New Astronomy最新文献

In this study, we build a charged star model with three layers with distinct equations of state. The core, intermediate layer, and envelope layer obey linear, polytropic, and Chaplygin equations of state, respectively. The model satisfies the physical requirements for the matter variables, gravitational potentials, and stability conditions. We have generated within-acceptable range masses and radii for stars. We also recover the masses and radii for the stars PSRJ1903+0327, PSRJ1614-2230, SAXJ1808.4-3658, Vela X-1, and EXO1785-248 from earlier investigations which shows astrophysical significance of our model.

The accuracy of absolute parameters’ estimation in contact binary systems is important for investigating their evolution and solving some challenges. The Gaia DR3 parallax is one of the methods used for estimating the absolute parameters, in cases where photometric data is the only one that is available. The use of this method includes advantages and limitations that we have described and examined in this study. We selected 48 contact binary systems whose mass ratios were mostly obtained by spectroscopic data, in addition to a number of photometric studies. The target systems were suitable for $A_V$ and the Re-normalized Unit Weight Error (RUWE), and their absolute parameters were calculated based on Gaia DR3 parallax, observational information, orbital period, and light cure solution from the literature and catalogs. The outcomes of OO Aql differed significantly from those reported in the literature. Upon analyzing the system’s light curve with TESS data, we concluded that the stars’ temperatures were the reason for this difference, and utilizing Gaia DR3 parallax provided reasonable results. We displayed the target systems on the Hertzsprung–Russell (HR), $q-L_{ratio}$, $P-M_V$, and $log{M}_{tot}-log{J}_0$ diagrams, and the systems are in good agreement with the theoretical fits. We showed that the estimation of absolute parameters with this method might be acceptable if $\Delta a\left(R_{\odot }\right)$ is less than $\sim 0.1\left(R_{\odot }\right)$. There are open questions regarding the existence of $l_3$ in the light curve analysis and its effect on the estimation of absolute parameters with this method.

In this study, we investigate the FRW model in the Chern–Simons modified gravity framework, considering holographic dark energy and Kaniadakis holographic dark energy models. Employing the field equation of Chern–Simons gravity, it is analyzed some important cosmological parameters such as density, equation of state, and deceleration parameters for both models. Our findings, presented visually through graphs, reveal that holographic dark energy places the equation of state within $\omega \in (-1,-0.4)$, while Kaniadakis holographic dark energy spans $\omega \in (-0.8,-0.4)$. These results demonstrate the dynamic nature of dark energy’s influence. Our study highlights the interplay of quintessence and $\Lambda \mathrm{CDM}$ across cosmic eras. We identify the ranges of $q\in (-0.89,-0.86)$ and $q\in (-0.9925,-0.9922)$ for Kaniadakis holographic dark energy and holographic dark energy, offering insights into their roles in cosmic inflation which implies that the universe attributes are impacted by both quintessence and the $\Lambda$CDM model in Chern–Simons modified gravity. In addition, this study implies that the universe’s expansion is decelerating in its current state.

This paper introduces an astronomical image alignment algorithm. This algorithm uses the means of the rows and columns of the original image for alignment, and finds the optimal offset corresponding to the maximum similarity by comparing different offsets between images. The similarity is evaluated by the standard deviation of the quotient divided by the means. This paper also discusses the theoretical feasibility of this algorithm. Through practical testing, it has been confirmed that the algorithm is fast and robust.

This paper is devoted to study the thermodynamic topological defects, Joule–Thomson ($J-T$) and Maxwell’s equal area law of Phantom RN AdS black holes (BHs). The inversion temperatures and inversion curves are obtained and by using the isenthalpic curves in the temperature–pressure ($T-P$) plane to locate the cooling and heating regions. Using Maxwell’s equal-area law, we select different independent conjugate variables to study the phase transitions of Phantom RN AdS BHs. We find that phase transition rely on the electric potential and horizon radius of the BH when its charge is constant. Phase transition of Phantom RN AdS BH are proportional to the ratio of event horizon to its cosmological constant, where the latter is assumed to be constant. Moreover, we consider the Phantom RN AdS BH as defects with a topological nature within thermodynamic domain and examine the local and global topology by computing the winding numbers at the defects, which concludes that the overall topological charge is either equal to 0 or 1.

