The birth kicks of black holes, arising from asymmetric mass ejection or neutrino emission during core-collapse supernovae, are of great interest for both observationally constraining supernova ...models and population-synthesis studies of binary evolution. Recently, several efforts were undertaken to estimate black hole birth kicks from observations of black hole low-mass X-ray binaries. We follow up on this work, specifically focusing on the highest estimated black hole kick velocities. We find that existing observations do not require black hole birth kicks in excess of approximately 80 km s−1, although higher kicks are not ruled out.
We combine the gravitational-wave measurement of the effective distance to the binary neutron star merger GW170817, the redshift of its host galaxy NGC 4993, and the latest Hubble constant ...measurement from the Dark Energy Survey to constrain the inclination between the orbital angular momentum of the binary and the line of sight to 18° 8° (less than 28° at 90% confidence). This provides a complementary constraint on models of potential afterglow observations.
ABSTRACT
Based on recent results from three-dimensional supernova simulations and semi-analytical parametrized models, we develop analytical prescriptions for the dependence of the mass of neutron ...stars and black holes and the natal kicks, if any, on the pre-supernova carbon–oxygen core and helium shell masses. Our recipes are probabilistic rather than deterministic in order to account for the intrinsic stochasticity of stellar evolution and supernovae. We anticipate that these recipes will be particularly useful for rapid population synthesis, and we illustrate their application to distributions of remnant masses and kicks for a population of single stars.
We explore a newly proposed channel to create binary black holes of stellar origin. This scenario applies to massive, tight binaries where mixing induced by rotation and tides transports the products ...of hydrogen burning throughout the stellar envelopes. This slowly enriches the entire star with helium, preventing the build-up of an internal chemical gradient. The stars remain compact as they evolve nearly chemically homogeneously, eventually forming two black holes, which we estimate typically merge 4–11 Gyr after formation. Like other proposed channels, this evolutionary pathway suffers from significant theoretical uncertainties, but could be constrained in the near future by data from advanced ground-based gravitational-wave detectors. We perform Monte Carlo simulations of the expected merger rate over cosmic time to explore the implications and uncertainties. Our default model for this channel yields a local binary black hole merger rate of about 10 Gpc−3 yr−1 at redshift z = 0, peaking at twice this rate at z = 0.5. This means that this channel is competitive, in terms of expected rates, with the conventional formation scenarios that involve a common-envelope phase during isolated binary evolution or dynamical interaction in a dense cluster. The events from this channel may be distinguished by the preference for nearly equal-mass components and high masses, with typical total masses between 50 and 110 M⊙. Unlike the conventional isolated binary evolution scenario that involves shrinkage of the orbit during a common-envelope phase, short time delays are unlikely for this channel, implying that we do not expect mergers at high redshift.
Abstract
Binary black holes (BBHs) may form both through isolated binary evolution and through dynamical interactions in dense stellar environments. The formation channel leaves an imprint on the ...alignment between the BH spins and the orbital angular momentum. Gravitational waves (GW) from these systems directly encode information about the spin–orbit misalignment angles, allowing them to be (weakly) constrained. Identifying subpopulations of spinning BBHs will inform us about compact binary formation and evolution. We simulate a mixed population of BBHs with spin–orbit misalignments modelled under a range of assumptions. We then develop a hierarchical analysis and apply it to mock GW observations of these populations. Assuming a population with dimensionless spin magnitudes of χ = 0.7, we show that tens of observations will make it possible to distinguish the presence of subpopulations of coalescing binary black holes based on their spin orientations. With 100 observations, it will be possible to infer the relative fraction of coalescing BBHs with isotropic spin directions (corresponding to dynamical formation in our models) with a fractional uncertainty of ∼40 per cent. Meanwhile, only ∼5 observations are sufficient to distinguish between extreme models – all BBHs either having exactly aligned spins or isotropic spin directions.
Gravitational-wave detections are enabling measurements of the rate of coalescences of binaries composed of two compact objects—neutron stars and/or black holes. The coalescence rate of binaries ...containing neutron stars is further constrained by electromagnetic observations, including Galactic radio binary pulsars and short gamma-ray bursts. Meanwhile, increasingly sophisticated models of compact objects merging through a variety of evolutionary channels produce a range of theoretically predicted rates. Rapid improvements in instrument sensitivity, along with plans for new and improved surveys, make this an opportune time to summarise the existing observational and theoretical knowledge of compact-binary coalescence rates.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
In the past five years, the number of known double neutron stars (DNSs) in the Milky Way has roughly doubled. We argue that the observed sample can be split into three distinct subpopulations based ...on their orbital characteristics: (i) short-period, low-eccentricity binaries; (ii) wide binaries; and (iii) short-period, high-eccentricity binaries. These subpopulations also exhibit distinct spin period and spindown rate properties. We focus on subpopulation (iii), which contains the Hulse-Taylor binary. Contrary to previous analysis, we demonstrate that, if they are the product of isolated binary evolution, the Porb and e distribution of these systems requires that the second-born NSs must have been formed with small natal kicks ( 25 km s−1) and have pre-SN masses narrowly distributed around 3.2 M . These constraints challenge binary evolution theory and further predict closely aligned spin and orbital axes, inconsistent with the Hulse-Taylor binary's measured spin-orbit misalignment angle of 20°. Motivated by the similarity of these DNSs to B2127+11C, a DNS residing in the globular cluster M15, we argue that this subpopulation is consistent with being formed in, and then ejected from, globular clusters. This scenario provides a pathway for the formation and merger of DNSs in stellar environments without recent star formation, as observed in the host galaxy population of short gamma-ray bursts and the recent detection by LIGO of a merging DNS in an old stellar population.
Abstract
Rapidly growing catalogs of compact binary mergers from advanced gravitational wave detectors allow us to explore the astrophysics of massive stellar binaries. Merger observations can ...constrain the uncertain parameters that describe the underlying processes in the evolution of stars and binary systems in population models. In this paper, we demonstrate that binary black hole populations—in particular, their detection rates, chirp masses, and redshifts—can be used to measure cosmological parameters describing the redshift-dependent star formation rate and metallicity distribution. We present a method that uses artificial neural networks to emulate binary population synthesis computer models, and construct a fast, flexible, parallelizable surrogate model that we use for inference.
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.
In general relativity, the spacetimes of black holes have three fundamental properties: (i) they are the same, to the lowest order in spin, as the metrics of stellar objects; (ii) they are ...independent of mass when expressed in geometric units; and (iii) they are described by the Kerr metric. In this paper, we quantify the upper bounds on potential black-hole metric deviations imposed by observations of black-hole shadows and of binary black-hole inspirals in order to explore the current experimental limits on possible violations of the last two predictions. We find that both types of experiments provide correlated constraints on deviation parameters that are primarily in the t t components of the spacetimes when expressed in areal coordinates. We conclude that, currently, there is no evidence for deviations from the Kerr metric across the 8 orders of magnitude in mass and 16 orders in curvature spanned by the two types of black holes. Moreover, because of the particular masses of black holes in the current sample of gravitational-wave sources, the correlations imposed by the two experiments are aligned and of similar magnitudes when expressed in terms of the far-field, post-Newtonian predictions of the metrics. If a future coalescing black-hole binary with two low-mass (e.g., ∼ 3 M⊙) components is discovered, the degeneracy between the deviation parameters can be broken by combining the inspiral constraints with those from the black-hole shadow measurements.
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