A Clear View of a Cloudy Brown Dwarf Companion from High-resolution Spectroscopy

Jerry W. Xuan; Jason Wang; Jean Baptiste Ruffio; Heather Knutson; Dimitri Mawet; Paul Mollière; Jared Kolecki; Arthur Vigan; Sagnick Mukherjee; Nicole Wallack; Ji Wang; Ashley Baker; Randall Bartos; Geoffrey A. Blake; Charlotte Z. Bond; Marta Bryan; Benjamin Calvin; Sylvain Cetre; Mark Chun; Jacques Robert Delorme; Greg Doppmann; Daniel Echeverri; Luke Finnerty; Michael P. Fitzgerald; Katelyn Horstman; Julie Inglis; Nemanja Jovanovic; Ronald López; Emily C. Martin; Evan Morris; Jacklyn Pezzato; Sam Ragland; Bin Ren; Garreth Ruane; Ben Sappey; Tobias Schofield; Andrew Skemer; Taylor Venenciano; J. Kent Wallace; Peter Wizinowich

doi:10.3847/1538-4357/ac8673

A Clear View of a Cloudy Brown Dwarf Companion from High-resolution Spectroscopy

Jerry W. Xuan, Jason Wang, Jean Baptiste Ruffio, Heather Knutson, Dimitri Mawet, Paul Mollière, Jared Kolecki, Arthur Vigan, Sagnick Mukherjee, Nicole Wallack, Ji Wang, Ashley Baker, Randall Bartos, Geoffrey A. Blake, Charlotte Z. Bond, Marta Bryan, Benjamin Calvin, Sylvain Cetre, Mark Chun, Jacques Robert DelormeGreg Doppmann, Daniel Echeverri, Luke Finnerty, Michael P. Fitzgerald, Katelyn Horstman, Julie Inglis, Nemanja Jovanovic, Ronald López, Emily C. Martin, Evan Morris, Jacklyn Pezzato, Sam Ragland, Bin Ren, Garreth Ruane, Ben Sappey, Tobias Schofield, Andrew Skemer, Taylor Venenciano, J. Kent Wallace, Peter Wizinowich

Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

43 Scopus citations

Abstract

Direct imaging studies have mainly used low-resolution spectroscopy (R ∼ 20-100) to study the atmospheres of giant exoplanets and brown dwarf companions, but the presence of clouds has often led to degeneracies in the retrieved atmospheric abundances (e.g., carbon-to-oxygen ratio, metallicity). This precludes clear insights into the formation mechanisms of these companions. The Keck Planet Imager and Characterizer (KPIC) uses adaptive optics and single-mode fibers to transport light into NIRSPEC (R ∼ 35,000 in the K band), and aims to address these challenges with high-resolution spectroscopy. Using an atmospheric retrieval framework based on petitRADTRANS, we analyze the KPIC high-resolution spectrum (2.29-2.49 μm) and the archival low-resolution spectrum (1-2.2 μm) of the benchmark brown dwarf HD 4747 B (m = 67.2 ± 1.8 M _Jup, a = 10.0 ± 0.2 au, T _eff ≈ 1400 K). We find that our measured C/O and metallicity for the companion from the KPIC high-resolution spectrum agree with those of its host star within 1σ-2σ. The retrieved parameters from the K-band high-resolution spectrum are also independent of our choice of cloud model. In contrast, the retrieved parameters from the low-resolution spectrum are highly sensitive to our chosen cloud model. Finally, we detect CO, H₂O, and CH₄ (volume-mixing ratio of log(CH₄) = −4.82 ± 0.23) in this L/T transition companion with the KPIC data. The relative molecular abundances allow us to constrain the degree of chemical disequilibrium in the atmosphere of HD 4747 B, and infer a vertical diffusion coefficient that is at the upper limit predicted from mixing length theory.

Original language	English (US)
Article number	54
Journal	Astrophysical Journal
Volume	937
Issue number	2
DOIs	https://doi.org/10.3847/1538-4357/ac8673
State	Published - Oct 1 2022

Funding

We wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This research has benefitted from the SpeX Prism Library maintained by Adam Burgasser at http://www.browndwarfs.org/spexprism . Funding for KPIC has been provided by the California Institute of Technology, the Jet Propulsion Laboratory, the Heising-Simons Foundation, the Simons Foundation, and the United States National Science Foundation grant No. AST-1611623. A.V. acknowledges funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program, grant agreement Nos. 757561 (HiRISE). H.A.K. acknowledges support from the President’s and Director’s Research & Development Fund Program, which is jointly funded by the Jet Propulsion Laboratory and the California Institute of Technology under a contract with the National Aeronautics and Space Administration. The computations presented here were conducted in the Resnick High Performance Center, a facility supported by Resnick Sustainability Institute at the California Institute of Technology.

