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Published November 1, 2017 | Submitted + Published
Journal Article Open

New Low-mass Eclipsing Binary Systems in Praesepe Discovered by K2


We present the discovery and characterization of four low-mass (M < 0.6 M⊙) eclipsing binary (EB) systems in the sub-Gyr old Praesepe open cluster using Kepler/K2 time series photometry and Keck/HIRES spectroscopy. We present a new Gaussian process EB model, GP–EBOP, as well as a method of simultaneously determining effective temperatures and distances for EBs. Three of the reported systems (AD 3814, AD 2615 and AD 1508) are detached and double-lined, and precise solutions are presented for the first two. We determine masses and radii to 1%–3% precision for AD 3814 and to 5%–6% for AD 2615. Together with effective temperatures determined to ~50 K precision, we test the PARSEC v1.2 and BHAC15 stellar evolution models. Our EB parameters are more consistent with the PARSEC models, primarily because the BHAC15 temperature scale is hotter than our data over the mid-M-dwarf mass range probed. Both ADs 3814 and 2615, which have orbital periods of 6.0 and 11.6 days, are circularized but not synchronized. This suggests that either synchronization proceeds more slowly in fully convective stars than the theory of equilibrium tides predicts, or magnetic braking is currently playing a more important role than tidal forces in the spin evolution of these binaries. The fourth system (AD 3116) comprises a brown dwarf transiting a mid-M-dwarf, which is the first such system discovered in a sub-Gyr open cluster. Finally, these new discoveries increase the number of characterized EBs in sub-Gyr open clusters by 20% (40%) below M < 1.5 M⊙ (M < 0.6 M⊙).

Additional Information

© 2017 The American Astronomical Society. Received 2017 April 4; revised 2017 June 7; accepted 2017 June 8; published 2017 October 24. We thank Pierre Maxted for interesting discussions and John Southworth for help compiling Table 6. This paper includes data collected by the Kepler/K2 mission. Funding for the K2 mission of Kepler is provided by the NASA Science Mission directorate. Some of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST) under support by the NASA Office of Space Science via grant NNX09AF08G and by other grants and contracts. Some of 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. Finally, we would like to thank the anonymous referee for their careful reading of the manuscript and helpful suggestions for improvement. Facilities: Kepler (K2 - ), Keck:I, - Sloan - , CTIO:2MASS, FLWO:2MASS - , WISE. - Software: astropy (Astropy Collaboration et al. 2013), emcee (Foreman-Mackey et al. 2013), george (Ambikasaran et al. 2014).

Attached Files

Published - Gillen_2017_ApJ_849_11.pdf

Submitted - 1706.03084.pdf


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August 19, 2023
October 17, 2023