 Vol. 836; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BINARY STARS
BORON 18
DECAY
ECLIPSE
EFFICIENCY
PLANETS
QUALITY FACTOR
SATELLITE ATMOSPHERES
SATELLITES
SPACE
TELESCOPES
VISIBLE RADIATION