Astrophysics and Space Science最新文献

We compute the linearised dispersion relations of shear waves, heat waves, and sound waves in relativistic “matter+radiation” fluids with grey absorption opacities. This is done by solving radiation hydrodynamics perturbatively in the ratio “radiation stress-energy”/“matter stress-energy”. The resulting expressions (omega , {=} , omega (k)) accurately describe the hydrodynamic evolution for any (k, {in }, mathbb{R}). General features of the dynamics (e.g., covariant stability, propagation speeds, and damping of discontinuities) are argued directly from the analytic form of these dispersion relations.

An unmagnetized plasma system comprising Maxwellian electrons, nonthermal ions, and variable negative charged dust grains is considered to investigate the consequence of head-on collision (such as interaction processes, and phase shifts) and the formation of dust acoustic soliton as well as shock structures in the Halley’s Comet (HC), Interstellar Clouds (IC), Noctilucent Clouds (NC), and Saturn’s Spokes (SS) environments. The two-sided Korteweg de Vries Burger (KdVB) and Korteweg de Vries (KdV) equations and corresponding phase shifts are derived employing the extended Poincaré-Lighthill-Kuo (ePLK) reductive perturbation technique (ePLKRPT). The coefficient of nonlinearities vanishes in each environment at the critical value of the plasma parameters. Consequently, the nonlinearity-coupled modified KdVB (mKdVB) and modified KdV (mKdV) equations, and the associated phase shifts have been derived. The concerned parameters play a crucial role in forming soliton and shock structures, phase shifts, and the interaction process of solitons and shocks in each environment. The compressive hump-shaped structures for mKdV solitons, as well as only positive phase shifts, are produced due to the influences of concerned parameters in each environment. In the collision processes, both the KdV and mKdV dust acoustic solitons follow the principle of superposition, but the shocks do not follow the principle of superposition.

In this study, we explore the dynamics of Bianchi type-III space-time within the framework of (f(T)) gravity, focusing on both linear and non-linear forms of (f(T)) function. We analyze the behavior of cosmological parameters by assuming the deceleration parameter (DP) as a simple linear function of the Hubble parameter. Key cosmological parameters such as the scale factor, Hubble parameter, DP, spatial volume, shear scalar, expansion scalar, energy density, pressure, and the equation of state (EoS) parameter are expressed in terms of the redshift parameter. Their dynamic behaviors are graphically presented for both linear and non-linear forms of (f(T)) gravity. Our results align with recent cosmological observations, with the non-linear form of (f(T)) exhibiting a stronger tendency toward accelerated cosmic expansion compared to the linear model. The EoS parameter indicates a quintessence phase, driving the universe’s accelerated expansion, as recently investigated by Varshney et al. (Can. J. Phys. 102(3):199–209, 2023). Additionally, we examine the violation of the strong energy conditions, a crucial aspect in modified gravity theories. The model parameter (xi ) and the current value of the Hubble parameter (H_{0}) are estimated using the Hubble data set and Pantheon+ SHOES data set, further validating our theoretical model.

In this paper, we investigated the orbital elements and stellar parameters of resolved spectroscopic binary systems. It is shown that resolved spectroscopic binary stars are an important (and sometimes indispensable) source of information on the distances to stars. We have compiled a comprehensive catalog of resolved spectroscopic binaries and conducted statistical analysis on 173 stars from this catalog. As a result, we have constructed distributions for orbital elements and component masses. In particular, it is shown that orbital parallaxes are preferable to trigonometric parallaxes in a certain semi-major axis ((a >) 26-27 AU) and brightness (V > 9-10 mag) range. Also, trigonometric parallaxes of distant ((d > approx )1 kpc) binaries seem to be overestimating the distance. We have shown also that the resolved spectroscopic binaries confirm the Zahn’s circularization theory.

Turbulence in astrophysical plasma transfers energy to kinetic scales, leading to proton acceleration or heating, yet the formation of suprathermal protons from such turbulence is not fully understood. While proton acceleration modeling based on the Fokker-Planck equation with diffusion through kinetic Alfvén waves (KAW) has been proposed to understand in-situ measurements of suprathermal protons in the interplanetary medium, more investigations using such modeling could help clarify the nature of particle acceleration in various astrophysical media beyond the interplanetary medium. Since the characteristics of KAW turbulence depend on the magnetization of the plasma system and the temperature anisotropy of the proton distribution function, proton acceleration mediated by KAW turbulence could also be influenced by these factors. By solving the Fokker-Planck equation, this study examines proton acceleration through KAW turbulence across strongly to weakly magnetized astrophysical plasmas, parameterized by plasma beta ((beta =0.01-10)), and the effects of proton temperature anisotropy. Particularly, our findings indicate that KAW turbulence significantly influences the presence of suprathermal protons in low-beta plasmas, such as the interplanetary medium, but is less impactful in high-beta environments, like the intergalactic and intracluster medium. Additionally, the proton temperature anisotropy significantly modulates the efficiency of proton diffusion in velocity space in low-beta environments.

