Abstract
The merger of two neutron stars or of a neutron star and a black hole often results in the ejection of a few percents of a solar mass of matter expanding at high speed in space. Being matter coming from the violent disruption of a neutron star, these ejecta are initially very dense, hot, and extremely rich in neutrons. The few available protons form heavy nuclei (“seeds”) that absorb the more abundant free neutrons, increasing their size. The neutron density is so high that a substantial number of neutron captures occur before the resulting unstable nuclei can decay toward more stable configurations, converting neutrons into protons. Depending mostly on the initial neutron richness, this mechanism leads to the formation of up to half of the heavy elements that we observe in nature, and it is called rapid neutron capture process (“r-process”). The prediction of the precise composition of the ejecta requires a detailed knowledge of the properties of very exotic nuclei that have never been produced in a laboratory. Despite having long been a speculative scenario, nowadays several observational evidences point to compact binary mergers as one of the major sites where heavy elements are formed in the universe. The most striking one was the detection of a kilonova following the merger of a neutron star binary: the light emitted by this astronomical transient is indeed powered by the radioactive decay of freshly synthesized neutron-rich nuclei and testifies the actual nature of compact binary mergers as cosmic forges.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
References
Abadie J et al (2010) TOPICAL REVIEW: predictions for the rates of compact binary coalescences observable by ground-based gravitational-wave detectors. Class Quantum Gravity 27(17):173001
Abbott BP et al (2017) GW170817: observation of gravitational waves from a binary neutron star inspiral. Phys Rev Lett 119(16):161101
Abbott BP et al (2017) Multi-messenger observations of a binary neutron star merger. Astrophys J Lett 848(2):L12
Abbott BP et al (2018) GW170817: measurements of neutron star radii and equation of state. Phys Rev Lett 121(16):161101
Abbott BP et al (2019) GWTC-1: a gravitational-wave transient catalog of compact binary mergers observed by LIGO and virgo during the first and second observing runs. Phys Rev X 9(3):031040
Barnes J, Kasen D, Wu M-R, Martínez-Pinedo G (2016) Radioactivity and thermalization in the ejecta of compact object mergers and their impact on kilonova light curves. Astrophys J 829(2):110
Bernuzzi S, Breschi M, Daszuta B, Endrizzi A, Logoteta D, Nedora V, Perego A, Radice D, Schianchi F, Zappa F, Bombaci I, Ortiz N (2020) Accretion-induced prompt black hole formation in asymmetric neutron star mergers, dynamical ejecta, and kilonova signals. Mon Not R Astron Soc 497(2):1488–1507
Burbidge EM, Burbidge GR, Fowler WA, Hoyle F (1957) Synthesis of the elements in stars. Rev Modern Phys 29(4):547–650
Cameron AGW (1957) Nuclear reactions in stars and nucleogenesis. Publ Astron Soc Pac 69(408):201
Clayton DD (1983) Principles of stellar evolution and nucleosynthesis. University of Chigaco Press, Chicago
Cowan JJ, Sneden C, Lawler JE, Aprahamian A, Wiescher M, Langanke K, Martínez-Pinedo G, Thielemann F-K (2019) Origin of the heaviest elements: the rapid neutron-capture process. arXiv e-prints, arXiv:1901.01410
Eichler D, Livio M, Piran T, Schramm DN (1989) Nucleosynthesis, neutrino bursts and γ-rays from coalescing neutron stars. Nature 340(6229):126–128
Eichler M, Arcones A, Kelic A, Korobkin O, Langanke K, Marketin T, Martinez-Pinedo G, Panov I, Rauscher T, Rosswog S, Winteler C, Zinner NT, Thielemann FK (2015) The role of fission in neutron star mergers and its impact on the r-process peaks. Astrophys J 808(1):30
Fernández R, Metzger BD (2016) Electromagnetic signatures of neutron star mergers in the advanced LIGO era. Annu Rev Nuclear Part Sci 66(1):23–45
