Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Most lithium-rich low-mass evolved stars revealed as red clump stars by asteroseismology and spectroscopy


Lithium has confused scientists for decades at almost every scale of the universe. Lithium-rich giants are peculiar stars with lithium abundances greater than model prediction. A large fraction of lithium-rich low-mass evolved stars are traditionally supposed to be red giant branch (RGB) stars. Recent studies, however, report that red clump (RC) stars are more frequent than RGB stars. Here, we present a uniquely large systematic study that combines direct asteroseismic analysis and spectroscopy of the lithium-rich stars. The majority of lithium-rich stars are confirmed to be RCs, whereas RGBs are a minority. We reveal that the distribution of lithium-rich RGBs declines steeply with increasing lithium abundance, with an upper limit of around 2.6 dex, whereas the lithium abundances of RCs extend to much higher values. We also find that the distributions of mass and nitrogen abundance are notably different between RC and RGB stars. These findings indicate that there is still an unknown process that significantly affects surface chemical composition in low-mass stellar evolution.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: The distribution of Li abundance in the entire sample.
Fig. 2: The Li abundance and classification of the high-resolution sample.
Fig. 3: The distribution of mass and [N/Fe] in the sample.
Fig. 4: Comparison of the Li abundances between the HeWD–RGB merger model prediction and the stars in our sample.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request. Souce data are provided with this paper for Figs. 13. The LAMOST DR7 data are available for registered users at The stellar evolution tracks and isochrones data of PARSEC are available at

Code availability

The codes that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request. The stellar evolution code MESA used to compute the HeWD–RGB merger is available at The code SPECTRUM used to compute the stellar templates for deriving the Li abundance for the low-resolution sample is available at The codes used to calculate the luminosity and surface gravity from the Gaia parallax are available at The codes involved in the plots are based on AstroLib, Coyote Library, Matplotlib, Pandas, NumPy and Astropy.


  1. 1.

    Freeman, K. & Bland-Hawthorn, J. The new Galaxy: signatures of its formation. Annu. Rev. Astron. Astrophys. 40, 487–537 (2002).

    ADS  Article  Google Scholar 

  2. 2.

    Spite, M. & Spite, F. Lithium abundance at the formation of the Galaxy. Nature 297, 483–485 (1982).

    ADS  Article  Google Scholar 

  3. 3.

    Iben, I. Jr. Stellar evolution. VI. Evolution from the main sequence to the red-giant branch for stars of mass 1 M, 1.25 M, and 1.5 M. Astrophys. J. 147, 624–649 (1967).

    ADS  Article  Google Scholar 

  4. 4.

    Brown, J. A., Sneden, C., Lambert, D. L. & Dutchover, E. Jr. A search for lithium-rich giant stars. Astrophys. J., Suppl. Ser. 71, 293–322 (1989).

    ADS  Article  Google Scholar 

  5. 5.

    Lind, K., Primas, F., Charbonnel, C., Grundahl, F. & Asplund, M. Signatures of intrinsic Li depletion and Li-Na anti-correlation in the metal-poor globular cluster NGC 6397. Astron. Astrophys. 503, 545–557 (2009).

    ADS  Article  Google Scholar 

  6. 6.

    Wallerstein, G. & Sneden, C. A K giant with an unusually high abundance of lithium: HD 112127. Astrophys. J. 255, 577–584 (1982).

    ADS  Article  Google Scholar 

  7. 7.

    Kumar, Y. B., Reddy, B. E. & Lambert, D. L. Origin of lithium enrichment in K giants. Astrophys. J. Lett. 730, L12 (2011).

    ADS  Article  Google Scholar 

  8. 8.

    Martell, S. L. & Shetrone, M. D. Lithium-rich field giants in the Sloan Digital Sky Survey. Mon. Not. R. Astron. Soc. 430, 611–620 (2013).

    ADS  Article  Google Scholar 

  9. 9.

    Smiljanic, R. et al. The Gaia-ESO Survey: properties of newly discovered Li-rich giants. Astron. Astrophys. 617, A4 (2018).

    Article  Google Scholar 

  10. 10.

    Deepak & Reddy, B. E. Study of lithium-rich giants with the GALAH spectroscopic survey. Mon. Not. R. Astron. Soc. 484, 2000–2008 (2019).

    ADS  Google Scholar 

  11. 11.

    Casey, A. R. et al. Tidal interactions between binary stars can drive lithium production in low-mass red giants. Astrophys. J. 880, 125 (2019).

