Day-side Fe I Emission, Day-Night Brightness Contrast and Phase Offset of the Exoplanet WASP-33b

Abstract

We report on Fe I in the day-side atmosphere of the ultra-hot Jupiter WASP-33b, providing evidence for a thermal inversion in the presence of an atomic species. We also introduce a new way to constrain the planet's brightness variation throughout its orbit, including its day-night contrast and peak phase offset, using high-resolution Doppler spectroscopy alone. We do so by analyzing high-resolution optical spectra of six arcs of the planet's phase curve, using ESPaDOnS on the Canada-France-Hawaii telescope and HDS on the Subaru telescope. By employing a likelihood mapping technique, we explore the marginalized distributions of parameterized atmospheric models, and detect Fe I emission at high significance ($>10.4\sigma$) in our combined data sets, located at $K_{\mathrm{p}}=222.1\pm 0.4$ km/s and $v_{\mathrm{sys}}=-6.5\pm 0.3$ km/s. Our values agree with previous reports. By accounting for WASP-33b's brightness variation, we find evidence that its night-side flux is $<10\%$ of the day-side flux and the emission peak is shifted westward of the substellar point, assuming the spectrum is dominated by Fe I. Our ESPaDOnS data, which cover phases before and after the secondary eclipse more evenly, weakly constrain the phase offset to $+22\pm 12$ degrees. We caution that the derived volume-mixing-ratio depends on our choice of temperature-pressure profile, but note it does not significantly influence our constraints on day-night contrast or phase offset. Finally, we use simulations to illustrate how observations with increased phase coverage and higher signal-to-noise ratios can improve these constraints, showcasing the expanding capabilities of high-resolution Doppler spectroscopy.

19 pages, 10 figures; accepted to AJ

References in corpus (25)

• On the radiative equilibrium of irradiated planetary atmospheres
• Atomic and Molecular Opacities for Brown Dwarf and Giant Planet Atmospheres
• Theoretical Spectral Models of the Planet HD 209458b with a Thermal Inversion and Water Emission Bands
• A spectral survey of an ultra-hot Jupiter: Detection of metals in the transmission spectrum of KELT-9 b
• Detection of Fe I in the atmosphere of the ultra-hot Jupiter WASP-121b, and a new likelihood-based approach for Doppler-resolved spectroscopy
• Changing Phases of Alien Worlds: Probing Atmospheres of Kepler Planets with High-Precision Photometry
• Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) IV. A spectral inventory of atoms and molecules in the high-resolution transmission spectrum of WASP-121 b
• High-Resolution Spectroscopic Detection of TiO and Stratosphere in the Day-side of WASP-33b
• Weighing The Non-Transiting Hot Jupiter Tau BOO b
• The 4.5 $\mu$m full-orbit phase curve of the hot Jupiter HD 209458b
• New Analysis Indicates No Thermal Inversion in the Atmosphere of HD 209458b
• Neutral Iron Emission Lines From The Day-side Of KELT-9b -- The GAPS Programme With HARPS-N At TNG XX
• Evidence against a strong thermal inversion in HD 209458 b from high-dispersion spectroscopy
• Detection of ionized calcium in the atmosphere of the ultra-hot Jupiter KELT-9b
• A temperature inversion with atomic iron in the ultra-hot dayside atmosphere of WASP-189b
• High-resolution Transmission Spectroscopy of MASCARA-2 b with EXPRES
• Detection of Fe\,{\sc i} Emission in the Day-side Spectrum of WASP-33b
• TESS unveils the phase curve of WASP-33b. Characterization of the planetary atmosphere and the pulsations from the star
• Precise photometric transit follow-up observations of five close-in exoplanets : update on their physical properties
• Arid or Cloudy: Characterizing the Atmosphere of the super-Earth 55 Cancri e using High-Resolution Spectroscopy
• Comprehensive time series analysis of the transiting extrasolar planet WASP-33b
• The GROUSE project III: Ks-band observations of the thermal emission from WASP-33b
• Is TiO emission present in the ultra-hot Jupiter WASP-33b? A reassessment using the improved ExoMol Toto line list
• Search for TiO and Optical Night-side Emission from the Exoplanet WASP-33b
• Spectroscopic Transit Search: a self-calibrating method for detecting planets around bright stars

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