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., de Mooij, E. J. W., Fortney, J. J., Gibson, N. P., Goyal, J. M., Helling, C., Mayne, N. J., & 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
• Electronic ISSN: 1365-2966
• 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
• Public URL: https://keele-repository.worktribe.com/output/420578
• Publisher URL: https://academic.oup.com/mnras/advance-article/doi/10.1093/mnras/stab1847/6315343