On the delay times of merging double neutron stars
Date Issued
2021
Author(s)
Abstract
The merging rate of double neutron stars (DNS) has a great impact on many
astrophysical issues, including the interpretation of gravitational waves
signals, of the short Gamma Ray Bursts (GRBs), and of the chemical properties
of stars in galaxies. Such rate depends on the distribution of the delay times
(DDT) of the merging events. In this paper we derive a theoretical DDT of
merging DNS following from the characteristics of the clock controlling their
evolution. We show that the shape of the DDT is governed by a few key
parameters, primarily the lower limit and the slope of the distribution of the
separation of the DNS systems at birth. With a parametric approach we
investigate on the observational constraints on the DDT from the cosmic rate of
short GRBs and the Europium to Iron ratio in Milky Way stars, taken as tracer
of the products of the explosion. We find that the local rate of DNS merging
requires that about 1 percent of neutron stars progenitors live in binary
systems which end their evolution as merging DNS within a Hubble time. The
redshift distribution of short GRBs does not yet provide a strong constraint on
the shape of the DDT, although the best fitting models have a shallow DDT. The
chemical pattern in Milky Way stars requires an additional source of Europium
besides the products from merging DNS, which weakens the related requirement on
the DDT. At present both constraints can be matched with the same DDT for
merging DNS.
Volume
500
Issue
2
Start page
1755
Issn Identifier
0035-8711
Ads BibCode
2021MNRAS.500.17554
Rights
open.access
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