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 of 4413−8333 Å with the FOcal Reducer Spectrograph (FORS2) on the Very Large Telescope. The FORS2 white light curves exhibit a significant time-correlated noise that 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. While our retrieval analysis results point towards clouds and hazes, further evidence is needed to definitively reject a clear-sky scenario.

Original language	English
Pages (from-to)	2853-2870
Number of pages	18
Journal	Monthly Notices of the Royal Astronomical Society
Volume	506
Issue number	2
Early online date	5 Jul 2021
DOIs	https://doi.org/10.1093/mnras/stab1847
Publication status	Published - 1 Sept 2021

Keywords

Methods: data analysis
Techniques: spectroscopic,
Planets and satellites: atmospheres
Stars: individual: WASP-88
Planetary systems

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10.1093/mnras/stab1847

Spyratos_2021_MNRAS_Transmission-spectroscopy_VoR
Copyright © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the final published version of the work, which was originally published at https://doi.org/10.1093/mnras/stab1847.
Final published version, 13.3 MB

H2020 MSCA ITN EJD 2019: H2020 MSCA ITN EJD 2019 CHAMELEON
Helling, C. (PI)
European Commission
1/06/20 → 31/05/24
Project: Standard

Cite this

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 of 4413−8333 {\AA} with the FOcal Reducer Spectrograph (FORS2) on the Very Large Telescope. The FORS2 white light curves exhibit a significant time-correlated noise that 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. While our retrieval analysis results point towards clouds and hazes, further evidence is needed to definitively reject a clear-sky scenario.",

keywords = "Methods: data analysis, Techniques: spectroscopic,, Planets and satellites: atmospheres, Stars: individual: WASP-88, Planetary systems",

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",

note = "PS was supported by a UK Science and Technology Facilities Council (STFC) studentship. CH acknowledges funding from the European Union H2020-MSCA-ITN2019 under grant agreement no. 860470 (CHAMELEON). NM acknowledges funding from the UKRI Future Leaders Scheme (MR/T040866/1), Science and Technology Facilities Council Consolidated Grant (ST/R000395/1), and Leverhulme Trust research project grant (RPG-2020-82).",

year = "2021",

month = sep,

day = "1",

doi = "10.1093/mnras/stab1847",

language = "English",

volume = "506",

pages = "2853--2870",

journal = "Monthly Notices of the Royal Astronomical Society",

issn = "0035-8711",

publisher = "Oxford University Press",

number = "2",

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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

T2 - 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

N1 - PS was supported by a UK Science and Technology Facilities Council (STFC) studentship. CH acknowledges funding from the European Union H2020-MSCA-ITN2019 under grant agreement no. 860470 (CHAMELEON). NM acknowledges funding from the UKRI Future Leaders Scheme (MR/T040866/1), Science and Technology Facilities Council Consolidated Grant (ST/R000395/1), and Leverhulme Trust research project grant (RPG-2020-82).

PY - 2021/9/1

Y1 - 2021/9/1

N2 - We present ground-based optical transmission spectroscopy of the low-density hot Jupiter WASP-88b covering the wavelength range of 4413−8333 Å with the FOcal Reducer Spectrograph (FORS2) on the Very Large Telescope. The FORS2 white light curves exhibit a significant time-correlated noise that 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. While our retrieval analysis results point towards 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 of 4413−8333 Å with the FOcal Reducer Spectrograph (FORS2) on the Very Large Telescope. The FORS2 white light curves exhibit a significant time-correlated noise that 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. While our retrieval analysis results point towards clouds and hazes, further evidence is needed to definitively reject a clear-sky scenario.

KW - Methods: data analysis

KW - Techniques: spectroscopic,

KW - Planets and satellites: atmospheres

KW - Stars: individual: WASP-88

KW - Planetary systems

U2 - 10.1093/mnras/stab1847

DO - 10.1093/mnras/stab1847

M3 - Article

SN - 0035-8711

VL - 506

SP - 2853

EP - 2870

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 2

ER -

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

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Keywords

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Projects

H2020 MSCA ITN EJD 2019: H2020 MSCA ITN EJD 2019 CHAMELEON

Cite this