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Characterization of Low-mass K2 Planet Hosts Using Near-infrared Spectroscopy

Rodríguez Martínez, Romy and Ballard, Sarah and Mayo, Andrew and Vanderburg, Andrew and Montet, Benjamin T. and Christiansen, Jessie L. (2019) Characterization of Low-mass K2 Planet Hosts Using Near-infrared Spectroscopy. Astronomical Journal, 158 (4). Art. No. 135. ISSN 1538-3881. doi:10.3847/1538-3881/ab3347.

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We present moderate resolution near-infrared spectra in the H, J, and K band of M-dwarf hosts to candidate transiting exoplanets discovered by NASA's K2 mission. We employ known empirical relationships between spectral features and physical stellar properties to measure the effective temperature, radius, metallicity, and luminosity of our sample. Out of an initial sample of 56 late-type stars in K2, we identify 35 objects as M dwarfs. For that subsample, we derive temperatures ranging from 2870 to 4187 K, radii of 0.09–0.83 R_⊙, luminosities of -2.67 < log L/L_⊙ < -0.67, and [Fe/H] metallicities between −0.49 and 0.51 dex. We then employ the stellar properties derived from spectra, in tandem with the K2 light curves, to characterize their planets. We report 33 exoplanet candidates with orbital periods ranging from 0.19 to 21.16 days, and median radii and equilibrium temperatures of 2.3 R_⊕ and 986 K, respectively. Using planet mass–radius relationships from the literature, we identify seven exoplanets as potentially rocky, although we conclude that probably none reside in the habitable zone of their parent stars.

Item Type:Article
Related URLs:
URLURL TypeDescription
Ballard, Sarah0000-0002-3247-5081
Mayo, Andrew0000-0002-7216-2135
Vanderburg, Andrew0000-0001-7246-5438
Montet, Benjamin T.0000-0001-7516-8308
Christiansen, Jessie L.0000-0002-8035-4778
Additional Information:© 2019 The American Astronomical Society. Received 2018 August 8; revised 2019 July 15; accepted 2019 July 16; published 2019 September 6. The authors thank the referee for the helpful comments that significantly improved the quality of this paper. The authors thank Juliette Becker for her assistance with the data reduction using Spextool. We also thank Nick Edwards, Yousef Lawrence, and Jonathan Swift (The Thacher School) for assisting with the data collection at Palomar Observatory. A.V.'s contribution to this study was performed in part under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. Work by B.T.M. was performed in part under contract with the Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. This work has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC; Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NASA Sagan Fellowship ProgramUNSPECIFIED
Gaia Multilateral AgreementUNSPECIFIED
NSF Graduate Research FellowshipUNSPECIFIED
Fulbright CommissionUNSPECIFIED
Subject Keywords:planetary systems – planets and satellites: fundamental parameters – stars: fundamental parameters – stars: late-type – stars: low-mass – techniques: spectroscopic
Issue or Number:4
Record Number:CaltechAUTHORS:20190926-155749759
Persistent URL:
Official Citation:Romy Rodríguez Martínez et al 2019 AJ 158 135
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98888
Deposited By: Tony Diaz
Deposited On:26 Sep 2019 23:20
Last Modified:16 Nov 2021 17:42

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