    ADS  Article  Google Scholar 

  12. 12.

    Gao, Q. et al. Lithium-rich giants in LAMOST survey. I. The catalog. Astrophys. J., Suppl. Ser. 245, 33 (2019).

    ADS  Article  Google Scholar 

  13. 13.

    Yan, H.-L. et al. The nature of the lithium enrichment in the most Li-rich giant star. Nat. Astron. 2, 790–795 (2018).

    ADS  Article  Google Scholar 

  14. 14.

    Charbonnel, C. & Balachandran, S. C. The nature of the lithium rich giants. Mixing episodes on the RGB and early-AGB. Astron. Astrophys. 359, 563–572 (2000).

    ADS  Google Scholar 

  15. 15.

    Sackmann, I.-J. & Boothroyd, A. I. Creation of 7Li and destruction of 3He, 9Be, 10B, and 11B in low-mass red giants, due to deep circulation. Astrophys. J. 510, 217–231 (1999).

    ADS  Article  Google Scholar 

  16. 16.

    Denissenkov, P. A. & Herwig, F. Enhanced extra mixing in low-mass red giants: lithium production and thermal stability. Astrophys. J. 612, 1081–1091 (2004).

    ADS  Article  Google Scholar 

  17. 17.

    Charbonnel, C. & Lagarde, N. Thermohaline instability and rotation-induced mixing. I. Low- and intermediate-mass solar metallicity stars up to the end of the AGB. Astron. Astrophys. 522, A10 (2010).

    ADS  Article  Google Scholar 

  18. 18.

    Silva Aguirre, V. et al. Old puzzle, new insights: a lithium-rich giant quietly burning helium in its core. Astrophys. J. 784, L16 (2014).

    ADS  Article  Google Scholar 

  19. 19.

    Carlberg, J. K. et al. The puzzling Li-rich red giant associated with NGC 6819. Astrophys. J. 802, 7 (2015).

    ADS  Article  Google Scholar 

  20. 20.

    Kumar, Y. B., Singh, R., Reddy, B. E. & Zhao, G. Two new super Li-rich core He-burning giants: a new twist to the long tale of Li enhancement in K giants. Astrophys. J. Lett. 858, L22 (2018).

    ADS  Article  Google Scholar 

  21. 21.

    Singh, R., Reddy, B. E., Kumar, Y. B. & Antia, H. M. Survey of Li-rich giants among Kepler and LAMOST fields: determination of Li-rich giants’ evolutionary phase. Astrophys. J. Lett. 878, L21 (2019).

    ADS  Article  Google Scholar 

  22. 22.

    Zhou, Y. et al. High-resolution spectroscopic analysis of a large sample of Li-rich giants found by LAMOST. Astrophys. J. 877, 104 (2019).

    ADS  Article  Google Scholar 

  23. 23.

    Martell, S., et al. The GALAH survey: lithium-rich giant stars require multiple formation channels. Preprint at (2020).

  24. 24.

    Kumar, Y. B., et al. Discovery of ubiquitous lithium production in low-mass stars. Nat. Astron., (2020).

  25. 25.

    Cui, X.-Q. et al. The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). Res. Astron. Astrophys. 12, 1197–1242 (2012).

    ADS  Article  Google Scholar 

  26. 26.

    Borucki, W. J. et al. Kepler planet-detection mission: introduction and first results. Science 327, 977–980 (2010).

    ADS  Article  Google Scholar 

  27. 27.

    Kirby, E. N. et al. Lithium-rich giants in globular clusters. Astrophys. J. 819, 135 (2016).

    ADS  Article  Google Scholar 

  28. 28.

    Hon, M., Stello, D. & Yu, J. Deep learning classification in asteroseismology. Mon. Not. R. Astron. Soc. 469, 4578–4583 (2017).

    ADS  Article  Google Scholar 

  29. 29.

    Bedding, T. R. et al. Gravity modes as a way to distinguish between hydrogen- and helium-burning red giant stars. Nature 471, 608–611 (2011).

    ADS  Article  Google Scholar 

  30. 30.

    Brown, T. M. et al. Detection of possible p-mode oscillations on Procyon. Astrophys. J. 368, 599–609 (1991).

    ADS  Article  Google Scholar 

  31. 31.

    Chaplin, W. J. et al. Evidence for the impact of stellar activity on the detectability of solar-like oscillations observed by Kepler. Astrophys. J. Lett. 732, L5 (2011).

    ADS  Article  Google Scholar 

  32. 32.

