HD 206893 B at High Spectral Resolution with the Keck Planet Imager and Characterizer
Abstract We present an atmospheric characterization and orbital analysis of HD 206893 B, an exceptionally red, L/T-transition substellar companion in a multiplanetary system, via Keck Planet Imager and Characterizer (KPIC) high-resolution ( R ∼ 35,000) K- band spectroscopy. Using PHOENIX atmospheric models in a forward-model framework that fits the spectrum of the companion and diffracted starlight simultaneously, we detect HD 206893 B at >8 σ significance via cross correlation in two epochs. We find an effective temperature for the companion of 1634 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow/> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>38</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>72</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> K and a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mi>g</mml:mi> </mml:math> of 4.55 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow/> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.22</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.17</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> . Only accounting for statistical uncertainties, we measure the carbon-oxygen ratio (C/O) of this companion to be 0.57 ± 0.02, or near-solar while assuming solar metallicity. The C/O ratio we measure fits the tentative trend of >4 M Jup companions having near-solar C/O ratios while less massive companions have greater-than-solar C/O ratios. Using substellar evolution models, we find an age of 112 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow/> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>22</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>36</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> Myr, a mass of 22.7 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow/> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1.7</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>2.5</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> M Jup , and a radius of 1.11 ± 0.03 R Jup for this companion. We also use KPIC radial velocity data to fit the orbit of HD 206893 B and analyze the orbital stability of this system. We find that the orbital stability is relatively independent of the mass of HD 206893 B, and favors an orbital configuration where B and its interior planetary companion, HD 206893 c, are coplanar. The measured C/O ratio coupled with the current architecture of the system cannot rule out the core accretion scenario, nor the disk fragmentation scenario regarding the formation pathway of HD 206893 B.
Authors
- Andrew Skemer (ORCID: https://orcid.org/0000-0001-6098-3924)
- Emily C. Martin (ORCID: https://orcid.org/0000-0002-0618-5128)
- Taylor Venenciano (ORCID: https://orcid.org/0000-0003-0122-8915)
- Aniket Sanghi (ORCID: https://orcid.org/0000-0002-1838-4757)
- Nemanja Jovanović (ORCID: https://orcid.org/0000-0001-5213-6207)
- Jacques-Robert Delorme (ORCID: https://orcid.org/0000-0001-8953-1008)
- Tobias Schofield
- Caprice L. Phillips (ORCID: https://orcid.org/0000-0001-5610-5328)
- Clarissa R. Do Ó (ORCID: https://orcid.org/0000-0001-5173-2947)
- Nicole L. Wallack (ORCID: https://orcid.org/0000-0003-0354-0187)
- Luke Finnerty (ORCID: https://orcid.org/0000-0002-1392-0768)
- Evan Morris (ORCID: https://orcid.org/0000-0003-3165-0922)
- Randall Bartos
- J. Kent Wallace (ORCID: https://orcid.org/0000-0001-5299-6899)
- Ashley Baker (ORCID: https://orcid.org/0000-0002-6525-7013)
- Jean-Baptiste Ruffio (ORCID: https://orcid.org/0000-0003-2233-4821)
- Julie Inglis (ORCID: https://orcid.org/0000-0001-9164-7966)
- Joshua Liberman (ORCID: https://orcid.org/0000-0002-4934-3042)
- Christopher A. Theissen (ORCID: https://orcid.org/0000-0002-9807-5435)
- Dimitri Mawet (ORCID: https://orcid.org/0000-0002-8895-4735)
- Sylvain Cetre
- Ji Wang (ORCID: https://orcid.org/0000-0002-4361-8885)
- Chih-Chun Hsu (ORCID: https://orcid.org/0000-0002-5370-7494)
- Daniel Echeverri (ORCID: https://orcid.org/0000-0002-1583-2040)
- Peter Wizinowich (ORCID: https://orcid.org/0000-0002-1646-442X)
- Quinn Konopacky (ORCID: https://orcid.org/0000-0002-9936-6285)
- Garreth Ruane (ORCID: https://orcid.org/0000-0003-4769-1665)
- Yinzi Xin (ORCID: https://orcid.org/0000-0002-6171-9081)
- Travis Barman (ORCID: https://orcid.org/0000-0002-7129-3002)
- Yapeng Zhang (ORCID: https://orcid.org/0000-0003-0097-4414)
- Geoffrey A. Blake (ORCID: https://orcid.org/0000-0003-0787-1610)
- Ronald López (ORCID: https://orcid.org/0000-0002-2019-4995)
- Ben Sappey (ORCID: https://orcid.org/0000-0003-1399-3593)
- Benjamin Calvin (ORCID: https://orcid.org/0000-0003-4737-5486)
- Greg Doppmann
- Michael P. Fitzgerald (ORCID: https://orcid.org/0000-0002-0176-8973)
- Jacklyn Pezzato-Rovner
- Jerry W. Xuan (ORCID: https://orcid.org/0000-0002-6618-1137)
- Jason Wang (ORCID: https://orcid.org/0000-0003-0774-6502)
- Charlotte Z. Bond
- Katelyn Hortsman
Publication Details
- Journal
- The Astronomical Journal
- Published
- 2025-02-26
- DOI
- https://doi.org/10.3847/1538-3881/adad70
- Citations
- 6
- Primary Topic
- Stellar, planetary, and galactic studies
- Type
- article
- Field-Weighted Citation Impact
- 6.93
Funders
- National Aeronautics and Space Administration
- Heising-Simons Foundation