Long-term Speckle Interferometric Monitoring of Binary Systems:2007–2023Positional Measurements and Orbits of Seven Objects

The results of seventeen years of speckle interferometric monitoring of seven objects(Chara 122Aa,GJ 3010,HIP1987,GJ 3076,HIP 11253,HIP 11352,and HIP 14929)are presented.Observational data were obtained at the 6 m Big Telescope Alt-azimuthal Special Astrophysical Observatory of the Russian Academy of Science(BTA SAO RAS)from 2007 to the present.Analysis of previously published and new measurements made it possible to construct completely new orbits for Chara 122Aa,HIP 11253,and HIP 14929.The orbit of GJ 3076 cannot be constructed accurately due to the large influence of the weights assigned to the measurements.The resulting orbital solutions are classified based on a grading scheme suggested by W.I.Hartkopf,B.D.Mason and C.E.Worley;most orbits are“definitive”(Grade 1).The mass sums and masses of components calculated by two independent methods using Hipparcos and Gaia DR2 and DR3 parallaxes were compared for the objects under study.

Cluster Analysis of the Roma-BZCAT Blazars

Based on the collected multiwavelength data, namely in the radio(NVSS, FIRST, RATAN-600), IR(WISE),optical(Pan-STARRS), UV(GALEX), and X-ray(ROSAT, Swift-XRT) ranges, we have performed a cluster analysis for the blazars of the Roma-BZCAT catalog. Using two machine learning methods, namely a combination of PCA with k-means clustering and Kohonen's self-organizing maps(SOMs), we have constructed an independent classification of the blazars(five classes) and compared the classes with the known Roma-BZCAT classification(FSRQs, BL Lacs, galaxy-dominated BL Lacs, and blazars of an uncertain type) as well as with the high synchrotron peaked(HSP) blazars from the 3HSP catalog and blazars from the TeVCat catalog. The obtained groups demonstrate concordance with the BL Lac/FSRQ classification along with a continuous character of the change in the properties. The group of HSP blazars stands out against the overall distribution. We examine the characteristics of the five groups and demonstrate distinctions in their spectral energy distribution shapes. The effectiveness of the clustering technique for objective analysis of multiparametric arrays of experimental data is demonstrated.

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

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] = +0.4.For the CMDs,we use data sets from Hubble Space Telescope,Gaia,and other sources utilizing,at least,25 photometric filters for each cluster.We 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 Pole.The 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.

Searching For Wide Binary Stars with Non-coeval Components in the Southern Sky

We have completed our observational program to search for wide binary systems with non-coeval components in the southern sky and report our results here.The final set of four systems was spectroscopically investigated in this paper.No binary systems with components of different ages were found among them.Taking into account our previous studies,we estimate the fraction of such binaries(i.e.,binaries formed,presumably,by capture)to be not higher than 0.06%.The study will be continued on the northern sky.

On the correctness of orbital solutions obtained from a small set of points.Orbit of HIP 53731

HIP 53731 is a binary consisting of stars of the spectral types K0 and K9.The orbit of this object was constructed previously by Cvetkovic et al.and improved by Tokovinin.It should be noted that there is a 180°ambiguity in the position angles of some published measurements.Speckle interferometric observations were obtained in 2007–2020(21 measurements)at the 6-m telescope of the SAO RAS(BTA)by the authors of this article.The analysis of new data together with previously published ones made it possible to construct an accurate orbit of HIP 53731 and to halve the already known values of the orbital period of the system.As a result of the study,the mass sum,the masses of each component and their spectral types were determined by two independent methods.According to the qualitative classification of orbits,the orbital solution has grade 2–"good"(observations cover more than half of the orbital period and correspond to different phases).

