Validation of Elemental and Isotopic Abundances in Late-M Spectral Types with the Benchmark HIP 55507 AB System

DOI
Publisher DOI
Abstract
M dwarfs are common host stars to exoplanets but often lack atmospheric abundance measurements. Late-M dwarfs are also good analogs to the youngest substellar companions, which share similar Teff ∼ 2300–2800 K. We present atmospheric analyses for the M7.5 companion HIP 55507 B and its K6V primary star with Keck/KPIC high-resolution (R ∼ 35,000) K-band spectroscopy. First, by including KPIC relative radial velocities between the primary and secondary in the orbit fit, we improve the dynamical mass precision by 60% and find MB = 88.0 +3.4-3.2 MJup, putting HIP 55507 B above the stellar–substellar boundary. We also find that HIP 55507 B orbits its K6V primary star with α = 38 +4-3 au and e = 0.40 ± 0.04. From atmospheric retrievals of HIP 55507 B, we measure [C/H] = 0.24 ± 0.13, [O/H] = 0.15 ± 0.13, and C/O = 0.67 ± 0.04. Moreover, we strongly detect 13CO (7.8σ significance) in the companion’s atmosphere and measure 12CO/13CO = 98 +28-22 and = H16 2/H18 2O = 240 +145 -80 after accounting for systematic errors. From a simplified retrieval analysis of HIP 55507 A, we measure 12CO/13CO = 79 +21-16 and = C16O/C182 = 288 +125 -70 for the primary star. These results demonstrate that HIP 55507 A and B have consistent 12C/13C and 16O/18O to the <1σ level, as expected for a chemically homogeneous binary system. Given the similar flux ratios and separations between HIP 55507 AB and systems with young substellar companions, our results open the door to systematically measuring 13CO and H 18 2 O abundances in the atmospheres of substellar or even planetary-mass companions with similar spectral types.
Date Issued
2024-02-01
Publication Type
Article
Subject(s)
Language(s)
en
Author(s)
Xuan, Jerry W.
Wang, Jason
Finnerty, Luke
Horstman, Katelyn
Peck, Anne E.
Nielsen, Eric
Knutson, Heather A.
Mawet, Dimitri
Isaacson, Howard
Howard, Andrew W.
Liu, Michael C.
Walker, Sam
Phillips, Mark W.
Blake, Geoffrey A.
Ruffio, Jean-Baptiste
Zhang, Yapeng
Inglis, Julie
Wallack, Nicole L.
Sanghi, Aniket
Gonzales, Erica J.
Dai, Fei
Baker, Ashley
Bartos, Randall
Bond, Charlotte Z.
Bryan, Marta L.
Calvin, Benjamin
Cetre, Sylvain
Delorme, Jacques-Robert
Echeverri, Daniel
Fitzgerald, Michael P.
Jovanovic, Nemanja
Liberman, Joshua
López, Ronald A.
Martin, Emily C.
Morris, Evan
Pezzato, Jacklyn
Ruane, Garreth
Sappey, Ben
Schofield, Tobias
Skemer, Andrew
Venenciano, Taylor
Wallace, J. Kent
Wizinowich, Peter
Xin, Yinzi
Agrawal, Shubh
Do Ó, Clarissa R.
Hsu, Chih-Chun
Phillips, Caprice L.
Additional Credits
Journal
The Astrophysical Journal
Publisher
American Astronomical Society
ISSN
0004-637X
1538-4357
Access(Rights)
open.access
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