Fong W, Berger E, Margutti R, Zauderer BA (2015) A decade of short-duration gamma-ray burst broadband afterglows: energetics, circumburst densities, and jet opening angles. Astrophys J 815(2):102
Freiburghaus C, Rembges JF, Rauscher T, Kolbe E, Thielemann FK, Kratz KL, Pfeiffer B, Cowan JJ (1999) The astrophysical r-process: a comparison of calculations following adiabatic expansion with classical calculations based on neutron densities and temperatures. Astrophys J 516(1):381–398
Freiburghaus C, Rosswog S, Thielemann FK (1999) R-process in neutron star mergers. Astrophys J Lett 525(2):L121–L124
Ghirlanda G, Salafia OS, Pescalli A, Ghisellini G, Salvaterra R, Chassande-Mottin E, Colpi M, Nappo F, D’Avanzo P, Melandri A, Bernardini MG, Branchesi M, Campana S, Ciolfi R, Covino S, Götz D, Vergani SD, Zennaro M, Tagliaferri G (2016) Short gamma-ray bursts at the dawn of the gravitational wave era. Astron Astrophys 594:A84
Goriely S, Sida JL, Lemaître JF, Panebianco S, Dubray N, Hilaire S, Bauswein A, Janka HT (2013) New fission fragment distributions and r-process origin of the rare-earth elements. Phys Rev Lett 111(24):242502
Hansen TT et al (2017) An r-process enhanced star in the dwarf galaxy tucana III. Astrophys J 838(1):44
Hoffman RD, Woosley SE, Qian YZ (1997) Nucleosynthesis in neutrino-driven winds. II. Implications for heavy element synthesis. Astrophys J 482(2):951–962
Honda S, Aoki W, Kajino T, Ando H, Beers TC, Izumiura H, Sadakane K, Takada-Hidai M (2004) Spectroscopic studies of extremely metal-poor stars with the subaru high dispersion spectrograph. II. The r-process elements, including thorium. Astrophys J 607(1):474–498
Hotokezaka K, Wanajo S, Tanaka M, Bamba A, Terada Y, Piran T (2016) Radioactive decay products in neutron star merger ejecta: heating efficiency and γ-ray emission. Mon Not R Astron Soc 459(1):35–43
Hotokezaka K, Beniamini P, Piran T (2018) Neutron star mergers as sites of r-process nucleosynthesis and short gamma-ray bursts. Int J Modern Phys D 27(13):1842005
Hotokezaka K, Piran T, Paul M (2015) Short-lived 244Pu points to compact binary mergers as sites for heavy r-process nucleosynthesis. Nat Phys 11(12):1042
Hulse RA, Taylor JH (1975) Discovery of a pulsar in a binary system. Astrophys J Lett 195:L51–L53
Iliadis C (2007) Nuclear physics of stars. Wiley-VCH, Weinheim
Ji AP, Frebel A, Chiti A, Simon JD (2016) R-process enrichment from a single event in an ancient dwarf galaxy. Nature 531(7596):610–613
Just O, Bauswein A, Ardevol Pulpillo R, Goriely S, Janka HT (2015) Comprehensive nucleosynthesis analysis for ejecta of compact binary mergers. Mon Not R Astron Soc 448(1):541–567
Kasen D, Badnell NR, Barnes J (2013) Opacities and spectra of the r-process ejecta from neutron star mergers. Astrophys J 774(1):25
Kasen D, Metzger B, Barnes J, Quataert E, Ramirez-Ruiz E (2017) Origin of the heavy elements in binary neutron-star mergers from a gravitational-wave event. Nature 551(7678):80–84
Korobkin O, Rosswog S, Arscones A, Winteler C On the astrophysical robustness of the neutron star merger r-process. Mon Not R Astron Soc 426(3):1940–1949 (2012)
Kratz K-L, Bitouzet J-P, Thielemann F-K, Moeller P, Pfeiffer B (1993) Isotopic r-process abundances and nuclear structure far from stability: implications for the r-process mechanism. Astrophys J 403:216
Lattimer JM, Schramm DN (1974) Black-hole-neutron-star collisions. Astrophys J Lett 192:L145–L147
Lattimer JM, Schramm DN (1976) The tidal disruption of neutron stars by black holes in close binaries. Astrophys J 210:549–567
Li L-X, Paczyński B (1998) Transient events from neutron star mergers. Astrophys J Lett 507(1):L59–L62
Lippuner J, Fernández R, Roberts LF, Foucart F, Kasen D, Metzger BD, Ott CD Signatures of hypermassive neutron star lifetimes on r-process nucleosynthesis in the disc ejecta from neutron star mergers. Mon Not R Astron Soc 472(1):904–918 (2017)