    Ricker, G. R. et al. Transiting Exoplanet Survey Satellite. J. Astron. Telesc. Instrum. Syst. 1, 014003 (2015).

    ADS  Article  Google Scholar 

  33. 33.

    García Pérez, A. E. et al. ASPCAP: the APOGEE Stellar Parameter and Chemical Abundances Pipeline. Astron. J. 151, 144 (2016).

    ADS  Article  Google Scholar 

  34. 34.

    Alexander, J. B. A possible source of lithium in the atmospheres of some red giants. Observatory 87, 238–240 (1967).

    ADS  Google Scholar 

  35. 35.

    Cameron, A. G. W. & Fowler, W. A. Lithium and the s-process in red-giant stars. Astrophys. J. 164, 111–114 (1971).

    ADS  Article  Google Scholar 

  36. 36.

    Lebzelter, T., Uttenthaler, S., Busso, M., Schultheis, M. & Aringer, B. Lithium abundances along the red giant branch: FLAMES-GIRAFFE spectra of a large sample of low-mass bulge stars. Astron. Astrophys. 538, A36 (2012).

    ADS  Article  Google Scholar 

  37. 37.

    Li, H. et al. Enormous Li enhancement preceding red giant phases in low-mass stars in the Milky Way halo. Astrophys. J. Lett. 852, L31 (2018).

    ADS  Article  Google Scholar 

  38. 38.

    Charbonnel, C. et al. Lithium in red giant stars: constraining non-standard mixing with large surveys in the Gaia era. Astron. Astrophys. 633, A34 (2020).

    Article  Google Scholar 

  39. 39.

    Aguilera-Gómez, C., Chanamé, J., Pinsonneault, M. H. & Carlberg, J. K. On lithium-rich red giants: engulfment on the giant branch of Trumpler 20. Astrophys. J. 833, L24 (2016).

    ADS  Article  Google Scholar 

  40. 40.

    Gratton, R. G., Sneden, C., Carretta, E. & Bragaglia, A. Mixing along the red giant branch in metal-poor field stars. Astron. Astrophys. 354, 169–187 (2000).

    ADS  Google Scholar 

  41. 41.

    Auvergne, M. et al. The CoRoT satellite in flight: description and performance. Astron. Astrophys. 506, 411–424 (2009).

    ADS  Article  Google Scholar 

  42. 42.

    Iwamoto, N. et al. Flash-driven convective mixing in low-mass, metal-deficient asymptotic giant branch stars: a new paradigm for lithium enrichment and a possible s-process. Astrophys. J. 602, 377–387 (2004).

    ADS  Article  Google Scholar 

  43. 43.

    Campbell, S. W., Lugaro, M. & Karakas, A. I. Evolution and nucleosynthesis of extremely metal-poor and metal-free low- and intermediate-mass stars. II. s-process nucleosynthesis during the core He flash. Astron. Astrophys. 522, L6 (2010).

    ADS  Article  Google Scholar 

  44. 44.

    Zhang, X. & Jeffery, C. S. White dwarf-red giant mergers, early-type R stars, J stars and lithium. Mon. Not. R. Astron. Soc. 430, 2113–2120 (2013).

    ADS  Article  Google Scholar 

  45. 45.

    Zhang, X., Jeffery, C. S., Li, Y. & Bi, S. Population synthesis of helium white dwarf–red giant star mergers and the formation of lithium-rich giants and carbon stars. Astron. J. 889, 33 (2020).

    ADS  Article  Google Scholar 

  46. 46.

    Martig, M. et al. Red giant masses and ages derived from carbon and nitrogen abundances. Mon. Not. R. Astron. Soc. 456, 3655–3670 (2016).

    ADS  Article  Google Scholar 

  47. 47.

    Lagarde, N. et al. Thermohaline instability and rotation-induced mixing. III. Grid of stellar models and asymptotic asteroseismic quantities from the pre-main sequence up to the AGB for low- and intermediate-mass stars of various metallicities. Astron. Astrophys. 543, A108 (2012).

    Article  Google Scholar 

  48. 48.

    Gonzalez, G. Parent stars of extrasolar planets — XIII. Additional evidence for Li abundance anomalies. Mon. Not. R. Astron. Soc. 441, 1201–1208 (2014).

    ADS  Article  Google Scholar 

  49. 49.

    Gao, S., Zhao, H., Yang, H. & Gao, R. The binarity of Galactic dwarf stars along with effective temperature and metallicity. Mon. Not. R. Astron. Soc. 469, L68–L72 (2017).

