Finding Extraterrestrial Life Using Ground-based High-dispersion Spectroscopy
\apj 764 (2013) 2
WTS-2 b: a hot Jupiter orbiting near its tidal destruction radius around a K dwarf
Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 440:2 (2014) 1470-1489
Abstract:
We report the discovery of WTS-2 b, an unusually close-in 1.02-d hot Jupiter (MP = 1.12MJ, RP = 1.30RJ) orbiting a K2V star, which has a possible gravitationally bound M-dwarf companion at 0.6 arcsec separation contributing ∼20 per cent of the total flux in the observed J-band light curve. The planet is only 1.5 times the separation from its host star at which it would be destroyed by Roche lobe overflow, and has a predicted remaining lifetime of just ∼40 Myr, assuming a tidal dissipation quality factor of Q′⋆=106. Q′⋆ is a key factor in determining how frictional processes within a host star affect the orbital evolution of its companion giant planets, but it is currently poorly constrained by observations. We calculate that the orbital decay of WTS-2 b would correspond to a shift in its transit arrival time of Tshift ∼ 17 s after 15 yr assuming Q′⋆=106. A shift less than this would place a direct observational constraint on the lower limit of Q′⋆ in this system. We also report a correction to the previously published expected Tshift for WASP-18 b, finding that Tshift = 356 s after 10 yr for Q′⋆=106, which is much larger than the estimated 28 s quoted in WASP-18 b discovery paper. We attempted to constrain Q′⋆ via a study of the entire population of known transiting hot Jupiters, but our results were inconclusive, requiring a more detailed treatment of transit survey sensitivities at long periods. We conclude that the most informative and straightforward constraints on Q′⋆ will be obtained by direct observational measurements of the shift in transit arrival times in individual hot Jupiter systems. We show that this is achievable across the mass spectrum of exoplanet host stars within a decade, and will directly probe the effects of stellar interior structure on tidal dissipation.Discovery and characterization of detached M dwarf eclipsing binaries in the WFCAM transit survey
Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 426:2 (2012) 1507-1532
Abstract:
We report the discovery of 16 detached M dwarf eclipsing binaries with J < 16 mag and provide a detailed characterization of three of them, using high-precision infrared light curves from the WFCAM Transit Survey (WTS). Such systems provide the most accurate and model-independent method for measuring the fundamental parameters of these poorly understood yet numerous stars, which currently lack sufficient observations to precisely calibrate stellar evolution models. We fully solve for the masses and radii of three of the systems, finding orbital periods in the range 1.5 < P < 4.9 d, with masses spanning 0.35–0.50 M⊙ and radii between 0.38 and 0.50 R⊙, with uncertainties of ∼3.5–6.4 per cent in mass and ∼2.7–5.5 per cent in radius. Close companions in short-period binaries are expected to be tidally locked into fast rotational velocities, resulting in high levels of magnetic activity. This is predicted to inflate their radii by inhibiting convective flow and increasing starspot coverage. The radii of the WTS systems are inflated above model predictions by ∼3–12 per cent, in agreement with the observed trend, despite an expected lower systematic contribution from starspot signals at infrared wavelengths. We searched for correlation between the orbital period and radius inflation by combining our results with all existing M dwarf radius measurements of comparable precision, but we found no statistically significant evidence for a decrease in radius inflation for longer period, less active systems. Radius inflation continues to exists in non-synchronized systems, indicating that the problem remains even for very low activity M dwarfs. Resolving this issue is vital not only for understanding the most populous stars in the Universe, but also for characterizing their planetary companions, which hold the best prospects for finding Earth-like planets in the traditional habitable zone.Four ultra-short-period eclipsing M-dwarf binaries in the WFCAM Transit Survey
\mnras 425 (2012) 2
Behind the mask: can HARMONI@ELT detect biosignatures in the reflected light of Proxima b?
Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 528:2 (2024) 3509-3522