We report the analysis of high-precision space-based photometric and high-resolution spectroscopic observations of HD 180347. The high-quality light curves from the Transiting Exoplanet Survey Satellite (TESS) under sectors 14, 15, and 26 were used. By visual inspection of the light curves and the Fourier transforms, only low-frequency signals (less than 1 d$^{-1}$) were detected. After using wavelet, autocorrelation, and composite spectrum analyses, HD 180347 is classified as a rotational variable with a period of about 4.1 $\pm$ 0.2 days. In reference to the observation limit of TESS, no pulsations were detected. For the spectroscopic analysis, we used data collected with the High Efficiency and Resolution Mercator Échelle Spectrograph (HERMES). We determined the spectral type of this star and obtained atmospheric parameters such as the effective temperature, the surface gravity, and the projected rotational, microturbulent, and radial velocities. We performed a detailed chemical abundance analysis. The LTE abundances were derived for 25 chemical elements. For 13 of them, including Ca, Sc, Sr, Zr, and Ba, which are important for the characterisation of chemical peculiarity, we also present the non-local thermodynamic equilibrium (NLTE) abundances. NLTE improves the accuracy of the derived abundances and confirms that Ca and Sc are depleted in HD 180347 relative to their solar abundances, while the heavy elements beyond Sr are enhanced, by more than 0.7 dex. Based on the spectral class and the element abundance pattern, we classify this star as Am (kA1hA8mA8).

1. Представлен обзор полученных разными авторами в результате высокоточных спектрополяриметрических наблюдений F0 – M0 гигантов и сверхгигантов. На сегодняшний день слабые магнитные поля зарегистрированы почти у четырех десятков медленно вращающихся красных гигантов: магнитное поле у некоторых объектов достигает нескольких десятков гаусс. Спектрополяриметрическая база наблюдений красных сверхгигантов включает три десятка объектов. Магнитное поле было обнаружено у трети. По наблюдениям в Крыму магнитное поле у сверхгиганта ε Gem достигает десятка гаусс. Поскольку магнитное поле вморожено в плазму, а звезды после главной последовательности значительно увеличивают свои размеры, ожидается, что без генерации и усиления магнитного поля магнитное поле гигантов не должно превышать один гаусс, а магнитное поле сверхгигантов будет составлять сотые и тысячные доли гаусса. Тем не менее индукция зарегистрированных магнитных полей у этих объектов значительно превышает названные. На основе литературных данных и крымских наблюдений подтверждается вывод, что генерация и усиление магнитного поля происходит с помощью работы динамо-механизмов на всех стадиях эволюции звезд с конвективными оболочками, начиная с эпохи формирования звезды (тип T Tauri) до Главной последовательности и заканчивая ее конечным состоянием сверхгиганта, перед трансформацией в объект с вырожденным состоянием материи.2. Как известно из физики Солнца, неоднородность магнитного поля указывает на наличие физических условий для работы динамо-механизмов. В настоящей работе приводятся результаты вычисления продольного компонента магнитного поля и факт обнаружения его неоднородности у гиганта δ CrB.3. Крымская методика обработки спектрополяриметрических наблюдений звезд (SL – Single Line), отличительной особенностью которой является использование центров тяжести спектральных линий для вычисления магнитного поля по каждой линии в отдельности, позволила разработать и применить методику анализа изменения величины магнитного поля с глубиной в атмосфере звезды. В результате выполненного анализа не было обнаружено статистически достоверных признаков наличия радиальных вариаций магнитного поля с глубиной в атмосфере гиганта δ CrB при том уровне отношения сигнал/шум, который присутствовал у наблюдательного материала. Сделан вывод о необходимости использования большего числа наблюдений для получения статистически обоснованного заключения о присутствии или отсутствии неоднородности поля с глубиной в атмосфере δ CrB.

