New Astronomy最新文献

In the present work we consider three modified Chevallier–Polarski–Linder (CPL) models with considering non-cold dark matter in the background of homogeneous and isotropic FLRW space–time model. From the observational data set ((Pantheon+)+BAO+HST) we find that all the parameters involved in the models having equation of dark energy state ${\omega }_{de}={\omega }_0+{\omega }_1\frac{a}{{(1+a)}^p}$ (Model II) and ${\omega }_{de}={\omega }_0+{\omega }_1\frac{1-a}{{(1+a)}^p}$ (Model III) do not depend on $p$. We also find that for all the models equation of state for dark matter is almost same and observe that Model I is more preferable than the other two proposed models.

We analyzed the light curve of the total eclipse contact binary V1320 Cas, obtained reliable photometric solutions, confirmed it to be a W-type contact binary with a mass ratio of 3.404 and a contact degree of 23.9%, a cool spot is discovered on the less massive component. Orbital period analysis indicates that the period of V1320 Cas is decreasing at a rate of $\frac{dP}{dt}=1.78\times 10^{-7}$ day yr⁻¹, superimposed with a cyclic modulation with a period of 1.425 yr, long-term period decrease may be caused by the combination of mass transfer and angular momentum loss, and the cyclic modulation may be caused by the third companion. Using the photometric solutions and Gaia distance, we calculated the absolute physical parameters and plotted mass-luminosity and mass–radius diagrams to analyze the evolutionary status of V1320 Cas, the more massive component is a main sequence star, while the less massive component has higher luminosity and radius than those of main sequence stars with the same mass. With the decreasing orbital period, the two components of V1320 Cas will be gradually closer, while the binary may evolve toward deep contact.

This paper presents properties of the intracluster medium (ICM) in the environment of a cool core cluster Abell 2566 (redshift $z$ $=$ 0.08247) based on the analysis of 20 ks Chandra X-ray data. 2D imaging analysis of the Chandra data from this cluster revealed spiral structures in the morphology of X-ray emission from within the central 109 kpc formed due to gas sloshing. This analysis also witness sharp edges in the surface brightness distribution along the south-east and north-west of the X-ray peaks at 41.6 kpc and 77.4 kpc, respectively. Spectral analysis of 0.5 – 7 keV X-ray photons along these discontinuities exhibited sharp temperature jumps from 2.3 to 3.1 keV and 1.8 to 2.8 keV, respectively, with consistency in the pressure profiles, implying their association with cold fronts due to gas sloshing of the gas. Further confirmation for such an association was provided by the deprojected broken power-law density function fit to the surface brightness distribution along these wedge shaped sectorial regions. This study also witness an offset of 4.6${}^{\prime \prime }$  (6.8 kpc) between the BCG and the X-ray peak, and interaction of the BCG with a sub-system in the central region, pointing towards the origin of the spiral structure due to a minor merger.

This study explores the impact of $f\left(\mathrm{G,T}\right)$ gravity, where $G$ is the Gauss Bonnet invariant and $T$ is the trace of the energy–momentum tensor, on the adiabatic anisotropic spherical gravitating source under the expansion-free condition. We coupled the relativistic matter with spherical symmetric structure by applying $f\left(\mathrm{G,T}\right)=\alpha G^n+\lambda T$ Gauss–Bonnet model with a linear trace. To derive the collapse equation, we used the perturbation method on the field equations and the contracted Bianchi identities. The dynamics of instability range is depicted in Newtonian ($N$) and post-Newtonian (pN) regimes. Furthermore, instead of using the adiabatic index, we establish the instability range by looking at the density profile and anisotropic pressure configuration. We investigate the analytic solutions that meets the expansion-free condition. Finally, we have successfully achieved the original results obtained by Herrera et al. (2012) in General Relativity by setting $\alpha =\lambda =0$ in proposed cosmological model.

This manuscript thoroughly explores the dynamics of a test particle around out-of-plane equilibrium points within the circular restricted eight-body problem. This particular scenario features a central primary emitting radiation, and it is a specific case derived from Kalvouridis and Hadjifotinou's analysis of Maxwell's ring problem in 2011. Our investigation uncovers two symmetrical out-of-plane equilibrium points denoted as E_1,2(0, 0, z₀), where z₀ is determined by the equation z₀ = ±a tanυ; υ = arcsin[(‒q/6)^1/3], with q falling within the range (‒6, 0). Here, a denotes the radius of the circular orbit of peripheral primaries around the radiating central primary, and q signifies the radiation factor due to the central primary. Significantly, for a critical radiation factor value, q_c = ‒3/√2, the equilibrium points E_1,2 precisely align along the z-axis on the sphere of radius a and centered at the central primary. Within the intervals of ‒6 < q < q_c and q_c < q < 0, equilibrium points E₁ and E₂ are situated outside and inside the mentioned sphere on the z-axis, respectively. Specifically, for q ≤ q_c, | z₀ | ≤ a, while for q > q_c, | z₀ | > a. The study further explores the linear stability of E_1,2. By analyzing characteristic curves derived from the variational equations of motion for infinitesimal mass around these equilibrium points, particularly for q values of ‒3/4, ‒3/√2, and ‒9√3/4, we observe that these out-of-plane equilibria, E_1,2, demonstrate linear instability. This insight provides a comprehensive understanding of the intricate dynamics in this specific multi-body problem. Finally, the research illustrates periodic orbits surrounding the out-of-plane equilibrium point for specific values of q.

