Astrophysical Bulletin最新文献

We continue the annual publications of the magnetic field measurements of chemically peculiar stars. Observations were carried out with the Main Stellar Spectrograph of the 6-m telescope at SAO RAS in 2016. We obtained 108 pairs of circularly polarized spectra for 64 stars. For five objects (HD 9050, HD 31592, HD 82093, HD 142502, and HD 190068), a magnetic field was discovered for the first time. We estimated the physical parameters (effective temperature (T_{textrm{eff}}), surface gravity (log g), projected rotation velocity (v_{e}sin i)) and the radial velocity (V_{r}) for all the objects.

Based on data from the ‘‘TESIS’’ scientific instrumentation aboard the ‘‘CORONAS–Photon’’ satellite, collected during the solar activity minimum of 2009, the positions on the disk of 1014 solar flares were analyzed, with X-ray classes ranging from A0.003 to C2.7. A change in the spatial distribution was found in the region of class A events. As flare power decreases, a transition is observed from their localization within the activity belts to a more uniform latitudinal distribution. An estimate of the asymmetry in the positioning of the events on the solar disk was also obtained—0.009. Thus, it was established that the number of flares in the southern and northern hemispheres is almost identical.

To search for and study the instabilities in the atmospheres of selected post-AGB stars, we have performed a long-term high-resolution spectroscopy ((Rgeq 60,000)) with the NES spectrograph of the 6-m BTA telescope. Low-amplitude pulsations, splitting and/or asymmetry of the absorption profiles with a low excitation potential (mainly absorptions of (s)-process metals), as well as variability of a complex (H_{alpha}) profile have been registered in the optical spectra of single stars associated with the IR sources IRASz02229+6208, IRAS 04296+3429, IRAS 07134+1005, IRAS 07430+1115, IRAS 19500(-)1709, IRAS 22223+4327, and IRAS 23304+6147 that had previously undergone the third mixing. The maximum pulsation amplitude (A_{V_{r}}) was detected for the stars in the IRAS 07134+1005 and IRAS 19500(-)1709 systems, which have the maximum temperatures among the stars in the studied sample. Stratification of radial velocity in the atmosphere was found for two stars in the sample. The luminosity of the studied stars was estimated based on the intensity of the IR oxygen triplet O I (lambda) 7774. Moreover, a luminosity of (log L/L_{odot}approx 3.1) was obtained for the star in the IRAS 07430+1115 system within the range of typical post-AGB star luminosity values, which eliminates the paradox of the luminosity and the initial mass of this object.

Based on the original version of the pulsating photosphere method that allows modeling the changes in the effective temperature, a revision of the physical characteristics of the unique binary Cepheid V350 Sgr was carried out. Previously published measurements of radial velocities were used, as well as new ones obtained by us, which allowed us to refine the parameters of the Cepheid orbit. The choice of the projection factor (PF=1.34) allowed us to reconcile our estimates of the cycle-averaged radius (langle{R}rangle_{I}/R_{odot}approx 41.3{-}41.9), luminosity (M_{V}approx-3overset{textrm{m}}{.}52{-}3overset{textrm{m}}{.}57), normal color ((B-V)_{0}approx 0overset{textrm{m}}{.}56pm 0overset{textrm{m}}{.}01), effective temperature (langlelog{}T_{textrm{eff}}rangle_{I}approx 3.788pm 0.002), distance (Dapprox 992pm 14) pc and color excess (E(B-V)approx 0overset{textrm{m}}{.}35pm 0overset{textrm{m}}{.}01) with MESA theoretical evolutionary tracks for the mass (5.1M_{odot}) and metallicity ([{textrm{Fe}}/{textrm{H}}]=-0.18) dex (or mass (5.2M_{odot}), ([{textrm{Fe}}/{textrm{H}}]approx-0.10) dex) and the PARSEC 2.0 track for the mass (5.2M_{odot}), (Zapprox 0.01). The evolutionary age of the Cepheid, which is in the phase of the third crossing of the instability strip, is estimated at 100 Myr. It is shown that the Gaia eDR3/DR3 catalogues provide a distance overestimated by approximately 25%. Using the mass function for the available estimates of the Cepheid and companion masses, the relative orbital plane inclination angle (iapprox 53^{circ}pm 3^{circ}) and the orbital semi-major axes (a_{1}approx 1.63pm 0.05) AU, (a_{2}approx 3.42pm 0.09) AU were determined for the first time, with the relative orbit size of about 5 AU.

The paper presents the results of statistical modeling of the entry of near-Earth asteroids (NEAs) into near-Earth space (NES)—a sphere with a radius of 0.01 AU around the Earth. Distributions of asteroids by direction and velocity of entry into NES are constructed. The NEA population was modeled using the NEOMOD software with subsequent integration of the dynamic evolution for 110 years using the REBOUND package. It is shown that: 1) the number of asteroids larger than 10 m entering NES is approximately 1000 per year; 2) up to half of the asteroids can enter NES from the dayside hemisphere; 3) the asteroid flux density is increased in the solar and antisolar directions. Typical velocities of approach to the Earth when entering the NES are approximately 7.5 km s({}^{-1}) (the velocities range is from 0 to 30 km s({}^{-1})). The distribution of entries by distance and velocity relative to an observer located at the Lagrange point (L_{1}) of the Sun–Earth system is also calculated. These distributions can be useful in designing the System of Observation of Daytime Asteroids (SODA).

