The Astrophysical Journal (Jan 2024)
Rotation and Abundances of the Benchmark Brown Dwarf HD 33632 Ab from Keck/KPIC High-resolution Spectroscopy
- Chih-Chun Hsu,
- Jason J. Wang,
- Jerry W. Xuan,
- Jean-Baptiste Ruffio,
- Evan Morris,
- Daniel Echeverri,
- Yinzi Xin,
- Joshua Liberman,
- Luke Finnerty,
- Katelyn Horstman,
- Ben Sappey,
- Gregory W. Doppmann,
- Dimitri Mawet,
- Nemanja Jovanovic,
- Michael P. Fitzgerald,
- Jacques-Robert Delorme,
- J. Kent Wallace,
- Ashley Baker,
- Randall Bartos,
- Geoffrey A. Blake,
- Benjamin Calvin,
- Sylvain Cetre,
- Ronald A. López,
- Jacklyn Pezzato,
- Tobias Schofield,
- Andrew Skemer,
- Ji Wang
Affiliations
- Chih-Chun Hsu
- ORCiD
- Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University , 1800 Sherman Ave, Evanston, IL 60201, USA ; [email protected]
- Jason J. Wang
- ORCiD
- Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University , 1800 Sherman Ave, Evanston, IL 60201, USA ; [email protected]; Department of Physics and Astronomy, Northwestern University , 2145 Sheridan Rd, Evanston, IL 60208, USA
- Jerry W. Xuan
- ORCiD
- Department of Astronomy, California Institute of Technology , Pasadena, CA 91125, USA
- Jean-Baptiste Ruffio
- ORCiD
- Department of Astronomy, California Institute of Technology , Pasadena, CA 91125, USA; Center for Astrophysics and Space Sciences, University of California , San Diego, La Jolla, CA 92093, USA
- Evan Morris
- ORCiD
- Department of Astronomy & Astrophysics, University of California , Santa Cruz, CA 95064, USA
- Daniel Echeverri
- ORCiD
- Department of Astronomy, California Institute of Technology , Pasadena, CA 91125, USA
- Yinzi Xin
- ORCiD
- Department of Astronomy, California Institute of Technology , Pasadena, CA 91125, USA
- Joshua Liberman
- ORCiD
- Department of Astronomy, California Institute of Technology , Pasadena, CA 91125, USA; James C. Wyant College of Optical Sciences, University of Arizona , Meinel Building 1630 E. University Blvd., Tucson, AZ 85721, USA
- Luke Finnerty
- ORCiD
- Department of Physics & Astronomy, 430 Portola Plaza, University of California , Los Angeles, CA 90095, USA
- Katelyn Horstman
- ORCiD
- Department of Astronomy, California Institute of Technology , Pasadena, CA 91125, USA
- Ben Sappey
- ORCiD
- Center for Astrophysics and Space Sciences, University of California , San Diego, La Jolla, CA 92093, USA
- Gregory W. Doppmann
- W. M. Keck Observatory , 65-1120 Mamalahoa Hwy, Kamuela, HI, USA
- Dimitri Mawet
- ORCiD
- Department of Astronomy, California Institute of Technology , Pasadena, CA 91125, USA; Jet Propulsion Laboratory, California Institute of Technology , 4800 Oak Grove Dr., Pasadena, CA 91109, USA
- Nemanja Jovanovic
- ORCiD
- Department of Astronomy, California Institute of Technology , Pasadena, CA 91125, USA
- Michael P. Fitzgerald
- ORCiD
- Department of Physics & Astronomy, 430 Portola Plaza, University of California , Los Angeles, CA 90095, USA
- Jacques-Robert Delorme
- ORCiD
- W. M. Keck Observatory , 65-1120 Mamalahoa Hwy, Kamuela, HI, USA
- J. Kent Wallace
- ORCiD
- Jet Propulsion Laboratory, California Institute of Technology , 4800 Oak Grove Dr., Pasadena, CA 91109, USA
- Ashley Baker
- ORCiD
- Department of Astronomy, California Institute of Technology , Pasadena, CA 91125, USA
- Randall Bartos
- Jet Propulsion Laboratory, California Institute of Technology , 4800 Oak Grove Dr., Pasadena, CA 91109, USA
- Geoffrey A. Blake
- ORCiD
- Division of Geological & Planetary Sciences, California Institute of Technology , Pasadena, CA 91125, USA
- Benjamin Calvin
- ORCiD
- Department of Astronomy, California Institute of Technology , Pasadena, CA 91125, USA; Department of Physics & Astronomy, 430 Portola Plaza, University of California , Los Angeles, CA 90095, USA
- Sylvain Cetre
- W. M. Keck Observatory , 65-1120 Mamalahoa Hwy, Kamuela, HI, USA
- Ronald A. López
- ORCiD
- Department of Physics & Astronomy, 430 Portola Plaza, University of California , Los Angeles, CA 90095, USA
- Jacklyn Pezzato
- Department of Astronomy, California Institute of Technology , Pasadena, CA 91125, USA
- Tobias Schofield
- Department of Astronomy, California Institute of Technology , Pasadena, CA 91125, USA
- Andrew Skemer
- ORCiD
- Department of Astronomy & Astrophysics, University of California , Santa Cruz, CA 95064, USA
- Ji Wang
- ORCiD
- Department of Astronomy, The Ohio State University , 100 W 18th Ave, Columbus, OH 43210, USA
- DOI
- https://doi.org/10.3847/1538-4357/ad58d3
- Journal volume & issue
-
Vol. 971,
no. 1
p. 9
Abstract
We present the projected rotational velocity and molecular abundances for HD 33632 Ab obtained via Keck Planet Imager and Characterizer (KPIC) high-resolution spectroscopy. HD 33632 Ab is a nearby benchmark brown dwarf companion at a separation of ∼20 au that straddles the L–T transition. Using a forward-modeling framework with on-axis host star spectra, which provides self-consistent substellar atmospheric and retrieval models for HD 33632 Ab, we derive a projected rotational velocity of 53 ± 3 km s ^−1 and carbon monoxide and water mass fractions of logCO = −2.3 ± 0.3 and logH _2 O = −2.7 ± 0.2, respectively. The inferred carbon-to-oxygen ratio (C/O = 0.58 ± 0.14), molecular abundances, and metallicity ([C/H] = 0.0 ± 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 to which we are sensitive. We parameterize the spin as the ratio of rotation to the breakup velocity, and compare HD 33632 Ab to a compilation of >200 very low-mass objects ( M ≲ 0.1 M _⊙ ) that have spin measurements in the literature. There appears to be no clear trend for the isolated low-mass field 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.
Keywords
- Brown dwarfs
- L dwarfs
- Atmospheric composition
- High resolution spectroscopy
- High angular resolution
- Stellar rotation
