A possible misaligned orbit for the young planet AU Mic c

Abstract

The AU Microscopii planetary system is only 24 Myr old, and its geometry may provide clues about the early dynamical history of planetary systems. Here, we present the first measurement of the Rossiter-McLaughlin effect for the warm sub-Neptune AU Mic c, using two transits observed simultaneously with the European Southern Observatory's (ESO's) Very Large Telescope (VLT)/Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO), CHaracterising ExOPlanet Satellite (CHEOPS), and Next-Generation Transit Survey (NGTS). After correcting for flares and for the magnetic activity of the host star, and accounting for transit-timing variations, we find the sky-projected spin-orbit angle of planet c to be in the range ${\lambda }_c=67.8_{-49.0}^{+31.7}$\,degrees (1-$\sigma$). We examine the possibility that planet c is misaligned with respect to the orbit of the inner planet b (${\lambda }_b=-2.96_{-10.30}^{+10.44}$\,degrees), and the equatorial plane of the host star, and discuss scenarios that could explain both this and the planet's high density, including secular interactions with other bodies in the system or a giant impact. We note that a significantly misaligned orbit for planet c is in some degree of tension with the dynamical stability of the system, and with the fact that we see both planets in transit, though these arguments alone do not preclude such an orbit. Further observations would be highly desirable to constrain the spin-orbit angle of planet c more precisely.

Accepted for publication in MNRAS

References in corpus (62)

• emcee: The MCMC Hammer
• Gaia Data Release 2. Summary of the contents and survey properties
• The Transiting Exoplanet Survey Satellite
• The Spitzer Space Telescope Mission
• batman: BAsic Transit Model cAlculatioN in Python
• Dynamical Outcomes of Planet-Planet Scattering
• The Occurrence and Architecture of Exoplanetary Systems
• Kepler planets: a tale of evaporation
• Planet Migration and Binary Companions: the case of HD 80606b
• ESPRESSO@VLT -- On-sky performance and first results
• PolyChord: nested sampling for cosmology
• PolyChord: next-generation nested sampling
• Spin-orbit angle measurements for six southern transiting planets; New insights into the dynamical origins of hot Jupiters
• Measurement of Spin-Orbit Alignment in an Extrasolar Planetary System
• On the age of the $\beta$ Pictoris moving group
• Characterization of exoplanets from their formation I: Models of combined planet formation and evolution
• Planet Formation by Coagulation: A Focus on Uranus and Neptune
• Prospects for the Characterization and Confirmation of Transiting Exoplanets via the Rossiter-McLaughlin Effect
• The CHEOPS mission
• Atmospheric Escape and the Evolution of Close-in Exoplanets
• The Next Generation Transit Survey (NGTS)
• Exoplanetary Spin-Orbit Alignment: Results from the Ensemble of Rossiter-McLaughlin Observations
• A planet within the debris disk around the pre-main-sequence star AU Microscopii
• Discovery of a large dust disk around the nearby star AU Microscopium
• High-precision photometry by telescope defocussing. I. The transiting planetary system WASP-5
• A pair of planets around HD 202206 or a circumbinary planet?
• Star-Disc-Binary Interactions in Protoplanetary Disc Systems and Primordial Spin-Orbit Misalignments
• The HARPS search for southern extra-solar planets XIX. Characterization and dynamics of the GJ876 planetary system
• Formation of close in Super-Earths \& Mini-Neptunes: Required Disk Masses \& Their Implications
• BANYAN. IV. Fundamental parameters of low-mass star candidates in nearby young stellar kinematic groups - Isochronal Age determination using Magnetic evolutionary models
• Expected performances of the Characterising Exoplanet Satellite (CHEOPS) III. Data reduction pipeline: architecture and simulated performances
• Dynamical traceback age of the $\beta$ Pictoris moving group
• New constraints on the planetary system around the young active star AU Mic. Two transiting warm Neptunes near mean-motion resonance
• Effect of the rotation and tidal dissipation history of stars on the evolution of close-in planets
• High-precision photometry by telescope defocussing. II. The transiting planetary system WASP-4
• New analytical expressions of the Rossiter-McLaughlin effect adapted to different observation techniques
• The magnetic field and multiple planets of the young dwarf AU~Mic
• Orbital evolution of a planet on an inclined orbit interacting with a disc
• YARARA: Significant improvement of RV precision through post-processing of spectral time-series
• Limits on the Spin-Orbit Angle and Atmospheric Escape for the 22 Myr-old Planet AU Mic b
• Diving Beneath the Sea of Stellar Activity: Chromatic Radial Velocities of the Young AU Mic Planetary System
• A disk-driven resonance as the origin of high inclinations of close-in planets
• The rotation - Lithium depletion correlation in the beta Pictoris association and LDB age determination
• The Rossiter-McLaughlin effect Revolutions: An ultra-short period planet and a warm mini-Neptune on perpendicular orbits
• RASSINE: Interactive tool for normalising stellar spectra I. Description and performance of the code
• Observations of fast-moving features in the debris disk of AU Mic on a three-year timescale: Confirmation and new discoveries
• Nearly Polar orbit of the sub-Neptune HD3167 c: Constraints on a multi-planet system dynamical history
• Simultaneous TESS and NGTS Transit Observations of WASP-166b
• Transmission spectroscopy and Rossiter-McLaughlin measurements of the young Neptune orbiting AU Mic
• One year of AU Mic with HARPS: I -- measuring the masses of the two transiting planets
• Evolution of eccentricity and orbital inclination of migrating planets in 2:1 mean motion resonance
• The Long-Term Dynamical Evolution of Planetary Systems
• Efficient Geometric Probabilities of Multi-Transiting Exoplanetary Systems from CORBITS
• Generating large misalignments in gapped and binary discs
• TASTE: The Asiago Search for Transit timing variations of Exoplanets. I. Overview and improved parameters for HAT-P-3b and HAT-P-14b
• Hidden Planetary Friends: On the Stability Of 2-Planet Systems in the Presence of a Distant, Inclined Companion
• The Rossiter-McLaughlin Effect of the Transiting Exoplanet XO-4b
• Lithium depletion boundary, stellar associations, and Gaia
• A Search for Planets Transiting the M Dwarf Debris Disk Host, AU Microscopii
• Shallow transit follow-up from NGTS: simultaneous observations of HD106315 with 11 identical telescopes
• Transit timing variations of AU Microscopii b and c
• Transit Probabilities in Secularly Evolving Planetary Systems

Cited by in corpus (1)

• Spin-Orbit Geometry of AU Mic b and c from Back-to-Back Transits Observed Contemporaneously with Magellan PFS, LCOGT, and CHEOPS