150 research outputs found
Testing Binary Population Synthesis Models with Hot Subdwarfs
Models of binary star interactions have been successful in explaining the
origin of field hot subdwarf (sdB) stars in short period systems, but
longer-period systems that formed via Roche-lobe overflow (RLOF) mass transfer
from the present sdB to its companion have received less attention. We map sets
of initial binaries into present-day binaries that include sdBs and
main-sequence stars, distinguishing "observable" sdBs from "hidden" ones. We
aim to find out whether (1) the existing catalogues of sdBs are sufficiently
fair samples of all the kinds of sdB binaries that theory predicts; or instead
whether (2) large predicted hidden populations mandate the construction of new
catalogues, perhaps using wide-field imaging surveys such as 2MASS, SDSS, and
Galex. We also report on a pilot study to identify hidden subdwarfs, using
2MASS and GALEX data.Comment: 3 pages with 2 figures. Uses AIP style files. To appear in Future
Directions in Ultraviolet Astronomy, ed. Michael E. VanSteenberg (AIP Conf
Proc
Dynamical Interactions and the Black Hole Merger Rate of the Universe
Binary black holes can form efficiently in dense young stellar clusters, such
as the progenitors of globular clusters, via a combination of gravitational
segregation and cluster evaporation. We use simple analytic arguments supported
by detailed N-body simulations to determine how frequently black holes born in
a single stellar cluster should form binaries, be ejected from the cluster, and
merge through the emission of gravitational radiation. We then convolve this
``transfer function'' relating cluster formation to black hole mergers with (i)
the distribution of observed cluster masses and (ii) the star formation history
of the universe, assuming that a significant fraction gcl of star formation
occurs in clusters and that a significant fraction gcand of clusters undergo
this segregation and evaporation process. We predict future ground--based
gravitational wave (GW) detectors could observe ~500 (gcl/0.5) (gcand/0.1)
double black hole mergers per year, and the presently operating LIGO
interferometer would have a chance (50%) at detecting a merger during its first
full year of science data. More realistically, advanced LIGO and similar
next-generation gravitational wave observatories provide unique opportunities
to constrain otherwise inaccessible properties of clusters formed in the early
universe.Comment: 4 pages, 2 figures. To appear in PRD Rapid Communication
Host Galaxies Catalog Used in LIGO Searches for Compact Binary Coalescence Events
An up-to-date catalog of nearby galaxies considered as hosts of binary
compact objects is provided with complete information about sky position,
distance, extinction-corrected blue luminosity and error estimates. With our
current understanding of binary evolution, rates of formation and coalescence
for binary compact objects scale with massive-star formation and hence the
(extinction-corrected) blue luminosity of host galaxies. Coalescence events in
binary compact objects are among the most promising gravitational-wave sources
for ground-based gravitational-wave detectors such as LIGO. Our catalog and
associated error estimates are important for the interpretation of analyses,
carried out for LIGO, to constrain the rates of compact binary coalescence,
given an astrophysical population model for the sources considered. We discuss
how the notion of effective distance, created to account for the antenna
pattern of a gravitational-wave detector, must be used in conjunction with our
catalog. We note that the catalog provided can be used on other astronomical
analysis of populations that scale with galaxy blue luminosity.Comment: 29 pages, 7 figures, Accepted to Astrophysical Journal. To appear in
March 20 2008 Astrophysical Journa
Impact of subdominant modes on the interpretation of gravitational-wave signals from heavy binary black hole systems
Over the past year, a handful of new gravitational wave models have been developed to include multiple harmonic modes thereby enabling for the first time fully Bayesian inference studies including higher modes to be performed. Using one recently developed numerical relativity surrogate model, NRHybSur3dq8, we investigate the importance of higher modes on parameter inference of coalescing massive binary black holes. We focus on examples relevant to the current three-detector network of observatories, with a detector-frame mass set to
120 M⊙ and with signal amplitude values that are consistent with plausible candidates for the next few observing runs. We show that for such systems the higher mode content will be important for interpreting coalescing binary black holes, reducing systematic bias, and computing properties of the remnant object. Even for comparable-mass binaries and at low signal amplitude, the omission of higher modes can influence posterior probability distributions. We discuss the impact of our results on source population inference and self-consistency tests of general relativity. Our work can be used to better understand asymmetric binary black hole merger events, such as GW190412. Higher modes are critical for such systems, and their omission usually produces substantial parameter biases
Distinguishing black-hole spin-orbit resonances by their gravitational-wave signatures
Effective Potentials and Morphological Transitions for Binary Black Hole Spin Precession
We derive an effective potential for binary black-hole (BBH) spin precession
at second post-Newtonian order. This effective potential allows us to solve the
orbit-averaged spin-precession equations analytically for arbitrary mass ratios
and spins. These solutions are quasiperiodic functions of time: after a fixed
period the BBH spins return to their initial relative orientations and jointly
precess about the total angular momentum by a fixed angle. Using these
solutions, we classify BBH spin precession into three distinct morphologies
between which BBHs can transition during their inspiral. We also derive a
precession-averaged evolution equation for the total angular momentum that can
be integrated on the radiation-reaction time and identify a new class of
spin-orbit resonances that can tilt the direction of the total angular momentum
during the inspiral. Our new results will help efforts to model and interpret
gravitational waves from generic BBH mergers and predict the distributions of
final spins and gravitational recoils.Comment: 5 pages, 2 figures, PRL accepted versio
Multiband gravitational-wave event rates and stellar physics
Joint gravitational-wave detections of stellar-mass black-hole binaries by ground- and space-based observatories will provide unprecedented opportunities for fundamental physics and astronomy. We present a semianalytic method to estimate multiband event rates by combining selection effects of ground-based interferometers (like LIGO/Virgo) and space missions (like LISA). We forecast the expected number of multiband detections first by using information from current LIGO/Virgo data, and then through population synthesis simulations of binary stars. We estimate that few to tens of LISA detections can be used to predict mergers detectable on the ground. Conversely, hundreds of events could potentially be extracted from the LISA data stream using prior information from ground detections. In general, the merger signal of binaries observable by LISA is strong enough to be unambiguously identified by both current and future ground-based detectors. Therefore third-generation detectors will not increase the number of multiband detections compared to LIGO/Virgo. We use population synthesis simulations of isolated binary stars to explore some of the stellar physics that could be constrained with multiband events, and we show that specific formation pathways might be overrepresented in multiband events compared to ground-only detections
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