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

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.