Astronomy Reports最新文献

An analysis of photometric observations of the star V647 Her (M3.5V) obtained at the 1.25-m telescope of the Crimean Astrophysical Observatory in 2022 is presented. The presence of a low-amplitude variability in brightness of the star with a period of 20.69 d, found from observations in 2019 was confirmed. It is shown that as the brightness decreases, the star becomes redder. The observed kind of photometric variability is due to the presence of cool spots on the surface of the star and rotational modulation of brightness with a full amplitude of no more than 0(^{{text{m}}}_{.})05. We perform a comparison of the photometric results obtained in 2019, 2022, and 2004. The locations of starspots at different epochs were determined from the analysis of phase curves. The distribution of starspots has been maintained for 40–100 days. Starspot parameters were estimated in the framework of the zonal model. The temperature of starspots is 2700–2800 K. The area they occupied in 2004 is 15% of the total surface area of the star. According to the 2019 and 2022 data, it increases up to 30%. The seasonal redistribution of starspots leads to the difference between the spottedness of hemispheres, which is less than 2%.

The short biography of one of the founders of stellar astronomy as a science, Pavel Petrovich Parenago, is presented. Considered the question of which scientific phenomena and objects in astronomy bear his name.

Observations of the dwarf nova SS Cyg were made in 2019–2021 at different brightness levels ((V sim 10{-} {{12}^{m}})) both at the brightness decay stage after the outburst maximum, and in the quite state between outbursts. Data were obtained in ({{R}_{c}}) (( sim {kern 1pt} 8650) observations, 3 sets) and V (( sim {kern 1pt} 50,000) points, 22 sets) bands. The value of the system’s orbital period obtained in 2019–2021 (({{P}_{{{text{orb}}}}}{{ = 0.27408(2)}^{d}})) used in this study is 0.4% less than the value obtained more than a quarter of a century ago (1983–1996). The time resolution between two successive measurements is 6–14 s depending on the equipment used. An extensive database of new observational data allowed us to perform a quantitative analysis of observations. Analysis of the data after taking into account orbital variability and other trends associated with changes in the system’s emission flux during the night showed the presence of cyclic fluctuations in brightness, usually 4–10 events per orbital cycle – flickering. For most series of observations, the Lafleur-Kinman method determined such a value of the oscillation period at which convolution of observations with it showed a single wave. The obtained values of the characteristic flickering times and their amplitudes show their dependence on the average brightness level of the system. With increasing luminosity of the system, both of these quantities decreased linearly. From the size ratios of the binary system components of SS Cyg, it was shown that the source of flickering is located in the interaction region of the gas flow with the near-disk halo: only this region in the SS Cyg system with parameters ((q), (i), ({{R}_{d}})), defined by the authors earlier, can be eclipsed at large radii disk, and is clearly visible in all other orbital phases of the system.

One of the most important tasks of studying seeing conditions of possible locations for the Eurasian Submillimeter Telescopes is to research the statistics of precipitated water vapor, optical depth and cloudiness. In this paper, the statistics of precipitated water vapor and total cloudiness in northern Eurasia are studied using ERA-5 reanalysis. Optical depth statistics at a wavelength of 3 mm were obtained using the Liebe model from the ERA-5 reanalysis for the region where the Large Altazimuth Telescope BTA is located. The most favorable astroclimatic zones of Eurasia, along with Tibet and the eastern Pamirs, are certain areas of the Sayan Mountains, mountainous Altai and mountainous Dagestan. The work verifies the ERA-5 reanalysis data using radiosounding, GNSS measurement data and radiometric measurements for 2021.

UBVR polarimetric observations of 12 main-belt mostly primitive asteroids located near perihelion heliocentric distances were carried out from December 2022 to April 2023 with Zeiss-2000 telescope at the Terskol Peak observatory. The purpose of the monitoring program was to search for changes in the polarimetric parameters of the asteroids caused by possible sublimation-dust activity, as a result of which the formation of rarefied dust exospheres of asteroids is possible. The objects of the program were asteroids: (1) Ceres, (53) Kalypso, (117) Lomia, (164) Eva, (214) Ashera, (324) Bamberga, (419) Aurelia, (505) Cava, (554) Peraga, (654) Zelinda, (704) Interamnia, (1021) Flammario. Polarimetric observations of asteroids (117) Lomia, (164) Eva and (505) Kava were made for the first time, the remaining asteroids were observed earlier. Only for two asteroids (1) Ceres and (704) Interamnia, according to spectrophotometric observations, temporal spectrophotometric variability was noted earlier. Analysis of temporal changes in the degree of polarization of asteroids and comparison of the results of observations with the data available in the literature showed that the stability of the observed degree of polarization is comparable with measurement errors of ( sim {kern 1pt} (0.02{-} 0.1))% for asteroids of different brightness. Thus, during the observation period, no noticeable polarization signs of temporary sublimation-dust activity of the observed asteroids were detected. Additionally, it is shown that the currently existing variants of the spectral taxonomy of asteroids, based on spectrophotometric data and albedo, demonstrate a significant scattering of the selected classes when compared with their polarimetric phase dependencies. The asteroid (554) Peraga has been confirmed to have a negative degree of polarization at angles less than the inversion angle. Measurements of the polarization of the asteroid (1) Ceres in a wide range of wavelengths did not confirm the previously suspected change in the angle of the polarization plane with the wavelength.

