Vol 101, No 12 (2024)

The aim of our work is to study the activity of the FK Com type star rapidly rotating G5 III IV giant HD 199178 (V1794 Cyg) on the base of available photometric data from TESS mission in five sectors. The light curves of the star characterized the variability caused by rotational modulation due to the presence of cool spots on the surface, power spectra and phase diagrams are studied. The dominant peak corresponds to the photometric period P = 3.28^d ± 0.12^d. It is suggested that the value of P decreases over time (over an interval of about 40 years) from 3.337^d up to 3.28^d may be due to the long-term evolution of the positions of the active areas (spots) on the surface of a differentially rotating star. The changes in the amplitude of the brightness variability and the shape of the phase curves of HD 199178 were analyzed and it was found that the fraction of the star’s surface occupied by spots varied from 7 to 12% of its surface area. The flare activity of the star has been studied. The parameters of the amplitude, duration and energy of the flares are determined for two of them. One of the considered flares is the strongest during the observations in five sectors (5.1 × 10³⁵ erg) and in magnitude can characterize the upper limit of the flare energies in a given state of star activity. Maps of the surface temperature inhomogeneities of the star are constructed.

This work is devoted to estimating of the contribution of the trimerization reaction of acetylene molecules on the surface of silicon carbide (SiC) particles with the formation of benzene molecules into the benzene abundance in the envelopes of asymptotic giant branch (AGB) stars. The reaction was included into an astrochemical model, using which modeling was carried out under conditions corresponding to the envelope of the AGB star IRC+10216. Based on the modeling results, it is shown that the trimerization reaction of acetylene on the SiC surface can effectively occur under the conditions of the envelopes of AGB stars and have a significant effect on the benzene abundance, and, as a consequence, other aromatic molecules. Accounting for acetylene trimerization can increase the benzene abundance in the gas by an order of magnitude, and at the surface the benzene abundance can be up to four orders of magnitude higher compared to estimates in the gas predicted by a model with only gas-phase reactions. The rate of benzene formation on the SiC surface significantly exceeds the rate of benzene formation in the gas during the early phases of the stellar pulsation. The efficiency of benzene formation in the trimerization reaction depends on currently unknown kinetic parameters of the reaction, in particular, on the desorption energy of the resulting benzene molecule. Determination of reaction parameters will help to perform more accurate quantitative modeling in the future.

An interpulse search was carried out in a sample of 96 pulsars observed on the Large Phased Array (LPA) radio telescope in the Pushchino Multibeams Pulsar Search (PUMPS). The pulsar sample is complete for pulsars having a signal-to-noise ratio (S/N) in the main pulse (MP) greater than 40. To search for weak interpulses (IP), the addition of average profiles over an interval of up to 10 years was used. Interpulses were detected in 12 pulsars (12.5% of the sample), of which 7 pulsars have an interpulse located near the 180◦ phase relative to the main pulse (probable orthogonal rotators), and 5 have phases far from 180◦ (probable coaxial rotators). The amplitude ratios of IP/MP are in the range of 0.004−0.023, the median value is 0.01. Estimates of the observed number of coaxial and orthogonal rotators with IP/MP ≥0.01 do not contradict the model according to which, during evolution, the magnetic axis and the axis of rotation become orthogonal.

An analysis of the north-south asymmetry (NSA) of the groups of sunspots and flares location during the growth phase of the 25th Schwabe-Wolf cycle of solar activity was performed. During the first four years of the cycle’s development, sunspot activity increased quasi-synchronously in the northern and southern hemispheres; the module of the NSA coefficient during this period decreased from 0.6 to 0.2. The longitudinal distribution of sunspots in the second half of 2023 was uneven and similar in both hemispheres; groups of sunspots appeared during this period mainly in the longitudinal intervals of 30–100°, as well as 200–280°, at other longitudes activity was reduced, as in the northern, and in the southern hemispheres. The number of flares of all classes was 45% in the northern hemisphere, 42% in the southern hemisphere, 13% were not identified. The flare index was distributed between the hemispheres in the ratio of 49.5% to 42%, 8.5% were not identified. A comparison with the 24th cycle shows that NSA in the distribution of sunspots and flares between the northern and southern hemispheres in the current (25th) cycle is significantly lower than in the previous one. A high degree of symmetry of activity can ensure a greater height of the 25th cycle compared to the 24th, as well as the single-peaked nature of the 25th cycle. It is hypothesized that in the 25th cycle there is a higher level of dipole parity of the global magnetic field compared to the 24th cycle.