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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Xuan, J. W., Wang, J., Ruffio, J. B., Knutson, H., Mawet, D., Mollière, P., Kolecki, J., Vigan, A., Mukherjee, S., Wallack, N., Wang, J., Baker, A., Bartos, R., Blake, G. A., Bond, C. Z., Bryan, M., Calvin, B., Cetre, S., Chun, M., ... Wizinowich, P. (2022). A Clear View of a Cloudy Brown Dwarf Companion from High-resolution Spectroscopy. Astrophysical Journal, 937(2), Article 54. https://doi.org/10.3847/1538-4357/ac8673

@article{32edac5ec2d94282ac2dfd26fcbda76c,

title = "A Clear View of a Cloudy Brown Dwarf Companion from High-resolution Spectroscopy",

abstract = "Direct imaging studies have mainly used low-resolution spectroscopy (R ∼ 20-100) to study the atmospheres of giant exoplanets and brown dwarf companions, but the presence of clouds has often led to degeneracies in the retrieved atmospheric abundances (e.g., carbon-to-oxygen ratio, metallicity). This precludes clear insights into the formation mechanisms of these companions. The Keck Planet Imager and Characterizer (KPIC) uses adaptive optics and single-mode fibers to transport light into NIRSPEC (R ∼ 35,000 in the K band), and aims to address these challenges with high-resolution spectroscopy. Using an atmospheric retrieval framework based on petitRADTRANS, we analyze the KPIC high-resolution spectrum (2.29-2.49 μm) and the archival low-resolution spectrum (1-2.2 μm) of the benchmark brown dwarf HD 4747 B (m = 67.2 ± 1.8 M Jup, a = 10.0 ± 0.2 au, T eff ≈ 1400 K). We find that our measured C/O and metallicity for the companion from the KPIC high-resolution spectrum agree with those of its host star within 1σ-2σ. The retrieved parameters from the K-band high-resolution spectrum are also independent of our choice of cloud model. In contrast, the retrieved parameters from the low-resolution spectrum are highly sensitive to our chosen cloud model. Finally, we detect CO, H2O, and CH4 (volume-mixing ratio of log(CH4) = −4.82 ± 0.23) in this L/T transition companion with the KPIC data. The relative molecular abundances allow us to constrain the degree of chemical disequilibrium in the atmosphere of HD 4747 B, and infer a vertical diffusion coefficient that is at the upper limit predicted from mixing length theory.",

author = "Xuan, {Jerry W.} and Jason Wang and Ruffio, {Jean Baptiste} and Heather Knutson and Dimitri Mawet and Paul Molli{\`e}re and Jared Kolecki and Arthur Vigan and Sagnick Mukherjee and Nicole Wallack and Ji Wang and Ashley Baker and Randall Bartos and Blake, {Geoffrey A.} and Bond, {Charlotte Z.} and Marta Bryan and Benjamin Calvin and Sylvain Cetre and Mark Chun and Delorme, {Jacques Robert} and Greg Doppmann and Daniel Echeverri and Luke Finnerty and Fitzgerald, {Michael P.} and Katelyn Horstman and Julie Inglis and Nemanja Jovanovic and Ronald L{\'o}pez and Martin, {Emily C.} and Evan Morris and Jacklyn Pezzato and Sam Ragland and Bin Ren and Garreth Ruane and Ben Sappey and Tobias Schofield and Andrew Skemer and Taylor Venenciano and Wallace, {J. Kent} and Peter Wizinowich",

note = "Publisher Copyright: {\textcopyright} 2022. The Author(s). Published by the American Astronomical Society.",

year = "2022",

month = oct,

day = "1",

doi = "10.3847/1538-4357/ac8673",

language = "English (US)",

volume = "937",

journal = "Astrophysical Journal",

issn = "0004-637X",

number = "2",

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Xuan, JW, Wang, J, Ruffio, JB, Knutson, H, Mawet, D, Mollière, P, Kolecki, J, Vigan, A, Mukherjee, S, Wallack, N, Wang, J, Baker, A, Bartos, R, Blake, GA, Bond, CZ, Bryan, M, Calvin, B, Cetre, S, Chun, M, Delorme, JR, Doppmann, G, Echeverri, D, Finnerty, L, Fitzgerald, MP, Horstman, K, Inglis, J, Jovanovic, N, López, R, Martin, EC, Morris, E, Pezzato, J, Ragland, S, Ren, B, Ruane, G, Sappey, B, Schofield, T, Skemer, A, Venenciano, T, Wallace, JK & Wizinowich, P 2022, 'A Clear View of a Cloudy Brown Dwarf Companion from High-resolution Spectroscopy', Astrophysical Journal, vol. 937, no. 2, 54. https://doi.org/10.3847/1538-4357/ac8673

TY - JOUR

T1 - A Clear View of a Cloudy Brown Dwarf Companion from High-resolution Spectroscopy

AU - Xuan, Jerry W.

