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Vol 100, No 11 (2023)
Articles
MODERN STELLAR ASTRONOMY – 2022
Abstract
We provide an analytic review of problems of the modern stellar astronomy. It mostly based on talks presented at the twelfth annual conference on Modern Stellar Astronomy, held in Caucasian Mountain Observatory of Sternberg Astronomical Institute (Kislovodsk, Russia) in November 2022.
929-938
EVOLUTION OF THE X-RAY BINARY SYSTEM Sco X-1
Abstract
The possible evolution of a bright low-mass X-ray binary system Sco X-1 is numerically investigated within the framework of a model assuming that the donor of the system (a satellite of a neutron star) fills its Roche lobe. The calculations take into account a strong induced stellar wind (ISW) of the donor, which occurs due to irradiation by hard radiation of an accreting relativistic star. At the same time, using the example of Sco X-1, three hypotheses are investigated, within the framework of which a high rate of mass exchange can be obtained for semi-separated X-ray binary stars. The first hypothesis is the presence of a strong ISW of the donor with standard magnetic braking. Calculations have shown that in this case it is possible to obtain a high rate of mass exchange, but at the same time the donor cannot fill the Roche lobe – it “goes under it”. The second hypothesis is an increase of magnetic braking, that is, an increase of the loss of angular momentum from the system due to the magnetic stellar wind of the donor (MSW). Such an amplification may be associated with the intense ISW of the donor in the presence of a strong magnetic field. Numerical modeling shows that with an increase of MSW by ~20 times, a high rate of mass exchange is possible when the donor fills the Roche lobe. The third hypothesis suggests the possibility of canceling the direct exchange of angular momentum between the orbital moment of the system and the moment of accreted matter passing from a low-mass donor to a more massive accretor. With such cancellation, the main process, increasing the semi-axis of the orbit, disappears. Calculations show that in this case it is possible to obtain a sufficiently high rate of mass exchange. However, the most likely reason for the increase of the rate of mass exchange in low-mass X-ray binary systems is probably the increase of magnetic braking.
939-957
INTERACTION OF THE EXOPLANET HAT–P–11b WITH THE STELLAR WIND
Abstract
This article discusses the possibility of the existence of a magnetodisk around the exoplanet HAT–P–11b. We used the available observational data to determine the properties of this exoplanet and the stellar wind passing by it, and obtained a rough estimate of the planetary magnetospheric scale. Our estimate was compared with the published results of calculations by the Particle-In-Cell method in a three-dimensional electromagnetic relativistic collisionless model of the magnetosphere. The resulting discrepancy between the magnetospheric scales obtained by these two methods is discussed, and its possible interpretation is proposed.
958-963
ON THE POSSIBILITY OF ESTIMATION OF THE ORBIT ECCENTRICITY OF A BINARY SYSTEM WITH AN EXOPLANET USING A TRANSIT LIGHT CURVE
Abstract
Working with both simulated and observed transit light curves, we studied a possibility of determining an orbital eccentricity of a binary star system with an exoplanet. It is shown that determining an exact eccentricity value from transit light curves is possible if a longitude of a periastron is known. In the absence of information about the longitude of periastron, analysis of the transit light curve makes it possible to impose restrictions on orbital eccentricity values. The influence of uncertainty in the orbital eccentricity on the accuracy of determination of other parameters of the system (a radius of the star, a radius of the planet, orbit inclination, and limb darkening coefficient) has been studied.
964-986
NO BIOMARKER: TRANSMISSION AND EMISSION METHODS FOR ITS POTENTIAL DETECTION IN EXOPLANET ATMOSPHERES WITH SPEKTR-UF (WSO-UV)
Abstract
Among all habitability factors for terrestrial exoplanets, one of the most important is the presence of a secondary N2–O2 dominant atmosphere in an exoplanet. This factor can potentially indicate the already existing geological and biological processes on the exoplanet. Meanwhile, direct characterization of the N2–O2 atmospheres of terrestrial exoplanets is a difficult observational task. There are only a few indicators (molecules) of such an atmosphere, among which one can single out a potential biomarker – a molecule of nitric oxide NO. The strongest spectral features of this molecule in the ultraviolet range are γ-bands (203–248 nm). An important role in the search for potential biomarkers on exoplanets, including the registration of NO γ‑bands, can be played by planned for the launch WSO-UV space observatory. In the paper estimates of the possibility of detecting the transmission of light in γ-bands in the atmospheres of exoplanets with this observatory are presented. The methods of emission and transmission spectroscopy are compared as applied to the detection of NO. Based on the results of this work, it is shown that there is a potential possibility of detecting a transmission signal in the NO γ-bands in the atmospheres of nearby exoplanets (<10 pc) using the LSS spectrograph of the WSO-UV observatory. At the same time, the imposed restrictions for the registration of this signal on more distant exoplanets are presented.
