When and where did GW150914 form? Lamberts, A; Garrison-Kimmel, S; Clausen, D. R ...
Monthly Notices of the Royal Astronomical Society Letters,
11/2016, Letnik:
463, Številka:
1
Journal Article
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The recent LIGO detection of gravitational waves (GW150914), likely originating from the merger of two ∼ 30M⊙ black holes suggests progenitor stars of low metallicity (Z/Z⊙ ≲ 0.3), constraining when ...and where the progenitor of GW150914 may have formed. We combine estimates of galaxy properties (star-forming gas metallicity, star formation rate and merger rate) across cosmic time to predict the low redshift black hole – black hole merger rate as a function of present day host galaxy mass, M
gal, the formation redshift of the progenitor system z
f and different progenitor metallicities Z
p. For
$Z_\mathrm{p}\geqslant 0.1 \rm Z_{{\odot }}$
, the signal is dominated by binaries in massive galaxies with z
f ≃ 2 while below
$Z_\mathrm{p}\leqslant 0.1\rm Z_{{\odot }}$
most mergers come from binaries formed around z
f ≃ 0.5 in dwarf galaxies. Additional gravitational wave detections from merging massive black holes will provide constraints on the mass–metallicity relation and massive star formation at high redshifts.
ABSTRACT
A handful of binary Wolf–Rayet stars are known to harbour spectacular spiral structures spanning a few hundred astronomical units. These systems host some of the highest dust production ...rates in the Universe and are therefore interesting candidates for addressing the origin of the enigmatic dust excess observed across galactic evolution. The substantial interaction between the winds of a Wolf–Rayet star and its companion constitutes a unique laboratory in which to study the mechanisms of dust nucleation in a hostile environment. Using the grid-based ramses code, we investigate this problem by performing a 3D hydrodynamic simulation of the inner region of the prototypical spiral nebula around WR 104. We then process the ramses results using the radiative transfer code RADMC3d to generate a candidate observable scene. This allows us to estimate the geometrical parameters of the shocked region. We link these quantities to the specific chemical pathway for dust nucleation, where the hydrogen-rich companion’s wind catalyses dust formation. The scaling laws we derive constitute a unique tool that can be directly compared with observations. Depending on the dust nucleation locus, the velocity field reveals a differential wind speed, implying that the initial dust speed could be more balanced between the speeds of the two stellar winds ($\sim$1600 km s–1). With RA DMC3d, we provide constraints on the dust nucleation radius for different combinations of the dust-to-gas ratio, hydrogen fraction, and dust grain properties. Finally, our models reveal that dust may escape beyond the boundaries of the spiral owing to hydrodynamical instabilities in the wind collision zone.
Abstract
The X-ray light curves of the early afterglow phase from gamma-ray bursts (GRBs) present a puzzling variability, including flares. The origin of these flares is still debated, and often ...associated with a late activity of the central engine. We discuss an alternative scenario where the central engine remains short-lived and flares are produced by the propagation of a long-lived reverse shock in a stratified ejecta. Here we focus on the hydrodynamics of the shock interactions. We perform one-dimensional ultrarelativistic hydrodynamic simulations with different initial internal structure in the GRB ejecta. We use them to extract bolometric light curves and compare with a previous study based on a simplified ballistic model. We find a good agreement between both approaches, with similar slopes and variability in the light curves, but identify several weaknesses in the ballistic model: the density is underestimated in the shocked regions, and more importantly, late shock reflections are not captured. With accurate dynamics provided by our hydrodynamic simulations, we confirm that internal shocks in the ejecta lead to the formation of dense shells. The interaction of the long-lived reverse shock with a dense shell then produces a fast and intense increase of the dissipated power. Assuming that the emission is due to the synchrotron radiation from shock-accelerated electrons, and that the external forward shock is radiatively inefficient, we find that this results in a bright flare in the X-ray light curve, with arrival times, shapes, and duration in agreement with the observed properties of X-ray flares in GRB afterglows.
