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arXiv · 2203.04969

Exoplanet atmospheres at high resolution through a modest-size telescope. Fe II in MASCARA-2b and KELT-9b with FIES on the Nordic Optical Telescope

Aaron Bello-Arufe·Lars A. Buchhave·João M. Mendonça·René Tronsgaard·Kevin Heng·H. Jens Hoeijmakers·Andrew W. Mayo
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Abstract

Ground-based, high-resolution spectrographs are providing us with an unprecedented view of the dynamics and chemistry of the atmospheres of planets outside the Solar System. While there is a large number of stable and precise high-resolution spectrographs on modest-size telescopes, it is the spectrographs at observatories with apertures larger than 3.5 metres that dominate the atmospheric follow-up of exoplanets. In this work, we explore the potential of characterising exoplanetary atmospheres with FIES, a high-resolution spectrograph at the 2.56 metre Nordic Optical Telescope. We observed two transits of MASCARA-2 b (also known as KELT-20 b) and one transit of KELT-9 b to search for atomic iron, a species that has been recently discovered in both neutral and ionised forms in the atmospheres of these ultra-hot Jupiters using large telescopes. Using a cross-correlation method, we detect a signal of Fe II at the $4.5σ$ and $4.0σ$ level in the transits of MASCARA-2 b. We also detect Fe II in the transit of KELT-9 b at the $8.5σ$ level. Although we do not find any significant Doppler shift in the signal of MASCARA-2 b, we do measure a moderate blueshift (3-6 km/s) of the feature in KELT-9 b, which might be a manifestation of high-velocity winds transporting Fe II from the planetary dayside to the nightside. Our work demonstrates the feasibility of investigating exoplanet atmospheres with FIES, potentially unlocking a wealth of additional atmosphere detections with this and other high-resolution spectrographs mounted on similar-size telescopes.

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Aaron Bello-Arufe, Lars A. Buchhave, João M. Mendonça, René Tronsgaard, Kevin Heng, H. Jens Hoeijmakers, Andrew W. Mayo. 2022-03-14. Exoplanet atmospheres at high resolution through a modest-size telescope. Fe II in MASCARA-2b and KELT-9b with FIES on the Nordic Optical Telescope. https://doi.org/10.1051/0004-6361%2F202142787

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