Ground-Based Transmission Spectroscopy with VLT FORS2: Evidence for faculae and clouds in the optical spectrum of the warm Saturn WASP-110b

Abstract

We present a ground-based optical transmission spectrum for the warm Saturn-mass exoplanet WASP-110b from two transit observations made with the FOcal Reducer and Spectrograph (FORS2) on the Very Large Telescope (VLT). The spectrum covers the wavelength range from 4000 to 8333Å, which is binned in 46 transit depths measured to an averaged precision of 220 parts per million (ppm) over an averaged 80Å~bin for a Vmag=12.8 star. The measured transit depths are unaffected by a dilution from a close A-type field dwarf, which was fully resolved. The overall main characteristic of the transmission spectrum is an increasing radius with wavelength and a lack of the theoretically predicted pressure-broadened sodium and potassium absorption features for a cloud-free atmosphere. We analyze archival high-resolution optical spectroscopy and find evidence for low to moderate activity of the host star, which we take into account in the atmospheric retrieval analysis. Using the AURA retrieval code, we find that the observed transmission spectrum can be best explained by a combination of unocculted stellar faculae and a cloud deck. Transmission spectra of cloud-free and hazy atmospheres are rejected at a high confidence. With a possible cloud deck at its terminator, WASP-110b joins the increasing population of irradiated hot-Jupiter exoplanets with cloudy atmospheres observed in transmission.

arXiv commentAccepted for publication in The Astronomical Journal

References in corpus (53)

• Astropy: A Community Python Package for Astronomy
• emcee: The MCMC Hammer
• Gaia Data Release 2. Summary of the contents and survey properties
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• Analytic Lightcurves for Planetary Transit Searches
• A new extensive library of PHOENIX stellar atmospheres and synthetic spectra
• The Man Behind the Curtain: X-rays Drive the UV through NIR Variability in the 2013 AGN Outburst in NGC 2617
• X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue
• The WASP Project and the SuperWASP Cameras
• batman: BAsic Transit Model cAlculatioN in Python
• A continuum from clear to cloudy hot-Jupiter exoplanets without primordial water depletion
• Achieving better than 1 minute accuracy in the Heliocentric and Barycentric Julian Dates
• The PPMXL catalog of positions and proper motions on the ICRS. Combining USNO-B1.0 and 2MASS
• A Unified Theory for the Atmospheres of the Hot and Very Hot Jupiters: Two Classes of Irradiated Atmospheres
• Theoretical Transmission Spectra During Extrasolar Giant Planet Transits
• A Temperature and Abundance Retrieval Method for Exoplanet Atmospheres
• The effect of red noise on planetary transit detection
• Line and Mean Opacities for Ultracool Dwarfs and Extrasolar Planets
• The prevalence of dust on the exoplanet HD 189733b from Hubble and Spitzer observations
• Gaseous Mean Opacities for Giant Planet and Ultracool Dwarf Atmospheres over a Range of Metallicities and Temperatures
• Water Vapor in the Spectrum of the Extrasolar Planet HD 189733b: 1. the Transit
• Transmission Spectra of Three-Dimensional Hot Jupiter Model Atmospheres
• A Gaussian process framework for modelling instrumental systematics: application to transmission spectroscopy
• The Near-Infrared and Optical Spectra of Methane Dwarfs and Brown Dwarfs
• Cosmic Rays and Climate
• Mass-Metallicity Trends in Transiting Exoplanets from Atmospheric Abundances of H${}_2$O, Na, and K
• Transmission spectral properties of clouds for hot Jupiter exoplanets
• Rotation periods of late-type dwarf stars from time-series high-resolution spectroscopy of chromospheric indicators
• The HST PanCET Program: Exospheric Mg II and Fe II in the Near-UV transmission spectrum of WASP-121b using Jitter Decorrelation
• An HST Optical to Near-IR Transmission Spectrum of the Hot Jupiter WASP-19b: Detection of Atmospheric Water and Likely Absence of TiO
• The ASAS-SN Catalog of Variable Stars III: Variables in the Southern TESS Continuous Viewing Zone
• ACCESS I: An Optical Transmission Spectrum of GJ 1214b Reveals a Heterogeneous Stellar Photosphere
• An absolute sodium abundance for a cloud-free 'hot Saturn' exoplanet
• Retrieval of planetary and stellar properties in transmission spectroscopy with Aura
• The Stagger-grid: A grid of 3D stellar atmosphere models - IV. Limb darkening coefficients
• A Gemini ground-based transmission spectrum of WASP-29b: a featureless spectrum from 515 to 720nm
• Transit Analysis Package (TAP and autoKep): IDL Graphical User Interfaces for Extrasolar Planet Transit Photometry
• Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) I. Detection of hot neutral sodium at high altitudes on WASP-49b
• VLT FORS2 comparative transmission spectroscopy: Detection of Na in the atmosphere of WASP-39b from the ground
• The optical transmission spectrum of the hot Jupiter HAT-P-32b: clouds explain the absence of broad spectral features?
• Simulating the cloudy atmospheres of HD 209458 b and HD 189733 b with the 3D Met Office Unified Model
• Limb-darkening and exoplanets II: Choosing the Best Law for Optimal Retrieval of Transit Parameters
• Long-Term Transit Timing Monitoring and Refined Light Curve Parameters of HAT-P-13b
• Implications of three-dimensional chemical transport in hot Jupiter atmospheres: results from a consistently coupled chemistry-radiation-hydrodynamics model
• New Avenues for Thermal Inversions in hot Jupiters
• Discovery and characterization of WASP-6b, an inflated sub-Jupiter mass planet transiting a solar-type star
• Reliable inference of exoplanet light curve parameters using deterministic and stochastic systematics models
• VLT/FORS2 comparative transmission spectroscopy II: confirmation of a cloud-deck and Rayleigh scattering in WASP-31b, but no potassium?
• LRG-BEASTS III: Ground-based transmission spectrum of the gas giant orbiting the cool dwarf WASP-80
• Detection of Na, K and H${}_2$O in the hazy atmosphere of WASP-6b
• Gemini/GMOS Transmission Spectral Survey: Complete Optical Transmission Spectrum of the hot Jupiter WASP-4b
• A feature-rich transmission spectrum for WASP-127b
• Ground-Based Transmission Spectroscopy with FORS2: A featureless optical transmission spectrum and detection of H${}_2$O for the ultra-hot Jupiter WASP-103b

Cited by in corpus (6)

• Solar-to-supersolar sodium and oxygen absolute abundances for a "hot Saturn" orbiting a metal-rich star
• Revisiting fundamental properties of TiO${}_2$ nanoclusters as condensation seeds in astrophysical environments
• Detection of faculae in the transit and transmission spectrum of WASP-69b
• A precise blue-optical transmission spectrum from the ground: Evidence for haze in the atmosphere of WASP-74b
• The Similar Seven: A set of very-alike exoplanets to test correlations between system parameters and atmospheric properties
• A new method to correct for host star variability in multi-epoch observations of exoplanet transmission spectra