High-resolution transmission spectroscopy of MASCARA-2 b with EXPRES

Hoeijmakers, Jens H.; Cabot, Samuel H. C.; Zhao, Lily; Buchhave, Lars A.; Tronsgaard, René; Davis, Allen B.; Kitzmann, Daniel; Grimm, Simon L.; Cegla, Heather M.; Bourrier, Vincent; Ehrenreich, David; Heng, Kevin; Lovis, Christophe; Fischer, Debra A. (2020). High-resolution transmission spectroscopy of MASCARA-2 b with EXPRES. Astronomy and astrophysics, 641(A120), A120. EDP Sciences 10.1051/0004-6361/202037437

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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 Fe I, Fe II, and Na I, which likely originate in the upper regions of the inflated atmosphere. In addition, we report significant detections of Mg I and Cr 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.

Item Type:

Journal Article (Original Article)


08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
08 Faculty of Science > Physics Institute
10 Strategic Research Centers > Center for Space and Habitability (CSH)
08 Faculty of Science > Physics Institute > NCCR PlanetS

UniBE Contributor:

Hoeijmakers, Herman Jens; Kitzmann, Daniel; Grimm, Simon Lukas and Heng, Kevin


500 Science
500 Science > 520 Astronomy
500 Science > 530 Physics




EDP Sciences




Danielle Zemp

Date Deposited:

15 Apr 2021 10:41

Last Modified:

18 Apr 2021 03:03

Publisher DOI:






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