Binary neutron stars and production of heavy elements

  • Francesca MatteucciEmail author
  • Donatella Romano
  • Gabriele Cescutti
  • Paolo Simonetti
A decade of AGILE
Part of the following topical collections:
  1. A Decade of AGILE: Results, Challenges and Prospects of Gamma-Ray Astrophysics


We show how merging neutron stars can be responsible for the production of heavy elements in the solar vicinity, in particular we study the evolution of the abundance of europium (Eu) relative to iron (Fe), as derived by stellar abundances measured in the Milky Way halo and disk stars. To do that, we adopt a detailed galactic chemical evolution model able to follow the evolution of the abundances of several chemical elements in the gas in our Galaxy. Merging of neutron stars after emission of gravitational waves has been observed for the first time in the event GW170817, which has represented the very first kilonova ever observed in the local universe. The production of heavy elements such as Eu (a typical r-process element) is discussed critically, pointing out that supernovae core collapse can produce some r-process elements but not enough to explain the solar abundance of Eu. On the other hand, the merging of compact objects can provide an amount of Eu much higher per single event than a single supernova. We discuss the various parameters involved, such as the merging timescales, the fraction of neutron star binaries and the present time rate of kilonova explosions. We compare model results with stellar data and conclude that merging of compact objects can be responsible for the bulk of Eu production in the Galaxy under some assumptions: (i) the merging binaries should have progenitors in the mass range 9–50\(M_{\odot }\), (ii) the merging timescales should be as short as 1 Myr and iii) each event should produce \(\sim 2 \times 10^{-6}M_{\odot }\). We also conclude that the Ligo/Virgo merging neutron star rate is consistent with our chemical evolution model and that if GW170817 is a representative event, then the merging neutron stars can be considered as the main r-process production sites.


Stellar nucleosynthesis Galaxy evolution 


Compliance with ethical standards

Conflict of interest

Author has declared that there is no conflict of interest.


  1. Abbott BP et al (2017) GW170814: a three-detector observation of gravitational waves from a binary black hole coalescence. Phys Rev Lett 119:1101Google Scholar
  2. Asplund M, Grevesse N, Sauval S, Scott P (2009) The chemical composition of the sun. ARA&A 47:481CrossRefGoogle Scholar
  3. Cescutti G et al (2015) The role of neutron star mergers in the chemical evolution of the Galactic halo. A&A 577:139CrossRefGoogle Scholar
  4. Chiappini C, Matteucci F, Gratton R (1997) The chemical evolution of the galaxy: the two-infall model. ApJ 477:765CrossRefGoogle Scholar
  5. Coté B et al (2018) The origin of r-process elements in the milky way. ApJ 855:99CrossRefGoogle Scholar
  6. Cowan JJ, Thielemann F-K, Truran JW (1991) The R-process and nucleochronology. PhR 208:267Google Scholar
  7. Evans PA et al (2017) Swift and NuSTAR observations of GW170817: detection of a blue kilonova. Science 358(6370):1565CrossRefGoogle Scholar
  8. Frebel A (2010) Stellar archaeology: exploring the Universe with metal-poor stars. Astronom Nachrichten 331(5):474CrossRefGoogle Scholar
  9. François et al (2007) First stars. VIII. Enrichment of the neutron-capture elements in the early Galaxy. A&A 476:935CrossRefGoogle Scholar
  10. Freiburghaus C, Rosswog S, Thielemann (1999) R-process in neutron star mergers. ApJ 525:L121CrossRefGoogle Scholar
  11. Kalogera V, Henninger M, Ivanova N, King AR (2004) An observational diagnostic for ultraluminous x-ray sources. ApJ 601:L41CrossRefGoogle Scholar
  12. Komiya Y, Yamada S, Suda T, Fujimoto MY (2014) The new model of chemical evolution of r-process elements based on the hierarchical galaxy formation. I. Ba and Eu. ApJ 783:132CrossRefGoogle Scholar
  13. Korobkin O, Rosswog S, Arcones A, Winteler (2012) On the astrophysical robustness of the neutron star merger r-process. MNRAS 426:1940CrossRefGoogle Scholar
  14. Lattimer JM, Schramm DN, Grossman L (1977) Supernovae, grains and the formation of the solar system. Nature 269:116CrossRefGoogle Scholar
  15. Matteucci F, Romano D, Arcones A, Korobkin O, Rosswog S (2014) Europium production: neutron star mergers versus core-collapse supernovae. MNRAS 438:2177 (M14)CrossRefGoogle Scholar
  16. Meyer BS (1989) Decompression of initially cold neutron star matter—a mechanism for the r-process? ApJ 343:254CrossRefGoogle Scholar
  17. Mishenina TV et al (2007) Abundances of neutron-capture elements in atmospheres of cool giants. Astron Rep 51(5):382CrossRefGoogle Scholar
  18. Ramya P, Reddy BE, Lambert DL (2012) Chemical compositions of stars in two stellar streams from the Galactic thick disc. MNRAS 425:3188CrossRefGoogle Scholar
  19. Reddy BE, Lambert DL, Allende Prieto C (2006) Elemental abundance survey of the Galactic thick disc. MNRAS 367:1329CrossRefGoogle Scholar
  20. Romano D, Karakas AI, Tosi M, Matteucci F (2010) Quantifying the uncertainties of chemical evolution studies. II. Stellar yields. A&A 522:32CrossRefGoogle Scholar
  21. Rosswog S et al (1999) Mass ejection in neutron star mergers. A&A 341:499Google Scholar
  22. Rosswog S, Davies MB, Thielemann F-K, Piran T (2000) Merging neutron stars: asymmetric systems. A&A 360:171Google Scholar
  23. Scalo JM (1986) The stellar initial mass function. FCPh 11:1Google Scholar
  24. Tanvir NR et al (2017) The emergence of a Lanthanide-rich Kilonova following the merger of two neutron stars. ApJ 848:L27CrossRefGoogle Scholar
  25. Thielemann F-K, Isern J, Perego A, von Ballmoos (2018) Nucleosynthesis in supernovae. SSRv 214:62Google Scholar
  26. Troja E et al (2017) The X-ray counterpart to the gravitational-wave event GW170817. Nature 551:71CrossRefGoogle Scholar
  27. Vangioni E et al (2015) The impact of star formation and gamma-ray burst rates at high redshift on cosmic chemical evolution and reionization. MNRAS 447:2575CrossRefGoogle Scholar
  28. Vescovi D, Busso M, Palmerini S (2018) On the origin of early solar system radioactivities: problems with the asymptotic giant branch and massive star scenarios. ApJ 863:115CrossRefGoogle Scholar
  29. Wanajo S et al (2001) The r-process in neutrino-driven winds from nascent, “Compact” neutron stars of core-collapse supernovae. ApJ 554:578CrossRefGoogle Scholar
  30. Winteler C et al (2012) Magnetorotationally driven supernovae as the origin of early galaxy r-process elements? ApJ 750:L22CrossRefGoogle Scholar
  31. Woosley SE et al (1994) The r-process and neutrino-heated supernova ejecta. ApJ 433:229CrossRefGoogle Scholar

Copyright information

© Accademia Nazionale dei Lincei 2019

Authors and Affiliations

  1. 1.Department of PhysicsTrieste UniversityTriesteItaly
  2. 2.INFN-TriesteTriesteItaly
  3. 3.INAF-BolognaBolognaItaly
  4. 4.INAF-TriesteTriesteItaly

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