The purpose of this study is to elaborate on the Morris–Thorne wormhole notion by creating a detailed model of a charged wormhole shape function. The classical embedding theory, which has played a significant role in the general theory of relativity, accomplishes this objective. Here, we assume redshift function along with charge i.e. $\psi (r,Q^2)=Log[1+\frac{Q^2}{r^2}]$ and $Q\left(r\right)=\xi \sqrt{r}$. For this particular choice, the surface redshift function remains positive and finite everywhere even for the larger range of radial coordinate $r$. In wormhole geometry, the violation of Null energy condition have a crucial role which leads to the exotic matter. We examined our solutions through energy bounds (Null, Weak and Strong energy bounds) to check their stable state and its viability. Interestingly, in present work we analyze that the presence of electric charge amplify the results and provides the traversable charged wormhole solutions without exotic matter near the throat in the context of general theory of relativity.

We study the radiation of the ultrarelativistic shell in the diffusion approximation, which takes place at the initial stage of a gamma-ray burst. We get the effective temperature, instantaneous and time-integrated spectra for the parabolic distribution of the initial internal energy of the shell. Also we considered the types of the equitemporal surfaces with a different type of the movement of the shell.

The light curves (LC(s)) of the shallow contact binary (SCB(s)) IR Vir were retrieved from the TESS, Kepler (K2), ASAS, ASAS-SN, and KWS databases and comprehensively analyzed in this paper. For IR Vir, a q search was conducted to determine the mass ratio, which was found to be $0.371\pm 0.008$. The analysis indicates that IR Vir was a typical A-type W UMa. Since the determination of absolute parameters is crucial for analyzing the evolution of such systems, the masses of the bodies of IR Vir were estimated as $M_1=1.03\pm 0.10$ M${}_{\odot }$, $M_2=0.38\pm 0.05$ M${}_{\odot }$, and the radii as $R_1=1.16\pm 0.06$ R${}_{\odot }$, $R_2=0.73\pm 0.04$ R${}_{\odot }$. In the analysis of the orbital period (OP(s)) for IR Vir, it was found that the OP of IR Vir was increasing, and this value was calculated to be 0.0376 s per year. The OP increase can be explained by the conserved mass exchange between the bodies, and it can be proposed to be from the low mass body to the more one. This value was calculated as $2.4\times 10^{-7}$ $M_{\odot }$ per year. Furthermore, a sinusoidal change in the OP was also identified, and it was proposed that this could be attributed to the presence of a third body or magnetic activity. Finally, to gain a better understanding of the nature of IR Vir, it was positioned in the logM${}_{tot}$ $-$ logJ and HR (Hertzsprung-Russell) diagrams.

We present light curve solution of V458 Mon firstly by using the Wilson-Devinney code. The total eclipse and deep minima of the light curves of V458 Mon enable us to determine reliable orbital parameters of the binary system. The solution suggests that V458 Mon is a low mass ratio binary system with about 0.2 possessing a moderate degree of contact. The long-term period investigation showed that the period of V458 Mon is increasing at $dP/dt=+2.59\times 10^{-7}days/yr$, which could be the reason of mass transfer from the less massive component to more massive primary one, together with a periodic change. The oscillation in orbital period may be due to an unseen tertiary companion with the mass about $M_3=1.8M_{\odot }$ . After removing these change, there is still a weak cyclic change maybe due to magnetic activity. With the increase in orbital period of binary, the separation increases and mass ratio decreases which eventually leads V458 Mon towards merger.

This paper studies the combined effects of radiation and galactic cosmic ray pressures on the gravitational instability of magnetized and rotating viscoelastic fluids. The dispersion relations are derived using the normal mode analysis and discussed in the hydrodynamic (weakly coupled fluid) and kinetic (strongly coupled fluid) limits. These dispersion relations are analyzed separately for transverse and longitudinal wave propagation modes. Jeans instability criteria are obtained for kinetic and hydrodynamic limits for both modes of wave propagation, and it is found that the critical Jeans wavenumbers in each case are modified due to the presence of viscoelastic effects, radiation and cosmic rays pressures, and Alfvên wave velocity. It is also observed that the radiation pressure, cosmic ray pressure and viscoelastic parameters suppress the growth rate and thus have stabilizing effects on the Jeans instability. However, cosmic ray diffusion has a destabilizing effect on the onset of gravitational instability. The effects of various parameters on the growth rate of instability are calculated numerically and the outcomes are depicted graphically. The results of the present analysis shall be helpful in understanding the impact of cosmic rays and radiative mechanisms on the gravitational collapse in the viscoelastic region of molecular cloud clumps.