The long-term evolution of neutron star merger remnants – I. The impact of r-process nucleosynthesis

By Stephan Rosswog, Oleg Korobkin, A. Arcones, Friedrich-Karl Thielemann, T. P. S. University, Okc, I. Darmstadt, U. Basel, R. I. O. Physics. 2013

226 citations recorded by the source corpus.

We follow the long-term evolution of the dynamic ejecta of neutron star mergers for up to 100 years and over a density range of roughly 40 orders of magnitude. We include the nuclear energy input from the freshly synthesized, radioactively decaying nuclei in our simulations and study its effects on the remnant dynamics. Although the nuclear heating substantially alters the long-term evolution, we find that running nuclear networks over purely hydrodynamic simulations (i.e. without heating) yields actually acceptable nucleosynthesis results. The main dynamic effect of the radioactive heating is to quickly smooth out inhomogeneities in the initial mass distribution, subsequently the evolution proceeds self-similarly and after 100 years the remnant still carries the memory of the initial binary mass ratio. We also explore the nucleosynthetic yields for two mass ejection channels. The dynamic ejecta very robustly produce 'strong' r-process elements with A > 130 with a pattern that is essentially independent of the details of the merging system. From a simple model we find that neutrino-driven winds yield 'weak' r-process contributions with 50 < A < 130 whose abundance patterns vary substantially between different merger cases. This is because their electron fraction, set by the ratio of neutrino luminosities, varies considerably from case to case. Such winds do not produce any Ni-56, but a range of radioactive isotopes that are long-lived enough to produce a second, radioactively powered electromagnetic transient in addition to the 'macronova' from the dynamic ejecta. While our wind model is very simple, it nevertheless demonstrates the potential of such neutrino-driven winds for electromagnetic transients and it motivates further, more detailed neutrino-hydrodynamic studies. The properties of the mentioned transients are discussed in more detail in a companion paper.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/a22586eaf0525a70c4c435c79e3f7ed64b0ec65b

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Nuclear and High Energy Physics

Citations in the corpus

Neutrino-driven winds from neutron star merger remnants (2014, background): “…32.1 <10−12 H4 0.353 16.40 78.4 31.7 <10−12 H5 0.373 18.35 76.8 31.0 <10−12 feedback of nuclear heating on the temperature, but we ignore its impact on the density, since previous studies have demonstrated that for the purposes of nucleosynthesis this impact can be neglected (Rosswog et al. 2014a).”
Neutron Star Mergers Might Not Be the Only Source of r-process Elements in the Milky Way (2018, background): “…rare cases where the ejecta were followed for a longer time, the ejecta distribution at the end of the initial simulation was mapped to a different code (Rosswog et al. 2014; Roberts et al. 2017; Martin et al. 2018), in order to study the impact of different heating sources on the dynamical ejecta.”
Chemical evolution with rotating massive star yields - I. The solar neighbourhood and the s-process elements (2018, background): “Alternative scenarios has been suggested, as neutron stars mergers (NSM) and/or neutronstar-black-hole pairs (Lattimer et al. 1977; Freiburghaus et al. 1999; Rosswog et al. 2014; Metzger et al. 2010; Kasen et al. 2013; Drout et al. 2017).”
Impact of ejecta morphology and composition on the electromagnetic signatures of neutron star mergers (2017, methodology): “Here, we explore both a sequence of toroidal dynamical ejecta configurations from binary neutron star merger simulations (Rosswog et al. 2014) and a sequence of spherically symmetric ejecta configurations from an analytic hydrodynamical model.”
Dynamical Mass Ejection from Binary Neutron Star Mergers (2016, background): “…of by-products of the rprocess in a macronova (sometimes also called kilonova) (e.g., Li & Paczynski 1998; Kulkarni 2005; Metzger et al. 2010; Roberts et al. 2011; Kasen et al. 2013; Barnes & Kasen 2013; Tanaka & Hotokezaka 2013; Rosswog et al. 2014; Grossman et al. 2014; Lippuner & Roberts 2015).”
PRODUCTION OF ALL THE r-PROCESS NUCLIDES IN THE DYNAMICAL EJECTA OF NEUTRON STAR MERGERS (2014, result): “Similar results were obtained from the Newtonian simulations of NS–NS and BH–NS mergers by Roberts et al. (2011), Korobkin et al. (2012), Rosswog et al. (2014).”
The Emergence of a Lanthanide-rich Kilonova Following the Merger of Two Neutron Stars (2017, background): “Twocomponent axisymmetric outflow consists of neutron-rich toroidal dynamical ejecta (Rosswog et al. 2014), and a slower spherically symmetric homologous outflow with higher electron fraction, broadly referred to as “wind.””
The first direct double neutron star merger detection: Implications for cosmic nucleosynthesis (2017, background): “Although the emergence of an additional blue component was discussed in theoretical work (Barnes et al. 2013; Rosswog 2014; Grossman et al. 2014; Metzger et al. 2014; Perego et al. 2014; Martin et al. 2015; Fernandez et al. 2015; Kasen et al. 2015), the brightness of the blue optical transient…”
Signatures of hypermassive neutron star lifetimes on r-process nucleosynthesis in the disc ejecta from neutron star mergers (2017, background): “Aside from smoothing of sharp features by radioactive heating at late times (Rosswog et al. 2014; Fernández et al. 2015b), this extrapolation of trajectories yields a good first approximation to the morphology of the homologously expanding disk wind ejecta.”
Light curves of the neutron star merger GW170817/SSS17a: Implications for r-process nucleosynthesis (2017, background): “A characteristic value for motivated by numerical simulations is about 3 (86,87), although in general the ejecta structure can be more complicated than in such simulations (16).”
A Magnetar Origin for the Kilonova Ejecta in GW170817 (2018, background): “Following the merger and any subsequent shock heating, e.g., by the GRB jet, the radial velocity structure of the ejecta ultimately approaches homologous expansion (e.g., Rosswog et al. 2014).”
THE r-PROCESS NUCLEOSYNTHESIS IN THE VARIOUS JET-LIKE EXPLOSIONS OF MAGNETOROTATIONAL CORE-COLLAPSE SUPERNOVAE (2015, background): “Beside the dynamical ejecta, winds from the accretion disk of central BH driven by strong neutrino flux are expected to fill this underproduction of lighter r-process elements (Wanajo & Janka 2012; Perego et al. 2014; Rosswog et al. 2014; Just et al. 2014).”
Comprehensive nucleosynthesis analysis for ejecta of compact binary mergers (2014, methodology): “This indicates that including the radioactive heating in a fully consistent manner is not necessary or at least does not lead to any significant changes of our modelling predictions (see also Rosswog et al. 2014, where a similar conclusion was drawn concerning the dynamical ejecta).”
Dawes Review 6: The Impact of Companions on Stellar Evolution (2016, background): “When neutron stars merge, they not only make r-process elements (Rosswog et al., 2014; Shen et al., 2015), but also gravitational waves that may be detectable in the near future (Agathos et al., 2015, Section 7.4).”
NEUTRINO-DRIVEN WINDS IN THE AFTERMATH OF A NEUTRON STAR MERGER: NUCLEOSYNTHESIS AND ELECTROMAGNETIC TRANSIENTS (2015, methodology): “…to as dynamic ejecta, has long been recognized as the likely source of the heaviest r-process nuclei (Freiburghaus et al. 1999b; Rosswog et al. 1999; Roberts et al. 2011; Goriely et al. 2011; Korobkin et al. 2012; Bauswein et al. 2013; Hotokezaka et al. 2013; Rosswog 2013; Rosswog et al. 2014).”