Accutely Characterizing the WASP-33 System

Accurate characterization of the stellar and orbital parameters of the exoplanetary system WASP-33 b from orbital dynamics

Author:

Iorio

Abstract:

By using the most recently published Doppler tomography measurements and accurate theoretical modeling of the oblateness-driven orbital precessions, we tightly constrain some of the physical and orbital parameters of the planetary system hosted by the fast rotating star WASP-33. In particular, the measurements of the orbital inclination ip to the plane of the sky and of the sky-projected spin-orbit misalignment λ at two epochs six years apart allowed for the determination of the longitude of the ascending node Ω and of the orbital inclination I to the apparent equatorial plane at the same epochs. As a consequence, average rates of change Ω˙exp, I˙exp of this two orbital elements, accurate to a ≈10−2 deg yr−1 level, were calculated as well. By comparing them to general theoretical expressions Ω˙J2, I˙J2 for their precessions induced by an arbitrarily oriented quadrupole mass moment, we were able to determine the angle i⋆ between the star's spin S and the line of sight and its first even zonal harmonic J⋆2 obtaining

Measurement of the Nodal Precession of hot Jupiter WASP-33b

Measurement of the Nodal Precession of WASP-33 b via Doppler Tomography

Authors:

Johnson et al

Abstract:

We have analyzed new and archival time series spectra taken six years apart during transits of the hot Jupiter WASP-33b, and spectroscopically resolved the line profile perturbation caused by the Rossiter-McLaughlin effect. The motion of this line profile perturbation is determined by the path of the planet across the stellar disk, which we show to have changed between the two epochs due to nodal precession of the planetary orbit. We measured rates of change of the impact parameter and the sky-projected spin-orbit misalignment of db/dt=−0.0228+0.0050−0.0018 yr−1 and dλ/dt=−0.487+0.089−0.076 ∘ yr−1, respectively, corresponding to a rate of nodal precession of dΩ/dt=0.117+0.012−0.029 ∘ yr−1. This is only the second measurement of nodal precession for a confirmed exoplanet transiting a single star. Finally, we used the rate of precession to set limits on the stellar gravitational quadrupole moment of 0.0017≤J2≤0.011.

Hot Jupiter WASP-33b's Atmosphere Does NOT Exhibit Temperature Inversion

A temperature inversion in WASP-33b? Large Binocular Telescope occultation data confirm significant thermal flux at short wavelengths

Authors:

von Essen

Abstract:

We observed a secondary eclipse of WASP-33b quasi-simultaneously in the optical (~0.55 {\mu}m) and the near-infrared (~1.05 {\mu}m) using the 2x8.4 m Large Binocular Telescope. WASP-33 is a {\delta} Scuti star pulsating with periods comparable to the eclipse duration, making the determination of the eclipse depth challenging. We use previously determined oscillation frequencies to model and remove the pulsation signal from the light curves, isolating the secondary eclipse. The determined eclipse depth is dF = 1.03 +/- 0.34 parts per thousand, corresponding to a brightness temperature of Tb = 3398 +/- 302 K. Combining previously published data with our new measurement we find the equilibrium temperature of WASP-33b to be Tb = 3358 +/- 165 K. We compare all existing eclipse data to a blackbody spectrum, to a carbon-rich non-inverted model and to a solar composition model with an inverted temperature structure. We find that current available data on WASP-33b's atmosphere can be best represented by a simple blackbody emission, without the need for more sophisticated atmospheric models with temperature inversions. Although our data cannot rule out models with or without a temperature inversion, they do confirm a high brightness temperature for the planet at short wavelengths. WASP-33b is one of the hottest exoplanets known till date, and its equilibrium temperature is consistent with rapid reradiation of the absorbed stellar light and a low albedo.

Temperature Inversion Detected in Hot Jupiter WASP-33b's Dayside Atmosphere

Spectroscopic Evidence for a Temperature Inversion in the Dayside Atmosphere of the Hot Jupiter WASP-33b

Authors:

Haynes et al

Abstract:

We present observations of two occultations of the extrasolar planet WASP-33b using the Wide Field Camera 3 (WFC3) on the HST, which allow us to constrain the temperature structure and composition of its dayside atmosphere. WASP-33b is the most highly irradiated hot Jupiter discovered to date, and the only exoplanet known to orbit a delta-Scuti star. We observed in spatial scan mode to decrease instrument systematic effects in the data, and removed fluctuations in the data due to stellar pulsations. The RMS for our final, binned spectrum is approximately 1.05 times the photon noise. We compare our final spectrum, along with previously published photometric data, to atmospheric models of WASP-33b spanning a wide range in temperature profiles and chemical compositions. We find that the data require models with an oxygen-rich chemical composition and a temperature profile that increases at high altitude. We also find that our spectrum displays an excess in the measured flux towards short wavelengths that is best explained as emission from TiO. If confirmed by additional measurements at shorter wavelengths, this planet would become the first hot Jupiter with a temperature inversion that can be definitively attributed to the presence of TiO in its dayside atmosphere.