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Age Determination in Upper Scorpius with Eclipsing Binaries

David, Trevor J. and Hillenbrand, Lynne A. and Gillen, Edward and Cody, Ann Marie and Howell, Steve B. and Isaacson, Howard T. and Livingston, John (2019) Age Determination in Upper Scorpius with Eclipsing Binaries. Astrophysical Journal, 872 (2). Art. No. 161. ISSN 1538-4357. doi:10.3847/1538-4357/aafe09.

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The Upper Scorpius OB association is the nearest region of recent massive star formation and thus an important benchmark for investigations concerning stellar evolution and planet formation timescales. We present nine eclipsing binaries (EBs) in Upper Scorpius, three of which are newly reported here and all of which were discovered from K2 photometry. Joint fitting of the eclipse photometry and radial velocities from newly acquired Keck I/HIRES spectra yields precise masses and radii for those systems that are spectroscopically double-lined. The binary orbital periods in our sample range from 0.6 to 100 days, with total masses ranging from 0.2 to 8 M⊙. At least 33% of the EBs reside in hierarchical multiples, including two triples and one quadruple. We use these EBs to develop an empirical mass–radius relation for pre-main-sequence stars and evaluate the predictions of widely used stellar evolutionary models. We report evidence for an age of 5–7 Myr, which is self-consistent in the mass range of 0.3–5 M⊙ and based on the fundamentally determined masses and radii of EBs. Evolutionary models including the effects of magnetic fields imply an age of 9–10 Myr. Our results are consistent with previous studies that indicate that many models systematically underestimate the masses of low-mass stars by 20%–60% based on Hertzsprung–Russell diagram analyses. We also consider the dynamical states of several binaries and compare with expectations from tidal dissipation theories. Finally, we identify RIK 72 b as a long-period transiting brown dwarf (M = 59.2 ± 6.8 M_(Jup), R = 3.10 ± 0.31 R_(Jup), P ≈ 97.8 days) and an ideal benchmark for brown dwarf cooling models at 5–10 Myr.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
David, Trevor J.0000-0001-6534-6246
Gillen, Edward0000-0003-2851-3070
Cody, Ann Marie0000-0002-3656-6706
Howell, Steve B.0000-0002-2532-2853
Isaacson, Howard T.0000-0002-0531-1073
Livingston, John0000-0002-4881-3620
Additional Information:© 2019 The American Astronomical Society. Received 2018 November 19; revised 2019 January 11; accepted 2019 January 11; published 2019 February 20. We are grateful to the anonymous referee for a thorough and thoughtful report. The authors wish to thank Mark Everett for reducing and analyzing the speckle-imaging data, Andrew Howard and the California Planet Search observers for monitoring of RIK 72, and Ji Wang for collaborating on EPIC 203868608. We also thank Eric Mamajek and John Stauffer for helpful comments on an early version of this manuscript. We thank Greg Feiden, Jim Fuller, B. J. Fulton, Adam Kraus, Luisa Rebull, Garrett Somers, Erik Petigura, Marc Pinsonneault, and Josh Winn for helpful discussions. T.J.D. gratefully acknowledges support from the Jet Propulsion Laboratory Exoplanetary Science Initiative. E.G. gratefully acknowledges support from Winton Philanthropies in the form of a Winton Exoplanet Fellowship. Some of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. This paper includes data collected by the K2 mission. Funding for the K2 mission is provided by the NASA Science Mission directorate. 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. Facilities: Keck:I (HIRES) - KECK I Telescope, Keck:II (NIRC2) - , Kepler - The Kepler Mission, Gemini:South (DSSI - , NESSI). - Software: emcee (Foreman-Mackey et al. 2013), gp-ebop (Gillen et al. 2017b), jktebop (Southworth 2013), scipy (Jones et al. 2001).
Group:Astronomy Department
Funding AgencyGrant Number
Winton PhilanthropiesUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:binaries: eclipsing – binaries: spectroscopic – Hertzsprung–Russell and C–M diagrams – open clusters and associations: individual (Upper Scorpius) – stars: evolution – stars: pre-main sequence
Issue or Number:2
Record Number:CaltechAUTHORS:20190220-084254439
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Official Citation:Trevor J. David et al 2019 ApJ 872 161
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92995
Deposited By: Tony Diaz
Deposited On:20 Feb 2019 18:34
Last Modified:16 Nov 2021 16:55

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