664 research outputs found
Event Rates for Binary Inspiral
Double compact objects (neutron stars and black holes) found in binaries with
small orbital separations are known to spiral in and are expected to coalesce
eventually because of the emission of gravitational waves. Such inspiral and
merger events are thought to be primary sources for ground based
gravitational-wave interferometric detectors (such as LIGO). Here, we present a
brief review of estimates of coalescence rates and we examine the origin and
relative importance of uncertainties associated with the rate estimates. For
the case of double neutron star systems, we compare the most recent rate
estimates to upper limits derived in a number of different ways. We also
discuss the implications of the formation of close binaries with two
non-recycled pulsars.Comment: 12 pages, to appear in AIP proceedings ``Astrophysical Sources of
Gravitational Radiation for Ground-Based Detectors.'
Constraining Binary Evolution with Gravitational Wave Measurements of Chirp Masses
Using the StarTrack binary population synthesis code we investigate the
properties of population of compact object binaries. Taking into account the
selection effects we calculate the expected properties of the observed
binaries.We analyze possible constraints on the stellar evolution models and
find that an observed sample of about one hundred mergers will yield strong
constraints on the binary evolution scenarios.Comment: Invited talk at "The Astrophysics of Gravitational Wave Sources"
Workshop; April 24-26, 2003, U. Maryland; 10 page
The distribution of mass ratios in compact object binaries
Using the StarTrack population synthesis code we compute the distribution of
masses of merging compact object (black hole or neutron star) binaries. The
shape of the mass distribution is sensitive to some of the parameters governing
the stellar binary evolution. We discuss the possibility of constraining
stellar evolution models using mass measurements obtained from the detection of
compact object inspiral with the upcoming gravitational-wave observatories.Comment: 10 pages, uses spie.cls, Proc of the SPIE Conference "Astronomical
Telescopes and Instrumentation
Merger rates of double neutron stars and stellar origin black holes: The Impact of Initial Conditions on Binary Evolution Predictions
The initial mass function (IMF), binary fraction and distributions of binary
parameters (mass ratios, separations and eccentricities) are indispensable
input for simulations of stellar populations. It is often claimed that these
are poorly constrained significantly affecting evolutionary predictions.
Recently, dedicated observing campaigns provided new constraints on the initial
conditions for massive stars. Findings include a larger close binary fraction
and a stronger preference for very tight systems. We investigate the impact on
the predicted merger rates of neutron stars and black holes.
Despite the changes with previous assumptions, we only find an increase of
less than a factor 2 (insignificant compared with evolutionary uncertainties of
typically a factor 10-100). We further show that the uncertainties in the new
initial binary properties do not significantly affect (within a factor of 2)
our predictions of double compact object merger rates. An exception is the
uncertainty in IMF (variations by a factor of 6 up and down). No significant
changes in the distributions of final component masses, mass ratios, chirp
masses and delay times are found.
We conclude that the predictions are, for practical purposes, robust against
uncertainties in the initial conditions concerning binary parameters with
exception of the IMF. This eliminates an important layer of the many uncertain
assumptions affecting the predictions of merger detection rates with the
gravitational wave detectors aLIGO/aVirgo.Comment: Accepted for publication in Ap
The eccentricity distribution of compact binaries
The current gravitational wave detectors have reached their operational
sensitivity and are nearing detection of compact object binaries. In the coming
years, we expect that the Advanced LIGO/VIRGO will start taking data. At the
same time, there are plans for third generation ground-based detectors such as
the Einstein Telescope, and space detectors such as DECIGO. We discuss the
eccentricity distribution of inspiral compact object binaries during they
inspiral phase. We analyze the expected distributions of eccentricities at
three frequencies that are characteristic of three future detectors: Advanced
LIGO/VIRGO (30 Hz), Einstein Telescope (3 Hz), and DECIGO (0.3 Hz). We use the
StarTrack binary population code to investigate the properties of the
population of compact binaries in formation. We evolve their orbits until the
point that they enter a given detector sensitivity window and analyze the
eccentricity distribution at that time. We find that the eccentricities of
BH-BH and BH-NS binaries are quite small when entering the Advanced LIGO/VIRGO
detector window for all considered models of binary evolution. Even in the case
of the DECIGO detector, the typical eccentricities of BH-BH binaries are below
10^{-4}, and the BH-NS eccentricities are smaller than 10^{-3}. Some fraction
of NS-NS binaries may have significant eccentricities. Within the range of
considered models, we found that a fraction of between 0.2% and 2% NS-NS
binaries will have an eccentricity above 0.01 for the Advanced LIGO/VIRGO
detectors. For the ET detector, this fraction is between 0.4% and 4%, and for
the DECIGO detector it lies between 2% and 27%.Comment: 8 pages, 5 figures, accepted by A&
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