Lippuner J, Roberts LF (2015) r-process lanthanide production and heating rates in kilonovae. Astrophys J 815(2):82
Lippuner J, Roberts LF (2017) SkyNet: a modular nuclear reaction network library. Astrophys J Suppl Ser 233(2):18
Martin D, Perego A, Arcones A, Thielemann FK, Korobkin O, Rosswog S (2015) Neutrino-driven winds in the aftermath of a neutron star merger: nucleosynthesis and electromagnetic transients. Astrophys J 813(1):2
Martínez-Pinedo G (2008) Selected topics in nuclear astrophysics. Eur Phys J Spec Top 156(1):123–149
Martínez-Pinedo G, Fischer T, Lohs A, Huther L (2012) Charged-current weak interaction processes in hot and dense matter and its impact on the spectra of neutrinos emitted from protoneutron star cooling. Phys Rev Lett 109(25):251104
Mendoza-Temis JDJ, Wu M-R, Langanke K, Martínez-Pinedo G, Bauswein A, Janka H-T (2015) Nuclear robustness of the r process in neutron-star mergers. Phys Rev C 92(5):055805
Metzger BD, Martínez-Pinedo G, Darbha S, Quataert E, Arcones A, Kasen D, Thomas R, Nugent P, Panov IV, Zinner NT (2010) Electromagnetic counterparts of compact object mergers powered by the radioactive decay of r-process nuclei. Mon Not R Astron Soc 406(4):2650–2662
Metzger BD (2019) Kilonovae. Living Rev Relat 23(1):1
Oertel M, Hempel M, Klähn T, Typel S (2017) Equations of state for supernovae and compact stars. Rev Modern Phys 89(1):015007
Perego A, Rosswog S, Cabezón RM, Korobkin O, Käppeli R, Arcones A, Liebendörfer M (2014) Neutrino-driven winds from neutron star merger remnants. Mon Not R Astron Soc 443(4):3134–3156
Perego A, Radice D, Bernuzzi S (2017) AT 2017gfo: an anisotropic and three-component kilonova counterpart of GW170817. Astrophys J Lett 850(2):L37
Pian E et al (2017) Spectroscopic identification of r-process nucleosynthesis in a double neutron-star merger. Nature 551(7678):67–70
Pol N, McLaughlin M, Lorimer DR (2019) Future prospects for ground-based gravitational-wave detectors: the galactic double neutron star merger rate revisited. Astrophys J 870(2):71
Prantzos N, Abia C, Cristallo S, Limongi M, Chieffi A (2020) Chemical evolution with rotating massive star yields II. A new assessment of the solar s- and r-process components. Mon Not R Astron Soc 491(2):1832–1850
Qian YZ, Woosley SE (1996) Nucleosynthesis in neutrino-driven winds. I. The physical conditions. Astrophys J 471:331
Radice D, Bernuzzi S, Perego A (2020) The dynamics of binary neutron star mergers and GW170817. Annu Rev Nuclear Part Sci 70(1):annurev
Radice D, Perego A, Hotokezaka K, Fromm SA, Bernuzzi S, Roberts LF (2018) Binary neutron star mergers: mass ejection, electromagnetic counterparts, and nucleosynthesis. Astrophys J 869(2):130
Roberts LF, Lippuner J, Duez MD, Faber JA, Foucart F, Lombardi JC Jr, Ning S, Ott CD, Ponce M (2017) The influence of neutrinos on r-process nucleosynthesis in the ejecta of black hole-neutron star mergers. Mon Not R Astron Soc 464(4):3907–3919
Roederer IU, Preston GW, Thompson IB, Shectman SA, Sneden C, Burley GS, Kelson DD (2014) A search for stars of very low metal abundance. VI. Detailed abundances of 313 metal-poor stars. Astron J 147(6):136
Rosswog S, Feindt U, Korobkin O, Wu MR, Sollerman J, Goobar A, Martinez-Pinedo G (2017) Detectability of compact binary merger macronovae. Class Quantum Gravity 34(10):104001
Rosswog S, Korobkin O, Arcones A, Thielemann FK, Piran T (2014) The long-term evolution of neutron star merger remnants – I. The impact of r-process nucleosynthesis. Mon Not R Astron Soc 439(1):744–756
Shibata M, Hotokezaka K (2019) Merger and mass ejection of neutron star binaries. Annu Rev Nuclear Part Sci 69:41–64
Smartt SJ et al (2017) A kilonova as the electromagnetic counterpart to a gravitational-wave source. Nature 551(7678):75–79
Sneden C, Cowan JJ, Gallino R (2008) Neutron-capture elements in the early galaxy. Annu Rev Astron Astrophys 46:241–288
