108 research outputs found
Compact Binary Mergers and Accretion-Induced Collapse: Event Rates
This paper is a brief review of the topic of binary systems as sources of
gravitational-wave emission for both LIGO and LISA. In particular I review the
current estimates of the associated Galactic event rates and their implications
for expected detection rates. I discuss the estimates for (i) the coalescence
of close binaries containing neutron stars or black holes, (ii) white dwarfs
going through accretion-induced collapse into neutron stars, and (iii) detached
but close binaries containing two white dwarfs. The relevant uncertainties and
robustness of the estimates are addressed along with ways of obtaining
conservative upper limits.Comment: 10 pages, 2 figures included, to appear in the proceedings of the 3rd
Amaldi Conference on Gravitational Wave
Orbital Characteristics of Binary Systems after Asymmetric Supernova Explosions
We present an analytical method for studying the changes of the orbital
characteristics of binary systems with circular orbits due to a kick velocity
imparted to the newborn neutron star during a supernova explosion (SN).
Assuming a Maxwellian distribution of kick velocities we derive analytical
expressions for the distribution functions of orbital separations and
eccentricities immediately after the explosion, of orbital separations after
circularization of the post-SN orbits, and of systemic velocities of binaries
that remain bound after the explosion. These distributions of binary
characteristics can be used to perform analytical population synthesis
calculations of various types of binaries, the formation of which involves a
supernova explosion. We study in detail the dependence of the derived
distributions on the kick velocity and the pre-SN characteristics, we identify
all the limits imposed on the post-SN orbital characteristics, and we discuss
their implications for the population of X-ray binaries and double neutron star
systems. We show that large kick velocities do not necessarily result in large
systemic velocities; for typical X-ray binary progenitors the maximum post-SN
systemic velocity is comparable to the relative orbital velocity prior to the
explosion. We also find that, unless accretion-induced collapse is a viable
formation channel, X-ray binaries in globular clusters have most probably been
formed by stellar dynamical interactions only, and not directly from primordial
binaries.Comment: 27 pages, 14 figures, aaspp4.sty, all tarred, gzipped and uuencoded
in one file. Accepted for publication in the Astrophysical Journal. If you
have any problems please contact [email protected]. One reference/comment
in the text has been remove
LIGO and the opening of a unique observational window on the universe
A unique window on the universe opened on September 14, 2015, with direct detection of gravitational waves by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors. This event culminated a half-century effort around the globe to develop terrestrial detectors of adequate sensitivity to achieve this goal. It also happened appropriately only a few months before the centennial of Einstein’s final paper introducing the general theory of relativity. This detection provided the surprising discovery of a coalescing pair of “heavy” black holes (more massive than ≃ 25 M_๏) leading to the formation of a spinning ≃ 62 solar mass black hole. One more binary black-hole detection and a significant candidate event demonstrated that a population of such merging binaries is formed in nature with a broad mass spectrum. This unique observational sample has already provided concrete measurements on the coalescence rates and has allowed us to test the theory of general relativity in the strong-field regime. As this nascent field of gravitational-wave astrophysics is emerging we are looking forward to the detection of binary mergers involving neutron stars and their electromagnetic counterparts, as well as continuous-wave sources, supernovae, a stochastic confusion background of compact-object mergers, known sources detected in unexpected ways, and completely unknown sources
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