Eclipsing, spectroscopic double-lined (SB2) binaries remain to be the prime source of precise and accurate fundamental properties of stars. Furthermore, high-cadence spectroscopic observations of the eclipse phases allow us to resolve the Rossiter-McLaughlin effect whose modelling offers the means to probe spin-orbit misalignment in binaries. In this study, we develop the LSDBinary algorithm that is capable of working with both in-eclipse and out-of-eclipse spectra of SB2 binaries as input and delivers the LSD profiles, LSD-based model spectra, and precise RVs of both binary components as output. We offer an option to account for the Rossiter-McLaughlin effect in the calculation of the initial guess LSD profiles and components' flux ratio such that the effect can be modelled within the algorithm itself. We provide an extensive test of the LSDBinary software package on simulated spectra of artificial binaries. We study the effects of signal-to-noise-ratio of input spectra, resolving power of the instrument, uncertain atmospheric parameters of stars, and orbital properties of the binary system on the resulting LSD profiles and RVs measured from them. We find that atmospheric parameters have negligible effect on the shape of the computed LSD profiles while affecting mostly their global scaling. Our results are barely sensitive to signal-to-noise ratio of the input spectra provided they contain sufficient number of spectral lines, such as in A-type stars and later. Finally, the orbital inclination angle and components' radii ratio are found to have the largest effect on the shapes of the LSD profiles and RV curves extracted from them. The LSDBinary algorithm is specifically developed to perform detailed spectroscopic studies of eclipsing SB2 systems whose orbital configuration and components' atmospheric parameters are estimated by other means.

We performed a detailed spectroscopic study of the SB2 system HD 60803 based on high-resolution spectra obtained with the different spectrographs. The analysis was done with two independent methods: a) the direct modelling of the observed binary spectrum by a sum of synthetic spectra varying a set of free parameters and minimizing a difference between the observed and theoretical spectra; b) spectrum disentangling and an independent modelling of the individual components. Being applied to binary spectra from different spectrographs both methods converge to a consistent solution for the fundamental parameters of the HD 60803 components: $T_{\rm eff}$=6055$\pm$70 K, $\log{g}$=4.08$\pm$0.12, $\zeta_{\rm RT}$=1.45$\pm$0.18 km s$^{-1}$, [M/H]=0.03$\pm$0.06 (primary), and $T_{\rm eff}$=6069$\pm$70 K, $\log{g}$=4.14$\pm$0.09, $\zeta_{\rm RT}$=1.48$\pm$0.18 km s$^{-1}$, [M/H]=0.03$\pm$0.06 (secondary). Differential abundance analysis of the components did not reveal any significant difference in their chemical composition. Besides Li both components have solar atmospheric abundances. Li abundance exceeds the solar one by $\sim$2 dex, but it agrees with Li abundance in main-sequence late F-stars. Relative-to-solar abundances in both components slightly correlate with the condensation temperature the same way as was found in the solar analogs with/without detected giant planets. The estimated age of the system is 5.5$\pm$0.5 Gyr.

Today, magnetic fields have been reliably detected in many classes of stars with convective envelopes, from young T~Tauri stars to supergiants. We present an overview of the results obtained with high-precision spectropolarimetric observations of selected single F0-M0 giants and supergiants. The measurements of the magnetic field in these objects were started in 1989 at the 2.6-meter ZTSh telescope of the Crimean Astrophysical Observatory. To date, weak magnetic fields have been recorded in nearly four dozen of slowly rotating red giants. The longitudinal component of the field in several cases reaches a few tens of gauss. A spectropolarimetric survey of red supergiants includes three dozen objects. The magnetic field was detected in dozen of them. For one of these targets, $\epsilon$~Gem, the magnetic field up to 10~G was reported. Because the magnetic field is frozen into the plasma, it is expected that the magnetic field of giants and supergiants should not exceed one gauss because stars have increased in size after the main sequence. Therefore, the main conclusion from the results of spectropolarimetric surveys of giants and supergiants with convective envelopes is that the most probable mechanism for the generation and amplification of the magnetic field in these objects is the dynamo action.

