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How Common can the Origin of Clusters Cha Ⅰ, Cha Ⅱ, ∈Cha and η Cha be?

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Research in Astronomy and Astrophysics 2024年第5期24卷 28-34页

作者： V.V.Bobylev A.T.Bajkova pulkovo Astronomical observatory St.-Petersburg 196140Russia

The trajectories of the groupings η Cha,∈Cha and Cha I,Cha II,constructed backward in time,have been *** concluded that the hypothesis about the joint formation of all four of these clusters from one molecular cloud cannot be completely ***,10–15 Myr ago,all these four clusters were located at approximately the same height above the plane of the ***,the gas-dust clouds from which all these four clusters were formed were located on one broad *** is possible that the appearance of the Cha I,Cha II,∈Cha and η Cha clusters may be associated with the impact on such a front of shock waves formed after supernova explosions in the Scorpius–Centaurus *** estimates of the kinematic ages of the clusters Cha I and Cha II are obtained as 0.12±0.19 and 0.05±0.15,*** is shown that the minimum size of the Cha I-north and Cha I-south clusters corresponded to the time of 0.55±0.24 Myr and 0.04±0.18 Myr ago,respectively,and approximately1.5 Myr ago the distance between the trajectories of these two groupings was minimal.

关键词： stars distances-stars kinematics and dynamics-galaxies star formation

Cross-method Analysis of Corotation Radii Data Set for Spiral Galaxies

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Research in Astronomy and Astrophysics 2024年第7期24卷 98-113页

作者： V.S.Kostiuk A.A.Marchuk A.S.Gusev Sternberg Astronomical Institute Lomonosov Moscow State University Central (pulkovo) Astronomical observatory Russian Academy of Sciences Saint Petersburg State University

A corotation radius is a key characteristic of disk galaxies that is essential to determine the angular speed of the spiral structure Ωp, and therefore understand its nature. In the literature, there are plenty of methods to estimate this value, but do these measurements have any consistency? In this work, we collected a data set of corotation radius measurements for 547 galaxies, 300 of which had at least two values. An initial analysis reveals that most objects have rather inconsistent corotation radius positions. Moreover, a significant fraction of galactic disks is distinguished by a large error coverage and almost uniform distribution of measurements. These findings do not have any relation to spiral type, Hubble classification, or presence of a bar. Among other reasons, obtained results could be explained by the transient nature of spirals in a considerable part of galaxies. We have made our collected data sample publicly available, and have demonstrated on one example how it could be useful for future research by investigating a winding time value for a sample of galaxies with possible multiple spiral arm patterns.

关键词： galaxies: fundamental parameters galaxies: kinematics and dynamics galaxies: structure

Dreicer Electric Field Definition and Runaway Electrons in Solar Flares

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Research in Astronomy and Astrophysics 2024年第2期24卷 180-184页

作者： Yu.T.Tsap A.V.Stepanov Yu.G.Kopylova Crimean Astrophysical observatory of the Russian Academy of Sciences Nauchny298409Russia pulkovo observatory of the Russian Academy of Sciences Pulkovskoje Shosse65/1St.Petersburg196140Russia

We analyze electron acceleration by a large-scale electric field E in a collisional hydrogen plasma under the solar flare coronal conditions based on approaches proposed by Dreicer and Spitzer for the dynamic friction force of *** Dreicer electric field EDr is determined as a critical electric field at which the entire electron population runs *** regimes of strong(E≲E_(Dr))and weak(E≪E_(Dr))electric field are *** is shown that the commonly used formal definition of the Dreicer field leads to an overestimation of its value by about five *** critical velocity at which the electrons of the"tail"of the Maxwell distribution become runaway under the action of the sub-Dreiser electric fields turns out to be underestimated by√3 times in some works because the Coulomb collisions between runaway and thermal electrons are not taken into *** electron acceleration by sub-Dreicer electric fields generated in the solar corona faces difficulties.

