Searching for Rapid Orbital Decay of WASP-18b
- Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States)
- Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE (United Kingdom)
- Department of Applied Mathematics, School of Mathematics, University of Leeds, Leeds LS2 9JT (United Kingdom)
- 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compiled published transit and secondary eclipse timing (as observed by WASP, TRAPPIST, and Spitzer ) with more recent unpublished light curves (as observed by TRAPPIST and Hubble Space Telescope ) with coverage spanning nine years.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, Vol. 836, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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