Astrophysical Bulletin最新文献

We present the results of a further investigation of the planetarysystem HD 109833, whose central star is a young, active solaranalog, presumably a member of the Lower Centaurus Cruxassociation (age: (27pm 3) Myr). Using digitized photographicplates from the Digital Access to a Sky Century@Harvard project(providing data on HD 109833 spanning a 100 year observationperiod) we made an additional attempt to study possible activitycycles of the star. Taking into account all uncertainties, itshould be noted that the derived estimates of the activity cycleperiod (P_{textrm{cycl}}) (including the earlier value obtainedfrom ASAS-3 data, (P_{textrm{cycl}}=5.3) years) are on the edgeof statistical reliability. Based on measurements of thechromospheric activity index (log R^{prime}_{HK}) forHD 109833 from the updated HARP SRV database and its empiricalrelation with (log F_{textrm{XUV}}), we estimated the XUVphoton flux to be (2.0times 10^{29}) erg s({}^{-1}). Theexoplanets HD 109833 b and c are located in the overlappingregion of two distinct populations on the ‘‘mass–radius’’diagram: rocky planets and planets rich in volatile compounds. Wepresent calculations of atmospheric mass loss rates (dot{M}) forHD 109833 b and c based on both the energy-limited escape model(EL) and the hydrodynamic approximation model (HA), usingdifferent planetary mass estimates. We also provide the ratios ofmass loss rates (dot{M}) obtained from EL and HA models (Ratio),and the values of the Jeans parameter (Lambda). It is suggestedthat the HA model significantly underestimates (dot{M}) in thecase of rocky planets, rendering this model inapplicable for suchhigh values of (Lambda). Our results are in reasonable agreementwith those of Foster et al. (2022), which describe the generalbehavior of (dot{M}), and fall within the observed spread of thisparameter.

This study is devoted to the cosmological ‘‘angular size–redshift’’ test. An analysis was performed of the angular and linear sizes of galaxies from the new ASTRODEEP-JWST catalog containing over 500 000 objects at high redshifts (up to (zsim 20) photometrically determined and up to (zsim 14) spectroscopically determined). For calculations, 6860 galaxies with reliably determined spectroscopic redshifts and 319 771 galaxies with known photometric redshifts were used. The linear sizes of galaxies were computed within the framework of two cosmological models—the standard ((Lambda)CDM) model and one of the static models (the so-called ‘‘tired light’’ model). We have shown that within the framework of the (Lambda)CDM model, a significant evolution of the linear sizes of galaxies is observed, with the evolutionary rate closely matching the rate of the cosmic expansion. In contrast, in the static model, the characteristic linear sizes of galaxies exhibit almost no evolution with increasing (z).

The paper studies the characteristics of optical emissionformation and determines the fundamental parameters of the FL Pscdwarf nova for the epochs before and after its superoutburst in2023. Moderate-resolution spectral sets were obtained in 2021,2023 and 2024 with the BTA-6 telescope of the SAO RAS.Observations in all epochs are dominated by the continuousspectrum of the white dwarf (WD) with H I, He I, He II, C II,Mg I, Ca I, Ca II, Fe I emissions and Fe II from theaccretion disk and a bright spot at its outer radius. Changes inemission intensities and their Doppler half-widths showed thatduring the transition from the relaxation stage to quiescence,the zone of maximum radiation shifted to the periphery of thedisk, and the temperature in it decreased to (T_{e}<8000) K. Ananalysis of the observed spectra for three epochs was performedusing model flux (i.e. in flux units) and normalized spectra ofthe WD and a modified method for determining the parameters oftheir atmospheres. As a result, the following estimates of theaccretor’s temperature were obtained for a single surface gravityvalue (log g=8.26pm 0.13): (T_{textrm{eff}}=17,700pm 1400) K, (26,700pm 1900) K and (19,600pm 1300) K in 2021,2023 and 2024, respectively. It is shown that the observedsystematic variations in the brightness of FL Psc after the end ofthe outburst are correctly explained by changes in the WDtemperature, taking into account the additional contribution ofemission lines. Based on the parameters found for the accretor’satmosphere, the complete set of fundamental parameters of thesystem is refined. Its Doppler tomography showed that 1.3 yearsafter the outburst, the accretion disk remained optically thick inthe H I lines, but became optically thin in the lines of otherelements. Analysis of the FL Psc maps suggests that the H I,He I and He II emissions are formed predominantly underthermalization conditions, while the Ca II and Fe II  emissionsare formed under the influence of the fluorescence effects of softultraviolet radiation from the WD in the accretion disk and thesurrounding gaseous envelope.