Symbalisty E, Schramm DN (1982) Neutron star collisions and the r-process. Astrophys J Lett 22:143
Tanaka M et al (2017) Kilonova from post-merger ejecta as an optical and near-infrared counterpart of GW170817. Publ Astron Soc Jpn 69(6):102
Tanaka M, Hotokezaka K (2013) Radiative transfer simulations of neutron star merger ejecta. Astrophys J 775(2):113
Tanvir NR et al (2017) The emergence of a lanthanide-rich kilonova following the merger of two neutron stars. Astrophys J Lett 848(2):L27
Tanvir NR, Levan AJ, Fruchter AS, Hjorth J, Hounsell RA, Wiersema K, Tunnicliffe RL (2013) A ‘kilonova’ associated with the short-duration γ-ray burst GRB 130603B. Nature 500(7464):547–549
Thielemann FK, Eichler M, Panov IV, Wehmeyer B (2017) Neutron star mergers and nucleosynthesis of heavy elements. Annu Rev Nuclear Part Sci 67:253–274
Villar VA, Guillochon J, Berger E, Metzger BD, Cowperthwaite PS, Nicholl M, Alexander KD, Blanchard PK, Chornock R, Eftekhari T, Fong W, Margutti R, Williams PKG (2017) The combined ultraviolet, optical, and near-infrared light curves of the kilonova associated with the binary neutron star merger GW170817: unified data set, analytic models, and physical implications. Astrophys J Lett 851(1):L21
Wanajo S, Janka H-T, Müller B (2011) Electron-capture supernovae as the origin of elements beyond iron. Astrophys J Lett 726(2):L15
Wanajo S, Sekiguchi Y, Nishimura N, Kiuchi K, Kyutoku K, Shibata M (2014) Production of all the r-process nuclides in the dynamical ejecta of neutron star mergers. Astrophys J Lett 789(2):L39
Wanderman D Piran T (2015) The rate, luminosity function and time delay of non-Collapsar short GRBs. Mon Not R Astron Soc 448(4):3026–3037
Watson D, Hansen CJ, Selsing J, Koch A, Malesani DB, Andersen AC, Johan Fynbo PU, Arcones A, Bauswein A, Covino S, Grado A, Heintz KE, Hunt L, Kouveliotou C, Leloudas G, Levan AJ, Mazzali P, Pian E (2019) Identification of strontium in the merger of two neutron stars. Nature 574(7779):497–500
Winteler C, Käppeli R, Perego A, Arcones A, Vasset N, Nishimura N, Liebendörfer M, Thielemann FK (2012) Magnetorotationally driven supernovae as the origin of early galaxy r-process elements? Astrophys J Lett 750(1):L22
Wollaeger RT, Korobkin O, Fontes CJ, Rosswog SK, Even WP, Fryer CL, Sollerman J, Hungerford AL, van Rossum DR, Wollaber AB (2018) Impact of ejecta morphology and composition on the electromagnetic signatures of neutron star mergers. Mon Not R Astron Soc 478(3):3298–3334
Wu M-R, Barnes J, Martínez-Pinedo G, Metzger BD (2019) Fingerprints of heavy-element nucleosynthesis in the late-time lightcurves of kilonovae. Phys Rev Lett 122(6):062701
Wu M-R, Fernández R, Martínez-Pinedo G, Metzger BD (2016) Production of the entire range of r-process nuclides by black hole accretion disc outflows from neutron star mergers. Mon Not R Astron Soc 463(3):2323–2334
Zhu Y, Wollaeger RT, Vassh N, Surman R, Sprouse TM, Mumpower MR, Möller P, McLaughlin GC, Korobkin O, Kawano T, Jaffke PJ, Holmbeck EM, Fryer CL, Even WP, Couture AJ, Barnes J (2018) Californium-254 and kilonova light curves. Astrophys J Lett 863(2):L23
Author information
Authors and Affiliations
Corresponding author
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2022 Springer Nature Singapore Pte Ltd.
About this entry
Cite this entry
Perego, A., Thielemann, F.K., Cescutti, G. (2022). r-Process Nucleosynthesis from Compact Binary Mergers. In: Bambi, C., Katsanevas, S., Kokkotas, K.D. (eds) Handbook of Gravitational Wave Astronomy. Springer, Singapore. https://doi.org/10.1007/978-981-16-4306-4_13
Download citation
DOI: https://doi.org/10.1007/978-981-16-4306-4_13
Published:
Publisher Name: Springer, Singapore
Print ISBN: 978-981-16-4305-7
Online ISBN: 978-981-16-4306-4
eBook Packages: Physics and AstronomyReference Module Physical and Materials ScienceReference Module Chemistry, Materials and Physics