Gemini/GMOS Transmission Spectral Survey: Complete Optical Transmission Spectrum of the hot Jupiter WASP-4b

Abstract

We present the complete optical transmission spectrum of the hot Jupiter WASP-4b from 440-940 nm at R ~ 400-1500 obtained with the Gemini Multi-Object Spectrometers (GMOS); this is the first result from a comparative exoplanetology survey program of close-in gas giants conducted with GMOS. WASP-4b has an equilibrium temperature of 1700 K and is favorable to study in transmission due to a large scale height (370 km). We derive the transmission spectrum of WASP-4b using 4 transits observed with the MOS technique. We demonstrate repeatable results across multiple epochs with GMOS, and derive a combined transmission spectrum at a precision about twice above photon noise, which is roughly equal to to one atmospheric scale height. The transmission spectrum is well fitted with a uniform opacity as a function of wavelength. The uniform opacity and absence of a Rayleigh slope from molecular hydrogen suggest that the atmosphere is dominated by clouds with condensate grain size of ~1 um. This result is consistent with previous observations of hot Jupiters since clouds have been seen in planets with similar equilibrium temperatures to WASP-4b. We describe a custom pipeline that we have written to reduce GMOS time-series data of exoplanet transits, and present a thorough analysis of the dominant noise sources in GMOS, which primarily consist of wavelength- and time- dependent displacements of the spectra on the detector, mainly due to a lack of atmospheric dispersion correction.

23 pages, 12 figures, accepted for publication in AJ, 2017 July 6

References in corpus (16)

• Achieving better than 1 minute accuracy in the Heliocentric and Barycentric Julian Dates
• Detection of atmospheric haze on an extrasolar planet: The 0.55 - 1.05 micron transmission spectrum of HD189733b with the Hubble Space Telescope
• Line and Mean Opacities for Ultracool Dwarfs and Extrasolar Planets
• A Precise Water Abundance Measurement for the Hot Jupiter WASP-43b
• Water Vapor in the Spectrum of the Extrasolar Planet HD 189733b: 1. the Transit
• Can TiO Explain Thermal Inversions in the Upper Atmospheres of Irradiated Giant Planets?
• HST hot-Jupiter transmission spectral survey: detection of potassium in WASP-31b along with a cloud deck and Rayleigh scattering
• HST/STIS Optical Transit Transmission Spectra of the hot-Jupiter HD209458b
• High temperature condensate clouds in super-hot Jupiter atmospheres
• WASP-4b: a 12th-magnitude transiting hot-Jupiter in the Southern hemisphere
• TiO and VO broad band absorption features in the optical spectrum of the atmosphere of the hot-Jupiter HD209458b
• HST hot-Jupiter transmission spectral survey: Haze in the atmosphere of WASP-6b
• A search for TiO in the optical high-resolution transmission spectrum of HD 209458b: Hindrance due to inaccuracies in the line database
• Determining atmospheric conditions at the terminator of the hot-Jupiter HD209458b
• The Transit Light Curve Project. XI. Submillimagnitude Photometry of Two Transits of the Bloated Planet WASP-4b
• Atmospheric Characterization of 5 Hot Jupiters with Wide Field Camera 3 on the Hubble Space Telescope

Cited by in corpus (23)

• The Transit Light Source Effect II: The Impact of Stellar Heterogeneity on Transmission Spectra of Planets Orbiting Broadly Sun-like Stars
• TESS Transit Timing of Hundreds of Hot Jupiters
• WASP-4b Arrived Early for the TESS Mission
• ExoClock Project III: 450 new exoplanet ephemerides from ground and space observations
• ExoClock project II: A large-scale integrated study with 180 updated exoplanet ephemerides
• LRG-BEASTS III: Ground-based transmission spectrum of the gas giant orbiting the cool dwarf WASP-80
• HST PanCET Program: A Complete Near-UV to Infrared Transmission Spectrum for the Hot Jupiter WASP-79b
• Dust in brown dwarfs and extra-solar planets. VII. Cloud formation in diffusive atmospheres
• The HST PanCET Program: An Optical to Infrared Transmission Spectrum of HAT-P-32Ab
• Detection of Na in WASP-21b's lower and upper atmosphere
• Examining the orbital decay targets KELT-9 b, KELT-16 b and WASP-4 b, and the transit-timing variations of HD 97658 b
• ACCESS: Ground-based Optical Transmission Spectroscopy of the Hot Jupiter WASP-4b
• A new method to measure the spectra of transiting exoplanet atmospheres using multi-object spectroscopy
• Gemini/GMOS Transmission Spectroscopy of the Grazing Planet Candidate WD 1856+534 b
• Effects of Thermal Emission on the Transmission Spectra of Hot Jupiters
• Atmospheric Characterization via Broadband Color Filters on the PLAnetary Transits and Oscillations of stars (PLATO) Mission
• Ground-Based Transmission Spectroscopy with VLT FORS2: Evidence for faculae and clouds in the optical spectrum of the warm Saturn WASP-110b
• LRG-BEASTS: Evidence for clouds in the transmission spectrum of HATS-46 b
• Science Commissioning of NIHTS: The Near-infrared High Throughput Spectrograph on the Lowell Discovery Telescope
• SPECtrophotometer for TRansmission spectroscopy of exoplanets (SPECTR)
• TOI-1201 b: A mini-Neptune transiting a bright and moderately young M dwarf
• A new method to correct for host star variability in multi-epoch observations of exoplanet transmission spectra
• Characterizing the WASP-4 system with TESS and radial velocity data: Constraints on the cause of the hot Jupiter's changing orbit and evidence of an outer planet