Search for TiO and Optical Night-side Emission from the Exoplanet WASP-33b

Abstract

With a temperature akin to an M-dwarf, WASP-33b is among the hottest Jupiters known, making it an ideal target for high-resolution optical spectroscopy. By analyzing both transmission and emission spectra, we aim to substantiate previous reports of atmospheric TiO and a thermal inversion within the planet's atmosphere. We observed two transits and six arcs of the phase curve with ESPaDOns on the Canada-France-Hawaii Telescope and HIRES on the Keck telescope, which provide high spectral resolution and ample wavelength coverage. We employ the Doppler cross-correlation technique to search for the molecular signatures of TiO and H${}_2$O in these spectra, using models based on the TiO line list of Plez (2012). Though we cannot exclude line-list-dependent effects, our data do not corroborate previous indications of a thermal inversion. Instead we place a $3\sigma$ upper limit of $10^{-9}$ on the volume mixing ratio of TiO for the T-P profile we consider. While we are unable to constrain the volume mixing ratio of water, our strongest constraint on TiO comes from day-side emission spectra. This apparent absence of a stratosphere sits in stark contrast to previous observations of WASP-33b as well as theoretical predictions for the atmospheres of highly irradiated planets. The discrepancy could be due to variances between line lists, and we stress that detection limits are only as good as the line list employed, and are only valid for the specific T-P profile considered due to the strong degeneracy between lapse rate ($dT/d\log P$) and molecular abundance.

Accepted to AJ. 20 pages, 17 figures

References in corpus (19)

• Sodium Absorption From the Exoplanetary Atmosphere of HD189733b Detected in the Optical Transmission Spectrum
• Accurate, Empirical Radii and Masses of Planets and their Host Stars with Gaia Parallaxes
• Spectrally resolved detection of sodium in the atmosphere of HD189733b with the HARPS spectrograph
• Can TiO Explain Thermal Inversions in the Upper Atmospheres of Irradiated Giant Planets?
• Theoretical Spectral Models of the Planet HD 209458b with a Thermal Inversion and Water Emission Bands
• Ground-based detection of sodium in the transmission spectrum of exoplanet HD209458b
• High-Resolution Spectroscopic Detection of TiO and Stratosphere in the Day-side of WASP-33b
• 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
• Re-Evaluating WASP-12b: Strong Emission at 2.315 micron, Deeper Occultations, and an Isothermal Atmosphere
• A search for TiO in the optical high-resolution transmission spectrum of HD 209458b: Hindrance due to inaccuracies in the line database
• Thermal Emission of Exoplanet XO-1b
• Exoplanet atmospheres with GIANO II. Detection of molecular absorption in the dayside spectrum of HD 102195b
• 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
• Molecular Cross Sections for High Resolution Spectroscopy of Super Earths, Warm Neptunes and Hot Jupiters
• 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
• Comprehensive time series analysis of the transiting extrasolar planet WASP-33b

Cited by in corpus (22)

• Titanium oxide and chemical inhomogeneity in the atmosphere of the exoplanet WASP-189b
• Five key exoplanet questions answered via the analysis of 25 hot Jupiter atmospheres in eclipse
• EXOPLINES: Molecular Absorption Cross-Section Database for Brown Dwarf and Giant Exoplanet Atmospheres
• An inventory of atomic species in the atmosphere of WASP-121b using UVES high-resolution spectroscopy
• Into the Storm: Diving into the winds of the ultra hot Jupiter WASP-76 b with HARPS and ESPRESSO
• Carbon monoxide emission lines reveal an inverted atmosphere in the ultra hot Jupiter WASP-33 b consistent with an eastward hot spot
• Detection of OH in the ultra-hot Jupiter WASP-76b
• Confirmation of Iron Emission Lines and Non-detection of TiO on the Dayside of KELT-9b with MAROON-X
• Detection of iron emission lines and a temperature inversion on the dayside of the ultra-hot Jupiter KELT-20b
• Gemini/GMOS Optical Transmission Spectroscopy of WASP-121b: signs of variability in an ultra-hot Jupiter?
• Atmospheric characterization of the ultra-hot Jupiter WASP-33b: Detection of Ti and V emission lines and retrieval of a broadened line profile
• Is TiO emission present in the ultra-hot Jupiter WASP-33b? A reassessment using the improved ExoMol Toto line list
• Silicon in the dayside atmospheres of two ultra-hot Jupiters
• The PEPSI Exoplanet Transit Survey (PETS). II. A Deep Search for Thermal Inversion Agents in KELT-20 b/MASCARA-2 b with Emission and Transmission Spectroscopy
• The GAPS Programme with HARPS-N at TNG. XXXI. The WASP-33 system revisited with HARPS-N
• The Mantis Network I: A standard grid of templates and masks for cross-correlation analyses of ultra-hot Jupiter transmission spectra
• Evidence for TiO in the atmosphere of the hot Jupiter HAT-P-65 b
• High-resolution Emission Spectroscopy of the Ultrahot Jupiter KELT-9b: Little Variation in Day- and Nightside Emission Line Contrasts
• Fibre Fabry-Pérot Astrophotonic Correlation Spectroscopy for Remote Gas Identification and Radial Velocity Measurements
• Tighter constraints on the atmosphere of GJ 436 b from combined high-resolution CARMENES and CRIRES${}^{+}$ observations
• Thermal emission spectra of the ultra-hot Jupiter WASP-33 b
• Day-side Fe I Emission, Day-Night Brightness Contrast and Phase Offset of the Exoplanet WASP-33b