Том 61, № 11 (2017)

The discovery of the possible existence of huge quasi-stationary envelopes around a number of hot Jupiters (i.e., with sizes appreciably exceeding their Roche lobes) and the need to correctly take into account their properties when interpreting observational data require a careful analysis of the main physical processes influencing their atmospheres. One important factor is the possibility that the planet has a magnetic field. It was shown earlier that the presence of even a modest dipolar magnetic field of a hot Jupiter (with a magnetic moment approximately 1/10 the magnetic moment of Jupiter) influences the properties of the planetary atmosphere, in particular, leading to expansion of the range of parameters for which a giant, quasi-closed envelope can form around the planet. It was also established that the presence of a planetary magnetic field reduced the mass-loss rate from the envelope, since matter flowing out from the inner Lagrange point moves perpendicular to the field lines. Three-dimensional magnetohydrodynamical (MHD) modeling on time scales appreciably exceeding the time for the formation of the envelope show that pulsations arise in the atmospheres of hot Jupiters possessing dipolar magnetic fields, with characteristic periods ~0.27P_orb. This behavior is easy to understand physically, since even in the case of a spherical atmosphere, the continuous expansion of the ionized atmsphere of a hot Jupiter can lead to the accumulation of matter in regions bounded by closed field lines, and to the periodic rupture of the atmosphere beyond the magnetic field. In the case considered, when the system contains a giant envelope fed by a stream of matter from the inner Lagrange point, the presence of such pulsations gives rise to appreciable variations in the gas-dynamical structure of the flow. In particular, pulsations of the atmosphere lead to tearing off of part of the flow and sharp fluctuations in the size of the envelope, leading to variations in the envelope’s observational properties.

The results of an analysis of timing data for the pulsar PSR B0329+54 obtained in 1968–2012 on the Large Scanning Antenna of the Pushchino Radio Astronomy Observatory at 111 MHz, the 64 m DSS-14 telescope of the Jet Propulsion Laboratory at 2.3 GHz, and the 64 m telescope of the Kalyazin Radio Astronomy Observatory at 610 MHz are presented. The astrometric and spin parameters of the pulsar are derived at a new epoch. The coordinates of the pulsar and its proper motion measured at the three frequencies differ. These differences have a systematic character, and are interpreted as a secular, refractive shift in the apparent position of the pulsar that arises because it is observed through large-scale inhomogeneities of the interstellar medium, leading to variations in the angle of refraction.

Data from long-term multi-frequency monitoring of the Active Galactic Nucleus (AGN) and blazar 3C 454.3 are analyzed. An unusually prolonged outburst in 2013–2017 had a duration that was twice the possible orbital period of the companion of the supermassive black hole (SMBH) located at the center of the host galaxy. It is proposed that the shape and duration of this outburst in 3C 454.3 could be the result of a coincidence between the plane of the accretion disk (AD) and the orbital plane of the companion. As a consequence, a prolonged energy release with enhanced intensity can be observed as the companion passes through the dense medium of the AD of the central SMBH. The presence of a 1.55-year orbital period in the variations of the emission of 3C 454.3 during this outburst also supports this hypothesis, as opposed to the possibility that the outburst was due to variations in γ and the Doppler factor. Small-scale flux-density fluctuations can arise during the outburst due to matter inhomogeneities with characteristic scales of about 1015 cm or more in the AD of the central SMBH and surrounding areas.

A mechanism for the separation of chemical elements and isotopes in the atmospheres of chemically peculiar (CP) stars due to light-induced drift (LID) of ions is discussed. The efficiency of separation due to LID is proportional to the relative difference of the transport frequencies for collisions of ions of heavy elements located in the excited state (collision frequency ν_e) and ground state (collision frequency ν_g) with neutral buffer particles (hydrogen and helium), (ν_e − ν_g)/ν_g. The known interaction potentials are used to numerically compute the relative difference (ν_e^H − ν_g^H )/νg H for collisions between the ions Be⁺, Mg⁺, Ca⁺, Sr⁺, Cd⁺, Ba⁺, Al⁺, and C⁺ and hydrogen atoms. These computations show that, at the temperatures characteristic of the atmospheres of CP stars, T = 7000−20 000 K, values of |ν_e^H −ν_g^H |/ν_g^H ≈ 0.1−0.4 are obtained. With such relative differences in the transport collision frequencies, the LID rate of ions in the atmospheres of coolCP stars (T < 10000 K) can reach ~0.1 cm/s,which exceeds the drift rate due to light pressure by an order of magnitude. This means that, under these conditions, the separation of chemical elements under the action of LID of ions could be an order of magnitude more efficient than separation due to light pressure. Roughly the same manifestations of LID and light pressure are also expected in the atmospheres of hotter stars (20 000 > T > 10 000 K). LID of heavy ions is manifest only weakly in very hot stars (T > 20 000 K).

Observations of the K2 continuation of Kepler Space Telescope program are used to estimate the spot coverage S (the fractional spotted area on the surface of an active star) for stars of the Pleiades cluster. The analysis is based on data on photometric variations of 759 confirmed clustermembers, together with their atmospheric parameters, masses, and rotation periods. The relationship between the activity (S) of these Pleiades stars and their effective temperatures shows considerable change in S for stars with temperatures T_eff less than 6100 K (this can be considered the limiting value for which spot formation activity begins) and a monotonic increase in S for cooler objects (a change in the slope for stars with Teff ~ 3700 K). The scatter in this parameter ΔS about its mean dependence on the (V −Ks)0 color index remains approximately the same over the entire (V−K_s)0 range, including cool, fully convective dwarfs. The computated S values do not indicate differences between slowly rotating and rapidly rotating stars with color indices 1.1 < (V−K_s)0 < 3.7. The main results of this study include measurements of the activity of a large number of stars having the same age (759 members of the Pleiades cluster), resulting in the first determination of the relationship between the spot-forming activity and masses of stars. For 27 stars with masses differing from the solarmass by nomore than 0.1M⊙, themean spot coverage is S = 0.031±0.003, suggesting that the activity of candidate young Suns is more pronounced than that of the present-day Sun. These stars rotate considerably faster than the Sun, with an average rotation period of 4.3^d. The results of this study of cool, low-mass dwarfs of the Pleiades cluster are compared to results from an earlier study of 1570 M stars.