    ADS  Article  Google Scholar 

  50. 50.

    Grisoni, V., Matteucci, F., Romano, D. & Fu, X. Evolution of lithium in the Milky Way halo, discs, and bulge. Mon. Not. R. Astron. Soc. 489, 3539–3546 (2019).

    ADS  Article  Google Scholar 

  51. 51.

    De Cat, P. et al. LAMOST observations in the Kepler field. I. Database of low-resolution spectra. Astrophys. J., Suppl. Ser. 220, 19 (2015).

    ADS  Article  Google Scholar 

  52. 52.

    Zong, W. et al. LAMOST observations in the Kepler field. II. Database of the low-resolution spectra from the five-year regular survey. Astrophys. J., Suppl. Ser.238, 30 (2018).

    ADS  Article  Google Scholar 

  53. 53.

    Luo, A.-L. et al. The first data release (DR1) of the LAMOST regular survey. Res. Astron. Astrophys. 15, 1095 (2015).

    ADS  Article  Google Scholar 

  54. 54.

    Jenkins, J. M. et al. Overview of the Kepler science processing pipeline. Astrophys. J. Lett. 713, L87 (2010).

    ADS  Article  Google Scholar 

  55. 55.

    Takeda, Y., Sato, B., Kambe, E., Sadakane, K. & Ohkubo, M. Spectroscopic determination of stellar atmospheric parameters: application to mid-F through early-K dwarfs and subgiants. Publ. Astron. Soc. Jpn. 54, 1041–1056 (2002).

    ADS  Article  Google Scholar 

  56. 56.

    Mashonkina, L., Gehren, T., Shi, J.-R., Korn, A. J. & Grupp, F. A non-LTE study of neutral and singly-ionized iron line spectra in 1D models of the Sun and selected late-type stars. Astron. Astrophys. 528, A87 (2011).

    ADS  Article  Google Scholar 

  57. 57.

    Carlberg, J. K., Cunha, K., Smith, V. V. & Majewski, S. R. Observable signatures of planet accretion in red giant stars. I. Rapid rotation and light element replenishment. Astrophys. J. 757, 109 (2012).

    ADS  Article  Google Scholar 

  58. 58.

    Kurucz, R. L., Furenlid, I., Brault, J. & Testerman, L. Solar Flux Atlas from 296 to 1300 nm National Solar Observatory Atlas No. 1 (US National Solar Observatory, 1984).

  59. 59.

    Sitnova, T. et al. Systematic non-LTE study of the −2.6 < [Fe/H] < 0.2 F and G dwarfs in the solar neighborhood. I. Stellar atmosphere parameters. Astrophys. J. 808, 148 (2015).

  60. 60.

    Bailer-Jones, C. A. L., Rybizki, J., Fouesneau, M., Mantelet, G. & Andrae, R. Estimating distance from parallaxes. IV. Distances to 1.33 billion stars in Gaia Data Release 2. Astron. J. 156, 58 (2018).

    ADS  Article  Google Scholar 

  61. 61.

    Schlafly, E. F. & Finkbeiner, D. P. Measuring reddening with Sloan Digital Sky Survey stellar spectra and recalibrating SFD. Astrophys. J. 737, 103 (2011).

    ADS  Article  Google Scholar 

  62. 62.

    Alonso, A., Arribas, S. & Martínez-Roger, C. The effective temperature scale of giant stars (F0–K5). II. Empirical calibration of Teff versus colours and [Fe/H]. Astron. Astrophys. Suppl. Ser. 140, 261–277 (1999).

    ADS  Article  Google Scholar 

  63. 63.

    Gustafsson, B. et al. A grid of MARCS model atmospheres for late-type stars. I. Methods and general properties. Astron. Astrophys. 486, 951–970 (2008).

    ADS  Article  Google Scholar 

  64. 64.

    Shi, J. R., Gehren, T., Zhang, H. W., Zeng, J. L. & Zhao, G. Lithium abundances in metal-poor stars. Astron. Astrophys. 465, 587–591 (2007).

    ADS  Article  Google Scholar 

  65. 65.

    Castelli, F., and Kurucz, R. L. New grids of ATLAS9 model atmospheres. In Proc. 210th Symposium of the International Astronomical Union, Modelling of Stellar Atmospheres (Eds. Piskunov, N. et al.) Poster A20 (2003).

  66. 66.

    Grevesse, N. & Sauval, A. J. Standard solar composition. Space Sci. Rev. 85, 161–174 (1998).

