Validation of Elemental and Isotopic Abundances in Late-M Spectral Types with the Benchmark HIP 55507 AB System
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Published:2024-02-01
Issue:1
Volume:962
Page:10
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ISSN:0004-637X
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Container-title:The Astrophysical Journal
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language:
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Short-container-title:ApJ
Author:
Xuan Jerry W.ORCID, Wang JasonORCID, Finnerty LukeORCID, Horstman Katelyn, Grimm Simon, Peck Anne E.ORCID, Nielsen EricORCID, Knutson Heather A.ORCID, Mawet Dimitri, Isaacson HowardORCID, Howard Andrew W.ORCID, Liu Michael C.ORCID, Walker SamORCID, Phillips Mark W., Blake Geoffrey A., Ruffio Jean-BaptisteORCID, Zhang YapengORCID, Inglis JulieORCID, Wallack Nicole L.ORCID, Sanghi AniketORCID, Gonzales Erica J.ORCID, Dai FeiORCID, Baker Ashley, Bartos Randall, Bond Charlotte Z., Bryan Marta L.ORCID, Calvin BenjaminORCID, Cetre Sylvain, Delorme Jacques-RobertORCID, Doppmann Greg, Echeverri Daniel, Fitzgerald Michael P.ORCID, Jovanovic NemanjaORCID, Liberman JoshuaORCID, López Ronald A.ORCID, Martin Emily C.ORCID, Morris Evan, Pezzato Jacklyn, Ruane GarrethORCID, Sappey BenORCID, Schofield Tobias, Skemer AndrewORCID, Venenciano Taylor, Wallace J. KentORCID, Wang JiORCID, Wizinowich Peter, Xin YinziORCID, Agrawal ShubhORCID, Do Ó Clarissa R.ORCID, Hsu Chih-ChunORCID, Phillips Caprice L.ORCID
Abstract
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 T
eff ∼ 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
M
B
=
88.0
−
3.2
+
3.4
M
Jup
, putting HIP 55507 B above the stellar–substellar boundary. We also find that HIP 55507 B orbits its K6V primary star with
a
=
38
−
3
+
4
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) and tentatively detect
H
2
18
O
(3.7σ significance) in the companion’s atmosphere and measure
12
CO
/
13
CO
=
98
−
22
+
28
and
H
2
16
O
/
H
2
18
O
=
240
−
80
+
145
after accounting for systematic errors. From a simplified retrieval analysis of HIP 55507 A, we measure
12
CO
/
13
CO
=
79
−
16
+
21
and
C
16
O
/
C
18
O
=
288
−
70
+
125
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
2
18
O
abundances in the atmospheres of substellar or even planetary-mass companions with similar spectral types.
Funder
Heising-Simons Foundation National Aeronautics and Space Administration National Science Foundation
Publisher
American Astronomical Society
Subject
Space and Planetary Science,Astronomy and Astrophysics
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