Astronomičeskij žurnal

In this work, the gravitational instability of small-scale perturbations with an azimuthal wave number m = 2 in disk-like self-gravitating systems is considered. Calculations of horizontal small-scale oscillation modes (m;N) = (2; 10) and (2; 20) against the background of a nonlinearly non-equilibrium anisotropic model of a self-gravitating disk are performed. Critical diagrams of the relationship between the virial parameter and the degree of rotation for these modes are constructed, and the increments of instability for different values of the rotation parameter are calculated. The results show that the instability for the oscillation mode (2; 10) begins at a virial parameter value of (2T/|U|)0 ≈ 0.217 at Ω = 0 and reaches 0.413 at Ω = 1. For the oscillation mode (2; 20), the instability starts at a virial parameter value of (2T/|U|)0 ≈ 0.128 at Ω = 0 and reaches 0.146 at Ω = 1. It is found that with an increase in the rotation parameter, the instability region also increases, while with an increase in the degree of small-scale structure, the instability region significantly decreases. The work is partially based on a talk presented at the Modern Stellar Astronomy 2024 conference.

In this work, we investigate the problem of gravitational instability in a generalized model of a nonlinearly radially pulsating disk with an anisotropic velocity diagram relative to sectoral modes of perturbations. This model is a non-stationary generalization of the equilibrium self-gravitating disk by Bisnovatyi-Kogan and Zeldovich. Exact expressions are obtained for the main physical characteristics of the generalized model, such as the components of the kinetic energy of the pulsating disk, velocity dispersions in the radial and transverse directions, the global anisotropy parameter, and others. We also found non-stationary analogs of dispersion equations (NADE) against the background of this generalized model for sectoral modes of perturbations. Based on the results of numerical calculations of NADE, graphs comparing the instability increments depending on the initial virial ratio of the system for various values of the parameters α and β, characterizing the difference and degree of anisotropy of nonlinearly non-stationary models of the self-gravitating disk, were constructed. In particular, it is shown that the development of bar-like mode instability will be the same for all anisotropic models, as the NADE of this mode does not depend on the parameters α and β. The work is partially based on a talk presented at the Modern Stellar Astronomy 2024 conference.

This paper presents the results of observations of the magnetar XINS 1308+2127 (RX J1308.6+2127, RBS 1223) at a frequency of 111 MHz. To search for pulsed emission, we used data from the BSA radio telescope of the Lebedev Physical Institute, which was recorded in the mode of 32 frequency channels with a time resolution of 0.0125 s and in a receiving band 2.5 MHz. As a result of data processing in the period of 2012–2022, emission was detected at the specified frequency. The work presents for the value of the dispersion measure DM = 3.7 ± 0.5 pc/cm3, peak flux density 0.28 ± 0.03 Jy, width at 10% W10 = 0.2 s, fluence 55 Jy·ms.

The results of a study on the existence of a quadratic local integral relative to the velocity components for stationary stellar systems in the absence of any symmetry of the gravitational potential are presented. This refers to a separate isolated invariant surface in phase space, allowing the velocity field to be determined immediately for certain specific initial conditions. All two-dimensional potentials that allow such a local integral for rotating systems are listed. In this first publication, we will limit ourselves to cases of constant energy expansion in powers and coinciding characteristics, which lead to both known and non-trivial potentials allowing a quadratic local integral. The work is partially based on a talk presented at the Modern Stellar Astronomy 2024 conference.