Abstract—Within the program for studying the variability of slow-rotating magnetic stars, we carried out magnetic monitoring of the Ap star HD 110066 (AX CVn), the expected variability period of which was estimated as 13.4 yrs. Based on our measurements of the magnetic field performed with the 1-m SAO RAS telescope and the literature data, we assumed that the most likely period of this star $$P = 6.4769 \pm 0.0011$$ days; we also estimated the parameters of the oblique rotator model describing the magnetic variability of the star HD 110066. In order to determine its chemical abundance, a high-resolution spectrum with ( $$R \approx 70{\kern 1pt} {\kern 1pt} 000$$ ) was obtained using the fiber-fed spectrometer of the 6-m telescope of SAO RAS. The chemical abundance estimates completely coincided with those from the spectrum obtained with a similar resolution with the ESPaDOnS spectrometer (CFHT, Mauna Kea, Hawaii).

(Abridged) Eclipsing, spectroscopic double-lined binary star systems (SB2) are excellent laboratories for calibrating theories of stellar interior structure and evolution. We aim to investigate the mass discrepancy in binary stars. We study the effect of near-core mixing on the mass of the convective core of the stars and interpret the results in the context of the mass discrepancy. Two scenarios are considered, where individual stellar components of a binary system are treated independent of each other and where they are forced to have the same age and initial chemical composition. We find that the mass discrepancy is present in our sample and that it is anti-correlated with the surface gravity of the star. No correlations are found with other fundamental and atmospheric parameters, including the stellar mass. The mass discrepancy can be partially accounted for by increasing the amount of near-core mixing in stellar evolution models. We also find that ignoring the microturbulent velocity and turbulent pressure in stellar atmosphere models of hot evolved stars results in overestimation of their effective temperature by up to 8%. Together with enhanced near-core mixing, this can almost entirely account for the 30% mass discrepancy found for the evolved primary component of V380 Cyg. We find a strong link between the mass discrepancy and the convective core mass. The mass discrepancy can be solved by considering the combined effect of extra near-core boundary mixing and consistent treatment in the spectrum analysis of hot evolved stars. Our binary modelling results in convective core masses between 17 and 35% of the stellar mass, in excellent agreement with results from gravity-mode asteroseismology of single stars. This implies larger helium core masses near the end of the main sequence than anticipated so far.

RZ Cas is a short-period Algol-type system showing episodes of mass transfer and Delta Sct-like oscillations of its mass-gaining primary component. We analyse high-resolution spectra of RZ Cas that we obtained during a spectroscopic long-term monitoring lasting from 2001 to 2017. Spectrum analysis resulted in precise atmospheric parameters of both components, in particular in surface abundances below solar values. We find that the variation of orbital period is semi-regular and derive different characteristic timescales for different epochs of observation. We show that the radial velocity variations with orbital phase can be modelled when including two cool spots on the surface of the secondary component. The modelling leads to precise masses and separation of the components. The seasonal variation of several parameters, such as vsin(i), rotation-orbit synchronisation factor, strength of the spots on the cool companion, and orbital period, can be characterised by a common timescale of the order of nine years. We interpret the timescale of nine years as the magnetic activity cycle of the cool companion. In particular the behaviour of the dark spots on the cool companion leads us to the interpretation that this timescale is based on an 18-year magnetic dynamo cycle. We conclude that the mass-transfer rate is controlled by the variable depth of the Wilson depression in the magnetic spot around the Lagrangian point L1. In the result, based on available data, we observe a damped activity cycle of the star, starting with a high mass-transfer episode around 2001, followed by quiet periods in 2006 and 2009, slightly higher activity around 2013 and 2014, and again followed by quiet periods in 2015 and 2016. However, owing to missing data for years 2010 and 2011, we cannot exclude that a second high mass-transfer episode occurred within this time span.

