• Issue front cover thumbnail

      Volume 32, Issue 3

      September 2011,   pages  359-423

    • Extragalactic Gamma Ray Excess from Coma Supercluster Direction

      Pantea Davoudifar S. Jalil Fatemi

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      The origin of extragalactic diffuse gamma ray is not accurately known, especially because our suggestions are related to many models that need to be considered either to compute the galactic diffuse gamma ray intensity or to consider the contribution of other extragalactic structures while surveying a specific portion of the sky. More precise analysis of EGRET data however, makes it possible to estimate the diffuse gamma ray in Coma supercluster (i.e., Coma\A1367 supercluster) direction with a value of 𝐼(𝐸 > 30MeV) ≃ 1.9 × 10-6 cm-2 s-1, which is considered to be an upper limit for the diffuse gamma ray due to Coma supercluster. The related total intensity (on average) is calculated to be ∼ 5% of the actual diffuse extragalactic background. The calculated intensity makes it possible to estimate the origin of extragalactic diffuse gamma ray.

    • Analytical Solution for Stellar Density in Globular Clusters

      M. A. Sharaf A. M. Sendi

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      In this paper, four parameters analytical solution will be established for the stellar density function in globular clusters. The solution could be used for any arbitrary order of outward decrease of the cluster’s density.

    • The Work Function Associated with Ultra-relativistic Electron Emission from Strongly Magnetized Neutron Star Surface

      Arpita Ghosh Somenath Chakrabarty

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      Following an extremely interesting idea (Schieber 1984), published long ago, the work function associated with the emission of ultra-relativistic electrons from magnetically deformed metallic crystal (mainly iron) at the outer crust of a magnetar is obtained using relativistic version of Thomas–Fermi type model for electron distribution around the nuclei in this region. In the present scenario, surprisingly, the work function becomes anisotropic; the longitudinal part is an increasing function of magnetic field strength, whereas the transverse part diverges.

    • The Potential Well-Depth $U^{(N)}_{\Sigma}$ Constraints on the Surface Gravitational Red-shift of a Proto Neutron Star

      Xian-Feng Zhao

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      The influence of the potential well depth $U^{(N)}_{\Sigma}$ of 𝛴 in nuclear matter on the surface gravitational red-shift of a proto neutron star is examined within the framework of the relativistic mean field theory for the baryon octet system. It is found that as $U^{(N)}_{\Sigma}$ increases from -35 MeV to +35 MeV, the surface gravitational red-shift increases and the influence of the negative $U^{(N)}_{\Sigma}$ on the surface gravitational red-shift is larger than that of the positive ones. Furthermore, the 𝑀max/𝑅 and the surface gravitational red-shift corresponding to the maximum mass all increase as the $U^{(N)}_{\Sigma}$ increases, 𝑀max and 𝑅 being the maximum mass of the proto neutron star and the corresponding radius respectively.

    • The Relative Phase Asynchronization between Sunspot Numbers and Polar Faculae

      L. H. Deng J. Y. Song Y. Y. Xiang Y. K. Tang

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      The monthly sunspot numbers compiled by Temmer et al. and the monthly polar faculae from observations of the National Astronomical Observatory of Japan, for the interval of March 1954 to March 1996, are used to investigate the phase relationship between polar faculae and sunspot activity for total solar disk and for both hemispheres in solar cycles 19, 20, 21 and 22. We found that (1) the polar faculae begin earlier than sunspot activity, and the phase difference exhibits a consistent behaviour for different hemispheres in each of the solar cycles, implying that this phenomenon should not be regarded as a stochastic fluctuation; (2) the inverse correlation between polar faculae and sunspot numbers is not only a long-term behaviour, but also exists in short time range; (3) the polar faculae show leads of about 50–71 months relative to sunspot numbers, and the phase difference between them varies with solar cycle; (4) the phase difference value in the northern hemisphere differs from that in the southern hemisphere in a solar cycle, which means that phase difference also existed between the two hemispheres. Moreover, the phase difference between the two hemispheres exhibits a periodical behaviour. Our results seem to support the finding of Hiremath (2010).

    • Collinear Equilibrium Solutions of Four-body Problem

      Muhammad Shoaib Ibrahima Faye

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      We discuss the equilibrium solutions of four different types of collinear four-body problems having two pairs of equal masses. Two of these four-body models are symmetric about the center-of-mass while the other two are non-symmetric.We define two mass ratios as 𝜇1 = 𝑚1/𝑀T and 𝜇2 = 𝑚2/MT, where 𝑚1 and 𝑚2 are the two unequal masses and 𝑀T is the total mass of the system. We discuss the existence of continuous family of equilibrium solutions for all the four types of four-body problems.

  • Journal of Astrophysics and Astronomy | News

    • Continuous Article Publication

      Posted on January 27, 2016

      Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

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