关键词： acceleration of particles-Sun flares-Physical Data and Processes

Isochrone Fitting of Galactic Globular Clusters—Ⅵ.High-latitude Clusters NGC 5024 (M53),NGC 5053,NGC 5272 (M3),NGC 5466,and NGC7099 (M30)

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Research in Astronomy and Astrophysics 2024年第6期24卷 170-190页

作者： G.A.Gontcharov S.S.Savchenko A.A.Marchuk C.J.Bonatto O.S.Ryutina M.Yu.Khovritchev V.B.Il'in A.V.Mosenkov D.M.Poliakov A.A.Smirnov Central(pulkovo)Astronomical observatory Russian Academy of SciencesPulkovskoye chaussee 65/1St.Petersburg 196140Russia Saint Petersburg State University Universitetskij pr.28St.Petersburg 198504Russia Special Astrophysical observatory Russian Academy of Sciences369167 Nizhnij ArkhyzRussia Departamento de Astronomia Instituto de FísicaUFRGSAv.Bento Gonçalves9500Porto AlegreRSBrazil Saint Petersburg University of Aerospace Instrumentation Bol.Morskaya ul.67ASt.Petersburg 190000Russia Department of Physics and Astronomy Brigham Young UniversityN283 ESCProvoUT 84602USA

We fit various color–magnitude diagrams(CMDs) of the high-latitude Galactic globular clusters NGC 5024(M53),NGC 5053,NGC 5272(M3),NGC 5466,and NGC 7099(M30) by isochrones from the Dartmouth Stellar Evolution Database and Bag of Stellar Tracks and Isochrones for α–enrichment [α/Fe] = +*** the CMDs,we use data sets from Hubble Space Telescope,Gaia,and other sources utilizing,at least,25 photometric filters for each *** obtain the following characteristics with their statistical uncertainties for NGC 5024,NGC 5053,NGC 5272,NGC 5466,and NGC 7099,respectively:metallicities [Fe/H] =-1.93 ± 0.02,-2.08 ± 0.03,-1.60 ± 0.02,-1.95 ± 0.02,and-2.07 ± 0.04 dex with their systematic uncertainty 0.1 dex;ages 13.00 ± 0.11,12.70 ± 0.11,11.63 ± 0.07,12.15 ± 0.11,and 12.80 ± 0.17 Gyr with their systematic uncertainty 0.8 Gyr;distances(systematic uncertainty added) 18.22 ± 0.06 ± 0.60,16.99 ± 0.06 ± 0.56,10.08 ± 0.04 ± 0.33,15.59 ±0.03 ± 0.51,and 8.29 ± 0.03 ± 0.27 kpc;reddenings E(B-V) = 0.023 ± 0.004,0.017 ± 0.004,0.023 ± 0.004,0.023 ± 0.003,and 0.045 ± 0.002 mag with their systematic uncertainty 0.01 mag;extinctions AV= 0.08 ± 0.01,0.06 ± 0.01,0.08 ± 0.01,0.08 ± 0.01,and 0.16 ± 0.01 mag with their systematic uncertainty 0.03 mag,which suggest the total Galactic extinction AV= 0.08 across the whole Galactic dust to extragalactic objects at the North Galactic *** horizontal branch morphology difference of these clusters is explained by their different metallicity,age,mass-loss efficiency,and loss of low-mass members in the evolution of the core-collapse cluster NGC 7099 and loose clusters NGC 5053 and NGC 5466.

关键词： (stars:)Hertzsprung Russell and C-M diagrams (ISM:)dust extinction (Galaxy:)globular clusters:general (Galaxy:)globular clusters:individual(NGC 5024,NGC 5053,NGC 5272,NGC 5466,NGC7099)

Dynamo saturation in rapidly rotating solar-type stars

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Research in Astronomy and Astrophysics 2015年第11期15卷 1801-1812页

作者： Leonid L.Kitchatinov Serge V.Olemskoy Institute for Solar-Terrestrial Physics pulkovo Astronomical observatory

The magnetic activity of solar-type stars generally increases with stellar rotation rate. The increase, however, saturates for fast rotation. The Babcock-Leighton mechanism of stellar dynamos saturates as well when the mean tilt angle of active regions approaches ninety degrees. Saturation of magnetic activity may be a consequence of this property of the Babcock-Leighton mechanism. Stellar dynamo models with a tilt angle proportional to the rotation rate are constructed to probe this *** versions of the model- treating the tilt angles globally and using Joy＇s law for its latitude dependence- are considered. Both models show a saturation of dynamogenerated magnetic flux at high rotation rates. The model with latitude-dependent tilt angles also shows a change in dynamo regime in the saturation region. The new regime combines a cyclic dynamo at low latitudes with an（almost） steady polar dynamo.