The first-born neutron star in a binary system will function as a pulsar for a few million years, and then die a natural death as its period lengthens. During mass transfer from the companion star, the dead pulsar will be resurrected from its graveyard. In its reincarnation, the recycled pulsar will have a short rotation period and a much smaller magnetic field than at birth. Although this idea is more than forty years old, with the coming of age of gamma-ray astronomy and the detection of gravitational waves, recycled pulsars have assumed contemporary importance. This article is intended to be a review of the recycling scenario – a history of the seminal ideas and the underlying physics.

Sun-Earth co-orbital motions have an important value in deep space explorations due to their unique orbital characteristics and spatial configurations. In this paper, we investigate the influence of the solar radiation pressure (SRP) on the Sun-Earth co-orbital motion. Firstly, we derive several analytical formulas of the effect of the SRP on orbital elements. Then, based on the analytical results, the orbital variables of perturbed distant retrograde orbits (DROs) and perturbed tadpole (TP) orbits around triangular libration points are studied, and the validity of those conclusions is demonstrated by numerical integration. Finally, we derive an approximate expression to analyze the drift trend of triangular libration points under the SRP and explain the drift phenomena of libration centers of perturbed co-orbital motions. The conclusions obtained in this paper could be used to design control laws of the perturbed Sun-Earth co-orbital motion in the future.

Research on the dynamics of multi-body motion in the Earth-Moon space is a crucial area in current spacecraft motion studies. Distant Retrograde Orbits (DROs) are highly valuable trajectories in the Earth-Moon space. Under the ephemeris model, DROs will become quasi-periodic. Efficiently computing quasi-periodic DROs in the ephemeris model is a pressing issue. This paper addresses the problems of high computational time cost and significant divergence over multiple orbit cycles when calculating quasi-periodic DROs under the ephemeris model and proposes an adaptive two-level differential correction algorithm based on differential evolution. The traditional two-level differential correction selects patch points at equal intervals, while the DRO states are different with different amplitudes, choosing patch points at equal intervals is simple but not suitable for most DRO. Each quasi-periodic DRO should have its own patch points position. The adaptive two-level differential correction algorithm firstly uses differential evolution to obtain the optimal solution of the position of the patch points and then two-level differential correction is played. This algorithm significantly improving both computational efficiency and orbital convergence. Simulation results show that this algorithm significantly reduces computational costs and achieves better convergence compared to traditional two-level differential correction algorithm. This study has a reference value for the design of long-term quasi-periodic DRO, and provides a new idea for the selection strategy of patch points in the two-level differential correction algorithm and the multiple shooting algorithm.

The Core Accretion model is widely accepted as the primary mechanism for forming planets up to a few Jupiter masses. However, the formation of super-massive planets remains a subject of debate, as their formation via the Core Accretion model requires super-solar metallicities. Assuming stellar atmospheric abundances reflect the composition of protoplanetary disks, and that disk mass scales linearly with stellar mass, we calculated the total amount of metals in planet-building materials that could contribute to the formation of massive planets. In this work, we studied a sample of 172 Jupiter-mass planets and 93 planets with masses exceeding 4 (M_{jupiter}). Our results consistently demonstrate that planets with masses above 4 (M_{jupiter}) form in disks with at least as much metal content as those hosting planets with masses between 1 and 4 (M_{jupiter}), often with slightly higher metallicity, typically exceeding that of the proto-solar disk. We interpret this as strong evidence that the formation of very massive Jupiters is feasible through Core Accretion and encourage planet formation modelers to test our observational conclusions.

This article explores the late-time acceleration phase of the universe through a novel (f(R,L_{m},T)) gravity model, particularly, (fleft (R,L_{m},Tright ) = R + alpha T + 2beta L_{m} ), where (alpha ) and (beta ) are free parameters of the model, in the presence of viscous fluid. We obtain the corresponding analytical solution and then we establish the constrain on arbitrary parameters of the solution by considering the Cosmic chronometers and Panthoen+SH0ES data. Further, we analyze the behavior of the obtained constrained solution through the deceleration, effective equation of state, and the Om diagnostic test. We find that the present (fleft (R,L_{m},Tright ) ) gravity model in the presence of viscous cosmic fluid successfully describe the late-time evolution phase of the universe with proper transition from the decelerated epoch to the accelerated one.