The current paper presents a double-layered neutral anisotropic stellar model in general relativistic setting. The model is developed by using Einstein field equations and class I embedding condition. We consider the core with quark matter obeying linear equation of state and envelope layer with gaseous matter admitting Chaplygin gas equation of state. The interior and exterior metric coefficients match smoothly at the interface of core and envelope layers and at the stellar surface. The profiles for matter variables, stability and energy conditions show acceptable trend for physical stellar models. In this model, stellar masses and radii consistent with compact stars HerX-1, 4U1538-52, SAXJ1808.4-3658, CenX-3 and SMCX-1 are generated. We note that studies of multi-layered stars with gaseous envelope and embedding class I condition are missing in investigations conducted in the past.

The detection and statistical analysis of molecular clumps can provide important clues for understanding star formation. In order to improve the reliability of candidates identified by molecular clump detection algorithm, we present a molecular clump verification network (called MCVnet) based on supervised learning in this paper. First, a molecular clump detection algorithm is used to identify the candidates for the clumps. Then the confidence level of each candidate clump is calculated using the MCVnet. Finally, the clumps are classified into three classes (”Yes”,”No”,”Uncertain”) according to the output confidence. The automatic verification algorithm eliminates the clump candidates with low confidence, thus improving the accuracy of the final detection performance. The validation effect of MCVnet is verified in the Milky Way Imaging Scroll Painting (MWISP) project within the region l=+180${}^{\circ }$ to +190${}^{\circ }$, b=-5${}^{\circ }$ to +5${}^{\circ }$ and v=-200 km s⁻¹ to +200 km s⁻¹. The experimental results show that the precision of MCVnet agree with the manual verification by more than 90%, which illustrates the effectiveness of the method in this paper for clump verification. Moreover, the combination of Local Density Clustering (LDC) and MCVnet increases the accuracy of LDC.

The main objective of this article is to study the fractal FRW cosmological model consisting two forms of dark energy. We studied behavior of the universe in a fractal framework using dark energy accommodated in our universe. The solution of field equations are obtained by using Hubble parameter for transit scale factor $H\left(z\right)=ϵ\left(a^{-\delta }+\lambda \right)$ . We have obtained the best fitting values of the model parameters $ϵ,\delta$ and $\lambda$ by constraining our model with latest Hubble and SNe-Ia data sets . Finally we perform state-finder diagnosis and observe that obtained model close to standard $\Lambda$CDM model.

Weak gravitational lensing of the primary scalar hair black hole is proposed within this work. We can figure out the deflection angle of light by applying the Gibbons and Werner approach with a primary scalar hair black hole. To do this, we compute the Gaussian curvature and find the deflection angle of the weak field limits by applying Gauss-Bonnet theorem. Furthermore, we compute the deflection angle of light when it comes across both plasma and non-plasma field. We also study how the deflection angle behaves graphically in both cases.

The main objective of this manuscript is to investigate the bouncing cosmology in the background of $f\left(Q\right)$ gravity, where $Q$ defines the non-metricity. For this purpose, we use the reconstruction approach and consider a flat Friedmann–Robertson–Walker spacetime with perfect matter configuration. We examine how the first contracting phase gives the expansion by using a temporal derivative of the scale factor, i.e., $\dot{a}<0$, $\dot{a}=0$ and $\dot{a}>0$ give contraction, bounce point and expansion phases, respectively. Further, we use the order reduction method to solve the modified field equations as these are very difficult due to the presence of additional non-linear expressions. It is analyzed that the original singularity of the universe diminishes for the required bounce conditions. We conclude that the acceleration occurs near the bouncing point and the considered $f\left(Q\right)$ models are consistent with the current cosmic accelerated expansion.