70,704 research outputs found
Black Holes: from Speculations to Observations
This paper provides a brief review of the history of our understanding and
knowledge of black holes. Starting with early speculations on ``dark stars'' I
discuss the Schwarzschild "black hole" solution to Einstein's field equations
and the development of its interpretation from "physically meaningless" to
describing the perhaps most exotic and yet "most perfect" macroscopic object in
the universe. I describe different astrophysical black hole populations and
discuss some of their observational evidence. Finally I close by speculating
about future observations of black holes with the new generation of
gravitational wave detectors.Comment: 15 pages, 6 Figures; to appear in the Proceedings of the Albert
Einstein Century International Conference, Paris, France, 200
Population synthesis of neutron stars, strange (quark) stars and black holes
We compute and present the distribution in mass of single and binary neutron
stars, strange stars, and black holes. The calculations were performed using a
stellar population synthesis code. We follow all phases of single and binary
evolution, starting from a ZAMS binary and ending in the creation of one
compact object (neutron star, black hole, strange star) and a white dwarf, or
two compact objects (single or binary). We assume that neutron stars are formed
in the collapse of iron/nickel cores in the mass range M0 < M < M1, quark stars
in the range M1 M2 and find that
the population of quark stars can easily be as large as the population of black
holes, even if there is only a small mass window for their formation.Comment: 4 pages, 4 figures, to appear in the proceedings of "The 4th Integral
Workshop
Modeling the Retention Probability of Black Holes in Globular Clusters: Kicks and Rates
We simulate black hole binary interactions to examine the probability of
mergers and black hole growth and gravitational radiation signals using a
specific initial distribution of masses for black holes in globular clusters
and a simple semi-analytic formalism for dynamical interactions. We include
3-body recoil and the latest results in numerical relativity for gravitational
radiation recoil. It is found that while 99% of binaries are ejected from low
metallicity, low mass clusters; metal rich massive clusters retain 5% of their
binaries. An interesting fraction of the ejected binaries, especially those
from high mass, high metallicity systems, merge on timescales short enough to
be gravitational radiation sources during their mergers with rates approaching
those expected for galactic field black hole binaries. While the merger rates
are comparable, the much larger mass of these binaries and their localization
will make them appealing targets for advanced LIGO. We single out two possible
Milky Way clusters (NGC 6441 and NGC 6388) as having the properties for a good
probability of retention
Compact Binary Coalescences in the Band of Ground-based Gravitational-Wave Detectors
As the ground-based gravitational-wave telescopes LIGO, Virgo, and GEO 600
approach the era of first detections, we review the current knowledge of the
coalescence rates and the mass and spin distributions of merging neutron-star
and black-hole binaries. We emphasize the bi-directional connection between
gravitational-wave astronomy and conventional astrophysics. Astrophysical input
will make possible informed decisions about optimal detector configurations and
search techniques. Meanwhile, rate upper limits, detected merger rates, and the
distribution of masses and spins measured by gravitational-wave searches will
constrain astrophysical parameters through comparisons with astrophysical
models. Future developments necessary to the success of gravitational-wave
astronomy are discussed.Comment: Replaced with version accepted by CQG
Low-frequency gravitational-wave science with eLISA/NGO
We review the expected science performance of the New Gravitational-Wave
Observatory (NGO, a.k.a. eLISA), a mission under study by the European Space
Agency for launch in the early 2020s. eLISA will survey the low-frequency
gravitational-wave sky (from 0.1 mHz to 1 Hz), detecting and characterizing a
broad variety of systems and events throughout the Universe, including the
coalescences of massive black holes brought together by galaxy mergers; the
inspirals of stellar-mass black holes and compact stars into central galactic
black holes; several millions of ultracompact binaries, both detached and mass
transferring, in the Galaxy; and possibly unforeseen sources such as the relic
gravitational-wave radiation from the early Universe. eLISA's high
signal-to-noise measurements will provide new insight into the structure and
history of the Universe, and they will test general relativity in its
strong-field dynamical regime.Comment: 20 pages, 8 figures, proceedings of the 9th Amaldi Conference on
Gravitational Waves. Final journal version. For a longer exposition of the
eLISA science case, see http://arxiv.org/abs/1201.362
Gravitational Radiation from Intermediate-Mass Black Holes
Recent X-ray observations of galaxies with ROSAT, ASCA, and Chandra have
revealed numerous bright off-center point sources which, if isotropic emitters,
are likely to be intermediate-mass black holes, with hundreds to thousands of
solar masses. The origin of these objects is under debate, but observations
suggest that a significant number of them currently reside in young
high-density stellar clusters. There is also growing evidence that some
Galactic globular clusters harbor black holes of similar mass, from
observations of stellar kinematics. In such high-density stellar environments,
the interactions of intermediate-mass black holes are promising sources of
gravitational waves for ground-based and space-based detectors. Here we explore
the signal strengths of binaries containing intermediate-mass black holes or
stellar-mass black holes in dense stellar clusters. We estimate that a few to
tens per year of these objects will be detectable during the last phase of
their inspiral with the advanced LIGO detector, and up to tens per year will be
seen during merger, depending on the spins of the black holes. We also find
that if these objects reside in globular clusters then tens of sources will be
detectable with LISA from the Galactic globular system in a five year
integration, and similar numbers will be detectable from more distant galaxies.
