New Astronomy最新文献

Solar radio bursts are sudden peaks in the low-frequency radio emissions originating from the sun. These emissions, while revealing important insights into underlying physical mechanisms in solar physics, can also help predict space weather events that could have adverse effects on satellite communications and the global energy grid. A thorough understanding of this phenomena demands the collection and analysis of solar emission data over vast geographical and time scales. In this regard, the e-CALLISTO network plays a major role through having already archived more than 20 years worth of solar radio burst data. Leveraging on the advances in data analysis techniques, this data can be used to review the statistical significance of burst properties of type II and type III solar radio bursts and hence more importantly the magnetic field measurements of the active regions. In order to process the e-CALLISTO data, a software containing several data reduction processes is introduced to optimize the data analysis via a graphical user interface (GUI). The program is capable of reading out data from any CALLISTO receiving station, while offering visualization capabilities such as the color-corrected spectrum view, the plot of frequencies of the highest intensity, the individual frequency spectrum, the solar burst isolation portal, the fitting model for the radio burst, and the drift rate curve of the burst. These are achieved through using the raw “fits” files of spectra to perform background RFI reduction, identify and isolate solar radio burst regions, model the peak frequency variation using curve fitting, and thereby determine the frequency drift rates. The method can be directly applied to Type II and III solar bursts while providing space for tailoring and modification. In this work, the slow drift type II radio bursts were fitted by exponential decay and the fast drift type III radio bursts were approximated as linear decay. Hence, the frequency drift rates were computed for type II and type III radio bursts. The application is used to analyze several Type II and Type III solar radio bursts and depending on the bust type shock speed and electron velocity were determined. The GUI interface eliminates the time-consuming subjective manual analysis of e-CALLISTO data thereby making the analysis of solar radio bursts a routine and rapid process.

LAMOST DR10 low resolution catalog (LRC) v1.0 has released 7,478,650 AFGK type stars with corresponding parameters and small parameter errors. These spectra are observed from October 2011 to July 2022. These AFGK stars are a large sample with very small stellar parameter errors, which are very suitable for statistical research work. The stars with [Fe/H] from -2.5 to -2.0, -1.5 to -1.3, and 0.5 to 1.0 were selected as representations for a statistical research. We analyze these stars with the distribution of effective temperature and surface gravity. In addition, we perform a cross-match research between our samples and the red giant branch (RGB) stars and red clump (RC) stars identified by Wang et al. Some low mass stars and medium mass stars are evolved using the stellar evolution code MESA. The calculated theoretical results are compared with the observed statistical data. Most of the stars are main-sequence (MS) stars with log$g$ around 4.0. The other stars are probably RGB stars or RC stars with log$g$ $\le$ 3.0. The very metal-poor stars ([Fe/H] from -2.5 to -2.0) probably are $n$-generation stars with a small value of $n$, which can help us to study the early universe. The stars with [Fe/H] from 0.5 to 1.0 are super metal-rich stars, which probably are $n$-generation stars with a large value of $n$. There is a gap around log$T_{eff}$ = 3.8 for the super metal-rich stars, which corresponds to the MS stars around 1.2 $M_{⨀}$. This will help us to study the formation process of super metal-rich stars. Rich observational data will greatly enhance our understanding to the truth of the universe.

We study the Morris-Thorne traversable asymptotically flat and non-flat wormholes in the galactic halo of the Milky Way Galaxy(MWG) based on the Einasto dark matter(DM) density profile. Our reported shape function is positive and increasing in nature, moreover, satisfies all the essential wormhole representing conditions i.e. the reported shape function forms wormhole like structures in the galactic halo region of the MWG. Furthermore, the wormhole containing the DM candidate of the halo shelters wormholes by violating the null energy condition(NEC) with respect to three different redshift functions. The wormholes, namely, WH1 and WH2 corresponding to the first two choices of redshift functions are asymptotically flat while the WH3 corresponding to the third choice of redshift function is asymptotically non-flat. We, here, also analyze the ANEC violating matter content, embedding surface, and proper radial distance for our solutions.

The blazar PG 1553＋113 is hypothesized to harbor a supermassive black hole binary system, a scenario that aligns with its observed physical characteristics. In this study, we re-examine the authenticity of the periodicity of PG 1553＋113 by conducting a comprehensive analysis of multi-wavebands periodic light variations, using the updated light curve data of more than 15 years. We used two methods to search for the light curves data of this blazar in $\gamma$-ray, $X$-ray, optical and radio bands. The multi-wavebands analysis approach enables a thorough verification of the observed periodic patterns. The result of $\gamma$-ray detection showed a quasi-periodic oscillation (QPO) of 2.16 years, which verified the results given by Ackermann et al. (2015). And the optical band shows a QPO of 2.24 years. We analyzed the correlation among $\gamma$-ray, optical and radio bands, and we found that there is a strong correlation among them, and the emission of different bands coming from the same region (the same electron group). Finally, we estimated the black hole mass of PG 1553＋113 to be $M\simeq 4.3\times 10^9{M}_{⨀}$ based on the binary black hole model.

