Rotation and Abundances of the Benchmark Brown Dwarf HD 33632 Ab from Keck/KPIC High-resolution Spectroscopy
2024
Online
report
Zugriff:
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 self-consistent substellar atmospheric and retrieval models for HD 33632 Ab, we derive a projected rotational velocity of 53 $\pm$ 3 km/s and water plus carbon monoxide 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.
Comment: Submitted to AAS Journals
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Rotation and Abundances of the Benchmark Brown Dwarf HD 33632 Ab from Keck/KPIC High-resolution Spectroscopy
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Autor/in / Beteiligte Person: | Hsu, Chih-Chun ; Wang, Jason J. ; Xuan, Jerry W. ; Ruffio, Jean-Baptiste ; Echeverri, Daniel ; Xin, Yinzi ; Liberman, Joshua ; Finnerty, Luke ; Morris, Evan ; Hortsman, Katelyn ; Sappey, Ben ; Doppmann, Gregory W. ; Mawet, Dimitri ; Jovanovic, Nemanja ; Fitzgerald, Michael P. ; Delorme, Jacques-Robert ; Wallace, J. Kent ; Baker, Ashley ; Bartos, Randall ; Blake, Geoffrey A. ; Calvin, Benjamin ; Cetre, Sylvain ; López, Ronald A. ; Pezzato, Jacklyn ; Schofield, Tobias ; Skemer, Andrew ; Wang, Ji |
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Veröffentlichung: | 2024 |
Medientyp: | report |
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