Context. RZ Cas is a short-period Algol-type system showing episodes of mass transfer and δ Sct-like oscillations of its mass-gaining primary component. This system exhibits temporal changes in orbital period, v sin i, and the oscillation pattern of the primary component. Aims. We analyse high-resolution spectra of RZ Cas that we obtained during a spectroscopic long-term monitoring lasting from 2001 to 2017. In this first part we investigate the atmospheric parameters of the stellar components and the time variation of orbital period, v sin i, and radial velocities (RVs), searching for seasonal changes that could be related to episodes of mass exchange and to a possible activity cycle of the system triggered by the magnetic cycle of the cool companion. Methods. We used spectrum synthesis to analyse the spectra of both components of RZ Cas. The study of variations of the orbital period is based on published times of primary minima. We used the least-squares deconvolved (LSD) binary program to derive separated RVs and LSD profiles of the components. From the LSD profiles of the primary we determined its v sin i. Using Markov chain Monte Carlo simulations with the PHOEBE program, we modelled the RV variations of both components. Results. Spectrum analysis resulted in precise atmospheric parameters of both components, in particular in surface abundances below solar values. We find that the variation of orbital period is semi-regular and derive different characteristic timescales for different epochs of observation. We show that the RV variations with orbital phase can be modelled when including two cool spots on the surface of the secondary component. The modelling leads to very precise masses and separation of the components. The seasonal variation of several parameters, such as v sin i, rotation-orbit synchronisation factor, strength of the spots on the cool companion, and orbital period, can be characterised by a common timescale of the order of nine years. Conclusions. We interpret the timescale of nine years as the magnetic activity cycle of the cool companion. In particular the behaviour of the dark spots on the cool companion leads us to the interpretation that this timescale is based on an 18-yr magnetic dynamo cycle. We conclude that the mass-transfer rate is controlled by the variable depth of the Wilson depression in the magnetic spot around the Lagrangian point L1. In the result, based on available data, we observe a damped activity cycle of the star, starting with a high mass-transfer episode around 2001 with a calculated mass-transfer rate of 1.510−6 M⊙ yr−1, followed by quiet periods in 2006 and 2009, slightly higher activity around 2013 and 2014, and again followed by quiet periods in 2015 and 2016. However, owing to missing data for years 2010 and 2011, we cannot exclude that a second high mass-transfer episode occurred within this time span.

We present a software package for fine abundance analysis based on NLTE line profile fitting to the observed spectrum. The SYNTHV code for spectrum synthesis in LTE assumption is modified to compute NLTE spectra via loading the precalculated departure coefficients for atomic levels of investigated species. The departure coefficients, calculated for each level in a given model atom and a given model atmosphere, can be applied for NLTE spectral synthesis of any atomic transition between these levels by identifying them in an input linelist extracted from the Vienna Atomic Line Database (VALD) in the 'Long format' mode. SYNTHV_NLTE is implemented in the IDL visualization code BINMAG6 (Kochukhov 2018), which returns the best fit synthetic spectrum and the NLTE abundance for a given spectral line.

We present an analysis of the spectra of the star V837 Tau, which belongs to a class of chromosphere-active RSCVn type stars. The observational material was obtained with the 1.5-m Russian-Turkish telescope RTT-150 and the 2.6-m Shajn telescope of the Crimean astrophysical observatory. To reveal signs of the photosphere spottedness of the primary and to isolate the faint secondary, we performed the deconvolution of the “averaged” spectral profile of the system. By describing the radial velocity curves, we refined the orbital elements of the binary system, and by modeling spectrawe determined the fundamental parameters of the components, as well as the chemical composition of the atmosphere of the bright component. Using the Doppler mapping method we reconstructed the distribution of spots on the surface of the bright star. We show that the spots are concentrated in a belt at medium (about 40) latitudes. The hydrogen line profiles have a variable emission feature in the bright component, and the Hα line exhibits traces of chromospheric activity in the secondary.