987-1004
THE NEAR INFRARED AND OPTICAL PHOTOMETRIC ACTIVITY OF V517 Cyg
Abstract
A near infrared and optical photometric study of Herbig star V517 Cyg has been carried out. Infrared data were obtained in 2003–2017 at the Campo Imperatory Observatory (Italy) with the Pulkovo telescope AZT-24 in Johnson’s \(JHK\) bands. Optical light curves in Johnson \(UBVR\) bands were obtained at the Maidanak observatory. Additional optical photometry from different sources (ASSAS, WISE, and AAVSO) was also used. It was shown that the behavior of V517 Cyg in the near infrared is typical for UX Ori stars. A considerable contribution to the near infrared variability is due to variable extinction along the line of sight, but the disk radiation becomes strong in the \(H\) and \(K\) bands: there is a significant correlation of \(V\) and \(J\) magnitudes (\(r \sim 0.84\)), while \(H\) and \(K\) bands correlates poorly with \(V\) band. The amplitude of variability in \(J\) is quite large (\( \sim {\kern 1pt} {{1.8}^{m}}\)). The deepest minimum (\(\Delta V \sim {{3.6}^{m}}\)) in the \(V\) band demonstrates quasi-periodic variations with an amplitude of \( \sim {\kern 1pt} {{0.8}^{m}}\) and a period of \( \sim {\kern 1pt} 19\) days, the origin of which is still unclear. It is possible that these quasi-periodic variations are related to rotation period of a second companion, a cold T Tauri star. The spectrum V517 Cyg reveals typical for UX Ori stars the double-peaked emission line Hα. The NaI D doublet has inverse P Cyg profiles, indicating intense accretion of gas onto the star. The accretion rate from an equivalent width of the Hα line is \({{\dot {M}}_{{acc}}} = 3.6 \times {{10}^{{ - 8}}}\,{{M}_{ \odot }}\) per year.
1005-1022
SCALE-INVARIANT MODE IN COLLISIONLESS SPHERICAL STELLAR SYSTEMS
Abstract
An analytical solution of the perturbed equations is obtained, which exists in all ergodic models of collisionless spherical stellar systems with a single length parameter. This solution corresponds to variations of this parameter, that is, the stretching/contraction of the sphere keeping the total mass constant. During the process, the system remains in an equilibrium state. The simplicity of the solution makes it possible to explicitly give expressions for the distribution function, potential, and density in all orders of perturbation theory. This, in turn, helps to clarify the concept of perturbation energy, which, being a second-order magnitude in amplitude, cannot be calculated in linear theory. The expression for the 2nd-order perturbation energy does not match the well-known quadratic form for perturbation energy derived from 1st-order perturbations in linear theory. However, both of these energies are integrals of motion and differ only by a constant. The obtained solution can be used to control the correctness of codes and the accuracy of calculations in the numerical study of collisionless stellar models.
1023-1032
NEXT GENERATION GRAVITY MISSIONS: STUDYING THE POSSIBILITIES OF MULTIPLE CONSTELLATION
Abstract
We study potential possibilities of space constellation consisting of two pairs of spacecraft moving in different orbits, the so-called next generation gravity missions, aimed at increasing the spatial and temporal resolution of measurements and improving the accuracy of the recovery of the Earth’s gravity field. As a result of numerical simulation of the orbital motion of the multiple spacecraft constellation and solving the inverse problem of recovering the Earth’s gravitational field based on model measurements performed in this constellation, a multiple configuration with orbital parameters \(h = 370\) km, \(i = 90.5^\circ \) and \(h = 370\) km, \(i = 70.0^\circ \), was found. Such a multiple constellation makes possible to increase both the spatial and temporal resolution of the Earth’s gravity field models with a significant refinement of zonal, sectorial and tesseral harmonics compared to the one-pair near-polar configuration.
1033-1045
PARAMETERS OF RADIO PULSARS AT DIFFERENT DISTANCES FROM THE “DEATH LINE”
Abstract
Calculations of angles \(\beta \) between magnetic moments and rotation axes have been carried out for radio pulsars located at different distances from the “death line”. It is shown that these angles decrease from 36° to 10° when pulsars move to the “death line”. Such values correspond to kinematic ages from 1 to 10 millions of years. It is detected also that for these ages radio luminosities of pulsars decrease. This means that radio pulsars fade out when their age increases.