AU - Wang, Jason

AU - Ruffio, Jean Baptiste

AU - Knutson, Heather

AU - Mawet, Dimitri

AU - Mollière, Paul

AU - Kolecki, Jared

AU - Vigan, Arthur

AU - Mukherjee, Sagnick

AU - Wallack, Nicole

AU - Wang, Ji

AU - Baker, Ashley

AU - Bartos, Randall

AU - Blake, Geoffrey A.

AU - Bond, Charlotte Z.

AU - Bryan, Marta

AU - Calvin, Benjamin

AU - Cetre, Sylvain

AU - Chun, Mark

AU - Delorme, Jacques Robert

AU - Doppmann, Greg

AU - Echeverri, Daniel

AU - Finnerty, Luke

AU - Fitzgerald, Michael P.

AU - Horstman, Katelyn

AU - Inglis, Julie

AU - Jovanovic, Nemanja

AU - López, Ronald

AU - Martin, Emily C.

AU - Morris, Evan

AU - Pezzato, Jacklyn

AU - Ragland, Sam

AU - Ren, Bin

AU - Ruane, Garreth

AU - Sappey, Ben

AU - Schofield, Tobias

AU - Skemer, Andrew

AU - Venenciano, Taylor

AU - Wallace, J. Kent

AU - Wizinowich, Peter

PY - 2022/10/1

Y1 - 2022/10/1

N2 - Direct imaging studies have mainly used low-resolution spectroscopy (R ∼ 20-100) to study the atmospheres of giant exoplanets and brown dwarf companions, but the presence of clouds has often led to degeneracies in the retrieved atmospheric abundances (e.g., carbon-to-oxygen ratio, metallicity). This precludes clear insights into the formation mechanisms of these companions. The Keck Planet Imager and Characterizer (KPIC) uses adaptive optics and single-mode fibers to transport light into NIRSPEC (R ∼ 35,000 in the K band), and aims to address these challenges with high-resolution spectroscopy. Using an atmospheric retrieval framework based on petitRADTRANS, we analyze the KPIC high-resolution spectrum (2.29-2.49 μm) and the archival low-resolution spectrum (1-2.2 μm) of the benchmark brown dwarf HD 4747 B (m = 67.2 ± 1.8 M Jup, a = 10.0 ± 0.2 au, T eff ≈ 1400 K). We find that our measured C/O and metallicity for the companion from the KPIC high-resolution spectrum agree with those of its host star within 1σ-2σ. The retrieved parameters from the K-band high-resolution spectrum are also independent of our choice of cloud model. In contrast, the retrieved parameters from the low-resolution spectrum are highly sensitive to our chosen cloud model. Finally, we detect CO, H2O, and CH4 (volume-mixing ratio of log(CH4) = −4.82 ± 0.23) in this L/T transition companion with the KPIC data. The relative molecular abundances allow us to constrain the degree of chemical disequilibrium in the atmosphere of HD 4747 B, and infer a vertical diffusion coefficient that is at the upper limit predicted from mixing length theory.

AB - Direct imaging studies have mainly used low-resolution spectroscopy (R ∼ 20-100) to study the atmospheres of giant exoplanets and brown dwarf companions, but the presence of clouds has often led to degeneracies in the retrieved atmospheric abundances (e.g., carbon-to-oxygen ratio, metallicity). This precludes clear insights into the formation mechanisms of these companions. The Keck Planet Imager and Characterizer (KPIC) uses adaptive optics and single-mode fibers to transport light into NIRSPEC (R ∼ 35,000 in the K band), and aims to address these challenges with high-resolution spectroscopy. Using an atmospheric retrieval framework based on petitRADTRANS, we analyze the KPIC high-resolution spectrum (2.29-2.49 μm) and the archival low-resolution spectrum (1-2.2 μm) of the benchmark brown dwarf HD 4747 B (m = 67.2 ± 1.8 M Jup, a = 10.0 ± 0.2 au, T eff ≈ 1400 K). We find that our measured C/O and metallicity for the companion from the KPIC high-resolution spectrum agree with those of its host star within 1σ-2σ. The retrieved parameters from the K-band high-resolution spectrum are also independent of our choice of cloud model. In contrast, the retrieved parameters from the low-resolution spectrum are highly sensitive to our chosen cloud model. Finally, we detect CO, H2O, and CH4 (volume-mixing ratio of log(CH4) = −4.82 ± 0.23) in this L/T transition companion with the KPIC data. The relative molecular abundances allow us to constrain the degree of chemical disequilibrium in the atmosphere of HD 4747 B, and infer a vertical diffusion coefficient that is at the upper limit predicted from mixing length theory.

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UR - http://www.scopus.com/inward/citedby.url?scp=85139217768&partnerID=8YFLogxK

U2 - 10.3847/1538-4357/ac8673

DO - 10.3847/1538-4357/ac8673

M3 - Article

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VL - 937

JO - Astrophysical Journal

JF - Astrophysical Journal

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M1 - 54

ER -

A Clear View of a Cloudy Brown Dwarf Companion from High-resolution Spectroscopy

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