Limits on the Spin-Orbit Angle and Atmospheric Escape for the 22 Myr-old Planet AU Mic b

Abstract

We obtained spectra of the pre-main sequence star AU Microscopii during a transit of its Neptune-sized planet to investigate its orbit and atmosphere. We used the high-dispersion near-infrared spectrograph IRD on the Subaru telescope to detect the Doppler "shadow" from the planet and constrain the projected stellar obliquity. Modeling of the observed planetary Doppler shadow suggests a spin-orbit alignment of the system ($\lambda =-4.7_{-6.4}^{+6.8}$ degrees), but additional observations are needed to confirm this finding. We use both the IRD data and spectra obtained with NIRSPEC on Keck-II to search for absorption in the 1083 nm line of metastable triplet He I by the planet's atmosphere and place an upper limit for the equivalent width of 3.7 mÅat 99 $\%$ confidence. With this limit and a Parker wind model we constrain the escape rate from the atmosphere to $<0.15-0.45M_{\oplus }$ Gyr${}^{-1}$, comparable to the rates predicted by an XUV energy-limited escape calculation and hydrodynamic models, but refinement of the planet mass is needed for rigorous tests.

arXiv comment10 pages, 5 figures, accepted for publication in ApJ Letters

References in corpus (43)

• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets
• Shrinking binary and planetary orbits by Kozai cycles with tidal friction
• Dynamical Outcomes of Planet-Planet Scattering
• Hot Stars with Hot Jupiters Have High Obliquities
• Planet-disk interaction and orbital evolution
• Obliquities of Hot Jupiter host stars: Evidence for tidal interactions and primordial misalignments
• Core-powered mass loss and the radius distribution of small exoplanets
• Roche lobe effects on the atmospheric loss of "Hot Jupiters"
• Measurement of Spin-Orbit Alignment in an Extrasolar Planetary System
• On the age of the $\beta$ Pictoris moving group
• An atmospheric radiation model for Cerro Paranal. I. The optical spectral range
• Line-profile tomography of exoplanet transits -- II. A gas-giant planet transiting a rapidly-rotating A5 star
• Atmospheric Escape and the Evolution of Close-in Exoplanets
• Hot super-Earths stripped by their host stars
• A planet within the debris disk around the pre-main-sequence star AU Microscopii
• A New Window into Escaping Exoplanet Atmospheres: 10830 Å Line of Helium
• New Debris Disks Around Young, Low Mass Stars Discovered With The Spitzer Space Telescope
• An advanced scattered moonlight model for Cerro Paranal
• The Intrinsic Extreme Ultraviolet Fluxes of F5 V to M5 V Stars
• A Neptune-sized transiting planet closely orbiting a 5-10-million-year-old star
• Improved Modeling of the Rossiter-McLaughlin Effect for Transiting Exoplanets
• Zodiacal Exoplanets in Time (ZEIT) III: A short-period planet orbiting a pre-main-sequence star in the Upper Scorpius OB Association
• TESS Hunt for Young and Maturing Exoplanets (THYME): A planet in the 45 Myr Tucana-Horologium association
• Zodiacal Exoplanets In Time (ZEIT) I: A Neptune-sized planet orbiting an M4.5 dwarf in the Hyades Star Cluster
• Four newborn planets transiting the young solar analog V1298 Tau
• Two 'b's in the Beehive: The Discovery of the First Hot Jupiters in an Open Cluster
• Overcoming the limitations of the energy-limited approximation for planet atmospheric escape
• Heating efficiency in hydrogen-dominated upper atmospheres
• Analytic Description of the Rossiter-McLaughlin Effect for Transiting Exoplanets: Cross-Correlation Method and Comparison with Simulated Data
• Zodiacal Exoplanets in Time (ZEIT) VI: a three-planet system in the Hyades cluster including an Earth-sized planet
• Semi-empirical Modeling of the Photosphere, Chromosphere, Transition Region, and Corona of the M-dwarf Host Star GJ 832
• Far-Ultraviolet Activity Levels of F, G, K, and M dwarf Exoplanet Host Stars
• A Search for Giant Planet Companions to T Tauri Stars
• The GAPS programme at TNG XXII. The GIARPS view of the extended helium atmosphere of HD189733 b accounting for stellar activity
• Spin-orbit Misalignment as a Driver of the Kepler Dichotomy
• The effects of stellar activity on optical high-resolution exoplanet transmission spectra
• HAZMAT III: The UV Evolution of Mid- to Late-M Stars with GALEX
• Evidence for Spin-orbit Alignment in the TRAPPIST-1 System
• Zodiacal Exoplanets in Time. X. The Orbit and Atmosphere of the Young "Neptune Desert"-Dwelling Planet K2-100b
• Spin-Orbit Misalignments of Three Jovian Planets via Doppler Tomography
• Estimates of Active Region Area Coverage through Simultaneous Measurements of He I $\lambda \lambda$ 5876 and 10830 Lines
• Effect of Core Cooling on the Radius of Sub-Neptune Planets