We study the effect of modifying the equation of state parameter ((w)) of dark energy on the results of the previous study [1] (hereafter Paper II), in which dark energy was assumed to be a cosmological constant. As a first step, solving the equation of motion, we found a relation between mass, (M), and the turn-around radius, ({{R}_{0}}). Then, we obtained a relationship between the velocity, ({v}), and radius, (R). The relation was fitted to data of the groups used in Paper II to obtain the Hubble parameter, and the mass, (M) of the groups. We observe a significant reduction of the mass, (M), comparing Paper II results (for which (w = - 1)) and the case (w = - 1{text{/}}3), while the Hubble constant increases going from (w = - 1) to (w = - 1{text{/}}3).

Our objective is to construct models of the velocity ellipsoid and the retrieved Solar motion for program stars with 4924 points within the Solar neighborhood (∼2 kpc). In which 1374 early types (B5, A0, A5, F0, and F5) and about 3550 late types (G0, G5, K0, and K5) with more recent data source with Gaia DR3. Based on space velocity vectors ((bar {U},bar {V},bar {W};;{text{km }}{{{text{s}}}^{{ - 1}}})), we have determined a velocity ellipsoid parameter for our program stars. We have derived the Solar velocity (({{S}_{ odot }})), which ranged from 13.39 ± 3.66 to 25.06 ± 5.06 km s^–1, and other Solar elements (({text{i}}.{text{e}}.,;{{l}_{{text{A}}}},;{{b}_{{text{A}}}},;{{{{alpha }}}_{{text{A}}}},;{{{{delta }}}_{{text{A}}}})), the velocity dispersion (left( sigma right)), ranging from 26.65 ± 5.16 to 57.29 ± 7.57 km s^–1 for considered program stars, the projected distances (({{X}_{ odot }},{{Y}_{ odot }},{{Z}_{ odot }};;{text{kpc}})), ratio of (left( {{{sigma }_{2}}{text{/}}{{sigma }_{1}}} right)), ranging from 0.52 to 0.92, which relates to Oort’s constants ((A,B;;{text{km}};{{{text{s}}}^{{ - 1}}}{text{ kp}}{{{text{c}}}^{{ - 1}}}),) and finally the ratio of (({{sigma }_{3}}{text{/}}{{sigma }_{1}})), ranging from 0.41 to 0.61.

An analytical model of a parabolic screen illuminating a black hole is proposed. This allows to avoid naturally the appearance of edge effects associated with photons moving along the plane of the screen illuminating the black hole. The temperature distribution along the radius of the screen corresponds to that for a relativistic disk (Novikov–Thorne disk). It is shown that the structure of the emerging black hole shadow differs significantly from the case when the photon source is a remote screen, since in the model considered, the photons subjected to strong gravitational lensing of the black hole are emitted by the “back side” of the screen, which would not be visible in the absence of a black hole. In the thin screen approximation, the shadow of a Schwarzschild black hole has been constructed in cases when the angle between the axis of symmetry of the illuminating screen and the direction towards the observer is 5°, 30°, 60°, and 80°. The images for the Kerr black hole are shown for the angles of 60° and 80°.

In this study, we expand on White’s model proposed in [1], which explores the post-collapse evolution of density peaks while incorporating the influence of angular momentum. Within a time scale smaller than the peak collapse, denoted as ({{t}_{0}}), the inner regions of the peak reach an equilibrium state, forming a cuspy profile, consistent with White’s findings. However, the power-law density profile is slightly flatter, specifically (rho propto {{r}^{{ - 1.52}}}), due to the incorporation of the specific angular momentum (J) obtained from theoretical models of its evolution in CDM universes, represented as (J propto {{M}^{{2/3}}}). The outcome above demonstrates the impact of angular momentum on the slope of the density profile, allowing us to reproduce a slightly flatter profile similar to the one observed in high-resolution numerical simulations, where (rho propto {{r}^{alpha }}) with (alpha simeq - 1.5). Notably, our model, like the simulations, does not account for adiabatic contraction. Therefore, conducting more comprehensive simulations may yield different values for the slope of the density profile, presenting an opportunity to enhance and refine our model.

Three light curves of the V1059 Cep eclipsing binary obtained in 2012, 2013, and 2021 were analyzed. We found the rapid apsidal motion in this system at the rate (domega {text{/}}dt = 7.2^circ ) per year. Assuming the equality of observed and theoretical apsidal motion rates we estimated physical characteristics of the components based on the data on their temperatures from the literature. According to our calculations the components are two very similar stars of the B7V–B7.5V spectral type with masses ( approx {kern 1pt} (3.4 pm 0.3){kern 1pt} {{M}_{ odot }}) and age (180 pm 30) million years.