This present work delves into the study of cosmological constant roll inflation, approaching it through the lens of Finsler-Barthel-Kropina geometry. This novel framework explains the conventional understanding of the large-scale structure of universe's homogeneity and isotropy with small-scale presence of anisotropy. The methodology employed in this work involves translating the concept of osculating Riemannian space into the context of Finsler spaces. By harnessing the unique metric structure of Kropina space, the primary focus is on unravelling the intricacies of the inflationary phenomenon. The study reveals that by introducing the anisotropic parameter $\eta$ into the metric structure and Hubble parameter, a comprehensive explanation for the anisotropic expansion of the universe can be achieved. Through a careful analysis of slow roll parameters, the research delves into the dynamics of inflation on a macroscopic scale, shedding light on the influence of anisotropy on both scalar and tensor perturbations within the power spectrum. Ultimately, the core aim of this study is to establish that the Finslerian analogy of inflation finds a coherent explanation within the framework of Kropina geometry.

This paper presents complexity measure of a dynamical spherical configuration with anisotropic distribution in energy–momentum squared gravity. The self-gravitating bodies become complex due to non-uniform energy density, asymmetrical pressure, heat loss and contribution of modified terms. By orthogonally decomposing the Riemann tensor, we analyze the structure scalars and obtain the complexity factor that accounts for all the fundamental characteristics of the system. Furthermore, by using the homologous mode as the simplest pattern of evolution, we study the dynamics of the celestial configuration. We also discuss dissipative/non-dissipative fluids in the context of homologous and complexity-free cases. Finally, we investigate a criterion for which the complexity-free condition remains stable throughout evolutionary process. It is concluded that the contribution of product as well as squared components of the considered framework leads to a more complex system.

This paper is suggested to analyze the gravitational weak lensing and fundamental frequencies in the framework of the Einstein–Euler–Heisenberg (EEH) black hole. We compute the deflection angle of light by the EEH black hole in weak field limits. Which represents that the bending of light is a global and topological effect. For this purpose, we deduce the Gaussian curvature and apply the Gauss–Bonnet theorem (GBT). Furthermore, we determine the deflection angle at which light is deflected by a plasma medium. We also look into how an EEH black hole behaves graphically in vacuum and plasma medium. Moreover, we study the fundamental frequencies with three different models of EEH black hole.

This paper is devoted to the study of curvature properties of Hayward black hole (briefly, HBH) spacetime, which is a solution of Einstein field equations (briefly, EFE) having non-vanishing cosmological constant. We have proved that the HBH spacetime is an Einstein manifold of level 2, 2-quasi Einstein, generalized quasi-Einstein and Roter type manifold. Also, it is shown that the nature of the HBH spacetime is pseudosymmetric and it obeys several types of pseudosymmetries, such as, pseudosymmetry due to concircular, conformal and conharmonic curvature (i.e., $F\cdot F=LQ(g,F)$ for $F=W,C,K$ with a smooth scalar function $L$), and it also possesses the relation $R\cdot R-LQ(g,C)=Q(S,R)$. It is engrossing to mention that the nature of energy momentum tensor of the HBH spacetime is pseudosymmetric. On the basis of curvature related properties, we have made a comparison among Reissner–Nordström spacetime, interior black hole spacetime and HBH spacetime. It is noteworthy to mention that the gravitational force of the point-like global monopole spacetime is much stronger than that of HBH spacetime. Also, it is shown that the HBH spacetime admits an almost $\eta$-Ricci soliton as well as an almost $\eta$-Ricci-Yamabe soliton. Finally, an elegant comparative study is delineated between the HBH spacetime and the point-like global monopole spacetime with respect to different kinds of symmetry, such as, motion, curvature collineation, curvature inheritance etc.

Properties of molecular clouds ($MCs$) lying in our Galaxy and their star formation scenarios have been investigated with the help of multivariate unsupervised machine learning techniques concerning several observable parameters. At first, the $MCs$ have been classified into four coherent groups using the standard K-means clustering method. Subsequently, the optimum number of groups has been estimated by applying the Elbow method as well as the computation of Silhouette widths for a robustness check. Later, the properties of the groups are studied through several observable parameters as mentioned along with computed ones e.g. star formation rates ($SFRs$), virial masses, mass-spectra, dynamical time scales ($T_d$), etc. to get a deeper understanding of the star formation process and dynamical evolution of these clouds. It is found that cluster 1 is suitable for the formation of field stars, binary pairs, or stellar associations, whereas the clouds in cluster 2 and cluster 3 are favorable sites for the formation of Galactic clusters of moderate masses, and cluster 4 may produce massive Galactic clusters as well as a few globular clusters. Surprisingly, for each cluster, clouds at around Galacto-centric radius $\sim$8 kpc, and on the near Galactic plane has a significantly low $SFR$. These occurrences indicate that the star formation phenomenon has yet not started or the proneness to start in that region.

This manuscript examines how effective matter variables influence the geometry of compact stellar objects with anisotropic matter configuration in modified $f(R,\phi ,\chi )$ gravity, where $R$ represents the Ricci scalar, $\phi$ is the scalar field and $\chi$ is a kinetic term depending on the scalar field. The unknown constants in the metric potentials are determined by the smooth matching of an interior region with the exterior spacetime. We then check the viability of some selected stars through various physical quantities, i.e., effective matter contents, anisotropy and energy constraints. We also examine the equilibrium and stable states through the Tolman–Oppenheimer–Volkoff equation and sound speed/adiabatic index, respectively. This comprehensive analysis ensures that viable and stable compact stars exist in this modified theory as all the necessary conditions are satisfied.