Evidence of Water Vapor in the Atmosphere of a Metal-rich Hot Saturn with High-resolution Transmission Spectroscopy

Transmission spectroscopy presents one of the most successful approaches for investigating the atmospheres of exoplanets. We analyzed the near-infrared high-resolution transmission spectrum of a hot Saturn, HD 149026 b, taken using CARMENES spectrograph ( R ∼ 80,400 ). We found evidence of H 2 O at...

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Bibliographic Details
Published in:The Astronomical journal 2024-09, Vol.168 (3), p.106
Main Authors: Rafi, Sayyed A., Nugroho, Stevanus K., Tamura, Motohide, Nortmann, Lisa, Sánchez-López, Alejandro
Format: Article
Language:English
Subjects:
Atmospheric dynamics
Atmospheric water vapor
Exoplanet atmospheres
Exoplanet atmospheric composition
Extrasolar planets
High resolution
High resolution spectroscopy
Information retrieval
Infrared analysis
Infrared astronomy
Infrared spectroscopy
Metallicity
Near infrared radiation
Orbital mechanics
Orbital velocity
Planetary atmospheres
Saturn
Saturn atmosphere
Signal to noise ratio
Spectroscopy
Spectrum analysis
Transmission spectroscopy
Water vapor
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Summary:Transmission spectroscopy presents one of the most successful approaches for investigating the atmospheres of exoplanets. We analyzed the near-infrared high-resolution transmission spectrum of a hot Saturn, HD 149026 b, taken using CARMENES spectrograph ( R ∼ 80,400 ). We found evidence of H 2 O at a signal-to-noise ratio (S/N) of ∼4.8. We also performed grid search using a Bayesian framework and constrained the orbital velocity K p and rest velocity V rest to 158.17 − 7.90 + 8.31 km s −1 and 2.57 − 0.57 + 0.54 km s −1 , respectively. While the retrieved K p value is consistent with theoretical prediction, the retrieved V rest value is highly redshifted (>3 σ ). This might be an indication of either anomalous atmospheric dynamics at play or an orbit with nonzero eccentricity. Additionally, we searched for HCN but no successful detection has been made, possibly due to the relatively low-S/N data set. The detection of H 2 O and subsequent retrieval of its abundance, coupled with analysis of other species such as CO in the K band, for example, might help us to get some information about the atmospheric C/O ratio and metallicity, which in turn could give us some insight into the planet’s formation scenario.
ISSN:0004-6256
1538-3881
DOI:10.3847/1538-3881/ad5be9