Astrometric Accelerations as Dynamical Beacons: A Giant Planet Imaged Inside the Debris Disk of the Young Star AF Lep

Abstract

We present the direct imaging discovery of a giant planet orbiting the young star AF Lep, a 1.2 $M_{\odot }$ member of the 24 $\pm$ 3 Myr $\beta$ Pic moving group. AF Lep was observed as part of our ongoing high-contrast imaging program targeting stars with astrometric accelerations between Hipparcos and Gaia that indicate the presence of substellar companions. Keck/NIRC2 observations in $L^{\prime }$ with the Vector Vortex Coronagraph reveal a point source, AF Lep b, at $\approx 340$ mas which exhibits orbital motion at the 6-$\sigma$ level over the course of 13 months. A joint orbit fit yields precise constraints on the planet's dynamical mass of 3.2${}_{-0.6}^{+0.7}$ $M_{\mathrm{Jup}}$, semi-major axis of $8.4_{-1.3}^{+1.1}$ au, and eccentricity of $0.24_{-0.15}^{+0.27}$. AF Lep hosts a debris disk located at $\sim$50 au, but it is unlikely to be sculpted by AF Lep b, implying there may be additional planets in the system at wider separations. The stellar inclination ($i_{\ast }=54_{-9}^{+11}{}^{\circ }$) and orbital inclination ($i_o=50_{-12}^{+9}{}^{\circ }$) are in good agreement, which is consistent with the system having spin-orbit alignment. AF Lep b is the lowest-mass imaged planet with a dynamical mass measurement and highlights the promise of using astrometric accelerations as a tool to find and characterize long-period planets.

14 pages, 3 figures, accepted to ApJL

References in corpus (29)

• Array Programming with NumPy
• scikit-image: Image processing in Python
• The Transiting Exoplanet Survey Satellite
• Direct Imaging of Multiple Planets Orbiting the Star HR 8799
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• The Evolution of L and T Dwarfs in Color-Magnitude Diagrams
• Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 parsecs: The Southern Sample
• On the Luminosity of Young Jupiters
• The Gemini Planet Imager Exoplanet Survey: Giant Planet and Brown Dwarf Demographics From 10-100 AU
• The Hipparcos-Gaia Catalog of Accelerations: Gaia EDR3 Edition
• Synthetic Spectra and Colors of Young Giant Planet Atmospheres: Effects of Initial Conditions and Atmospheric Metallicity
• The Hawaii Infrared Parallax Program. II. Young Ultracool Field Dwarfs
• VIP: Vortex Image Processing package for high-contrast direct imaging
• Discovery of a warm, dusty giant planet around HIP65426
• Population-Level Eccentricity Distributions of Imaged Exoplanets and Brown Dwarf Companions: Dynamical Evidence for Distinct Formation Channels
• On the Inference of a Star's Inclination Angle from its Rotation Velocity and Projected Rotation Velocity
• A catalog of chromospherically active binary stars (third edition)
• A Volume-Limited Sample of Ultracool Dwarfs. I. Construction, Space Density, and a Gap in the L/T Transition
• AF Lep b: the lowest mass planet detected coupling astrometric and direct imaging data
• Direct imaging discovery of a super-Jovian around the young Sun-like star AF Leporis
• A Direct Imaging Survey of Spitzer detected debris disks: Occurrence of giant planets in dusty systems
• The W. M. Keck Observatory infrared vortex coronagraph and a first image of HIP79124 B
• Rotation Periods, Inclinations, and Obliquities of Cool Stars Hosting Directly Imaged Substellar Companions: Spin-Orbit Misalignments are Common
• Planet populations inferred from debris discs: insights from 178 debris systems in the ISPY, LEECH and LIStEN planet-hunting surveys
• The First Dynamical Mass Measurement in the HR 8799 System
• On-sky performance of the QACITS pointing control technique with the Keck/NIRC2 vortex coronagraph
• A $75\%$ Occurrence Rate of Debris Discs around F stars in the $\beta$ Pic Moving Group
• The beta Pictoris association low-mass members: membership assessment, rotation period distribution, and dependence on multiplicity
• The Possible Astrometric Signature of a Planetary-mass Companion to the Nearby Young Star TW Piscis Austrini (Fomalhaut B): Constraints from Astrometry, Radial Velocities, and Direct Imaging

