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Tidal Interactions between Binary Stars Can Drive Lithium Production in Low-mass Red Giants

Casey, Andrew R. and Ho, Anna Y. Q. and Ness, Melissa and Hogg, David W. and Rix, Hans-Walter and Angelou, George C. and Hekker, Saskia and Tout, Christopher A. and Lattanzio, John C. and Karakas, Amanda I. and Woods, Tyrone E. and Price-Whelan, Adrian M. and Schlaufman, Kevin C. (2019) Tidal Interactions between Binary Stars Can Drive Lithium Production in Low-mass Red Giants. Astrophysical Journal, 880 (2). Art. No. 125. ISSN 1538-4357.

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Theoretical models of stellar evolution predict that most of the lithium inside a star is destroyed as the star becomes a red giant. However, observations reveal that about 1% of red giants are peculiarly rich in lithium, often exceeding the amount in the interstellar medium or predicted from the big bang. With only about 150 lithium-rich giants discovered in the past four decades, and no distinguishing properties other than lithium enhancement, the origin of lithium-rich giant stars is one of the oldest problems in stellar astrophysics. Here we report the discovery of 2330 low-mass (1–3 M ⊙) lithium-rich giant stars, which we argue are consistent with internal lithium production that is driven by tidal spin-up by a binary companion. Our sample reveals that most lithium-rich giants have helium-burning cores (80^(+7)_(−6)%), and that the frequency of lithium-rich giants rises with increasing stellar metallicity. We find that while planet accretion may explain some lithium-rich giants, it cannot account for the majority that have helium-burning cores. We rule out most other proposed explanations for the origin of lithium-rich giants. Our analysis shows that giants remain lithium-rich for only about two million years. A prediction from this lithium depletion timescale is that most lithium-rich giants with a helium-burning core have a binary companion.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Casey, Andrew R.0000-0003-0174-0564
Ho, Anna Y. Q.0000-0002-9017-3567
Ness, Melissa0000-0001-5082-6693
Hogg, David W.0000-0003-2866-9403
Rix, Hans-Walter0000-0003-4996-9069
Angelou, George C.0000-0003-4463-1907
Hekker, Saskia0000-0002-1463-726X
Tout, Christopher A.0000-0002-1556-9449
Lattanzio, John C.0000-0003-2952-859X
Karakas, Amanda I.0000-0002-3625-6951
Woods, Tyrone E.0000-0003-1428-5775
Price-Whelan, Adrian M.0000-0003-0872-7098
Schlaufman, Kevin C.0000-0001-5761-6779
Additional Information:© 2019 The American Astronomical Society. Received 2019 February 11; revised 2019 May 23; accepted 2019 June 5; published 2019 August 1. A. R. C. is supported through an Australian Research Council Discovery Project under grant DP160100637. A. Y. Q. H. is grateful to the community at the MPIA for their support and hospitality during the period in which much of this work was performed. A. Y. Q. H. was supported by a Fulbright grant through the German-American Fulbright Commission and a National Science Foundation Graduate Research Fellowship under grant No. DGE-1144469. M. K. N. and H.-W. R. have received funding for this research from the European Research Council under the European Union's Seventh Framework Programme (FP 7) ERC grant Agreement No. [321035]. C. A. T. thanks Churchill College for his fellowship and Monash University for hosting him as a Kevin Westfold distinguished visitor. This work was supported by the GROWTH project funded by the National Science Foundation under PIRE grant No. 1545949. The research leading to the presented results has received funding from the European Research Council under the European Community's Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement (No. 338251, StellarAges). This research has made use of NASA's Astrophysics Data System. 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. Guoshoujing Telescope (the Large Sky Area Multi-Object Fiber Spectroscopic Telescope LAMOST) is a National Major Scientific Project built by the Chinese Academy of Sciences. Funding for the project has been provided by the National Development and Reform Commission. LAMOST is operated and managed by the National Astronomical Observatories, Chinese Academy of Sciences. This paper includes data collected by the Kepler mission. Funding for the Kepler mission is provided by the NASA Science Mission directorate. This paper includes data collected by the K2 mission. Funding for the K2 mission is provided by the NASA Science Mission directorate. Facilities: LAMOST - , Kepler - , Gaia. - Software: AstroPy (Astropy Collaboration et al. 2013, 2018), numpy (Van Der Walt et al. 2011), scipy (Jones et al. 2001), matplotlib (Hunter et al. 2007), The Cannon (Ness et al. 2015; Casey et al. 2016; Ho et al. 2017a, 2017b).
Funding AgencyGrant Number
Australian Research CouncilDP160100637
Fulbright CommissionUNSPECIFIED
NSF Graduate Research FellowshipDGE-1144469
European Research Council (ERC)321035
Churchill CollegeUNSPECIFIED
European Research Council (ERC)338251
Gaia Multilateral AgreementUNSPECIFIED
National Development and Reform CommissionUNSPECIFIED
Subject Keywords:binaries: general – stars: abundances – stars: low-mass
Issue or Number:2
Record Number:CaltechAUTHORS:20190801-145038616
Persistent URL:
Official Citation:Andrew R. Casey et al 2019 ApJ 880 125
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:97608
Deposited By: Tony Diaz
Deposited On:01 Aug 2019 22:06
Last Modified:09 Mar 2020 13:19

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