Transmission spectroscopy and Rossiter-McLaughlin measurements of the young Neptune orbiting AU Mic

Palle, E. and Oshagh, M. and Casasayas-Barris, N. and Hirano, T. and Stangret, M. and Luque, R. and Strachan, J. and Gaidos, E. and Anglada-Escude, G. and Plavchan, P. and Addison, B. ORCID: https://orcid.org/0000-0003-3216-0626 (2020) Transmission spectroscopy and Rossiter-McLaughlin measurements of the young Neptune orbiting AU Mic. Astronomy & Astrophysics, 643:A25. pp. 1-10. ISSN 0004-6361


Abstract

AU Mic b is a Neptune-sized planet on an 8.47-day orbit around the nearest pre-main sequence (~20 Myr) star to the Sun, the bright (V = 8.81) M dwarf AU Mic. The planet was preliminary detected in Doppler radial velocity time series and recently confirmed to be transiting with data from the TESS mission. AU Mic b is likely to be cooling and contracting and might be accompanied by a second, more massive planet, in an outer orbit. Here, we present the observations of the transit of AU Mic b using ESPRESSO on the Very Large Telescope. We obtained a high-resolution time series of spectra to measure the Rossiter-McLaughlin effect, to constrain the spin-orbit alignment of the star and planet, and to simultaneously attempt to retrieve the planet's atmospheric transmission spectrum. These observations allowed us to study, for the first time, the early phases of the dynamical evolution of young systems. We applied different methodologies to derive the spin-orbit angle of AU Mic b, and all of them retrieve values consistent with the planet being aligned with the rotation plane of the star. We determined a conservative spin-orbit angle λ value of -2.96<SUB>-10.30</SUB><SUP>+10.44</SUP> degrees, indicative that the formation and migration of the planets of the AU Mic system occurred within the disc. Unfortunately, and despite the large signal-to-noise ratio of our measurements, the degree of stellar activity prevented us from detecting any features from the planetary atmosphere. In fact, our results suggest that transmission spectroscopy for recently formed planets around active young stars is going to remain very challenging, if at all possible, for the near future.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Astrophysics (1 Aug 2018 -)
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Astrophysics (1 Aug 2018 -)
Date Deposited: 25 Jan 2021 06:50
Last Modified: 29 Jan 2021 04:51
Uncontrolled Keywords: planets and satellites: atmospheres - techniques: radial velocities -; planets and satellites: formation - planets and satellites: individual:; Au Mic; Astrophysics - Earth and Planetary Astrophysics; Astrophysics -; Solar and Stellar Astrophysics
Fields of Research (2008): 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5101 Astronomical sciences > 510109 Stellar astronomy and planetary systems
Socio-Economic Objectives (2008): E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Socio-Economic Objectives (2020): 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280120 Expanding knowledge in the physical sciences
Identification Number or DOI: https://doi.org/10.1051/0004-6361/202038583
URI: http://eprints.usq.edu.au/id/eprint/40621

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