New Astronomy最新文献

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.

We present BVR${}_C$+TESS differential photometry of an eclipsing binary system NSVS 2910034. A period analysis reveals unusual variations that are inconsistent with systemic orbital period changes and may be due to surface activity. The best fit models are consistent with a W-type W UMa overcontact binary, consisting of a less massive G7 spectral type star and a more massive K1 spectral type star. An O’Connell effect is present and analyzed. The best fit model represents a very large hot spot that may indicate significant chromospheric activity across a large portion of the stellar surface of the K star.

I identify a point-symmetric morphology of the supernova remnant (SNR) G352.7-0.1 and propose that the outer axially-symmetric structure is the remnant of a common envelope evolution (CEE) of the progenitor system, while the inner structure is the ejecta of a thermonuclear explosion triggered by the merger of a white dwarf (WD) and the core of an asymptotic giant branch (AGB) star. The main radio structure of SNR G352.7-0.1 forms an outer (large) ellipse. The bright X-ray emitting gas forms a smaller ellipse with a symmetry axis inclined to the symmetry axis of the large radio ellipse. The high abundance of iron and the energy of its X-ray lines suggest a type Ia supernova (SN Ia). The massive swept-up gas suggests a relatively massive progenitor system. I propose a scenario with progenitors of initial masses of $M_{\mathrm{ZAMS,1}}\simeq 5\text{–}7M_{\odot }$ and $M_{\mathrm{ZAMS,2}}\simeq 4\text{–}5M_{\odot }$. At a later phase, the WD remnant of the primary star and the AGB secondary star experience a CEE that ejects the circumstellar material that swept up more ISM to form the large elliptical radio structure. An explosion during the merger of the WD with the core of the AGB star triggered a super-Chandrasekhar thermonuclear explosion that formed the inner structure that is bright in X-ray. A tertiary star in the system caused the misalignment of the two symmetry axes. This study adds to the wide variety of evolutionary routes within the scenarios of normal and peculiar SNe Ia.

The second-largest outflow system on Mars is Kasei Valles. The southern branch of Kasei Valles includes two inner channels among the best-preserved examples of glacial and/or fluvial erosion. This study focuses on the landforms formed by surface processes within the midstream part of the southern branch of the Kasei Valles. We mapped the landforms and built a morpho-stratigraphical chronology using their cross-cutting relationships, and numerical crater dating. We interpret a complex geomorphological history, with various landforms in the study area, including fans, landslides, topographic barriers, strandlines, terraces and deeply incised canyons. Two coluvaial fans and a large landslide temporarily blocked the valles, forming topographical barriers to impound fluids (e.g., lava, mudflow, water). It has been suggested that the structures observed in the channels were formed by Bingham or Newtonian fluid. However, these fluids have disappeared but they have left the terraces and strandlines as their geomorphic imprints. The surface texture of the terraces implies that they were probably formed by a very low viscosity fluid that carved the fan, valley floor and formed terrace staircases and deep canyons. Crater statistics reveal two different temporal clusters of colluvial fan formation. The age of the older fan cluster in the Early Amazonian period, and the age of the younger fan cluster in the Late-Middle Amazonian period. The landslide is much younger and estimated to have formed 122 Ma ago, allowing us to constrain the timing of the latest erosional period. The youngest studied geomorphic features are the platy-textured deposits emplaced either as lavas or mudflows, aged 90 Ma, covering the floor of the valles. The strandlines defining the limits of the youngest erosional (thermal) process within the study area truncate the landslide but not the platy-textured features. Therefore, they are older than 90 Ma but younger than 122 Ma, implying environmental conditions sufficient to have allowed a liquid fluid body at the Martian surface during the Latest Amazonian period. Our data suggest that the presence of well-developed terraces between strandlines requires the presence of a fluid (e.g. water, liquid lava, mud) that ponded and subsequently evacuated from the study area.