关键词： saturation stellar latitude rotation rotating stars polar regime meridional consequence

Orbits of 152 globular clusters of the Milky Way galaxy constructed from Gaia DR2

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Research in Astronomy and Astrophysics 2021年第7期21卷 177-191页

作者： Anisa Talgatovna Bajkova Vadim Vadimovich Bobylev pulkovo Astronomical observatory St.Petersburg 196140Russia

We present orbits and their properties for 152 globular clusters of the Milky Way galaxy obtained using average Gaia DR2 proper motions and other astrometric data from the list of Vasiliev. For orbital integration we have applied the axisymmetric model of the Galactic potential based on the Navarro-Frenk-White dark halo, and modified by Bajkova & Bobylev utilizing circular velocities of Galactic objects in a wide region of Galactocentric distances(up to 200 kpc) from the Bhattacharjee et al. catalog. Based on the analysis of the obtained orbits, we have modified the composition of the subsystems of globular clusters presented in Massari et al..

关键词： (Galaxy) globular clusters general

3D Kinematics of Classical Cepheids According to Gaia EDR3 Catalog

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Research in Astronomy and Astrophysics 2023年第4期23卷 1-14页

作者： V.V.Bobylev A.T.Bajkova pulkovo Astronomical observatory St.-Petersburg 196140Russia

The kinematics of about 2000 classical Cepheids of the Milky Way with data from Gaia EDR3 catalog has been *** some of these stars,there are line-of-sight *** the basis of the nonlinear rotation model,the parameters of the rotation curve of the Galaxy were *** circular linear rotation velocity of the near-solar neighborhood around the Galaxy center was V0=236±3 km s^(−1) for the assumed Sun's galactocentric distance R0=8.1±0.1 *** of residual velocities of Cepheids based on the linear Ogorodnikov–Milne model showed the presence of the following significantly different from zero gradients:∂U/∂x,∂U/∂z,∂V/∂x,∂V/∂z and∂W/∂x,which behave differently depending on the selection *** most interesting is the gradient∂W/∂x∼−0.5±0.1 km s^(−1) kpc^(−1)(positive rotation of this star system around the Galactic axis y,Ωy)since the velocities W are free of Galactic *** we have an indirect influence of various effects leading to a perturbation of the vertical velocities of the Galactic disk *** on a simpler model,a more accurate estimate of this rotation is obtained,Ωy=0.51±0.07 km s^(−1) kpc^(−1).

关键词： stars distances-Galaxy kinematics and dynamics-stars variables Cepheids

Estimating masses of selected stars in the pulkovo program by means of astrometry methods

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Research in Astronomy and Astrophysics 2018年第8期18卷 45-52页

作者： Natalia A.Shakht Denis L.Gorshanov Olga O.Vasilkova Central(pulkovo)Astronomical observatory of Russian Academy of Sciences Saint Petersburg196140 Russia

Stars in the pulkovo observatory program are observed with a 65-cm refractor during many years to study their positions and movements. We present examples of two visual binary stars, for which orbits and masses of components were determined, and two astrometric stars, for which masses of their unseen companions were estimated. The first two stars are ADS 14636 （61 Cygni） and ADS 7251, and the others are Gliese 623 and ADS 8035 （Alpha UMa）. Direct astrometric methods are used for estimation of mass-ratio and masses.

关键词： stellar masses - orbits - binaries individual (61 Cygni Alpha UMa Gliese 623 ADS 7251)

Variability of emission lines in the optical spectra of the Herbig Be binary system HD 200775

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Research in Astronomy and Astrophysics 2019年第3期19卷 31-34页

作者： Anastasia P.Bisyarina ANDrey M.Sobolev Stanislav Yu.Gorda Anatoly S.Miroshnichenko Astronomical observatory of the Ural Federal University Department of Physics and Astronomy University of North Carolina at Greensboro Main (pulkovo) Astronomical observatory of the Russian Academy of Sciences Fesenkov Astrophysical Institute

In our previous papers we have improved the value of the orbital period of the binary Herbig Be star HD 200775 and showed that the [O I] and Si II 6347 and 6371 ?A emission lines displayed variations which correlate with the orbital period. In this paper we provide evidences that other broad emission lines of metals in the spectra of HD 200775 also exhibit variability, which is probably related to the orbital cycle of the binary. Analysis was performed based on the high-resolution spectral data collected over a time span of 6 years at the Kourovka Astronomical observatory of the Ural Federal University(Russia) and the Three College observatory of the University of North Carolina at Greensboro(USA) as well as archival spectral data compiled since 1994. We report new data points in the radial velocity curve of the He I 5876 ?A line near the extremal values of the radial velocity.

关键词： techniques spectroscopic-stars variables T Tauri,Herbig Ae/Be-stars individual HD 200775