Том 62, № 6 (2018)

The creation of a specialized network of large, wide-angle telescopes for distributed observations of near-Earth space using a Russian–Cuban Observatory is considered. An extremely important goal of routine monitoring of near-Earth and near-Sun space is warding off threats with both natural and technogenic origins. Natural threats are associated with asteroids or comets, and technogenic threats with man-made debris in near-Earth space. A modern network of ground-based optical instruments designed to ward off such threats must: (a) have a global and, if possible, uniform geographic distribution, (b) be suitable for wide-angle, high-accuracy precision survey observations, and (c) be created and operated within a single network-oriented framework. Experience at the Institute of Astronomy on the development of one-meter-class wide-angle telescopes and elements of a super-wide-angle telescope cluster is applied to determine preferences for the composition of each node of such a network. The efficiency of distributed observations in attaining maximally accurate predictions of the motions of potentially dangerous celestial bodies as they approach the Earth and in observations of space debris and man-made satellites is estimated. The first estimates of astroclimatic conditions at the proposed site of the future Russian–Cuban Observatory in the mountains of the Sierra del Rosario Biosphere Reserve are obtained. Special attention is given to the possible use of the network to carry out a wide range of astrophysical studies, including optical support for the localization of gravitational waves and other transient events.

A mechanism for the segregation of calcium isotopes in the atmospheres of chemically peculiar (CP) stars due to light-induced drift (LID) of singly charged ⁴⁸Ca⁺ ions is discussed. One peculiarity of Ca⁺ is that an adequate description of the effect of LID requires taking into account several energy levels of Ca⁺, and thus several pairs of relative differences (ν_i − ν_k)/ν_i for the transport frequencies for collisions of levels i and k with neutral atoms (hydrogen, helium). The known real (calculated ab initio) interaction potentials are used to numerically calculate the factors (ν_i − ν_k)/ν_i for several states of Ca⁺ for collisions with H and He atoms. These computations show that, at the temperatures characteristic of the atmospheres of CP stars, T = 6600−12 000 K, fairly high values are obtained for Ca⁺ ions, (ν_i − ν_k)/ν_i ≈ 0.4−0.6. Simple, transparent computations demonstrate that the LID rates of Ca⁺ ions in the atmospheres of cool CP stars (T_eff = 6600 K) exceed the drift rate due to light pressure by two orders of magnitude. The LID is directed upward in the stellar atmosphere, and the heavy isotope ⁴⁸Ca is pushed into upper layers of the atmosphere. This can explain the observed predominance of the heavy isotope ⁴⁸Ca in the upper atmospheric layers of CP stars; according to the radiative-diffusion theory, the action of light pressure alone (in the absence of LID) would lead to sinking of the isotope ⁴⁸Ca deeper into stellar atmosphere, following the lighter main isotope ⁴⁰Ca. The ⁴⁸Ca⁺ LIDrate decreases and its drift rate due to light pressure increases with growth of the effective temperatures in the atmospheres of CP stars. The manifestations of LID and light pressure are roughly comparable in the atmospheres of CP stars with effective temperatures near T_eff = 9500 K.

The results of an analysis of observations of the cool (M8) dwarf TRAPPIST-1 obtained on the Kepler Space Telescope (the K2 continuation mission) are presented. TRAPPIST-1 possesses a planetary system containing at least seven planets. In all, the observations consist of 105 584 individual brightness measurements made over a total duration of 79 days. Brightness power spectra computed for TRAPPIST-1 exhibit a peak corresponding to P₀ = 3.296 ± 0.007^d. There are also two peaks with lower significances at P₁ = 2.908^d and P₂ = 2.869^d, which cannot be explained by the presence of differential rotation. The observational material available for TRAPPIST-1 is subdivided into 21 datasets, each covering one stellar rotation period. Each of the individual light curves was used to construct a map of the star’s temperature inhomogeneities. On average, the total spotted area of TRAPPIST-1 was S = 5% of the entire visible area. The difference between the angular rotation rates at the equator and at the pole is estimated to be ΔΩ = 0.006. The new results obtained together with data from the literature are used to investigate the properties of this unique star and compare them to the properties of other cool dwarfs. Special attention is paid to the star’s evolutionary status (its age). All age estimates for TRAPPIST-1 based on its activity characteristics (rotation, spot coverage, UV and X-ray flux, etc.) indicate that the star is young.