ABSTRACT
With its last observing run, the LIGO, Virgo, and KAGRA collaboration has detected almost one hundred gravitational waves from compact binary coalescences. A common approach to studying the ...population properties of the observed binaries is to use phenomenological models to describe the spin, mass, and redshift distributions. More recently, with the aim of providing a clearer link to astrophysical processes forming the observed compact binaries coalescences, several authors have proposed to employ synthetic catalogues for population studies. In this paper, we review how to employ and interpret synthetic binary catalogues for gravitational-wave progenitors studies. We describe how to build multichannel merger rates and describe their associated probabilities focusing on stellar progenitor properties. We introduce a method to quantify the match between the phenomenological reconstruction of merger rates with synthetic catalogues. We detail the implementation of synthetic catalogues for multichannel hierarchical Bayesian inference, highlighting computational aspects and issues related to hyper-prior choice. We find that when inferring stellar progenitors’ properties from gravitational-wave observations, the relative efficiency in compact objects production should be taken into account. Finally, by simulating binary black hole detections with LIGO and Virgo sensitivity expected for the O4 observing run, we present two case studies related to the inference of the common envelope efficiency and progenitor metallicity of the binary black holes. We finally discuss how progenitors’ properties can be linked to binary black hole properties.
Context. The collision of winds from massive stars in binaries results in the formation of a double-shock structure with observed signatures from radio to X-rays. Aims. We study the structure and ...stability of the colliding wind region as it turns into a spiral owing to the orbital motion. We focus on adiabatic winds, where mixing between the two winds is expected to be restricted to the Kelvin-Helmholtz instability. Mixing of the Wolf-Rayet wind with hydrogen-rich material is important for dust formation in pinwheel nebulae such as WR 104, where the spiral structure has been resolved in infrared. Methods. We use the hydrodynamical code RAMSES to solve the equations of hydrodynamics on an adaptive grid. A wide range of binary systems with different wind velocities and mass-loss rates are studied with two-dimensional simulations. A specific three-dimensional simulation is performed to model WR 104. Results. Orbital motion leads to the formation of two distinct spiral arms where the Kelvin-Helmholtz instability develops differently. We find that the spiral structure is destroyed when there is a large velocity gradient between the winds, unless the collimated wind is much faster. We argue that the Kelvin-Helmholtz instability plays a major role in determining whether the structure is maintained. We discuss the consequences for various colliding-wind binaries. When their spiral structure is stable, there is no straightforward relationship between the spatial step of the spiral, the wind velocities, and the orbital period. Our 3D simulation of WR 104 indicates that the colder, well-mixed trailing arm has more favourable conditions for dust formation than the leading arm. The single-arm infrared spiral follows more closely the mixing map than the density map, suggesting that the dust-to-gas ratio may vary between the leading and trailing density spirals. However, the density is much lower than what dust formation models require. Including radiative cooling would lead to higher densities, and also to thin shell instabilities whose impact on the large-scale structure remains unknown.
Background
Non‐bullous pemphigoid (NBP) is a pemphigoid variant which frequently resembles other pruritic skin diseases. In contrast with bullous pemphigoid (BP), blisters are absent. In BP, previous ...studies showed that IgE autoantibodies may be involved in its pathogenesis. IgE‐activated mast cells, basophils and eosinophils may participate in BP by inducing pruritus and possibly blister formation, although the differential role of IgE in NBP compared with BP has not yet been described.
Objective
To assess IgE in serum and skin of NBP and BP patients.
Methods
We examined total IgE and pemphigoid‐specific IgE in the serum of 68 NBP and 50 BP patients by enzyme‐linked immunosorbent assay (ELISA). Sera of 25 pemphigus patients and 25 elderly patients with pruritus were included as controls. Skin biopsies of 14 NBP and 14 BP patients with the highest IgE titres to NC16A were stained for IgE by immunofluorescence techniques.
