The GTC exoplanet transit spectroscopy survey VIII. Flat transmission spectrum for the warm gas giant WASP-80

Abstract

We set out to study the atmosphere of WASP-80b, a warm inflated gas giant with an equilibrium temperature of $\sim$800~K, using ground-based transmission spectroscopy covering the spectral range from 520~to~910~nm. The observations allow us to probe the existence and abundance of K and Na in WASP-80b's atmosphere, existence of high-altitude clouds, and Rayleigh-scattering in the blue end of the spectrum. We observed two spectroscopic time series of WASP-80b transits with the OSIRIS spectrograph installed in the Gran Telescopio CANARIAS, and use the observations to estimate the planet's transmission spectrum between 520~nm and 910~nm in 20~nm-wide passbands, and around the K~I and Na~I resonance doublets in 6~nm-wide passbands. We model three previously published broadband datasets consisting of 27 light curves jointly prior to the transmission spectroscopy analysis in order to obtain improved prior estimates for the planet's orbital parameters, average radius ratio, and stellar density. We recover a flat transmission spectrum with no evidence of Rayleigh scattering or K~I or Na~I absorption, and obtain an improved system characterisation as a by-product of the broadband- and GTC-dataset modelling. The transmission spectra estimated separately from the two observing runs are consistent with each other, as are the transmission spectra estimated using either a parametric or nonparametric systematics models. The flat transmission spectrum favours an atmosphere model with high-altitude clouds over cloud-free models with stellar or sub-stellar metallicities.

Accepted to A&A 6.9.2017

References in corpus (8)

• The NumPy array: a structure for efficient numerical computation
• Impact of occultations of stellar active regions on transmission spectra: Can occultation of a plage mimic the signature of a blue sky?
• Exo-Transmit: An Open-Source Code for Calculating Transmission Spectra for Exoplanet Atmospheres of Varied Composition
• WASP-80b: a gas giant transiting a cool dwarf
• WASP-80b has a dayside within the T-dwarf range
• Multi-band, Multi-epoch Observations of the Transiting Warm Jupiter WASP-80b
• Probing the atmosphere of a sub-Jovian planet orbiting a cool dwarf
• The GTC exoplanet transit spectroscopy survey VIII. Flat transmission spectrum for the warm gas giant WASP-80

Cited by in corpus (13)

• The Transit Light Source Effect II: The Impact of Stellar Heterogeneity on Transmission Spectra of Planets Orbiting Broadly Sun-like Stars
• A Comparative Study of Atmospheric Chemistry with VULCAN
• The Upper Edge of the Neptune Desert Is Stable Against Photoevaporation
• The GAPS Programme at TNG XXXIX -- Multiple molecular species in the atmosphere of the warm giant planet WASP-80 b unveiled at high resolution with GIANO-B
• Detection of Na in WASP-21b's lower and upper atmosphere
• Evidence of a Clear Atmosphere for WASP-62b: the Only Known Transiting Gas Giant in the JWST Continuous Viewing Zone
• The GTC exoplanet transit spectroscopy survey VIII. Flat transmission spectrum for the warm gas giant WASP-80
• Role of the impact parameter in exoplanet transmission spectroscopy
• Tentative detection of titanium oxide in the atmosphere of WASP-69 b with a 4m ground-based telescope
• A Population Analysis of 20 Exoplanets Observed from the Optical to the Near-infrared Wavelengths with HST: Evidence for Widespread Stellar Contamination
• The GAPS programme at TNG LXVI. A homogeneous search for Na i and its possible variability in ten gas giant exoplanets
• Evidence for stellar contamination and water absorption in NGTS-5b's transmission spectra with GTC/OSIRIS
• The Hubble PanCET Program: A Featureless Transmission Spectrum for WASP-29b and Evidence of Enhanced Atmospheric Metallicity on WASP-80b