Rotation and Abundances of the Benchmark Brown Dwarf HD 33632 Ab from Keck/KPIC High-resolution Spectroscopy

Abstract

We present the projected rotational velocity and molecular abundances for HD 33632 Ab obtained via Keck Planet Imager and Characterizer high-resolution spectroscopy. HD 33632 Ab is a nearby benchmark brown dwarf companion at a separation of $\sim$20 au that straddles the L/T transition. Using a forward-modeling framework with on-axis host star spectra, self-consistent substellar atmospheric and retrieval models for HD 33632 Ab, we derive a projected rotational velocity of 53 $\pm$ 3 km/s and carbon/water mass fractions of log CO = $-$2.3 $\pm$ 0.3 and log H${}_2$O = $-$2.7 $\pm$ 0.2. The inferred carbon-to-oxygen ratio (C/O = 0.58 $\pm$ 0.14), molecular abundances, and metallicity ([C/H] = 0.0 $\pm$ 0.2 dex) of HD 33632 Ab are consistent with its host star. Although detectable methane opacities are expected in L/T transition objects, we did not recover methane in our KPIC spectra, partly due to the high $v\sin i$ and to disequilibrium chemistry at the pressures we are sensitive to. We parameterize the spin as the ratio of rotation over break-up velocity, and compare HD 33632 Ab to a compilation of >200 very low-mass objects (M$\lesssim$0.1 M${}_{\odot }$) that have spin measurements in the literature. There appears to be no clear trend for the isolated field low-mass objects versus mass, but a tentative trend is identified for low-mass companions and directly imaged exoplanets, similar to previous findings. A larger sample of close-in gas giant exoplanets and brown dwarfs will critically examine our understanding of their formation and evolution through rotation and chemical abundance measurements.

arXiv commentAccepted for publication in the Astrophysical Journal. 36 pages, 15 figures, 5 tables

