Dynamical Mass of the Young Substellar Companion HD 984 B

Abstract

Model-independent masses of substellar companions are critical tools to validate models of planet and brown dwarf cooling, test their input physics, and determine the formation and evolution of these objects. In this work, we measure the dynamical mass and orbit of the young substellar companion HD 984 B. We obtained new high-contrast imaging of the HD 984 system with Keck/NIRC2 which expands the baseline of relative astrometry from 3 to 8 years. We also present new radial velocities of the host star with the Habitable-Zone Planet Finder spectrograph at the Hobby-Eberly Telescope. Furthermore, HD 984 exhibits a significant proper motion difference between Hipparcos and Gaia EDR3. Our joint orbit fit of the relative astrometry, proper motions, and radial velocities yields a dynamical mass of $61\pm 4$ ${\mathrm{M}}_{\mathrm{Jup}}$ for HD 984 B, placing the companion firmly in the brown dwarf regime. The new fit also reveals a higher eccentricity for the companion ($e=0.76\pm 0.05$) compared to previous orbit fits. Given the broad age constraint for HD 984, this mass is consistent with predictions from evolutionary models. HD 984 B's dynamical mass places it among a small but growing list of giant planet and brown dwarf companions with direct mass measurements.

23 pages, accepted to AJ

References in corpus (44)

• Array Programming with NumPy
• scikit-image: Image processing in Python
• The Transiting Exoplanet Survey Satellite
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey
• The Evolution of L and T Dwarfs in Color-Magnitude Diagrams
• On the Luminosity of Young Jupiters
• The Gemini Planet Imager Exoplanet Survey: Giant Planet and Brown Dwarf Demographics From 10-100 AU
• Spectrum radial velocity analyser (SERVAL). High-precision radial velocities and two alternative spectral indicators
• The Hipparcos-Gaia Catalog of Accelerations: Gaia EDR3 Edition
• Parallax Systematics and Photocenter Motions of Benchmark Eclipsing Binaries in Gaia EDR3
• Synthetic Spectra and Colors of Young Giant Planet Atmospheres: Effects of Initial Conditions and Atmospheric Metallicity
• CLES, Code Liegeois d'Evolution Stellaire
• VIP: Vortex Image Processing package for high-contrast direct imaging
• Population-Level Eccentricity Distributions of Imaged Exoplanets and Brown Dwarf Companions: Dynamical Evidence for Distinct Formation Channels
• A new equation of state for dense hydrogen-helium mixtures
• High-Dispersion Optical Spectra of Nearby Stars Younger Than The Sun
• orbitize!: A Comprehensive Orbit-fitting Software Package for the High-contrast Imaging Community
• Stellar Spectroscopy in the Near-infrared with a Laser Frequency Comb
• Direct confirmation of the radial-velocity planet $\beta$ Pic c
• Python Leap Second Management and Implementation of Precise Barycentric Correction (barycorrpy)
• orvara: An Efficient Code to Fit Orbits using Radial Velocity, Absolute, and/or Relative Astrometry
• A Versatile Technique to Enable sub-milli-Kelvin Instrument Stability for Precise Radial Velocity Measurements: Tests with the Habitable-zone Planet Finder
• Improved Dynamical Masses for Six Brown Dwarf Companions Using Hipparcos and Gaia EDR3
• A Model-Independent Mass and Moderate Eccentricity for $\beta$ Pic b
• Precise Dynamical Masses and Orbital Fits for $\beta$ Pic b and $\beta$ Pic c
• New Evidence for a Substellar Luminosity Problem: Dynamical Mass for the Brown Dwarf Binary Gl 417BC
• TESS Hunt for Young and Maturing Exoplanets (THYME) V: A Sub-Neptune Transiting a Young Star in a Newly Discovered 250 Myr Association
• A Unified tool to estimate Distances, Ages and Masses (UniDAM) from spectrophotometric data
• Dynamical Mass of GJ 802B: a brown dwarf in a triple system
• SCExAO/CHARIS Direct Imaging Discovery of a 20 au Separation, Low-Mass Ratio Brown Dwarf Companion to an Accelerating Sun-like Star
• Planets Around Low-Mass Stars (PALMS). VI. Discovery of a Remarkably Red Planetary-Mass Companion to the AB Dor Moving Group Candidate 2MASS J22362452+4751425
• BAFFLES: Bayesian Ages for Field Lower-Mass Stars
• The First Dynamical Mass Measurement in the HR 8799 System
• Search for associations containing young stars (SACY) VIII. An updated census of spectroscopic binary systems showing hints of non-universal multiplicity among these associations
• The Second Discovery from the COol Companions ON Ultrawide orbiTS (COCONUTS) Program: A Cold Wide-Orbit Exoplanet around a Young Field M Dwarf at 10.9 pc
• A HARPS RV search for planets around young nearby stars
• Evolutionary models for ultracool dwarfs
• The McDonald Accelerating Stars Survey (MASS): White Dwarf Companions Accelerating the Sun-like Stars 12 Psc and HD 159062
• The McDonald Accelerating Stars Survey (MASS): Discovery of a Long-Period Substellar Companion Orbiting the Old Solar Analog HD 47127
• The Epoch of Giant Planet Migration Planet Search Program. I. Near-Infrared Radial Velocity Jitter of Young Sun-like Stars
• Following the Lithium: Tracing Li-bearing Molecules Across Age, Mass, and Gravity in Brown Dwarfs
• BANYAN. X. Discovery of a wide, low-gravity L-type companion to a fast-rotating M3 dwarf

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• Direct Imaging Discovery and Dynamical Mass of a Substellar Companion Orbiting an Accelerating Hyades Sun-like Star with SCExAO/CHARIS
• Astrometric Accelerations as Dynamical Beacons: Discovery and Characterization of HIP 21152 B, the First T-Dwarf Companion in the Hyades
• Surveying Nearby Brown Dwarfs with HGCA: Direct Imaging Discovery of a Faint, High-Mass Brown Dwarf Orbiting HD 176535 A
• The McDonald Accelerating Stars Survey (MASS): Architecture of the Ancient Five-Planet Host System Kepler-444
• Weighing the Darkness III: How Gaia Could, but Probably Won't, Astrometrically Detect Free-Floating Black Holes
• The Directly-Imaged Exoplanet Host Star 51 Eridani is a Gamma Doradus Pulsator
• Searching for Embedded Protoplanets with the Keck/NIRC2 Vortex Coronagraph: Confirmation of a Core-accretion Planet in the Narrow Gap of the Elias 2-24 Disk