Results
Total IgE was elevated in 63% of NBP and 60% of BP patients, and in 20% of pemphigus controls, as well as 60% of elderly controls. IgE ELISAs were more frequently positive in BP than in NBP (NC16A 18% vs. 9%, P = 0.139; BP230 34% vs. 22%, P = 0.149). IgE ELISAs for NC16A and BP230 were positive in 8% and 20% of elderly controls, respectively, while all pemphigus controls were negative. Two of 28 biopsies (7%; one NBP, one BP) showed linear IgE along the basement membrane zone, while in most biopsies (71% NBP; 86% BP) IgE was bound to dermal cells.
Conclusion
Since IgE was present in the serum and skin of both NBP and BP patients, this supports IgE‐dependent mechanisms common to both diseases, such as pruritus. However, it remains to be elucidated whether IgE contributes to blister formation in BP.
Linked Commentary: I. Kortekaas Krohn. J Eur Acad Dermatol Venereol 2021; 35: 781–782. https://doi.org/10.1111/jdv.17164.
We investigate the hydrodynamics of the interaction of two supersonic winds in binary systems. The collision of the winds creates two shocks separated by a contact discontinuity. The overall ...structure depends on the momentum flux ratio η of the winds. We use the code ramses with adaptive mesh refinement to study the shock structure up to smaller values of η, higher spatial resolution and greater spatial scales than have been previously achieved. 2D and 3D simulations, neglecting orbital motion, are compared to widely used analytic results and their applicability is discussed. In the adiabatic limit, velocity shear at the contact discontinuity triggers the Kelvin-Helmholtz instability. We quantify the amplitude of the resulting fluctuations and find that they can be significant even with a modest initial shear. Using an isothermal equation of state leads to the development of thin shell instabilities. The initial evolution and growth rates enables us to formally identify the non-linear thin shell instability (NTSI) close to the binary axis. Some analogue of the transverse acceleration instability is present further away. The NTSI produces large amplitude fluctuations and dominates the long-term behaviour. We point out the computational cost of properly following these instabilities. Our study provides a basic framework to which the results of more complex simulations, including additional physical effects, can be compared.
Context. Gamma-ray binaries are composed of a massive star and a rotation-powered pulsar with a highly relativistic wind. The collision between the winds from both objects creates a shock structure ...where particles are accelerated, which results in the observed high-energy emission. Aims. We want to understand the impact of the relativistic nature of the pulsar wind on the structure and stability of the colliding wind region and highlight the differences with colliding winds from massive stars. We focus on how the structure evolves with increasing values of the Lorentz factor of the pulsar wind, keeping in mind that current simulations are unable to reach the expected values of pulsar wind Lorentz factors by orders of magnitude. Methods. We use high-resolution numerical simulations with a relativistic extension to the hydrodynamics code RAMSES we have developed. We perform two-dimensional simulations, and focus on the region close to the binary, where orbital motion can be neglected. We model different values of the Lorentz factor of the pulsar wind, up to 16. Results. We determine analytic scaling relations between stellar wind collisions and gamma-ray binaries. They provide the position of the contact discontinuity. The position of the shocks strongly depends on the Lorentz factor. We find that the relativistic wind is more collimated than expected based on non-relativistic simulations. Beyond a certain distance, the shocked flow is accelerated to its initial velocity and follows adiabatic expansion. Finally, we provide guidance for extrapolation towards more realistic values of the Lorentz factor of the pulsar wind. Conclusions. We extended the adaptive mesh refinement code RAMSES to relativistic hydrodynamics. This code is suited to studying astrophysical objects, such as pulsar wind nebulae, gamma-ray bursts, or relativistic jets, and will be part of the next public release of RAMSES. Using this code we performed simulations of gamma-ray binaries up to Γp = 16 and highlighted the limits and possibilities of current hydrodynamical models of gamma-ray binaries.
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