Vol 100, No 5 (2023)

To study the influence of the central black hole on the formation of the bulge of spiral galaxies, we analyzed the relationship between the masses of supermassive black holes (SMBHs) and the parameters of their bulges. Unlike other authors, we consider only spiral galaxies. In this paper, we present empirical formulas derived from observations of 54 spiral galaxies, establishing connections between the mass of the central black hole (MBH), the bulge stellar mass (Mbulge), and the velocity dispersion (σ) of stars in it. A non-linear non-stationary disk model with an anisotropic velocity diagram is constructed. Within this model, the instabilities of individual perturbation modes are studied. The increments of instability are calculated depending on the physical parameters of the model. These values are compared across three perturbation modes. The paper is partly based on the report presented at the conference “Modern Stellar Astronomy-2022,” held at the Caucasian Mountain Observatory of the Sternberg Astronomical Institute of Lomonosov Moscow State University, on November 8–10, 2022.

The thermal instability of accretion disks is widely used to explain the activity of cataclysmic variables, but its manifestation in gas and dust disks in young stars has been studied in less detail. A semi-analytical stationary model is presented for calculating the equatorial temperature of a gas and dust disk around a young star. The model considers the opacity caused by dust and gas, as well as the evaporation of dust at temperatures above 1000 K. Using this model, the distributions of the equatorial temperature of the gas and dust disk are calculated under various assumptions on the source of opacity and the presence of dust. It is shown that when all the above processes are considered, the thermal balance equation in the region r<1 AU has multiple temperature solutions. Thus, the conditions for thermal instability are satisfied in this region. As an illustration of the possible influence of instability on the nature of accretion in a protoplanetary disk, we consider a viscous disk model with α-parametrization of turbulent viscosity. It is shown that in such a model a non-stationary mode of disk evolution is realized with alternating phases of accumulation of matter in the inner disk and phases of its rapid accretion onto the star, which leads to a burst character of accretion. The results obtained indicate the need to take this instability into account when modeling the evolution of protoplanetary disks.

The triple system of young stars T Tauri was discovered relatively recently and has attracted the attention of numerous researchers. Many papers have been dedicated to the study of the physical properties of the system’s stars, which are surrounded by a disk of dust and gas. Our work is focused on the astrometric analysis of this triple system using the method of apparent motion parameters (AMP). Currently, the orbit of the inner pair Sa-Sb with a period of 27 years is well-established. Based on the Gaia DR3 parallax, its total mass MSa + Sb=2.49M⊙. Relying on the published high-precision uniform observations with the Keck 1 and VLT telescopes, we employed the AMP method to derive two orbits for the outer pair N-S, one of which is almost circular. For a circular orbit, it is possible to calculate the orbital elements and dynamic parallax for a given mass solely using the apparent motion parameters. This enabled a comparison between the dynamic parallax and the high-precision parallax from the Gaia DR3 catalog, facilitating the calculation of masses of each component based on the mass of the inner subsystem: MN=(2.4±0.2)M⊙, MSa=(2.09±0.05)M⊙, MSb=(0.40±0.05)M⊙. The boundaries for the orbital period were estimated to be 500⩽P⩽700 years.

Coronal holes on the Sun have been observed at individual frequencies for quite a long time in the wavelength range from radio to X-rays. Observations in a wide range of radio frequencies are carried out with the RATAN-600 radio telescope. An analysis of long-term spectral observations of the RATAN-600 radio telescope showed that the emission spectrum of coronal holes is radically different from the spectrum of active formations above sunspots, but, differing markedly from the spectrum of the quiet Sun, it also has similarities with it. It has been established that the radio emission of coronal holes has an adiabatic spectrum and does not contain noticeable coherent radiation, that is, recombination radio lines and lines of the fine structure of hydrogen and other elements.