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Published March 2018 | Published + Accepted Version
Journal Article Open

HAT-TR-318-007: A Double-lined M Dwarf Binary with Total Secondary Eclipses Discovered by HATNet and Observed by K2


We report the discovery by the HATNet survey of HAT-TR-318-007, a P = 3.34395390 ± 0.00000020 day period detached double-lined M dwarf binary with total secondary eclipses. We combine radial velocity (RV) measurements from TRES/FLWO 1.5 m and time-series photometry from HATNet, FLWO 1.2 m, BOS 0.8 m, and NASA K2 Campaign 5, to determine the masses and radii of the component stars: M_A = 0.448 ± 0.011 M^N⊙, M_B = 0.2721^(+0.0041)_(-0.0042) M^N⊙, R_A = 0.4548^(+0.0035)_(-0.0036) R^N⊙, and R_B = 0.2913^(+0.0023)_(-0.0024) R^N⊙. We obtained a FIRE/Magellan near-infrared spectrum of the primary star during a total secondary eclipse, and we use this to obtain disentangled spectra of both components. We determine spectral types of ST_A = M3.71 ± 0.69 and ST_B = M5.01 ± 0.73 and effective temperatures of T_(eff,A) = 3190 ± 110 K and T(_eff,B) = 3100 ± 110 K for the primary and secondary star, respectively. We also measure a metallicity of [Fe/H] = +0.298 ± 0.080 for the system. We find that the system has a small, but significant, nonzero eccentricity of 0.0136 ± 0.0026. The K2 light curve shows a coherent variation at a period of 3.41315^(+0.00030)_(-0.00032) days, which is slightly longer than the orbital period, and which we demonstrate comes from the primary star. We interpret this as the rotation period of the primary. We perform a quantitative comparison between the Dartmouth stellar evolution models and the seven systems, including HAT-TR-318-007, that contain M dwarfs with 0.0 M^N⊙ < M < 0.5 M^N⊙, have metallicity measurements, and have masses and radii determined to better than 5% precision. Discrepancies between the predicted and observed masses and radii are found for three of the systems.

Additional Information

© 2018 The American Astronomical Society. Received 2017 November 17; revised 2018 January 9; accepted 2018 January 10; published 2018 February 14. Based in part on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. Partial support for the work reported here was provided by NASA grants NNX09AB29G, NNX13AJ15G, NNX14AE87G, and NNX17AB61G and NSF grant AST-1108686. G.T. acknowledges partial support for this work from NSF grant AST-1509375. Some of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX09AF08G and by other grants and contracts. This paper includes data collected by the Kepler mission. Funding for the Kepler mission is provided by the NASA Science Mission directorate.

Attached Files

Published - Hartman_2018_AJ_155_114.pdf

Accepted Version - 1801.03570.pdf


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August 19, 2023
October 18, 2023