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Unresolved Binary Exoplanet Host Stars Fit as Single Stars: Effects on the Stellar Parameters

Furlan, E. and Howell, S. B. (2020) Unresolved Binary Exoplanet Host Stars Fit as Single Stars: Effects on the Stellar Parameters. Astrophysical Journal, 898 (1). Art. No. 47. ISSN 1538-4357. https://resolver.caltech.edu/CaltechAUTHORS:20200722-104705900

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Abstract

In this work, we quantify the effect of an unresolved companion star on the derived stellar parameters of the primary star if a blended spectrum is fit assuming the star is single. Fitting tools that determine stellar parameters from spectra typically fit for a single star, but we know that up to half of all exoplanet host stars may have one or more companion stars. We use high-resolution spectra of planet host stars in the Kepler field from the California-Kepler Survey to create simulated binaries; we select eight stellar pairs and vary the contribution of the secondary star, then determine stellar parameters with SpecMatch-Emp and compare them to the parameters derived for the primary star alone. We find that, in most cases, the effective temperature, surface gravity, metallicity, and stellar radius derived from the composite spectrum are within 2–3σ of the values determined from the unblended spectrum, but the deviations depend on the properties of the two stars. Relatively bright companion stars that are similar to the primary star have the largest effect on the derived parameters; in these cases, the stellar radii can be overestimated by up to 60%. We find that metallicities are generally underestimated, with values up to eight times smaller than the typical uncertainty in [Fe/H]. Our study shows that follow-up observations are necessary to detect or set limits on stellar companions of planetary host stars so that stellar (and planet) parameters are as accurate as possible.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3847/1538-4357/ab9c9cDOIArticle
https://arxiv.org/abs/2006.06528arXivDiscussion Paper
ORCID:
AuthorORCID
Furlan, E.0000-0001-9800-6248
Howell, S. B.0000-0002-2532-2853
Additional Information:© 2020 The American Astronomical Society. Received 2020 March 10; revised 2020 June 1; accepted 2020 June 10; published 2020 July 22. We thank Johanna Teske and David Ciardi for constructive feedback that improved the paper. We also thank the referee, whose comments made the discussion presented in this paper clearer and more thorough. Support for this work was provided by NASA through the NASA Exoplanet Exploration Program Office. This research has made use of NASA's Astrophysics Data System Bibliographic Services. It has also made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with NASA under the Exoplanet Exploration Program.
Group:Infrared Processing and Analysis Center (IPAC)
Funders:
Funding AgencyGrant Number
NASAUNSPECIFIED
Subject Keywords:Stellar spectral lines ; Stellar properties ; Fundamental parameters of stars ; High resolution spectroscopy ; Binary stars ; Planet hosting stars
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Stellar spectral lines (1630); Stellar properties (1624); Fundamental parameters of stars (555); High resolution spectroscopy (2096); Binary stars (154); Planet hosting stars (1242)
Record Number:CaltechAUTHORS:20200722-104705900
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200722-104705900
Official Citation:E. Furlan and S. B. Howell 2020 ApJ 898 47
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104507
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:22 Jul 2020 18:41
Last Modified:22 Jul 2020 18:41

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