New Astronomy最新文献

This paper uses the gravitational decoupling through the minimal geometric deformation approach and extends a known isotropic solution for a self-gravitating interior to two types of anisotropic spherical solutions in Rastall gravity in the presence of electromagnetic field. By deforming only the radial metric component, the field equations are decoupled into two sets, the first of which corresponds to an isotropic distribution of matter while the second set contains the anisotropic source. We obtain a solution of the first set by employing the charged isotropic Finch-Skea ansatz, whereas a solution for the second set is obtained by adopting two mimic constraints on the pressure and density. The matching conditions at the stellar surface are explored with the exterior geometry given by the deformed Reissner–Nordström spacetime. For the two fixed values of the Rastall and charge parameters, we investigate physical features of both solutions through graphical analysis of the energy conditions, equation of state parameters, surface redshift and compactness function. The stability of both solutions is also studied through the Herrera cracking approach and causality condition. We deduce that while both solutions are physically viable, only the solution corresponding to the pressure-like constraint is stable.

The search for the simplest amino acid, glycine ($\text{NH2CH2COOH}$), in the interstellar medium (ISM) has become a never-ending story for astrochemistry and astrophysics researchers because that molecule plays a possible connection between the Universe and the origin of life. In the last forty years, all searches for $\text{NH2CH2COOH}$ in the ISM at millimeter and submillimeter wavelengths have failed. Since the detection of $\text{NH2CH2COOH}$ in the ISM is extremely difficult, we aime to search for the possible precursors of $\text{NH2CH2COOH}$. Earlier, many laboratory experiments have suggested that methylamine ($\text{CH3NH2}$) plays an important role in the ISM as a possible precursor of $\text{NH2CH2COOH}$. After spectral analysis using the local thermodynamic equilibrium (LTE) model, we identified the rotational emission lines of $\text{CH3NH2}$ towards the hot molecular core G358.93–0.03 MM1 using the Atacama Large Millimeter/Submillimeter Array (ALMA). The column density of $\text{CH3NH2}$ towards the G358.93–0.03 MM1 is estimated to be (1.10 ± 0.31)$\times$10¹⁷ cm⁻² with an excitation temperature of 180.8 ± 25.5 K. The fractional abundance of $\text{CH3NH2}$ with respect to $\text{H2}$ towards the G358.93–0.03 MM1 is (8.80 ± 2.60)$\times$10⁻⁸. The column density ratio of $\text{CH3NH2}$ and $\text{NH2CN}$ towards G358.93–0.03 MM1 is (1.86 ± 0.95)$\times$10². The estimated fractional abundance of $\text{CH3NH2}$ towards the G358.93–0.03 MM1 agrees fairly well with the previous three-phase warm-up chemical modelling abundance of $\text{CH3NH2}$. We also discuss the possible formation mechanism of $\text{CH3NH2}$, and we find that $\text{CH3NH2}$ is most probably formed via the reactions of radical $\text{CH3}$ and radical $\text{NH2}$ on the grain surface of G358.93–0.03 MM1.

In this article, we introduce an efficient numerical approach for finding the numerical solution for coupled Lane–Emden–Fower type equations using the variational iteration method combined with the Adomian polynomial. The convergence analysis of the proposed approach is investigated under very general conditions. A couple of numerical examples are included and contrasted with the existing methods (Singh et al., 2021;Sinha et al., 2023;Duan et al., 2015) and the exact solution to check the robustness and effectiveness of the proposed approach. The present method shows faster convergence, computational efficiency, time efficiency and simplicity of implementation.

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.