Dayside Fe i Emission, Day–Night Brightness Contrast and Phase Offset of the Exoplanet WASP-33b

• Published in: The Astronomical journal 2022-06, Vol.163 (6), p.248
• Main Authors: Herman, Miranda K., de Mooij, Ernst J. W., Nugroho, Stevanus K., Gibson, Neale P., Jayawardhana, Ray
• Format: Article
• Language: English
• Subjects: Astronomy; Astronomy data analysis; Atmospheric models; Brightness; Emissions; Exoplanet atmospheres; Exoplanet atmospheric composition; Exoplanets; Extrasolar gaseous giant planets; Extrasolar planets; High resolution; High resolution spectroscopy; Hot Jupiters; Introduced species; Jupiter; Jupiter atmosphere; Mixing ratio; Night; Reflecting telescopes; Spectroscopy; Spectrum analysis
• ISSN: 0004-6256; 1538-3881
• DOI: 10.3847/1538-3881/ac5f4d

We report on Fe i in the dayside 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 Echelle SpectroPolarimetric Device for the Observation of Stars (ESPaDOnS) on the Canada–France–Hawaii telescope and High Dispersion Spectrograph 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 σ ) in our combined data sets, located at K p = 222.1 ± 0.4 km s −1 and v sys = −6.5 ± 0.3 km s −1 . Our values agree with previous reports. By accounting for WASP-33b’s brightness variation, we find evidence that its nightside flux is