43 research outputs found
On the Impact of Neutron Star Binaries Natal-Kick Distribution on the Galactic r-process Enrichment
We study the impact of the neutron star binaries' (NSBs) natal kick
distribution on the Galactic r-process enrichment. We model the growth of a
Milky Way type halo based on N-body simulation results and its star formation
history based on multi epoch abundance matching techniques. We consider the
NSBs that merge well beyond the galaxy's effective radius () do not contribute to Galactic r-process enrichment. Assuming a
power-law delay-time distribution (DTD) function () with
Myr for binaries' coalescence timescales, and an
exponential profile for their natal kick distribution with an average value of
180 km s, we show that up to 40% of all formed NSBs do not
contribute to r-process enrichment by , either because they merge far from
the galaxy at a given redshift (up to 25%) or have not yet merged by
today (15%). Our result is largely insensitive to the details of the DTD
function. Assuming a constant coalescence timescale of 100 Myr well
approximates the adopted DTD with 30% of the NSBs not contributing to r-process
enrichment. Our results, although rather dependent on the adopted natal kick
distribution, represent a first step towards estimating the impact of natal
kicks and DTD functions on r-process enrichment of galaxies that would need to
be incorporated in the hydrodynamical simulations.Comment: 7 pages, 3 figures, MNRAS Accepte
How can LISA probe a population of GW190425-like binary neutron stars in the Milky Way?
The nature of GW190425, a presumed binary neutron star (BNS) merger detected
by the LIGO/Virgo Scientific Collaboration (LVC) with a total mass of
M, remains a mystery. With such a large total
mass, GW190425 stands at five standard deviations away from the total mass
distribution of Galactic BNSs of M. LVC suggested that
this system could be a BNS formed from a fast-merging channel rendering its
non-detection at radio wavelengths due to selection effects. BNSs with orbital
periods less than a few hours - progenitors of LIGO/Virgo mergers - are prime
target candidates for the future Laser Interferometer Space Antenna (LISA). If
GW190425-like binaries exist in the Milky Way, LISA will detect them within the
volume of our Galaxy and will measure their chirp masses to better than 10% for
those binaries with gravitational wave frequencies larger than 2 mHz. This work
explores how we can probe a population of Galactic GW190425-like BNSs with LISA
and investigate their origin. We assume that the Milky Way's BNS population
consists of two distinct sub-populations: a fraction that follows the
observed Galactic BNS chirp mass distribution and that resembles chirp
mass of GW190425. We show that LISA's accuracy on recovering the fraction of
GW190425-like binaries depends on the BNS merger rate. For the merger rates
reported in the literature, Myr, the error on the recovered
fractions varies between %.Comment: accepted by MNRA