References in corpus (109)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Astropy: A Community Python Package for Astronomy
• emcee: The MCMC Hammer
• The chemical composition of the Sun
• Gaia Data Release 2. Summary of the contents and survey properties
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The Gaia mission
• Gaia Data Release 3: Summary of the content and survey properties
• Validation of the new Hipparcos reduction
• Intrinsic Colors, Temperatures, and Bolometric Corrections of Pre-Main Sequence Stars
• dynesty: A Dynamic Nested Sampling Package for Estimating Bayesian Posteriors and Evidences
• A new extensive library of PHOENIX stellar atmospheres and synthetic spectra
• Direct Imaging of Multiple Planets Orbiting the Star HR 8799
• Evolutionary models for cool brown dwarfs and extrasolar giant planets. The case of HD 20945
• The Geneva-Copenhagen survey of the Solar neighbourhood: Ages, metallicities, and kinematic properties of 14,000 F and G dwarfs
• A Non-Gray Theory of Extrasolar Giant Planets and Brown Dwarfs
• The effects of snowlines on C/O in planetary atmospheres
• The Revised TESS Input Catalog and Candidate Target List
• Models of Stars, Brown Dwarfs and Exoplanets
• Precipitating Condensation Clouds in Substellar Atmospheres
• New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey
• The Theory of Brown Dwarfs and Extrasolar Giant Planets
• petitRADTRANS: a Python radiative transfer package for exoplanet characterization and retrieval
• The Geneva-Copenhagen Survey of the Solar neighbourhood III. Improved distances, ages, and kinematics
• Discovery and spectroscopy of the young Jovian planet 51 Eri b with the Gemini Planet Imager
• BANYAN. XI. The BANYAN $\Sigma$ multivariate Bayesian algorithm to identify members of young associations within 150 pc
• Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 parsecs: The Northern Sample I
• C/O ratio as a Dimension for Characterizing Exoplanetary Atmospheres
• Detection of Carbon Monoxide and Water Absorption Lines in an Exoplanet Atmosphere
• Fundamental Parameters and Spectral Energy Distributions of Young and Field Age Objects with Masses Spanning the Stellar to Planetary Regime
• Modeling optical properties of cosmic dust grains using a distribution of hollow spheres
• Pulkovo Compilation of Radial Velocities for 35495 Hipparcos Stars in a Common System
• Chemical composition of 90 F and G disk dwarfs
• The NASA-UC-UH Eta-Earth Program: IV. A Low-mass Planet Orbiting an M Dwarf 3.6 PC from Earth
• The Hipparcos-Gaia Catalog of Accelerations: Gaia EDR3 Edition
• Weather on Other Worlds. II. Survey Results: Spots Are Ubiquitous on L and T Dwarfs
• The Tucana/Horologium, Columba, AB Doradus, and Argus Associations: New Members and Dusty Debris Disks
• The PASTEL catalogue of stellar parameters
• Aerosol Composition of Hot Giant Exoplanets Dominated by Silicates and Hydrocarbon Hazes
• An accurate, extensive, and practical line list of methane for the HITEMP database
• The N2K Consortium. IV. New temperatures and metallicities for 100,000+ FGK dwarfs
• Methane, Carbon Monoxide, and Ammonia in Brown Dwarfs and Self-Luminous Giant Planets
• Retrieving scattering clouds and disequilibrium chemistry in the atmosphere of HR 8799e
• The PASTEL catalogue: 2016 version
• The effects of seeing on Sersic profiles. II. The Moffat PSF
• Large Amplitude Variations of an L/T Transition Brown Dwarf: Multi-Wavelength Observations of Patchy, High-Contrast Cloud Features
• The NIRSPEC Ultracool Dwarf Radial Velocity Survey
• XHIP: An Extended Hipparcos Compilation
• Astrophysical supplements to the ASCC-2.5. Ia. Radial velocities of about 55000 stars and mean radial velocities of 516 Galactic open clusters and associations
• On the correlation of elemental abundances with kinematics among galactic disk stars
• orbitize!: A Comprehensive Orbit-fitting Software Package for the High-contrast Imaging Community
• HELIOS-Retrieval: An Open-source, Nested Sampling Atmospheric Retrieval Code, Application to the HR 8799 Exoplanets and Inferred Constraints for Planet Formation
• Retrieval of atmospheric properties of cloudy L dwarfs
• Multiwavelength optical properties of compact dust aggregates in protoplanetary disks
• The Twenty-Five Year Lick Planet Search
• Spectroscopic rotational velocities of brown dwarfs
• On the Terminal Rotation Rates of Giant Planets
• The Solar Neighborhood XXX: Fomalhaut C
• Cloud busting: enstatite and quartz clouds in the atmosphere of 2M2224-0158
• The Viewing Geometry of Brown Dwarfs Influences Their Observed Colours and Variability Properties
• Doppler Imaging of Exoplanets and Brown Dwarfs