The signal strength depends on the eccentricity distribution, but we show that
there is promise for strong detection of pericenter precession and
Lense-Thirring precession of the orbital plane. We conclude by discussing what
could be learned about binaries, dense stellar systems, and strong gravity if
such signals are detected.Comment: Minor changes, accepted by ApJ (December 10, 2002
Testing the nature of dark compact objects: a status report
Very compact objects probe extreme gravitational fields and may be the key to
understand outstanding puzzles in fundamental physics. These include the nature
of dark matter, the fate of spacetime singularities, or the loss of unitarity
in Hawking evaporation. The standard astrophysical description of collapsing
objects tells us that massive, dark and compact objects are black holes. Any
observation suggesting otherwise would be an indication of
beyond-the-standard-model physics. Null results strengthen and quantify the
Kerr black hole paradigm. The advent of gravitational-wave astronomy and
precise measurements with very long baseline interferometry allow one to
finally probe into such foundational issues. We overview the physics of exotic
dark compact objects and their observational status, including the
observational evidence for black holes with current and future experiments.Comment: 76 pages + references. Invited review article for Living Reviews in
Relativity. v3: Overall improvements and references added, a few typos
corrected. Version to appear in LR
Evolution of Black Holes in the Galaxy
In this article we consider the formation and evolution of black holes,
especially those in binary stars where radiation from the matter falling on
them can be seen. We consider a number of effects introduced by some of us,
which are not traditionally included in binary evolution of massive stars.
These are (i) hypercritical accretion, which allows neutron stars to accrete
enough matter to collapse to a black hole during their spiral-in into another
star. (ii) the strong mass loss of helium stars, which causes their evolution
to differ from that of the helium core of a massive star. (iii) The direct
formation of low-mass black holes (M\sim2\msun) from single stars, a
consequence of a significant strange-matter content of the nuclear-matter
equation of state at high density. We discuss these processes here, and then
review how they affect various populations of binaries with black holes and
neutron stars.Comment: 46 pages, 1 figure, to be published in Physics Repor
Binary Encounters With Supermassive Black Holes: Zero-Eccentricity LISA Events
Current simulations of the rate at which stellar-mass compact objects merge
with supermassive black holes (called extreme mass ratio inspirals, or EMRIs)
focus on two-body capture by emission of gravitational radiation. The
gravitational wave signal of such events will likely involve a significant
eccentricity in the sensitivity range of the Laser Interferometer Space Antenna
(LISA). We show that tidal separation of stellar-mass compact object binaries
by supermassive black holes will instead produce events whose eccentricity is
nearly zero in the LISA band. Compared to two-body capture events, tidal
separations have a high cross section and result in orbits that have a large
pericenter and small apocenter. Therefore, the rate of interactions per binary
is high and the resulting systems are very unlikely to be perturbed by other
stars into nearly radial plunges. Depending on the fraction of compact objects
that are in binaries within a few parsecs of the center, the rate of
low-eccentricity LISA events could be comparable to or larger than the rate of
high-eccentricity events.Comment: Final accepted version: ApJ Letters 2005, 631, L11
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