Papers › High-resolution emission spectroscopy retrievals of MASCARA-1b with CRIRES+: Strong...
High-resolution emission spectroscopy retrievals of MASCARA-1b with CRIRES+: Strong detections of CO, H₂O and Fe emission lines and a C$/$O consistent with solar
Swaetha Ramkumar, Neale P. Gibson, Stevanus K. Nugroho, Cathal Maguire, Mark Fortune
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The characterization of exoplanet atmospheres has proven to be successful using high-resolution spectroscopy. Phase curve observations of hot/ultra-hot Jupiters can reveal their compositions and thermal structures, thereby allowing the detection of molecules and atoms in the planetary atmosphere using the cross-correlation technique. We present pre-eclipse observations of the ultra-hot Jupiter, MASCARA-1b, observed with the recently upgraded CRIRES+ high-resolution infrared spectrograph at the VLT. We report a detection of Fe (≈8.3σ) in the K-band and confirm previous detections of CO (>15σ) and H₂O (>10σ) in the day-side atmosphere of MASCARA-1b. Using a Bayesian inference framework, we retrieve the abundances of the detected species and constrain planetary orbital velocities, T-P profiles, and the carbon-to-oxygen ratio (C/O). A free retrieval results in an elevated CO abundance (log₁₀(χ_(¹²CO)) = -2.85^(+0.57)_(-0.69)), leading to a super-solar C/O ratio. More realistically, allowing for vertically-varying chemistry in the atmosphere by incorporating a chemical-equilibrium model results in a C/O of 0.68^(+0.12)_(-0.22) and a metallicity of [M/H] = 0.62^(+0.28)_(-0.55), both consistent with solar values. Finally, we also report a slight offset of the Fe feature in both Kₚ and v_(sys) that could be a signature of atmospheric dynamics. Due to the 3D structure of exoplanet atmospheres and the exclusion of time/phase dependence in our 1D forward models, further follow-up observations and analysis are required to confirm or refute this result.
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