We review 61 papers devoted to stellar magnetism and published in 2023. The main interest of researchers is focused on the search for new magnetic stars, monitoring the magnetic fields of CP stars and other types of objects. Interest in the study of radio and X-ray emission from magnetic stars has increased. Most of the new data are based on the Gaia astrometry, TESS, and Kepler photometry, and LAMOST low-resolution spectroscopy.

We present an analysis of the relative abundance features of a number of chemical elements in the atmospheres of metal-rich (({textrm{[Fe/H]}}>-1)) Galactic-field RR Lyrae variable stars and the kinematic characteristics of these stars. We have previously shown that the relative abundances of some (alpha) elements: magnesium, silicon, calcium, and to a greater extent of titanium, as well as yttrium and scandium in such stars are lower than in most other types of stars bearing similar metallicity. It is found here that some of these metal-rich RR Lyrae stars also have very low relative abundances of sodium, aluminum, and nickel. The orbital parameters of all the metal-rich RR Lyrae variables studied in this paper are typical of the Galactic thin or thick disk objects, however, the unusual chemical composition let us to suggest a possible extragalactic origin for some of them.

The structure of sound waves in baryonic gas generated during the evolution of spherically symmetric dark matter halos with a mass less than the Jeans mass has been calculated. In this case, the source of the gravitational field that creates the wave can be at both the linear stage (evolving perturbation in dark matter) and the nonlinear stage (separated and virialized object). Peculiar motions of baryons in a sound wave in the second order in speed cause the absorption of relict radiation in the 21 cm line. It is shown that this additional absorption on sound waves is a fraction of a percent at redshifts (zsim 15{-}20) of the absorption value in the model of a homogeneous Universe, however, the additional absorption can be larger in the case of a non-standard spectrum of cosmological perturbations of matter density on small scales.

The rest wavelengths of diffuse interstellar bands (DIBs) are parameters of fundamental importance owing to the lack of unambiguous identification for these mysterious features. Usually the wavelengths of DIBs are estimated using known interstellar atomic or molecular lines serving to shift the spectrum to the rest wavelengths velocity scale. However, the latter may not share in fact the same parts of a cloud which the carriers of diffuse bands occupy. Here we argue that the narrowest known diffuse interstellar band 6196 Å is the best reference feature for building the ‘‘interstellar’’ wavelength scale. Also, we offer the geometrical center of gravity (the effective wavelength) of the diffuse bands as a rest wavelength measurer for these generally asymmetric features. We assessed the magnitude of variation of the center of gravity of the diffuse bands at 5780, 5797, 6284, and 7224 Å measured in 41 lines of sight in the broad range of interstellar reddening ((E_{B-V}) varies in the range of 0.13–1.06 stellar magnitudes) with the lack of evident Doppler-split in the profiles of interstellar atomic/molecular lines. We demonstrated that diffuse bands show gradual broadening of their profile widths, accompanied with the red-shift of the center of gravity, i.e., the red wing of the profiles is their most variable part. To estimate the width of the diffuse bands, we offer to apply an ‘‘effective width’’ parameter (W_{textrm{eff}}), which is the relation of the equivalent width ((EW)) to the depth of the feature. In contrast to habitual half width at half maximum ((FWHM)), the parameter originally introduced by us in 2008 (Galazutdinov, LoCurto, Krełowski) is not sensitive to the profile shape irregularities. (W_{textrm{eff}}) provides lower measurement uncertainties than the (FWHM) does. The gradual increase of (W_{textrm{eff}}), accompanied with the red-shift of the center of gravity of the profile, may suggest populating of higher transitions of the P branch of the bands of molecules, assuming the latter are DIB carriers. It is also shown, that diffuse bands are broader although more shallow in the harsh conditions of (sigma)-clouds, where atomic and molecular lines are weakened and/or totally absent. The difference of the effective width of DIBs in (zeta) and (sigma) clouds is discussed as well.

We report the results of laboratory studies of the main optical properties of the slitless spectrograph developed for a small telescope with a 0.5 m-diameter primary mirror and a focal ratio of (1:6.8). The spectrograph operates in the 450–950 nm wavelength interval and has a field of (35overset{prime}{.}6times 7overset{prime}{.}2). Its distinctive feature is the use of a composite grism subdivided into two subapertures with independently optimized parameters. Measurements show that the use of such a grism makes it possible to achieve a spectral resolving power (R) from 461 to 1041 with the grating diffraction efficiency as high as 45(%). We demonstrate that our solution provides better optical characteristics compared to the classical grism and that our measurements agree well with the results of modeling.