Volume 101, Nº 9 (2024)

In the paper using 1D aeronomic model the impact of a stellar flare on the upper atmosphere of hot Jupiter is investigated. The atmosphere is assumed to have a hydrogen-helium chemical composition, and calculations were carried out for the hot Jupiter HD 209458b. We examined single and repeated flares in which the flux of hard UV radiation increases by 10, 100 and 1000 times compared to the quiescent state of the star. The active phase of the dynamic response of the atmosphere lasts 12–15 hours after the flare, and the characteristic period of relaxation to the initial state is about a day. From the results obtained it follows that the flare activity of solar-type stars does not have a significant effect on the evolution of the planetary atmospheres of hot Jupiters. However, the interpretation of transit observations of the disturbed atmospheres of hot Jupiters will make it possible to separate from each other the observational effects associated with the interaction of stellar flares and coronal mass ejections with the upper atmospheres and envelopes of these planets. This will make it possible to more accurately determine the parameters of the stellar wind and coronal mass ejections of solar-type parent stars.

New high-precision photometric measurements of the eclipsing star V839 Cep (P = 9.96^d, V_A+B = 9.64^m, e = 0.07, B6 V + B7 V), which is the “A” component of the visual double star J21035+5925AB, have established that component “B” is also an eclipsing variable (P = 4.075^d, B9 V + G8 V). For component “A”, the apsidal rotation rate was measured to be ${\dot{\mathrm{\omega }}}_{\mathrm{obs}} = 0.027° /\mathrm{year}$, which exceeds the theoretical value under the condition of synchronism ${\dot{\mathrm{\omega }}}_{\mathrm{theor}} = 0.021° /\mathrm{year}$. The physical parameters of the component stars of the eclipsing pair “A” were obtained: T₁ = 13 200 ± 300 K, M₁ = (3.7 ± 0.15) M_⊙, R₁ = (2.57 ± 0.05) R_⊙, T₂ = 11 900 ± 250 K, M₂ = (3.2 ± 0.15) M_⊙, R₂ = (2.42 ± 0.05) R_⊙ and components of the eclipsing pair “B”:  T₁ = 10 600 ± 200 K, M₁ = (2.6 ± 0.2) M_⊙, R₁ = (1.97 ± 0.05) R_⊙, T₂ = 5540 ± 50 K, M₂ = (0.88 ± 0.05) M_⊙, R₂ = (0.84 ± 0.05) R_⊙. The age of the system is determined to be 70 million years with solar chemical composition. The components of star “A” are pulsating variable stars of the slow β Cephei (SBC) type.

An analysis is performed of data concerning the [N/C] value, one of the most sensitive indicators of stellar evolution, for 20 red giants with magnetic fields in comparison with similar data for 7 non-magnetic giants. For the most giants in question the [N/C] value showed a dependence on the age t and mass M. In particular, the [N/C] value for the most of magnetic giants decreases from 1.2 to 0.9 when logt increases from 8.2 to 9.8 and M increases from 1 to 4 M_⊙. It was shown that for the most of magnetic giants the [N/C] values are lowered (up to 0.4 dex) as compared with non-magnetic giants with the same values of t or M. The supposition was made that such differences in the [N/C] values between these two groups of stars are explained by different ways of stellar evolution of red giants with magnetic fields (on the main sequence (MS) stage the fields could be strong) and giants without magnetic fields. In particular, the magnetic field can suppress the mixing process on the MS stage already and especially in the First Dredge-Up (FDU) phase; that leads to the [N/C] lowering in magnetic giants.