211,191 research outputs found
Dark matter spikes in the vicinity of Kerr black holes
The growth of a massive black hole will steepen the cold dark matter density
at the center of a galaxy into a dense spike, enhancing the prospects for
indirect detection. We study the impact of black hole spin on the density
profile using the exact Kerr geometry of the black whole in a fully
relativistic adiabatic growth framework. We find that, despite the transfer of
angular momentum from the hole to the halo, rotation increases significantly
the dark matter density close to the black hole. The gravitational effects are
still dominated by the black hole within its influence radius, but the larger
dark matter annihilation fluxes might be relevant for indirect detection
estimates.Comment: Published version plus corrected typo in Fig 1
On the distribution of stellar-sized black hole spins
Black hole spin will have a large impact on searches for gravitational waves
with advanced detectors. While only a few stellar mass black hole spins have
been measured using X-ray techniques, gravitational wave detectors have the
capacity to greatly increase the statistics of black hole spin measurements. We
show what we might learn from these measurements and how the black hole spin
values are influenced by their formation channels.Comment: 4 pages, 2 figures, pre-GW150914 detection, refereed and accepted
contribution to proceedings of 11th Edoardo Amaldi Conference on
Gravitational Waves, June 2015, Gwangju, Kore
Matched Filtering of Numerical Relativity Templates of Spinning Binary Black Holes
Tremendous progress has been made towards the solution of the
binary-black-hole problem in numerical relativity. The waveforms produced by
numerical relativity will play a role in gravitational wave detection as either
test-beds for analytic template banks or as template banks themselves. As the
parameter space explored by numerical relativity expands, the importance of
quantifying the effect that each parameter has on first the detection of
gravitational waves and then the parameter estimation of their sources
increases. In light of this, we present a study of equal-mass, spinning
binary-black-hole evolutions through matched filtering techniques commonly used
in data analysis. We study how the match between two numerical waveforms varies
with numerical resolution, initial angular momentum of the black holes and the
inclination angle between the source and the detector. This study is limited by
the fact that the spinning black-hole-binaries are oriented axially and the
waveforms only contain approximately two and a half orbits before merger. We
find that for detection purposes, spinning black holes require the inclusion of
the higher harmonics in addition to the dominant mode, a condition that becomes
more important as the black-hole-spins increase. In addition, we conduct a
preliminary investigation of how well a template of fixed spin and inclination
angle can detect target templates of arbitrary spin and inclination for the
axial case considered here
Black hole mergers in the universe
Mergers of black-hole binaries are expected to release large amounts of
energy in the form of gravitational radiation. However, binary evolution models
predict merger rates too low to be of observational interest. In this paper we
explore the possibility that black holes become members of close binaries via
dynamical interactions with other stars in dense stellar systems. In star
clusters, black holes become the most massive objects within a few tens of
millions of years; dynamical relaxation then causes them to sink to the cluster
core, where they form binaries. These black-hole binaries become more tightly
bound by superelastic encounters with other cluster members, and are ultimately
ejected from the cluster. The majority of escaping black-hole binaries have
orbital periods short enough and eccentricities high enough that the emission
of gravitational radiation causes them to coalesce within a few billion years.
We predict a black-hole merger rate of about per year per
cubic megaparsec, implying gravity wave detection rates substantially greater
than the corresponding rates from neutron star mergers. For the first
generation Laser Interferometer Gravitational-Wave Observatory (LIGO-I), we
expect about one detection during the first two years of operation. For its
successor LIGO-II, the rate rises to roughly one detection per day. The
uncertainties in these numbers are large. Event rates may drop by about an
order of magnitude if the most massive clusters eject their black hole binaries
early in their evolution.Comment: 12 pages, ApJL in pres
Escape of black holes from the brane
TeV-scale gravity theories allow the possibility of producing small black
holes at energies that soon will be explored at the LHC or at the Auger
observatory. One of the expected signatures is the detection of Hawking
radiation, that might eventually terminate if the black hole, once perturbed,
leaves the brane. Here, we study how the `black hole plus brane' system evolves
once the black hole is given an initial velocity, that mimics, for instance,
the recoil due to the emission of a graviton. The results of our dynamical
analysis show that the brane bends around the black hole, suggesting that the
black hole eventually escapes into the extra dimensions once two portions of
the brane come in contact and reconnect. This gives a dynamical mechanism for
the creation of baby branes.Comment: 4 pages, 6 figure
Black hole particle emission in higher-dimensional spacetimes
In models with extra dimensions, a black hole evaporates both in the bulk and
on the visible brane, where standard model fields live. The exact emissivities
of each particle species are needed to determine how the black hole decay
proceeds. We compute and discuss the absorption cross-sections, the relative
emissivities and the total power output of all known fields in the evaporation
phase. Graviton emissivity is highly enhanced as the spacetime dimensionality
increases. Therefore, a black hole loses a significant fraction of its mass in
the bulk. This result has important consequences for the phenomenology of black
holes in models with extra dimensions and black hole detection in particle
colliders.Comment: 4 pages, RevTeX 4. v3: Misprints in Tables correcte
Theoretical Black Hole Mass Distributions
We derive the theoretical distribution function of black hole masses by
studying the formation processes of black holes. We use the results of recent
2D simulations of core-collapse to obtain the relation between remnant and
progenitor masses and fold it with an initial mass function for the
progenitors. We examine how the calculated black-hole mass distributions are
modified by (i) strong wind mass loss at different evolutionary stages of the
progenitors, and (ii) the presence of close binary companions to the black-hole
progenitors. Thus, we are able to derive the binary black hole mass
distribution. The compact remnant distribution is dominated by neutron stars in
the mass range 1.2-1.6Msun and falls off exponentially at higher remnant
masses. Our results are most sensitive to mass loss from winds which is even
more important in close binaries. Wind mass-loss causes the black hole
distribution to become flatter and limits the maximum possible black-hole mass
(<10-15Msun). We also study the effects of the uncertainties in the explosion
and unbinding energies for different progenitors. The distributions are
continuous and extend over a broad range. We find no evidence for a gap at low
values (3-5Msun) or for a peak at higher values (~7Msun) of black hole masses,
but we argue that our black hole mass distribution for binaries is consistent
with the current sample of measured black-hole masses in X-ray transients. We
discuss possible biases against the detection or formation of X-ray transients
with low-mass black holes. We also comment on the possibility of black-hole
kicks and their effect on binaries.Comment: 22 pages, submitted to Ap
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