The PEPSI Exoplanet Transit Survey (PETS)

III. The detection of Fe I, Cr I, and Ti I in the atmosphere of MASCARA-1 b through high-resolution emission spectroscopy

¹ INAF - Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy
e-mail: gaetano.scandariato@inaf.it
² INAF - Osservatorio Astronomico di Brera, Via E. Bianchi, 46, 23807 Merate (LC), Italy
³ INAF - Osservatorio Astrofisico di Torino, Strada Osservatorio 20, 10025 Pino Torinese, Italy
⁴ Department of Astronomy, The Ohio State University, 4055 McPherson Laboratory, 140 West 18th Ae., Columbus, OH 43210, USA
⁵ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁶ Leibniz-Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
⁷ INAF - Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy
⁸ Dipartimento di Fisica e Astronomia "Galileo Galilei", Universita degli Studi di Padova, 35122 Padova, Italy
⁹ Universitäts-Sternwarte, Ludwig-Maximilians-Universität München, Scheinerstrasse 1, 81679 München, Germany
¹⁰ Exzellenzcluster Origins, Boltzmannstraße 2, 85748 Garching, Germany
¹¹ School of Earth and Space Exploration, Arizona State University, 660 S. Mill Ave., Tempe, AZ 85281, USA
¹² INAF - Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
¹³ Institute of Physics & Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany
¹⁴ Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721, USA
¹⁵ Large Binocular Telescope Observatory, 933 N. Cherry Ave., Tucson, AZ 85721, USA
¹⁶ Department of Astronomy, University of Science and Technology of China, Hefei 230026, PR China
¹⁷ Institute of Astrophysics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany

Received: 23 November 2022
Accepted: 6 April 2023

Abstract

Context. Hot giant planets such as MASCARA-1 b are expected to have thermally inverted atmospheres, which makes them perfect laboratories for atmospheric characterization through high-resolution spectroscopy. Nonetheless, previous attempts at detecting the atmosphere of MASCARA-1 b in transmission have led to negative results.

Aims. We aim to detect the optical emission spectrum of MASCARA-1 b.

Methods. We used the high-resolution spectrograph PEPSI to observe MASCARA-1 (spectral type A8) near the secondary eclipse of the planet. We cross-correlated the spectra with synthetic templates computed for several atomic and molecular species.

Results. We detect Fe I, Cr I, and Ti I in the atmosphere of MASCARA-1 b with a S/N ≈ 7, 4, and 5, respectively, and confirm the expected systemic velocity of ≈13 km s⁻¹ and the radial velocity semi-amplitude of MASCARA-1 b of ≈200 km s⁻¹. The detection of Ti is of particular importance in the context of the recently proposed phenomenon of Ti cold-trapping below a certain planetary equilibrium temperature.

Conclusions. We confirm the presence of an atmosphere around MASCARA-1 b through emission spectroscopy. We conclude that the atmospheric non-detection in transmission spectroscopy is due to the strong gravity of the planet and/or to the overlap between the planetary track and its Doppler shadow.