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

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

doi:10.1093/mnras/stab1847

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

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

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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.

Original language	English
Pages (from-to)	2853–2870
Journal	Monthly Notices of the Royal Astronomical Society
Volume	506
Issue number	2
DOIs	https://doi.org/10.1093/mnras/stab1847
Publication status	Published - 05 Jul 2021

Keywords

Space and Planetary Science
Astronomy and Astrophysics

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Transmission spectroscopy with VLT FORS2: a featureless spectrum for the low-density transiting exoplanet WASP-88b
Copyright 2021 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This work is made available online in accordance with the publisher’s policies. Please refer to any applicable terms of use of the publisher.
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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

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

abstract = "We present ground-based optical transmission spectroscopy of the low-density hot Jupiter WASP-88b covering the wavelength range 4413 − 8333 {\AA} 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.",

keywords = "Space and Planetary Science, Astronomy and Astrophysics",

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

year = "2021",

month = jul,

day = "5",

doi = "10.1093/mnras/stab1847",

language = "English",

volume = "506",

pages = "2853–2870",

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Spyratos, P, Nikolov, N, Southworth, J, Constantinou, S, Madhusudhan, N, Carter, AL, de Mooij, EJW, Fortney, JJ, Gibson, NP, Goyal, JM, Helling, C, Mayne, NJ & 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, vol. 506, no. 2, pp. 2853–2870. https://doi.org/10.1093/mnras/stab1847

TY - JOUR

T1 - Transmission spectroscopy with VLT FORS2: a featureless spectrum for the low-density transiting exoplanet WASP-88b

AU - Spyratos, Petros

AU - Nikolov, Nikolay

AU - Southworth, John

AU - Constantinou, Savvas

AU - Madhusudhan, Nikku

AU - Carter, Aarynn L

AU - de Mooij, Ernst J W

AU - Fortney, Jonathan J

AU - Gibson, Neale P

AU - Goyal, Jayesh M

AU - Helling, Christiane

AU - Mayne, Nathan J

AU - Mikal-Evans, Thomas

PY - 2021/7/5

Y1 - 2021/7/5

N2 - 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.

AB - 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.

KW - Space and Planetary Science

KW - Astronomy and Astrophysics

U2 - 10.1093/mnras/stab1847

DO - 10.1093/mnras/stab1847

M3 - Article

VL - 506

SP - 2853

EP - 2870

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 2

ER -

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

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