Galactic orbital parameters of 519 type II Cepheids classified asBL Her, W Vir and RV Tau variable stars were calculated usingBayesian distances, proper motions, and Gaia DR3 radialvelocities. It is shown that at least 27 BL Her type variables outof 100, 17 W Vir type variables out of 308 and 8 RV Tau typevariables out of 111 are characterized by a spatial distributionand galactic orbital parameters typical of the population of thethin/old disk of the Galaxy. At the same time, their luminositiesare significantly lower than those of classical Cepheids (DCEP),and correspond to the luminosities of type II Cepheids. It issuggested that the region of the instability strip occupied byshort-period Cepheids of the BL Her type may contain stars of theold disk with initial masses of about (0.95 M_{odot}), whichevolved from the main sequence to the stage of the onset of heliumburning in the core and reached the instability strip over a timeof about 9 Gyr. The presence of evolutionary ‘‘loops’’ explainsthe existence of a number of BL Her type Cepheids, whichdemonstrate an evolutionary decrease in period. Thus, bothlow-mass stars in the phase of evolution of a double-layer sourceand stars at the stage of the onset of helium burning in the corewith a larger initial mass can coexist in the instability strip ofBL Her variables. To refine the classification of type IICepheids, more detailed evolutionary and pulsation calculationsand additional comprehensive studies are needed, including, forexample, estimates of pulsation radii.

This paper presents the results of a statistical analysis of the properties of coronal mass ejections (CMEs) associated with solar flares that exhibit a helioseismic response (‘‘sunquakes’’) in comparison with flares that do not show photospheric disturbances. The analysis is based on observations of the solar corona in the ultraviolet range (from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, SDO/AIA) and the visible range (from the Large Angle Spectroscopic Coronagraph on board the Solar and Heliospheric Observatory, SOHO/LASCO). We considered samples of flares with different lower thresholds based on the Geostationary Operational Environmental Satellites (GOES) classification: above M1.0, M5.0, and M7.0. A correlation analysis was also carried out between CME parameters and the total energy of the sunquakes. Additionally, for flares above M7.0-class, information on the presence of radio bursts across a wide range of wavelengths, as well as hard X-ray emission, was analyzed. It was found that CMEs accompanying flares with a helioseismic response tend to have higher velocities in the lower corona (according to AIA data) compared to flares without photospheric disturbances. The distribution of CME masses is approximately the same regardless of the presence or absence of sunquakes during the flares. An analysis of dimming properties showed that they are more impulsive in terms of temporal dynamics in flares with sunquakes. CMEs in flares above M7.0-class that exhibit helioseismic responses are less massive and slower in the outer corona according to LASCO data. The correlation analysis did not reveal strong relationships between acoustic energy and CME parameters based on AIA observations, but for several parameters (kinetic energy, CME mass, and dimming depth), statistically significant correlations were identified according to the (t)-criterion. In contrast to flares with sunquakes, there was an almost complete absence of type III radio bursts and a rare occurrence of type II bursts in the M7.0-class flares without photospheric disturbances. The spectral peak of microwave bursts tends to occur at higher frequencies in flares with sunquakes than in those without. According to our analysis, flares with sunquakes likely possess the ability to efficiently generate fast coronal dimmings and shock waves, even in the presence of poorly developed CMEs in the upper corona (in comparison to flares without photospheric disturbances). These events are also characterized by pronounced signatures of electron acceleration, with particles escaping the acceleration region both toward the solar surface and outward from it. In our view, this indicates that the possibility of an eruptive origin for sunquakes cannot be ruled out. Accelerated electrons may act as both the primary and secondary agents responsible for initiating the photospheric perturbation.

We present the results of testing an iXon Ultra 888 EMCCD camera to determine the operating parameters for short-exposure photometry of stars. As a result of the testing, those camera modes were selected in which the temporal instability of the electron multiplication charge does not significantly affect the light curves. In addition, the photometry of the eclipsing variable star ZTF J 0038+2030, obtained with the Zeiss-1000 telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences, is presented. We have shown the advantages and disadvantages of 1-s exposures for studying variable stars.

