Journal Article

HD 206893 B at High Spectral Resolution with the Keck Planet Imager and Characterizer

Wang, Ji, Ruffio, Jean-Baptiste, Cetre, Sylvain, Schofield, Tobias, Hsu, Chih-Chun, Blake, Geoffrey A, Sanghi, Aniket, Ruane, Garreth, Finnerty, Luke, Xin, Yinzi, López, Ronald A, Xuan, Jerry, Echeverri, Daniel, Martin, Emily C, Konopacky, Quinn, Inglis, Julie, Venenciano, Taylor, Delorme, Jacques-Robert, Morris, Evan, Baker, Ashley, Jovanovic, Nemanja, Wang, Jason, Calvin, Benjamin, Bartos, Randall, Fitzgerald, Michael P, Barman, Travis, Sappey, Ben, Wallace, J. Kent, Wizinowich, Peter, Hortsman, Katelyn, Liberman, Joshua, Theissen, Christopher A, Zhang, Yapeng, Skemer, Andrew, Ó, Clarissa R. Do, Bond, Charlotte Z, Wallack, Nicole L, Phillips, Caprice L, Mawet, Dimitri, Doppmann, Greg, Pezzato-Rovner, Jacklyn

2025

Overview

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 >8σ significance via cross correlation in two epochs. We find an effective temperature for the companion of 1634 −38+72 K and a logg of 4.55 −0.22+0.17 . 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 MJup 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 −22+36 Myr, a mass of 22.7 −1.7+2.5 MJup, and a radius of 1.11 ± 0.03 RJup 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.

• Publisher: IOP Publishing
• Subject: Accretion disks / Astronomy / Astrophysics / Atmospheric models / Cross correlation / Metallicity / Observatories / Orbital stability / Planet detection / Radial velocity / Ratios / Spectral resolution / Spectroscopy / Spectrum analysis