Astrophysics and Space Science最新文献

In this paper, an efficient wavelet-based algorithm is introduced to investigate the approximate solutions for a few nonlinear singular initial value problems arising in astrophysics. Ultraspherical wavelet method (USWM) is utilized for solving the Lane-Emden type equations. The proposed method is utilized to convert the given nonlinear singular value differential equations into a system of algebraic equations using operational matrices of derivatives. Convergence analysis of the method is discussed. The obtained solutions are compared with LWM, CWM and exact solutions. A few numerical experiments are given to demonstrate the accuracy and efficiency of the proposed method. Satisfactory agreement with exact and other numerical solutions is observed. The efficiency of the proposed method is confirmed by means of computational CPU runtime. Moreover, the use of USWM is investigated to be simple, accurate and less computational cost.

We studied the dependence of selected structural and kinematic properties of early-type galaxies (ETGs) on their environments. The selected sample, extracted from the SDSS-DR17 MaNGA survey, consists of 946 ETGs in clusters (cETGs) and 288 isolated ETGs (iETGs) within a spectroscopic redshift (zleq 0.15). We investigated the distribution of these galaxies in the Fundamental Plane (FP), Kormendy Relation (KR), Faber-Jackson Relation (FJR) and the Mass-Size Relation (MSR). We found that massive galaxies, whose stellar masses (M_{*}> 10^{11}M_{odot }), are predominantly elliptical ((>65%)). The analysis of the four scaling relations showed that the effect of the host environment is negligible for massive ((M_{*}>10^{11.5}M_{odot })) ETGs, most likely because of their passive evolution through dry mergers and/or stellar aging. On the other hand, low-mass ETGs are influenced by their environment, where iETGs with (M_{*}<10^{10}M_{odot }) and velocity dispersion (sigma _{0}leq 100) km/sec are (25%) more luminous and (11.5%) larger than cETGs. Low-mass cETGs may have suffered processes that removed their gas content and hence quenched star formation while low-mass iETGs may have experienced a recent wet merger that triggered star formation and led to their, currently, observed low mass-to-light ratio. However, further spectral analysis is needed to confirm these findings.

On 28 January 2018, the High Energy Stereoscopic System (H.E.S.S.) reported a significant very-high-energy (VHE) gamma-ray activity, occurring nearly 11 days after the high-energy (HE) gamma-ray flare observed by Fermi-LAT from the blazar 3C 279. It has long been considered a candidate site for accelerating particles to ultra-high energies (UHE) and producing subsequent secondaries. Such an event can be crucial to explore the different phenomena of secondary production from the UHEs and viable to understand the energetics of the sources. Our study finds that the multi-wavelength flare, spanning UV, optical, X-rays, and HE gamma rays, originates from leptonic emissions, whereas the delayed VHE activity by proton synchrotron emission within the source, results from the extended duration of particle acceleration. To explain the prolonged electromagnetic emission, our model requires a magnetic field luminosity ((L^{prime }_{B})) (6.9 times 10^{43}) erg/sec, a proton luminosity ((L^{prime }_{p})) (1.2 times 10^{46}) erg/sec in the jet frame.

We have applied the effective field theory (EFT) approach to achieve the astrophysical s-factor for the transition to the first (2P_{1/2^{-}}) excited state of (^{7}Li) nucleus in the (^{3}H(alpha ,gamma )^{7}Li) radiative capture reaction. The (E_{1}) electrical transition from the (2S_{1/2}, 2P_{1/2}) and (3S_{1}) incoming states have studied in the range of (Eleq 1.5) MeV up to leading order (LO) in the presence of Coulomb effects. This work has been performed in continuation of our studies on the (^{3}H-alpha ) reaction for the transition to the ground (2P_{3/2^{-}}) state of (^{7}Li). Both the results have been summed up to obtain the (S_{34}(E)) and compared with the available theoretical and experimental data.

Magnetic holes (MHs) have been widely observed in astrophysical and space plasmas. However, due to the lack of reconstruction method, the effects of MH shape on electron distribution function and wave properties are still unclear. In this study, we report a series of MHs in Earth’s magnetotail. We particularly focus on two of them with the clearest data features, reconstruct their topologies using the Second-Order Taylor Expansion (SOTE) method, and find their shapes to be bulging and deflated. Comparatively, the bulging MH exhibits a donut electron distribution, which may be attributed to the combined effects of internal expansion-induced betatron cooling and boundary contraction-induced betatron acceleration, while the deflated MH presents a pancake electron distribution. The beam instability and temperature anisotropy inside the bulging MH also excite electron cyclotron waves and whistler waves, respectively, while the deflated MH does not exhibit these types of waves. All these findings help us understand the geometric properties and evolutions of MHs.

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.