1046-1055
A PLANET OR PRIMORDIAL BLACK HOLE IN THE OUTER REGION OF THE SOLAR SYSTEM AND THE DUST FLOW NEAR EARTH’S ORBIT
Abstract
In recent years, evidence has been obtained that in the outer region of the Solar System (in the inner Oort cloud) at a distance of ~300–700 AU from the Sun, there may be a captured planet or a primordial black hole. In this paper, we show that the gravitational scattering on this object of dust particles located in the same region can transfer them to new elongated orbits reaching the Earth’s orbit. With the mass of the captured object of the order of 5–10 Earth masses, the calculated dust flow near the Earth is ~0.1–3 μg m–2 year–1 is comparable in order of magnitude with the observed flow. This effect gives a joint restriction on the parameters of the captured object and on the amount of dust in the Oort cloud.
1056-1068
TO THE QUESTION OF THE LOCALIZATION OF CME GENERATION ON THE SUN
Abstract
The localization of CME occurrence zones on the Sun from November 2006 to February 2007 was studied using the SOHO catalog. A method is described for comparing such zones with active regions (ARs) both in the visible and invisible hemispheres of the Sun. It is shown that a simple linear continuation of the projections of the CME trajectory on the Sun in many cases passes by the AO. 63.5% of CMEs managed to be tied to ARs, 19% failed, and for 17.5% a choice must be made between ARs and flare sites, where spots were observed 1–3 rotations of the Sun earlier. The hypothesis is discussed that the displacement of the beginning of the CME trajectory from the AR centroid is associated with the asymmetry of the location of the magnetic rope, on the basis of which the CME is formed, with respect to the AO: one base of the rope is located near the strong magnetic fields of sunspots, the second is in the region of weak fields on the periphery or outside the AO.
1069-1080
STATISTICS OF THERMAL PLASMA PARAMETERS AND NON-THERMAL X-RAY SPECTRA OF SOLAR FLARES WITH HELIOSEISMIC RESPONSE
Abstract
We present the results of statistical analysis of various thermal plasma parameters and non-thermal X-ray spectra of helioseismically active (producing “sunquakes”) solar flares of the 24th solar cycle up to February 2014. Two samples of flares are compared: with helioseismic activity in the form of sunquakes and a sample of flares without photospheric disturbances. The dependences of the considered flare parameters on the energy of helioseismic disturbances are also investigated. Quantitative parameters of solar flares are taken from the statistical work of the Global Energetics series by Markus Ashwanden in 2014–2019. We consider thermodynamic plasma parameters derived from the analysis of RHESSI X-ray spectra and differential emission measure (from AIA EUV images), as well as the characterization of non-thermal X-ray spectra from RHE-SSI. Statistical analysis confirmed that helioseismically active solar flares are characterized by significantly larger fluxes of non-thermal X-ray emission compared to flares without photospheric perturbations. A good linear relationship between helioseismic energy and the total flux of non-thermal X-ray radiation and the total energy of accelerated electrons is found. It is shown that the power-law index of the nonthermal X‑ray spectrum is not the parameter by which one can separate the two groups of flares under consideration. The analysis of the X-ray thermal spectra shows a slight difference between the flares with the sunsets.
1081-1102
GRAVITATIONAL CAPTURE AS A POSSIBLE SCENARIO ORIGIN OF THE MOON
Abstract
The article is devoted to the problem of the origin of the Moon. Discussed modern scenarios for the formation of the Earth-Moon system: simultaneous formation of the Earth and the Moon in the circumsolar gas of dust disk; impact partial destruction of the Earth by a massive asteroid; gravitational capture of the Moon by the Earth; destruction of the double moon at the beginning when approaching the Earth with possible subsequent absorption components of smaller mass by the Earth. We offer two-stage scenario of gravitational capture of the Moon by the Earth in the early stages Solar system. In the first stage, using a hybrid numerical model in the formulation of the three-body problem (Sun, Earth and Moon) and N-bodies, the search and selection of temporary orbits of the Moon around the Earth is carried out. Using the backward integration method in the formulation N-body problem, the influence of tidal forces on pumping of orbital moment of the Moon (\(P_{{{\text{orb}}}}^{M}\)) relative to the Earth at its own moment \(P_{s}^{M}\) is estimated. As the simulation shows, actions tidal forces alone are not enough to capture the Moon by the Earth in a short time time scale \( \sim 100\) years (\(\Delta P_{s}^{M} \sim {{10}^{{ - 6}}}P_{{{\text{orb}}}}^{M}\)). At the second stage, the factor is taken into account viscous-dissipative environment leading to additional “slowing down” of the Moon, due, for example, to collisions with asteroids and the transition of tidal energy into heat, which helps the Moon get rid of excess kinetic energy and gain constant orbit around the Earth.
1103-1118