Transmission spectroscopy with VLT FORS2: a featureless spectrum for the low-density transiting exoplanet WASP-88b

Spyratos, Petros; Nikolov, Nikolay; Southworth, John; Constantinou, Savvas; Madhusudhan, Nikku; Carter, Aarynn L; de Mooij, Ernst J W; Fortney, Jonathan J; Gibson, Neale P; Goyal, Jayesh M; Helling, Christiane; Mayne, Nathan J; Mikal-Evans, Thomas

Abstract

We present ground-based optical transmission spectroscopy of the low-density hot Jupiter WASP-88b covering the wavelength range 4413 - 8333 Å with the FORS2 spectrograph on the Very Large Telescope. The FORS2 white light curves exhibit a significant time-correlated noise which we model using a Gaussian Process and remove as a wavelength-independent component from the spectroscopic light curves. We analyse complementary photometric observations from the Transiting Exoplanet Survey Satellite and refine the system properties and ephemeris. We find a featureless transmission spectrum with increased absorption towards shorter wavelengths. We perform an atmospheric retrieval analysis with the aura code, finding tentative evidence for haze in the upper atmospheric layers and a lower likelihood for a dense cloud deck. Whilst our retrieval analysis results point toward clouds and hazes, further evidence is needed to definitively reject a clear-sky scenario.

Citation

Spyratos, P., Nikolov, N., Southworth, J., Constantinou, S., Madhusudhan, N., Carter, A. L., …Mikal-Evans, T. (2021). Transmission spectroscopy with VLT FORS2: a featureless spectrum for the low-density transiting exoplanet WASP-88b. Monthly Notices of the Royal Astronomical Society, 506(2), 2853-2870. https://doi.org/10.1093/mnras/stab1847

• Journal Article Type: Article
• Acceptance Date: Jun 24, 2021
• Online Publication Date: Jul 5, 2021
• Publication Date: 2021-09
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 506
• Issue: 2
• Pages: 2853-2870
• DOI: https://doi.org/10.1093/mnras/stab1847
• Keywords: methods: data analysis, techniques: spectroscopic, planets and satellites: atmospheres, stars: individual: WASP-88, planetary systems
• Publisher URL: https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stab1847/6315343