The determination of white dwarf parameters in dwarf novae by optical spectral modeling

This paper presents the results of a model analysis of optical spectra and determination of the parameters of three individual SU UMa and WZ Sge type dwarf novae.The moderate resolution spectra of TY Psc,FL Psc and V455 And were obtained at the 6-m BTA of the SAO RAS in the low state of these systems with the determination of white dwarf radiation.The theoretical spectra were calculated using the grid models of hydrogen dwarf atmospheres of white dwarfs by varying the parameters(T_(eff) and log g) to reach the best agreement with the observed ones.We highlight different effects of the parameters on the shape and intensity of the HI lines.Therefore,it is possible to unambiguously determine T_(eff) and log g from the analysis of observations.The fundamental parameters of white dwarfs(M and R) were found by comparing the parameters of atmospheres with theoretical models of the internal structure.The obtained parameters of the primaries of TY Psc,FL Psc and V455 And are consistent with the average values for SU UMa and WZ Sge systems.As a result,we demonstrate the efficiency of the method for determining the parameters of such systems based on the analysis of a limited set of observed optical spectra.

Photometric and Spectroscopic Analysis of LBV Candidate J004341.84+411112.0 in M31

We study Luminous Blue Variable(LBV)candidate J004341.84+411112.0 in the Andromeda galaxy.We present optical spectra of the object obtained with the 6 m telescope of BTA SAO RAS.The candidate shows typical LBV features in its spectra:broad and strong hydrogen lines and the He I lines with P Cygni profiles.Its remarkable spectral resemblance to the well known LBV P Cygni suggests a common nature of the objects and supports LBV classification of J004341.84+411112.0.We estimate the temperature,reddening,radius and luminosity of the star using its spectral energy distribution.Obtained bolometric luminosity of the candidate(M_(bol)=-10.41±0.12 mag)is quite similar to those of known LBV stars in the Andromeda galaxy.We analyzed a ten year light curve of the object in R filter.The candidate demonstrates photometric variations of the order of 0.4 mag,with an overall brightness increasing trendΔR>0.1 mag.Therewith,the corresponding color variations of the object are fully consistent with LBV behavior when a star become cooler and brighter in the optical spectral range with a nearly constant bolometric luminosity.LBV-type variability of the object,similarity of its spectrum and estimated luminosity to those of known LBVs allow us to classify J004341.84+411112.0 as an LBV.

Research on the HIP 18856 binary system

The results of a study on the binary HIP 18856 and construction of its orbit are presented.New observational data were obtained at the BTA of SAO RAS in 2007-2019.Earlier,Cvetkovic et al.constructed the orbit for this system.However,it is based on six measurements,which cover a small part of the orbit.The positional parameters of the ESA astrometric satellite Hipparcos published speckle interferometric data(Mason et al.,Balega et al.,Horch et al.)and new ones were used in this study.Based on the new orbital parameters,the mass sum was calculated and the physical parameters of the components were found.The obtained orbital and fundamental parameters were compared with the data from the study by Cvetkovic et al..The comparison shows that the new orbital solution is better than the old one,since it fits new observational data accurately.Also based on a qualitative evaluation performed by Worley&Heintz,the new orbit was classified as"reliable",which means data cover more than half of the orbit with sufficient quantities of residuals of measurements.

Searching for the brightest stars in galaxies outside the Local Group

This paper introduces a technique for searching for bright massive stars in galaxies beyond the Local Group.To search for massive stars,we processed the results of stellar photometry from the Hubble Space Telescope(HST)images using the DAOPHOT and DOLPHOT packages.The results of such searches are demonstrated with examples of the galaxies DDO 68,M94 and NGC 1672.In the galaxy DDO 68,the LBV star changes its brightness,and massive stars in M94 can be identified by excess in the Ha band.For the galaxy NGC 1672,we measure the distance for the first time by the TRGB method,which enabled determining the luminosities of the brightest stars,likely hypergiants,in the young star formation region.So far,we have performed stellar photometry on HST images of 320 northern sky galaxies located at a distance less than 12 Mpc.This allowed us to identify 53 galaxies with probable hypergiants.Further photometric and spectral observations of these galaxies are planned to search for massive stars.