Cited by in corpus (29)

• Protoplanetary disks in $K_s$-band total intensity and polarized light
• JWST-TST High Contrast: Living on the Wedge, or, NIRCam Bar Coronagraphy Reveals CO${}_2$ in the HR 8799 and 51 Eri Exoplanets' Atmospheres
• Atmospheric properties of AF Lep b with forward modeling
• Rotation and Abundances of the Benchmark Brown Dwarf HD 33632 Ab from Keck/KPIC High-resolution Spectroscopy
• Direct-imaging Discovery of a Substellar Companion Orbiting the Accelerating Variable Star, HIP 39017
• One-third of Sun-like stars are born with misaligned planet-forming disks
• Combining Gaia and GRAVITY: Characterising five new Directly Detected Substellar Companions
• The COBREX archival survey: improved constraints on the occurrence rate of wide-orbit substellar companions. I. A uniform re-analysis of 400 stars from the GPIES survey
• Use the 4S (Signal-Safe Speckle Subtraction): Explainable Machine Learning reveals the Giant Exoplanet AF Lep b in High-Contrast Imaging Data from 2011
• Instrumentation prospects for rocky exoplanet atmospheres studies with high resolution spectroscopy
• Exomoon search with VLTI/GRAVITY around the substellar companion HD 206893 B
• The SPHERE infrared survey for exoplanets (SHINE). V. Complete observations, data reduction and analysis, detection performances, and final results
• The ExoGRAVITY survey: A K-band spectral library of giant exoplanet and brown dwarf companions
• WIde Separation Planets In Time (WISPIT): Two directly imaged exoplanets around the Sun-like stellar binary WISPIT 1
• High-contrast spectroscopy with the new VLT/ERIS instrument: Molecular maps and radial velocity of the gas giant AF Lep b
• Astrometric view of companions in the inner dust cavities of protoplanetary disks
• Searching for substellar companion candidates with Gaia. II. A catalog of 9,698 planet candidate solar-type hosts
• Astrometric and photometric characterization of $\eta$ Tel B combining two decades of observations
• GPI+SPHERE detection of a 6.1 $M_{\text{Jup}}$ circumbinary planet around HD 143811
• A multi-technique detection of an eccentric giant planet around accelerating star HD 57625
• Distinct Rotational Evolution of Giant Planets and Brown Dwarf Companions
• SCExAO/CHARIS and Gaia Direct Imaging and Astrometric Discovery of a Superjovian Planet 3--4 lambda/D from the Accelerating Star HIP 54515
• HD 143811 AB b: A Directly Imaged Planet Orbiting a Spectroscopic Binary in Sco-Cen
• OASIS Survey Direct Imaging and Astrometric Discovery of HIP 71618 B: A Substellar Companion Suitable for the Roman Coronagraph Technology Demonstration
• Direct Images of CO2 Absorption in the Atmosphere of a Super-Jupiter: Enhanced Metallicity Suggestive of Formation in a Disk
• Apache Point Observatory follow-up of ACcelerating Candidate ExopLanet host Stars (APO ACCELS): Ages for 166 Accelerating Stars in the Northern Hemisphere
• Direct Imaging Discovery of Giant Exoplanet $\beta$ Pictoris d: A Decade-Long Game of Hide-and-Seek
• Keck Observations in the INfrared of Taurus and $\rho$ Oph Exoplanets And Ultracool dwarfs (KOINTREAU) II: Two Young Bound Companions to Ophiuchus Stars
• A planetary-mass candidate imaged in the Young Suns Exoplanet Survey