• Let the Great World Spin: Revealing the Stormy, Turbulent Nature of Young Giant Exoplanet Analogs with the Spitzer Space Telescope
• The CARMENES search for exoplanets around M dwarfs. Two planets on the opposite sides of the radius gap transiting the nearby M dwarf LTT 3780
• AF Lep b: the lowest mass planet detected coupling astrometric and direct imaging data
• Radial Velocity Measurements of HR 8799 b and c with Medium Resolution Spectroscopy
• Detection and Bulk Properties of the HR 8799 Planets with High Resolution Spectroscopy
• Direct imaging discovery of a super-Jovian around the young Sun-like star AF Leporis
• Survey of Surveys I: The largest catalogue of radial velocities for the Galaxy
• Astrometric Accelerations as Dynamical Beacons: A Giant Planet Imaged Inside the Debris Disk of the Young Star AF Lep
• SIMP J013656.5+093347 is Likely a Planetary-Mass Object in the Carina-Near Moving Group
• A Clear View of a Cloudy Brown Dwarf Companion from High-Resolution Spectroscopy
• The W. M. Keck Observatory infrared vortex coronagraph and a first image of HIP79124 B
• Weather on Other Worlds. V. The Three Most Rapidly Rotating Ultra-Cool Dwarfs
• Deep exploration of the planets HR 8799 b, c, and d with moderate resolution spectroscopy
• A medium-resolution spectrum of the exoplanet HIP 65426 b
• Radial velocities for the Hipparcos-Gaia Hundred-Thousand-Proper-Motion project
• A Search for Variability in Exoplanet Analogues and Low-Gravity Brown Dwarfs
• Variability of the Lowest Mass Objects in the AB Doradus Moving Group
• Evaluating Rotation Periods of M Dwarfs Across the Ages
• Assessing the C/O Ratio Formation Diagnostic: A Potential Trend with Companion Mass
• Detecting exomoons from radial velocity measurements of self-luminous planets: application to observations of HR 7672 B and future prospects
• SCExAO/CHARIS Direct Imaging Discovery of a 20 au Separation, Low-Mass Ratio Brown Dwarf Companion to an Accelerating Sun-like Star
• Atmospheric retrievals with petitRADTRANS
• Empirically Determining Substellar Cloud Compositions in the era of JWST
• As the Worlds Turn: Constraining Spin Evolution in the Planetary-Mass Regime
• Retrieval of SDSS J1416+1348AB
• Retrieving the C and O Abundances of HR 7672~AB: a Solar-Type Primary Star with a Benchmark Brown Dwarf
• Retrieving C and O Abundance of HR 8799 c by Combining High- and Low-Resolution Data
• Physical parameters of T dwarfs derived from high-resolution near-infrared spectra
• Direct characterization of young giant exoplanets at high spectral resolution by coupling SPHERE and CRIRES+
• Direct emission spectroscopy of exoplanets with the medium resolution imaging spectrometer on board JWST MIRI: I. Molecular mapping and sensitivity to instrumental effects
• Stellar Characterization of Keck HIRES Spectra with The Cannon
• Retrieval study of cool, directly imaged exoplanet 51 Eri b
• 2MASS J13243553+6358281 is an Early T-Type Planetary-Mass Object in the AB Doradus Moving Group
• The 3-D Kinematics of the Orion Nebula Cluster: NIRSPEC-AO Radial Velocities of the Core Population
• Moderate-Resolution $K$-Band Spectroscopy of Substellar Companion $\kappa$ Andromedae b
• Optimizing the subwavelength grating of L-band Annular Groove Phase Masks for high coronagraphic performance
• Breaking the centrifugal barrier to giant planet contraction by magnetic disc braking
• The Orbit of the L dwarf + T dwarf Spectral Binary SDSS J080531.84+481233.0
• A Rotation Rate for the Planetary-Mass Companion DH Tau b
• An astrometric planetary companion candidate to the M9 Dwarf TVLM 513-46546
• A Wide Planetary Mass Companion Discovered Through the Citizen Science Project Backyard Worlds: Planet 9
• Simulated performance of the molecular mapping for young giant exoplanets with the Medium Resolution Spectrometer of JWST/MIRI
• Redder than Red: Discovery of an Exceptionally Red L/T Transition Dwarf
• Understanding Fundamental Properties and Atmospheric Features of Subdwarfs via a Case Study of SDSS J125637.13-022452.4
• Radial Velocity Variability of Field Brown Dwarfs
• Discovery of the Exceptionally Short Period Ultracool Dwarf Binary LP 413-53AB
• On-sky speckle nulling through a single-mode fiber with the Keck Planet Imager and Characterizer

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• PDS 70b Shows Stellar-like Carbon-to-oxygen Ratio
• Atmospheric abundances and bulk properties of the binary brown dwarf Gliese 229 Bab from JWST/MIRI spectroscopy
• Distinct Rotational Evolution of Giant Planets and Brown Dwarf Companions
• Dynamical Architectures of S-type Transiting Planets in Binaries II: A Dichotomy in Orbital Alignment of Small Planets in Close Binary Systems