    ADS  Article  Google Scholar 

  67. 67.

    Yu, J. et al. Asteroseismology of 16,000 Kepler red giants: global oscillation parameters, masses, and radii. Astrophys. J. Suppl. Ser. 236, 42 (2018).

    ADS  Article  Google Scholar 

  68. 68.

    Unno, W., Osaki, Y. et al. Nonradial Oscillations of Stars 2nd edn (Univ. of Tokyo Press, 1989).

  69. 69.

    Shibahashi, H. Modal analysis of stellar nonradial oscillations by an asymptotic method. Publ. Astron. Soc. Jpn. 31, 87–104 (1979).

    ADS  Google Scholar 

  70. 70.

    Mosser, B., Vrard, M., Belkacem, K., Deheuvels, S. & Goupil, M. J. Period spacings in red giants. I. Disentangling rotation and revealing core structure discontinuities. Astron. Astrophys. 584, A50 (2015).

    ADS  Article  Google Scholar 

  71. 71.

    Kjeldsen, H. & Bedding, T. R. Amplitudes of stellar oscillations: the implications for asteroseismology. Astron. Astrophys. 293, 87–106 (1995).

    ADS  Google Scholar 

  72. 72.

    Sharma, S., Stello, D., Bland-Hawthorn, J., Huber, D. & Bedding, T. R. Stellar population synthesis based modeling of the Milky Way using asteroseismology of 13,000 Kepler red giants. Astrophys. J. 822, 15 (2016).

    ADS  Article  Google Scholar 

  73. 73.

    Bressan, A. et al. PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code. Mon. Not. R. Astron. Soc. 427, 127–145 (2012).

    ADS  Article  Google Scholar 

  74. 74.

    Lilliefors, H. W. On the Kolmogorov–Smirnov test for the exponential distribution with mean unknown. J. Am. Stat. Assoc. 64, 387–389 (1969).

    Article  Google Scholar 

  75. 75.

    Barr, D. R. & Davidson, T. A Kolmogorov–Smirnov test for censored samples. Technometrics 15, 739–757 (1973).

    MathSciNet  MATH  Article  Google Scholar 

  76. 76.

    Hurley, J. R. Nuclear and dynamical evolution of stellar systems. Observatory 120, 426–427 (2000).

    ADS  Google Scholar 

  77. 77.

    Hurley, J. R., Tout, C. A. & Pols, O. R. Evolution of binary stars and the effect of tides on binary populations. Mon. Not. R. Astron. Soc. 329, 897–928 (2002).

    ADS  Article  Google Scholar 

  78. 78.

    Izzard, R. G., Jeffery, C. S. & Lattanzio, J. Origin of the early-type R stars: a binary-merger solution to a century-old problem? Astron. Astrophys. 470, 661–673 (2007).

    ADS  Article  Google Scholar 

  79. 79.

    Zhang, X., Jeffery, C. S., Chen, X. & Han, Z. Post-merger evolution of carbon–oxygen + helium white dwarf binaries and the origin of R Coronae Borealis and extreme helium stars. Mon. Not. R. Astron. Soc. 445, 660–673 (2014).

    ADS  Article  Google Scholar 

  80. 80.

    Zhang, X., Hall, P. D., Jeffery, C. S. & Bi, S. Evolution models of helium white dwarf–main-sequence star merger remnants. Astrophys. J. 835, 242 (2017).

    ADS  Article  Google Scholar 

  81. 81.

    Paxton, B. et al. Modules for experiments in stellar astrophysics (MESA). Astrophys. J., Suppl. Ser. 192, 3 (2011).

    ADS  Article  Google Scholar 

  82. 82.

    Paxton, B. et al. Modules for experiments in stellar astrophysics (MESA): planets, oscillations, rotation, and massive stars. Astrophys. J., Suppl. Ser. 208, 4 (2013).

    ADS  Article  Google Scholar 

  83. 83.

    Paxton, B. et al. Modules for experiments in stellar astrophysics (MESA): binaries, pulsations, and explosions. Astrophys. J., Suppl. Ser. 220, 15 (2015).

    ADS  Article  Google Scholar 

  84. 84.

    Dotter, A. MESA Isochrones and Stellar Tracks (MIST) 0: methods for the construction of stellar isochrones. Astrophys. J., Suppl. Ser. 222, 8 (2016).

    ADS  Article  Google Scholar 

  85. 85.

    Choi, J. et al. Mesa Isochrones and Stellar Tracks (MIST). I. Solar-scaled models. Astrophys. J. 823, 102 (2016).