A mobile W-DIMM device was used to measure seeing at the Crimean station of Sternberg Astronomical Institute of Moscow State University over seven nights, from June 23 to 30, 2024. Seeing estimates for altitudes greater than 500 m were inferred from scintillations in the sensor apertures separate from the total optical turbulence power. The zenith-adjusted seeing values were (beta_{textrm{med}}approx 1overset{primeprime}{.}15), the corresponding seeing for the upper atmosphere was found to be of about (0overset{primeprime}{.}28). A comparison of the seeing estimates obtained on these nights at telescopes with long exposures agrees well with the readings of the mobile differential image motion monitor. Some climatic parameters were also obtained both from a stationary weather station near the observation point and from satellite data.

An analysis of the activity evidence of the chromospherically active solar-type dwarf HD 284521, which has a sub-Neptune-type planet, is presented. Based on the data from the Kepler and TESS missions, the stellar rotation period was estimated ((P_{textrm{rot}}=13{-}14) days) and the evolution of cold spots on its surface was examined. Estimates of the areas of these spots were obtained, which, according to the data from the Kepler mission, equaled about 3.2(%) and, according to TESS observations, about 2.3, 1.2, 2.3, and 2.5(%) of its surface area. Based on the data from the long-term Kamogata Wide-field Survey (KWS) and data from the All Sky Automated Survey (ASAS) observation archive, the value of the star’s long-term activity cycle was found to be about 3800 days (10.4 yrs). The cycle length is comparable to that of the Sun, but HD 284521 rotates about twice as fast as the Sun. An analysis of measurements of the (S) index characterizing the chromospheric activity of the star also indicates the presence of a long-period variability. The results obtained from studying the stellar activity were used to estimate the loss of atmospheric matter from the planet HD 284521 b. An approximation formula corresponding to the energy-constrained atmospheric loss model was applied. Based on 135 estimates of the (S) parameter, the matter loss from the atmosphere of HD 284521 b over an interval of 1886 days (approximately five years) was calculated. The matter losses ((log M_{textrm{loss}})) of the atmosphere of the planet HD 284521 b are in the range of 9.8 to 10.3 with a median value of 10.2. The high amount of matter loss from the atmosphere of this planet is due to a significant flux of XUV photons caused by the high activity of the solar-type star. The study of the planetary system HD 284521 continues our series of studies of planetary systems, in which the central star is an analog of the Sun.

DEFPOS Fabry–Perot spectrometer, located at the coude exit of the RTT-150 telescope (Bakirlitepe, Antalya, Turkey), has been used to measure the ionized gas within the Lagoon Nebula (M 8) which is an H II region (Sh2-25). Eighty-four H(alpha) emission line spectra obtained from the H II region provide detailed information about some physical properties of the gas surrounding the H II region. The line widths, (V_{textrm{LSR}}) velocities, and ({I_{textrm{ H}{alpha}}}) intensities of the H(alpha) emission spectra were found to be in the range from (27.5pm 5.80) to (41.50pm 1.99) km s({}^{-1}) (mean (35.50pm 2.05) km s({}^{-1})), (-13.67pm 0.58) and (3.19pm 0.72) km s({}^{-1}) (mean (-4.92pm 0.32) km s({}^{-1})), and (173.35pm 9.97) R and (13834.20pm 21.56) R (mean (2247.65pm 8.33) R), respectively. The mean LSR velocity and line width of the nebula were also compared with previous works. Since there is not enough information on intensities and LSR velocities of such galactic sources with low angular size in the literature, we believe that DEFPOS spectrometer will provide a powerful tool for the study of the diffuse ionized gas, and these new results may have significant contributions to the literature.

The results of photometric observations of three SU UMa type cataclysmic variables in the quiescent state ((18overset{textrm{m}}{.}3-20overset{textrm{m}}{.}5)) are presented. It is shown that the objects have different ouburst amplitudes: (5^{textrm{ m}})—CRTS J000130+050624; (3overset{textrm{m}}{.}7)—1RXS J003828.7+250920 and (2overset{textrm{m}}{.}5)—V452 Cas. The orbital period was first discovered for CRTS J000130+050624—0.09055(19) days, V452 Cas—0.084898(2) days, and updated for 1RXS J003828.7+250920—0.09451123(5) days. Ephemeris have been determined for the light curve minima of these objects associated with the orbital period. Estimates of the mass ratio of the components are (q=0.181(6)), (0.198(1)), (0.183(2)) for 1RXS J003828.7+250920, CRTS J000130+050624, and V452 Cas, respectively. It is shown that these dwarf novae are located in the vicinity of the theoretical short-period boundary of the period gap and are in good agreement with known empirical data.