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An extreme-mass ratio, short-period eclipsing binary consisting of a B dwarf primary and a pre-main-sequence M star companion discovered by KELT

Stevens, Daniel J. and Zhou, George and Johnson, Marshall C. and Rizzuto, Aaron C. and Rodriguez, Joseph E. and Bieryla, Allyson and Collins, Karen A. and Villanueva, Steven, Jr. and Wright, Jason T. and Gaudi, B. Scott and Latham, David W. and Beatty, Thomas G. and Lund, Michael B. and Siverd, Robert J. and Kraus, Adam L. and Wachiraphan, Patcharapol and Berlind, Perry and Calkins, Michael L. and Esquerdo, Gilbert A. and Kielkopf, John F. and Kuhn, Rudolf B. and Manner, Mark and Pepper, Joshua and Stassun, Keivan G. (2020) An extreme-mass ratio, short-period eclipsing binary consisting of a B dwarf primary and a pre-main-sequence M star companion discovered by KELT. Monthly Notices of the Royal Astronomical Society, 499 (3). pp. 3775-3791. ISSN 0035-8711. doi:10.1093/mnras/staa3142.

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We present the discovery of KELT J072709 + 072007 (HD 58730), a very low mass ratio (q ≡ M₂/M₁ ≈ 0.07) eclipsing binary (EB) identified by the Kilodegree Extremely Little Telescope (KELT) survey. We present the discovery light curve and perform a global analysis of four high-precision ground-based light curves, the Transiting Exoplanets Survey Satellite (TESS) light curve, radial velocity (RV) measurements, Doppler Tomography (DT) measurements, and the broad-band spectral energy distribution. Results from the global analysis are consistent with a fully convective (⁠M₂ = 0.22±0.02 M_⊙) M star transiting a late-B primary (⁠M₁ = 3.34^(+0.07)_(−0.09) M_⊙ and T_(eff,₁) = 11960^(+430)_(−520) K⁠). We infer that the primary star is 183^(+33)_(−30) Myr old and that the companion star’s radius is inflated by 26±8 per cent relative to the predicted value from a low-mass isochrone of similar age. We separately and analytically fit for the variability in the out-of-eclipse TESS phase curve, finding good agreement between the resulting stellar parameters and those from the global fit. Such systems are valuable for testing theories of binary star formation and understanding how the environment of a star in a close-but-detached binary affects its physical properties. In particular, we examine how a star’s properties in such a binary might differ from the properties it would have in isolation.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Stevens, Daniel J.0000-0002-5951-8328
Zhou, George0000-0002-4891-3517
Johnson, Marshall C.0000-0002-5099-8185
Rizzuto, Aaron C.0000-0001-9982-1332
Rodriguez, Joseph E.0000-0001-8812-0565
Bieryla, Allyson0000-0001-6637-5401
Collins, Karen A.0000-0001-6588-9574
Villanueva, Steven, Jr.0000-0001-6213-8804
Wright, Jason T.0000-0001-6160-5888
Gaudi, B. Scott0000-0003-0395-9869
Latham, David W.0000-0001-9911-7388
Beatty, Thomas G.0000-0002-9539-4203
Lund, Michael B.0000-0003-2527-1598
Siverd, Robert J.0000-0001-5016-3359
Kraus, Adam L.0000-0001-9811-568X
Wachiraphan, Patcharapol0000-0001-6484-7559
Calkins, Michael L.0000-0002-2830-5661
Esquerdo, Gilbert A.0000-0002-9789-5474
Kielkopf, John F.0000-0003-0497-2651
Kuhn, Rudolf B.0000-0002-4236-9020
Manner, Mark0000-0002-9411-7271
Pepper, Joshua0000-0002-3827-8417
Stassun, Keivan G.0000-0002-3481-9052
Additional Information:© 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2020 October 1. Received 2020 September 28; in original form 2019 October 18. Published: 12 October 2020. The authors thank Avi Shporer and Chelsea Huang for their expertise on analysing and processing TESS photometry, respectively. The authors also thank the anonymous reviewer for the helpful comments and suggestions. DJS is supported as an Eberly Research Fellow by the Eberly College of Science at the Pennsylvania State University. The Center for Exoplanets and Habitable Worlds is supported by the Pennsylvania State University, the Eberly College of Science, and the Pennsylvania Space Grant Consortium. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Data Availability: This project makes use of data from the KELT survey, including support from The Ohio State University, Vanderbilt University, and Lehigh University, along with the KELT follow-up collaboration. This paper includes data taken at The McDonald Observatory of The University of Texas at Austin. This paper also includes data gathered with the 6.5-m Magellan Telescopes located at Las Campanas Observatory, Chile. 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. These data are available through the Keck Observatory Archive ( The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. This publication makes use of data products from the 2MASS, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. 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. This research has made use of NASA’s Astrophysics Data System; ASTROPY,2 a community-developed core PYTHON package for Astronomy (Astropy Collaboration et al. 2013; Price-Whelan et al. 2018); and the SIMBAD data base, operated at CDS, Strasbourg, France (Wenger et al. 2000).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Eberly College of ScienceUNSPECIFIED
Pennsylvania State UniversityUNSPECIFIED
Pennsylvania Space Grant ConsortiumUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Gaia Multilateral AgreementUNSPECIFIED
Subject Keywords:eclipses, binaries: eclipsing, stars: early-type, stars: low-mass, stars: pre-main-sequence
Issue or Number:3
Record Number:CaltechAUTHORS:20210113-101526102
Persistent URL:
Official Citation:Daniel J Stevens, George Zhou, Marshall C Johnson, Aaron C Rizzuto, Joseph E Rodriguez, Allyson Bieryla, Karen A Collins, Steven Villanueva, Jr, Jason T Wright, B Scott Gaudi, David W Latham, Thomas G Beatty, Michael B Lund, Robert J Siverd, Adam L Kraus, Patcharapol Wachiraphan, Perry Berlind, Michael L Calkins, Gilbert A Esquerdo, John F Kielkopf, Rudolf B Kuhn, Mark Manner, Joshua Pepper, Keivan G Stassun, An extreme-mass ratio, short-period eclipsing binary consisting of a B dwarf primary and a pre-main-sequence M star companion discovered by KELT, Monthly Notices of the Royal Astronomical Society, Volume 499, Issue 3, December 2020, Pages 3775–3791,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107451
Deposited By: Tony Diaz
Deposited On:13 Jan 2021 19:50
Last Modified:16 Nov 2021 19:03

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