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• Cluster Difference Imaging Photometric Survey. II. TOI 837: A Young Validated Planet in IC 2602
• No escaping helium from 55 Cnc e
• A tentative detection of He I in the atmosphere of GJ 1214b
• One year of AU Mic with HARPS: I -- measuring the masses of the two transiting planets
• AU Microscopii in the FUV: Observations in Quiescence, During Flares, and Implications for AU Mic b and c
• DREAM II. The spin-orbit angle distribution of close-in exoplanets under the lens of tides
• H-alpha and Ca II Infrared Triplet Variations During a Transit of the 23 Myr Planet V1298 Tau c
• Giant white-light flares on fully convective stars occur at high latitudes
• Orbital misalignment of the super-Earth $\pi$ Men c with the spin of its star
• Homogeneous search for helium in the atmosphere of 11 gas giant exoplanets with SPIRou
• An Aligned Orbit for the Young Planet V1298 Tau b
• The MOPYS project: A survey of 70 planets in search of extended He I and H atmospheres. No evidence of enhanced evaporation in young planets
• Zodiacal Exoplanets in Time. XI. The Orbit and Radiation Environment of the Young M Dwarf-Hosted Planet K2-25b
• The mass determination of TOI-519 b: a close-in giant planet transiting a metal-rich mid-M dwarf
• TOI-3984 A b and TOI-5293 A b: two temperate gas giants transiting mid-M dwarfs in wide binary systems
• TESS Investigation -- Demographics of Young Exoplanets (TI-DYE) II: a second giant planet in the 17-Myr system HIP 67522
• TOI-942b: A Prograde Neptune in a ~60 Myr old Multi-transiting System
• DREAM: III.A helium survey in exoplanets on the edge of the hot Neptune desert with GIANO-B@TNG
• The obliquity of HIP 67522 b: a 17 Myr old transiting hot Jupiter-sized planet
• Zodiacal Exoplanets in Time (ZEIT) XIII: Planet Orbits and Atmospheres in the V1298 Tau System, a Keystone in Studies of Early Planetary Evolution
• NEID Rossiter-McLaughlin Measurement of TOI-1268b: A Young Warm Saturn Aligned with Its Cool Host Star
• Planet(esimal)s Around Stars with TESS (PAST) III: A Search for Triplet He I in the Atmospheres of Two 200 Myr-old Planets
• Complex Modulation of Rapidly Rotating Young M Dwarfs: Adding Pieces to the Puzzle
• Evidence for Primordial Alignment: Insights from Stellar Obliquity Measurements for Compact Sub-Saturn Systems
• Probing atmospheric escape through metastable He I triplet lines in 15 exoplanets observed with SPIRou
• A Framework for Characterizing Transmission Spectra of Exoplanets with Circumplanetary Rings
• Measuring the Obliquities of the TRAPPIST-1 Planets with MAROON-X
• The Maximum Mass-Loss Efficiency for a Photoionization-Driven Isothermal Parker Wind
• TOI-4562 b: A highly eccentric temperate Jupiter analog orbiting a young field star
• Helium in Exoplanet Exospheres: Orbital and Stellar Influences
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• Evolution of helium triplet transits of close-in gas giants orbiting K-dwarfs
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• The Aligned Orbit of a Hot Jupiter around the M Dwarf TOI-4201
• Evidence for Primordial Alignment II: Insights from Stellar Obliquity Measurements for Hot Jupiters in Compact Multiplanet Systems
• True spin-orbit obliquities distribution: data-driven confirmation of no clustering of misaligned planets
• 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
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• Spin-Orbit Geometry of AU Mic b and c from Back-to-Back Transits Observed Contemporaneously with Magellan PFS, LCOGT, and CHEOPS
• TOI-1201 b: A mini-Neptune transiting a bright and moderately young M dwarf
• Grain Growth in Escaping Atmospheres: Implications for the Radius Inflation of Super-Puffs
• AU Mic b is the Youngest Planet to have a Spin-Orbit Alignment Measurement