2021MNRAS.503....1C -
Mon. Not. R. Astron. Soc., 503, 1-12 (2021/May-1)
Neutron stars mergers in a stochastic chemical evolution model: impact of time delay distributions.
CAVALLO L., CESCUTTI G. and MATTEUCCI F.
Abstract (from CDS):
We study the evolution of the [Eu/Fe] ratio in the Galactic halo by means of a stochastic chemical evolution model considering merging neutron stars as polluters of europium. We improved our previous stochastic chemical evolution model by adding a time delay distribution for the coalescence of the neutron stars, instead of constant delays. The stochastic chemical evolution model can reproduce the trend and the observed spread in the [Eu/Fe] data with neutron star mergers as unique producers if we assume: (i) a delay time distribution ∝t–1.5, (ii) an M_ Eu_= 3 ×10–6 M☉ per event, (iii) progenitors of neutron stars in the range 9-50 M☉, and (iv) a constant fraction of massive stars in the initial mass function (0.02) that produce neutron star mergers. Our best model is obtained by relaxing point (iv) and assuming a fraction that varies with metallicity. We confirm that the mixed scenario with both merging neutron stars and supernovae as europium producers can provide a good agreement with the data relaxing the constraints on the distribution time delays for the coalescence of neutron stars. Adopting our best model, we also reproduce the dispersion of [Eu/Fe] at a given metallicity, which depends on the fraction of massive stars that produce neutron star mergers. Future high-resolution spectroscopic surveys, such as 4MOST and WEAVE, will produce the necessary statistics to constrain at best this parameter.
Abstract Copyright:
© 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society
Journal keyword(s):
nuclear reactions, nucleosynthesis, abundances - stars: abundances - binaries: close - stars: neutron - Galaxy: evolution - Galaxy: halo
Simbad objects:
2
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