We report detections of atomic species in the atmosphere of MASCARA-2 b, using the first transit observations obtained with the newly commissioned EXPRES spectrograph. EXPRES is a highly stabilized optical echelle spectrograph, designed to detect stellar reflex motions with amplitudes down to 30 cm s-1, and has recently been deployed at the Lowell Discovery Telescope. By analyzing the transmission spectrum of the ultra-hot Jupiter MASCARA-2 b using the cross-correlation method, we confirm previous detections of Feâ€» I, Feâ€» II, and Naâ€» I, which likely originate in the upper regions of the inflated atmosphere. In addition, we report significant detections of Mgâ€» I and Crâ€» II. The absorption strengths change slightly with time, possibly indicating different temperatures and chemistry in the day- and nightside terminators. Using the effective stellar line-shape variation induced by the transiting planet, we constrain the projected spin-orbit misalignment of the system to 1.6 ± 3.1 degrees, consistent with an aligned orbit. We demonstrate that EXPRES joins a suite of instruments capable of phase-resolved spectroscopy of exoplanet atmospheres.
- Instrumentation: spectrographs
- Planets and satellites: atmospheres
- Techniques: spectroscopic
- Planets and satellites: gaseous planets