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Retrieving the C and O Abundances of HR 7672 AB: A Solar-type Primary Star with a Benchmark Brown Dwarf

Wang, Ji and Kolecki, Jared R. and Ruffio, Jean-Baptiste and Wang, Jason J. and Mawet, Dimitri and Baker, Ashley and Bartos, Randall and Blake, Geoffrey A. and Bond, Charlotte Z. and Calvin, Benjamin and Cetre, Sylvain and Delorme, Jacques-Robert and Doppmann, Greg and Echeverri, Daniel and Finnerty, Luke and Fitzgerald, Michael P. and Jovanovic, Nemanja and Liu, Michael C. and Lopez, Ronald and Morris, Evan and Pai Asnodkar, Anusha and Pezzato, Jacklyn and Ragland, Sam and Roy, Arpita and Ruane, Garreth and Sappey, Ben and Schofield, Tobias and Skemer, Andrew and Venenciano, Taylor and Wallace, J. Kent and Wallack, Nicole L. and Wizinowich, Peter and Xuan, Jerry W. (2022) Retrieving the C and O Abundances of HR 7672 AB: A Solar-type Primary Star with a Benchmark Brown Dwarf. Astronomical Journal, 163 (4). Art. No. 189. ISSN 1538-3881. doi:10.3847/1538-3881/ac56e2.

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A benchmark brown dwarf (BD) is a BD whose properties (e.g., mass and chemical composition) are precisely and independently measured. Benchmark BDs are valuable in testing theoretical evolutionary tracks, spectral synthesis, and atmospheric retrievals for substellar objects. Here, we report results of atmospheric retrieval on a synthetic spectrum and a benchmark BD, HR 7672 B, with petitRADTRANS. First, we test the retrieval framework on a synthetic PHOENIX BT-Settl spectrum with a solar composition. We show that the retrieved C and O abundances are consistent with solar values, but the retrieved C/O is overestimated by 0.13–0.18, which is about four times higher than the formal error bar. Second, we perform retrieval on HR 7672 B using high spectral-resolution data (R = 35,000) from the Keck Planet Imager and Characterizer and near-infrared photometry. We retrieve [C/H], [O/H], and C/O to be −0.24 ± 0.05, −0.19 ± 0.04, and 0.52 ± 0.02. These values are consistent with those of HR 7672 A within 1.5σ. As such, HR 7672 B is among only a few benchmark BDs (along with Gl 570 D and HD 3651 B) that have been demonstrated to have consistent elemental abundances with their primary stars. Our work provides a practical procedure of testing and performing atmospheric retrieval, and sheds light on potential systematics of future retrievals using high- and low-resolution data.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Wang, Ji0000-0002-4361-8885
Kolecki, Jared R.0000-0002-6267-0849
Ruffio, Jean-Baptiste0000-0003-2233-4821
Wang, Jason J.0000-0003-0774-6502
Mawet, Dimitri0000-0002-8895-4735
Baker, Ashley0000-0002-6525-7013
Blake, Geoffrey A.0000-0003-0787-1610
Calvin, Benjamin0000-0003-4737-5486
Delorme, Jacques-Robert0000-0001-8953-1008
Echeverri, Daniel0000-0002-1583-2040
Finnerty, Luke0000-0002-1392-0768
Fitzgerald, Michael P.0000-0002-0176-8973
Jovanovic, Nemanja0000-0001-5213-6207
Liu, Michael C.0000-0003-2232-7664
Pai Asnodkar, Anusha0000-0002-8823-8237
Ragland, Sam0000-0002-0696-1780
Roy, Arpita0000-0001-8127-5775
Ruane, Garreth0000-0003-4769-1665
Skemer, Andrew0000-0001-6098-3924
Wallace, J. Kent0000-0001-5299-6899
Wallack, Nicole L.0000-0003-0354-0187
Wizinowich, Peter0000-0002-1646-442X
Xuan, Jerry W.0000-0002-6618-1137
Additional Information:© 2022 The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 December 30; revised 2022 February 17; accepted 2022 February 18; published 2022 March 25. We thank the anonymous referee whose comments and suggestions significantly improve the paper. We would like to thank Paul Molliere for the help in setting up and running petitRADTRANS. We thank Anjali Piette for helpful discussion on the P–T profile. We thank the Heising-Simons Foundation for supporting the workshop on combining high-resolution spectroscopy and high-contrast imaging for exoplanet characterization, where the idea originated of combining photometric data and spectral data of different resolutions. KPIC has been supported by the Heising-Simons Foundation through grants #2015-129, #2017-318, and #2019-1312. This work was also partially supported by the Simons Foundation. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors 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.
Group:Astronomy Department
Funding AgencyGrant Number
Heising-Simons Foundation2015-129
Heising-Simons Foundation2017-318
Heising-Simons Foundation2019-1312
Simons FoundationUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:Exoplanet atmospheric composition; Brown dwarfs; Chemical abundances
Issue or Number:4
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanet atmospheric composition (2021); Brown dwarfs (185); Chemical abundances (224)
Record Number:CaltechAUTHORS:20220224-200938684
Persistent URL:
Official Citation:Ji Wang et al 2022 AJ 163 189
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:113605
Deposited By: George Porter
Deposited On:01 Mar 2022 19:26
Last Modified:05 Apr 2022 20:15

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