Physical properties and CNO abundances for high-mass stars in four main-sequence detached eclipsing binaries: V478 Cyg, AH Cep, V453 Cyg, and V578 Mon

Pavlovski, K; Southworth, J; Tamajo, E

Abstract

We present ten high-precision light curves of four transits in the XO-1 planetary system, obtained using u, g, r, redshifted Ha, I and z filters. We use these to measure the physical properties, orbital ephemeris, and a transmission spectrum of the planet covering the full optical wavelength range. We augment this with published HST/WFC3 observations to construct a transmission spectrum of the planet covering 0.37 to 1.65 µm. Our best-fitting model to this spectrum is for a H2/He-rich atmosphere containing water (3.05s confidence), nitrogen-bearing molecules NH3 and HCN (1.5s) and patchy cloud (1.3s). We find that adding the optical to the near-infrared data does not lead to more precise constraints on the planetary atmosphere in this case. We conduct a detailed investigation into the effect of stellar limb darkening on our results, concluding that the choice of limb darkening law and coefficients is unimportant; such conclusions may not hold for other systems so should be reassessed for all high-quality datasets. The planet radius we measure in the g-band is anomalously low and should be investigated with future observations at a higher spectral resolution. From the measured times of transit we determine an improved orbital ephemeris, calculate a lower limit on the modified stellar tidal quality factor of Q'?>105.6, and rule out a previously postulated sinusoidal variation in the transit times.

Citation

Pavlovski, K., Southworth, J., & Tamajo, E. (2018). Physical properties and CNO abundances for high-mass stars in four main-sequence detached eclipsing binaries: V478 Cyg, AH Cep, V453 Cyg, and V578 Mon. Monthly Notices of the Royal Astronomical Society, 481(3), 3129 -3147. https://doi.org/10.1093/mnras/sty2516

• Journal Article Type: Article
• Acceptance Date: Sep 10, 2018
• Online Publication Date: Sep 14, 2018
• Publication Date: 2018-12
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 481
• Issue: 3
• Pages: 3129 -3147
• DOI: https://doi.org/10.1093/mnras/sty2516
• Keywords: stars, planetary systems, planets and satellites, atmospheres, fundamental parameters, individual, XO-1
• Publisher URL: http://dx.doi.org/10.1093/mnras/sty2516