    ADS  Article  Google Scholar 

  86. 86.

    Thoul, A. A., Bahcall, J. N. & Loeb, A. Element diffusion in the solar interior. Astrophys. J. 421, 828–842 (1994).

    ADS  Article  Google Scholar 

Download references


This research is supported by the National Key R&D Program of China (grant no. 2019YFA0405502), the National Natural Science Foundation of China (grant nos. 11988101, 11833006, 11833002, 11890694, 11973052, 11973042, 11603037 and 11973049), and the Strategic Priority Research Program of the Chinese Academy of Sciences (CAS) (grant no. XDB34020205). We acknowledge support by the International Partnership Program of the CAS (grant no. 114A32KYSB20160049). H.-L.Y. acknowledges support from the Youth Innovation Promotion Association of the CAS (grant no. 2019060). T.M. is supported by a Grant-in-Aid for Fellows of the Japan Society for the Promotion of Science (JSPS) (grant no. 18J11326). K.P. acknowledges support from a Mt. Cuba Astronomical Foundation grant. This work is partially based on data collected at the Subaru telescope, which is operated by the National Astronomical Observatory of Japan, and was supported by a JSPS–CAS joint research programme. We acknowledge support from the staff at the Lijiang 2.4 m and 1.8 m telescopes, and support from the Telescope Access Program for accessing the Automated Planet Finder telescope. We acknowledge support from the Cultivation Project for LAMOST Scientific Payoff and Research Achievement of CAMS-CAS, and support from the Astronomical Big Data Joint Research Center, which is co-funded by the National Astronomical Observatories of the CAS and the Alibaba Cloud. The Guoshoujing telescope (LAMOST) is a National Major Scientific Project built by the CAS. Funding for the project has been provided by the National Development and Reform Commission. LAMOST is operated and managed by the National Astronomical Observatories of the CAS. We acknowledge the use of Gaia, APOGEE and Gaia-ESO data, and of the VizieR catalogue access tool. We also thank J.-J. Mao and X.-T. Fu for discussions.

Author information




H.-L.Y., J.-R.S. and G.Z. proposed and designed this study. H.-L.Y., Y.-T.Z. and J.-R.S. led the data analysis with contributions from Q.G., W.A., T.M., X.-D.X., H.L., and Y.-J.L., X.Z., Yan Li, S.-L.B. and T.S. contributed to the model calculations and discussions. Yaguang Li, Y.-Q.W., M.-Q.J., B.M. and J.-N.F. performed the asteroseismology analysis and derived the evolutionary phases. W.A., H.L. and K.P. carried out the high-resolution spectroscopic observations. J.-K.Z. and X.-L.L. performed the statistical calculation and tests. All of the authors discussed the results and contributed to the writing of the manuscript.

Corresponding authors

Correspondence to Jian-Rong Shi or Gang Zhao.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

Extended Data Fig. 1 The distributions of mass and [N/Fe] for the Li-rich stars and Li-normal stars.

The gray histogram indicate the Li-normal RGB stars or RC star (as noted in each panel) of which the evolutionary phases identified by Hon et al. 201728, the masses are from Yu et al. 201867, and the [N/Fe] are from ASPCAP33. The bin size is as same as Fig. 3.

Extended Data Fig. 2 The mass versus [N/Fe] in our sample.

Martig et al. (2016) mapped the correlations46 of stellar masses with ASPCAP [N/Fe] using machine learning. Their ‘predicted’ masses of the common sources in our sample are plotted as the grey dots. The red and blue dots are Li-rich RC and RGB stars in our sample, respectively. The region marked with light blue is the most clumped mass range predicted by the HeWD-RGB merger model. For the predicted mass range of 0.8-1.8 M by the HeWD-RGB model, a fraction of stars indeed show much larger [N/Fe] (also see Fig. 3) compared to other RC stars within this mass range, but there seems no evident correlation between stars with high-mass and stars with high-[N/Fe].

Supplementary information

Supplementary Information

Supplementary Figs. 1–4 and Tables 1–3.

Source data

Source Data Fig. 1

The data that support the plots of Fig. 1.

Source Data Fig. 2

The data that support the plots of Fig. 2.

Source Data Fig. 3

The data that support the plots of Fig. 3.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Yan, HL., Zhou, YT., Zhang, X. et al. Most lithium-rich low-mass evolved stars revealed as red clump stars by asteroseismology and spectroscopy. Nat Astron 5, 86–93 (2021).

Download citation


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing