Investigating the young AU~Mic system with SPIRou: large-scale stellar magnetic field and close-in planet mass

Abstract

We present a velocimetric and spectropolarimetric analysis of 27 observations of the 22-Myr M1 star AU Microscopii (Au Mic) collected with the high-resolution $YJHK$ (0.98-2.35 $\mu$m) spectropolarimeter SPIRou from 2019 September 18 to November 14. Our radial velocity (RV) time-series exhibits activity-induced fluctuations of 45 m/s RMS, about three times smaller than those measured in the optical domain, that we filter using Gaussian Process Regression. We report a 3.9$\sigma$-detection of the recently-discovered 8.46-d transiting planet AU Mic b, with an estimated mass of $17.1_{-4.5}^{+4.7}$ M${}_{\odot }$ and a bulk density of $1.3\pm 0.4$ g/cm${}^{-3}$, inducing a RV signature of semi-amplitude $K=8.5_{-2.2}^{+2.3}$ m/s in the spectrum of its host star. A consistent detection is independently obtained when we simultaneously image stellar surface inhomogeneities and estimate the planet parameters with Zeeman-Doppler Imaging (ZDI). Using ZDI, we invert the time series of unpolarized and circularly-polarized spectra into surface brightness and large-scale magnetic maps. We find a mainly poloidal and axisymmetric field of 475 G, featuring, in particular, a dipole of 450 G tilted at 19° to the rotation axis. Moreover, we detect a strong differential rotation of d$\Omega =0.167\pm 0.009$ rad/d shearing the large-scale field, about twice stronger than that shearing the brightness distribution, suggesting that both observables probe different layers of the convective zone. Even though we caution that more RV measurements are needed to accurately pin down the planet mass, AU Mic b already appears as a prime target for constraining planet formation models, studying the interactions with the surrounding debris disk, and characterizing its atmosphere with upcoming space- and ground-based missions.

arXiv comment19 pages, 20 figures, MNRAS, in press

References in corpus (97)

• emcee: The MCMC Hammer
• Gaia Data Release 2. Summary of the contents and survey properties
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• Dynamical Outcomes of Planet-Planet Scattering
• Kepler planets: a tale of evaporation
• No planet for HD 166435
• How to Constrain Your M Dwarf: measuring effective temperature, bolometric luminosity, mass, and radius
• Understanding the Mass-Radius Relation for Sub-Neptunes: Radius as a Proxy for Composition
• Models of Giant Planet formation with migration and disc evolution
• Magnetic fields of non-degenerate stars
• Dynamical Origin of Extrasolar Planet Eccentricity Distribution
• Planets and Stellar Activity: Hide and Seek in the CoRoT-7 system
• The Role of Core Mass in Controlling Evaporation: the Kepler Radius Distribution and the Kepler-36 Density Dichotomy
• The surprising magnetic topology of tauSco: fossil remnant or dynamo output?
• Large-scale magnetic topologies of late M dwarfs
• Large-scale magnetic topologies of mid-M dwarfs
• A Gaussian process framework for modelling stellar activity signals in radial velocity data
• Planetary population synthesis coupled with atmospheric escape: a statistical view of evaporation
• On the age of the $\beta$ Pictoris moving group
• Exoplanetary Atmospheres: Key Insights, Challenges and Prospects
• Large-scale magnetic topologies of early M dwarfs
• Characterization of exoplanets from their formation I: Models of combined planet formation and evolution
• Trumpeting M Dwarfs with CONCH-SHELL: a Catalog of Nearby Cool Host-Stars for Habitable ExopLanets and Life
• Compositional imprints in density-distance-time: a rocky composition for close-in low-mass exoplanets from the location of the valley of evaporation
• Characterization of exoplanets from their formation II: The planetary mass-radius relationship
• The HARPS search for southern extra-solar planets. X. A m sin i = 11 Mearth planet around the nearby spotted M dwarf GJ 674
• Discovery of a large dust disk around the nearby star AU Microscopium
• A planet within the debris disk around the pre-main-sequence star AU Microscopii
• Stellar activity of planetary host star HD 189733
• Long-term magnetic activity of a sample of M-dwarf stars from the HARPS program I. Comparison of activity indices
• A High-Precision NIR Survey for RV Variable Low-Mass Stars
• New Debris Disks Around Young, Low Mass Stars Discovered With The Spitzer Space Telescope
• Hubble PanCET: An extended upper atmosphere of neutral hydrogen around the warm Neptune GJ 3470 b
• PASTIS: Bayesian extrasolar planet validation. I. General framework, models, and performance
• Observations of Cool-Star Magnetic Fields
• Identifying the Young Low-mass Stars within 25 pc. I. Spectroscopic Observations
• A Neptune-sized transiting planet closely orbiting a 5-10-million-year-old star
• The Sun as a planet-host star: Proxies from SDO images for HARPS radial-velocity variations
• Accretion funnels onto weakly magnetized young stars
• Zodiacal Exoplanets in Time (ZEIT) III: A short-period planet orbiting a pre-main-sequence star in the Upper Scorpius OB Association
• SPIRou: nIR velocimetry & spectropolarimetry at the CFHT
• M-dwarf stellar winds: the effects of realistic magnetic geometry on rotational evolution and planets
• Searching for links between magnetic fields and stellar evolution. II. The evolution of magnetic fields as revealed by observations of Ap stars in open clusters and associations
• Four newborn planets transiting the young solar analog V1298 Tau
• A hot Jupiter orbiting a 2-Myr-old solar-mass T Tauri star
• BANYAN. IV. Fundamental parameters of low-mass star candidates in nearby young stellar kinematic groups - Isochronal Age determination using Magnetic evolutionary models
• Temporal fluctuations in the differential rotation of cool active stars
• Strong dipole magnetic fields in fast rotating fully convective stars
• Planetary evolution with atmospheric photoevaporation I. Analytical derivation and numerical study of the evaporation valley and transition from super-Earths to sub-Neptunes
• Revisiting Proxima with ESPRESSO
• Millimeter Emission Structure in the first ALMA Image of the AU Mic Debris Disk
• Magnetic games between a planet and its host star: the key role of topology
• The CARMENES search for exoplanets around M dwarfs. Activity indicators at visible and near-infrared wavelengths
• A Candidate Young Massive Planet in Orbit around the Classical T Tauri Star CI Tau
• Modeling the RV jitter of early M dwarfs using tomographic imaging
• A hot Jupiter around the very active weak-line T Tauri star TAP 26
• A warm Jupiter-sized planet transiting the pre-main sequence star V1298 Tau
• Formation, Orbital and Internal Evolutions of Young Planetary Systems
• Modelling the magnetic activity & filtering radial velocity curves of young Suns: the weak-line T Tauri star LkCa 4
• A Bayesian periodogram finds evidence for three planets in HD 11964
• A Search for Giant Planet Companions to T Tauri Stars
• Limits on the Spin-Orbit Angle and Atmospheric Escape for the 22 Myr-old Planet AU Mic b
• Rotational velocities of nearby young stars
• SPIRou Input Catalog: Activity, Rotation and Magnetic Field of Cool Dwarfs
• The rotation - Lithium depletion correlation in the beta Pictoris association and LDB age determination
• Starspot-induced optical and infrared radial velocity variability in T Tauri star Hubble 4
• Quantifying the Bayesian Evidence for a Planet in Radial Velocity Data
• Exoplanets as probes of the winds of host stars: the case of the M dwarf GJ 436
• Rotation and activity of pre-main-sequence stars
• Observations of fast-moving features in the debris disk of AU Mic on a three-year timescale: Confirmation and new discoveries
• Predicting radio emission from the newborn hot Jupiter V830 Tau and its host star
• Unsigned magnetic flux as a proxy for radial-velocity variations in Sun-like stars
• The Mass of Stirring Bodies in the AU Mic Debris Disk Inferred from Resolved Vertical Structure
• Transmission spectroscopy and Rossiter-McLaughlin measurements of the young Neptune orbiting AU Mic
• A Resolved Millimeter Emission Belt in the AU Mic Debris Disk
• The AU Mic Debris Disk: far-infrared and submillimeter resolved imaging
• Telluric-line subtraction in high-accuracy velocimetry: a PCA-based approach
• Spin-orbit alignment and magnetic activity in the young planetary system AU Mic
• Active cool stars and He I 10830 Å: the coronal connection
• Probing the Flare Atmospheres of M dwarfs Using Infrared Emission Lines
• A sudden change of the global magnetic field of the active M dwarf AD Leo revealed by full Stokes spectropolarimetric observations
• Magnetic field, activity and companions of V410 Tau
• First long-term activity study of AU Microscopii: a possible chromospheric cycle
• Expelled grains from an unseen parent body around AU Mic
• SPIRou: a nIR spectropolarimeter / high-precision velocimeter for the CFHT
• AD Leonis: Radial velocity signal of stellar rotation or spin-orbit resonance?
• Stellar Winds and Dust Avalanches in the AU Mic Debris Disk
• Complexity of magnetic fields on red dwarfs
• Early science with SPIRou: near-infrared radial velocity and spectropolarimetry of the planet-hosting star HD 189733
• Magnetic topologies of young suns: The weak-line T Tauri stars TWA 6 and TWA 8A
• Identifying solar-like magnetic cycles with Zeeman-Doppler-Imaging (ZDI)
• A maximum entropy approach to detect close-in giant planets around active stars
• High Fidelity Imaging of the Inner AU Mic Debris Disk: Evidence of Differential Wind Sculpting?
• Simulating Radial Velocity Observations of Trappist-1 with SPIRou
• Simulated mass measurements of the young planet K2-33b
• Detection of the Molecular Zeeman Effect in Circular Polarization on Cool Active Stars