The first results of observations of lunar occultations in different spectral ranges at the 6-m telescope of the SAO RAS

Observations by the method of lunar occultations at the 6-m telescope of the SAO RAS reach a resolution limit better than 1mas.We have devised a new method of observation,which allows obtaining the curves of lunar occultations simultaneously in different ranges of the visible part of the spectrum,and conducted the first observations using amodified optical system.In January 2019,applying the newmethod,the magnitude differences of the components of the binary star HD 36524 in the R and I bands were measured,which were 1.5 and 1.3mag,respectively,in good agreement with values calculated from the Gaia mission.According to the obtained data,it was determined that with this method it is possible to reach a signal-to-noise ratio of about 5–10 for stars of 10th magnitude.We discuss the applicability of the proposed optical scheme for the study of binary stars.

Age and chemical composition of the globular cluster NGC 6652

We present the results of determination of the age,helium mass fraction(Y),metallicity([Fe/H]),and abundances of the elements C,N,O,Na,Mg,Ca,Ti,C and Mn for the Galactic globular cluster NGC 6652.We use its medium-resolution integrated-light spectrum from the library of Schiavon and our population synthesis method to fulfill this task.We select the evolutionary isochrone and stellar mass function for our analysis,which provide the best approximation to the shapes and intensities of the observed Balmer line profiles.The determined elemental abundances,age and metallicity are characteristic of stellar populations in the Galactic Bulge.

High Resolution Spectroscopy of Halo Stars in the Near UV and Blue Region I. Spectra in the Wavelength Region 3550-5000 A

An atlas of high resolution （R = 60 000） CCD-spectra in the wavelength range 3500-5000A is presented for four objects in metallicity range -3.0 〈 [Fe/H] 〈 -0.6, temperature range 4750 〈 Teff 〈 5900K, and surface gravity range 1.6 〈 Igg 〈 5.0. We describe the calibration of the stellar atmospheric parameters using Alonso＇s formula based on the method of infrared flux and outline the determination of the abundances of a total number of 25 chemical elements. An analysis of the abundance determination errors for different chemical elements is carried out, and a method is provided for the observations and reduction of spectral material. Properties of the method of producing an atlas of spectra and line identifications are described.

Investigation of the parameters of spiral pattern in galaxies:the arm width

In this work,we determine the parameters of spiral structure for a sample of face-on spiral galaxies.In practice,the solution to this problem is a hard task because of the diversity of observed characteristics associated with spiral structure,such as the number of arms,their shape,arm contrast,etc.We study spiral structure in galaxies based on an analysis of photometric cuts perpendicular to the arm direction.The method is based on an approximation of these slices with an analytical function and derivation of the parameters of spiral structure(arm width,asymmetry,pitch angle)using the fitted parameters from this approximation.The algorithm has been applied to a sample of 155 galaxies selected from the Sloan Digital Sky Survey in different passbands.In this paper,we only consider the results on arm width:most spirals exhibit an increase in their width with galactocentric distance.Only 14 per cent of galaxies in our sample show an opposite trend or have an almost constant arm width at all radii.

GSC 4560–02157: a new long-period eclipsing cataclysmic variable star

We study the newly discovered variable star GSC 4560-02157. CCD photometry was performed in 2013-2014 at the Tien Shan Astronomical Observatory,and a spectrum was obtained with the 6-m telescope of the Special Astrophysical Observatory in June, 2014. GSC 4560-02157 is demonstrated to be an eclipsing variable star（P = 0.265359d）. All its flat-bottom primary minima are approximately at the same brightness level, but the star＇s out-of-eclipse brightness and brightness at secondary minima vary considerably（by up to 0.6m） from cycle to cycle. Moreover,there are short-term（time scale of 0.03-0.04 days） small-amplitude brightness variations out of eclipse. This behavior suggests a cataclysmic nature for the star, which is confirmed with a spectrum taken on 2014 June 5. The spectrum shows numerous emissions of the hydrogen Balmer series, He Ⅰ and He Ⅱ.