Cited by in corpus (58)

• New constraints on the planetary system around the young active star AU Mic. Two transiting warm Neptunes near mean-motion resonance
• Planet-induced radio emission from the coronae of M dwarfs: the case of Prox Cen and AU Mic
• TESS Hunt for Young and Maturing Exoplanets (THYME) VI: an 11 Myr giant planet transiting a very low-mass star in Lower Centaurus Crux
• The magnetic field and multiple planets of the young dwarf AU~Mic
• Diving Beneath the Sea of Stellar Activity: Chromatic Radial Velocities of the Young AU Mic Planetary System
• Rapid contraction of giant planets orbiting the 20 million-years old star V1298 Tau
• One year of AU Mic with HARPS: II -- stellar activity and star-planet interaction
• One year of AU Mic with HARPS: I -- measuring the masses of the two transiting planets
• The young HD 73583 (TOI-560) planetary system: Two 10-M${}_{\oplus }$ mini-Neptunes transiting a 500-Myr-old, bright, and active K dwarf
• TOI-2076 and TOI-1807: Two young, comoving planetary systems within 50 pc identified by TESS that are ideal candidates for further follow-up
• AU Microscopii in the FUV: Observations in Quiescence, During Flares, and Implications for AU Mic b and c
• Simulating the Space Weather in the AU Mic System: Stellar Winds and Extreme Coronal Mass Ejections
• TOI-530b: A giant planet transiting an M dwarf detected by TESS
• Homogeneous search for helium in the atmosphere of 11 gas giant exoplanets with SPIRou
• Constraining atmospheric parameters and surface magnetic fields with $\text{ZeeTurbo}$: an application to SPIRou spectra
• Starspot mapping with adaptive parallel tempering. II. Application to TESS data for M-dwarf flare stars, AU Microscopii, YZ Canis Minoris, and EV Lacertae
• Characterizing exoplanetary atmospheres at high resolution with SPIRou: Detection of water on HD 189733 b
• Detection Limits of Low-mass, Long-period Exoplanets Using Gaussian Processes Applied to HARPS-N Solar RVs
• The CARMENES search for exoplanets around M dwarfs: Benchmarking the impact of activity in high-precision radial velocity measurements
• Monitoring the large-scale magnetic field of AD~Leo with SPIRou, ESPaDOnS and Narval. Toward a magnetic polarity reversal?
• Searching for flaring star-planet interactions in AU Mic TESS observations
• Space Weather-driven Variations in Ly$\alpha$ Absorption Signatures of Exoplanet Atmospheric Escape: MHD Simulations and the Case of AU Mic b
• Mitigating stellar activity jitter with different line lists for least-squares deconvolution: analysis of a parametric and a randomised line selection
• TESS discovery of a sub-Neptune orbiting a mid-M dwarf TOI-2136
• Optical and near-infrared stellar activity characterization of the early M dwarf Gl~205 with SOPHIE and SPIRou
• The T Tauri star V410 Tau in the eyes of SPIRou and TESS
• The space weather around the exoplanet GJ 436b
• Star-disk interaction in the T Tauri star V2129 Oph: An evolving accretion-ejection structure
• Probing atmospheric escape through metastable He I triplet lines in 15 exoplanets observed with SPIRou
• Short term variability of DS Tuc A observed with TESS
• A Machine Learning approach for correcting radial velocities using physical observables
• Mapping time-dependent magnetic topologies of active stars
• Multiwavelength Vertical Structure in the AU Mic Debris Disk: Characterizing the Collisional Cascade
• The Variable Detection of Atmospheric Escape around the young, Hot Neptune AU Mic b
• TOI-179: a young system with a transiting compact Neptune-mass planet and a low-mass companion in outer orbit
• The active weak-line T Tauri star LkCa 4 observed with SPIRou and TESS
• TOI-1801 b: A temperate mini-Neptune around a young M0.5 dwarf
• Updated Planetary Mass Constraints of the Young V1298 Tau System Using MAROON-X
• Magnetic field of the eclipsing binary UV Piscium
• A BCool survey of stellar magnetic cycles
• Hyades Member K2-136c: The Smallest Planet in an Open Cluster with a Precisely Measured Mass
• Dynamical masses of two young transiting sub-Neptunes orbiting HD 63433
• Stellar Energetic Particle Transport in the Turbulent and CME-disrupted Stellar Wind of AU~Microscopii
• The strong suppression of Galactic cosmic rays reaching AU Mic b, c and Prox Cen b
• Probing the innermost region of the AU~Microscopii debris disk
• Spectroscopic observations of flares and superflares on AU Mic
• Correlations between laboratory line lists for FeH, CrH, and NiH and M-star spectra collected with ESPaDOnS and SPIRou
• HADES RV programme with HARPS-N at TNG XIV. A candidate super-Earth orbiting the M-dwarf GJ 9689 with a period close to half the stellar rotation period
• The changing transit shape of TOI-3884 b
• Using Doppler Imaging to model stellar activity and search for planets around Sun-like stars
• The CARMENES search for exoplanets around M dwarfs : Understanding the wavelength dependence of radial velocity measurements
• On stellar hotspots due to star-planet magnetic interactions: How much power can actually be transmitted to the chromosphere?
• gaspery: Optimized Scheduling of Radial Velocity Follow-Up Observations for Active Host Stars
• Far-ultraviolet flares and variability of the young M dwarf AU Mic: a non-detection of planet c in transit at Lyman-alpha
• The changing face of AU Mic b: stellar spots, spin-orbit commensurability, and Transit Timing Variations as seen by CHEOPS and TESS
• A Search for Planetary Metastable Helium Absorption in the V1298 Tau System
• Magnetic geometry of M dwarfs in the southern PLATO field
• Near-IR and optical radial velocities of the active M dwarf star Gl 388 (AD Leo) with SPIRou at CFHT and SOPHIE at OHP: A 2.23 day rotation period and no evidence for a corotating planet