We present a radial velocity analysis of 20 solar neighborhood RR Lyrae and 3 Population II Cepheids variables. We obtained high-resolution, moderate-to-high signal-to-noise ratio spectra for most stars and obtained spectra were covering different pulsation phases for each star. To estimate the gamma (center-of-mass) velocities of the program stars, we use two independent methods. The first, `classic' method is based on RR Lyrae radial velocity curve templates. The second method is based on the analysis of absorption line profile asymmetry to determine both the pulsational and the gamma velocities. This second method is based on the Least Squares Deconvolution (LSD) technique applied to analyze the line asymmetry that occurs in the spectra. We obtain measurements of the pulsation component of the radial velocity with an accuracy of $\pm$ 3.5 km s$^{-1}$. The gamma velocity was determined with an accuracy $\pm$ 10 km s$^{-1}$, even for those stars having a small number of spectra. The main advantage of this method is the possibility to get the estimation of gamma velocity even from one spectroscopic observation with uncertain pulsation phase. A detailed investigation of the LSD profile asymmetry shows that the projection factor $p$ varies as a function of the pulsation phase -- this is a key parameter which converts observed spectral line radial velocity variations into photospheric pulsation velocities. As a byproduct of our study, we present 41 densely-spaced synthetic grids of LSD profile bisectors that are based on atmospheric models of RR Lyr covering all pulsation phases.

We analysed photometric time series of the active, semidetached Algol-type system RZ Cas obtained in 1999-2009, in order to search for seasonal and short-term variations in the oscillation spectrum of RZ Cas A. The orbital period shows +/- 1 s cyclic variations on time-scales of 6-9 years. We detected six low-degree p-mode oscillations with periods between 22.3 and 26.22 min and obtained safe mode identifications using the periodic spatial filter method. The amplitudes and frequencies of all modes vary. We tested and confirm the hypothesis that rapid variations in the pulsation spectrum of the mass-accreting component and rapid increases in the orbital period are driven by high mass transfer and accretion outbursts caused by the cyclic magnetic activity of the Roche lobe-filling donor star. Two rapid pulsation-amplitude decays observed in 2001 and 2009 can be explained by high-mass transfer events separated by the duration of the last 9-yr long magnetic cycle. We also tested and confirm the hypothesis of an acceleration of the outer envelope of the pulsating component. We discovered synchronous, modal m-dependent variations in the frequencies of three identified modes, in good agreement with results of our mode identification using the periodic spatial filter method. We suggest that m-dependent pulsation frequency variations are caused via the Doppler-effect by variations of the rotation speed of the outer envelope of the pulsating gainer. With this method, we obtained the first asteroseismic detection and accurate measurement of the accretion driven acceleration of the outer envelope of the mass-accreting component of an Algol-type star.

R Canis Majoris is the prototype of a small group of Algol-type stars showing short orbital periods and low mass ratios. A previous detection of short-term oscillations in its light curve has not yet been confirmed. We investigate a new time series of high-resolution spectra with the aim to derive improved stellar and system parameters, to search for the possible impact of a third component in the observed spectra, to look for indications of activity in the Algol system, and to search for short-term variations in radial velocities. We disentangled the composite spectra into the spectra of the binary components. Then we analysed the resulting high signal-to-noise spectra of both stars. Using a newly developed program code based on an improved method of least-squares deconvolution, we were able to determine the radial velocities of both components also during primary eclipse. This allowed us to develop a better model of the system including the Rossiter–McLaughlin effect and to derive improved orbital parameters. Combining the results with those from spectrum analysis, we obtain accurate stellar and system parameters. We further deduce at least one oscillation frequency of 21.38 c d−1. It could be detected during primary eclipses only and confirms a previous photometric finding. Results point to an amplitude amplification of non-radial pulsation modes due to the eclipse mapping effect. The presence of a He I line in the spectra indicates mass transfer in the R CMa system. Calculations of its Roche geometry give evidence that the cool secondary component may fill its Roche lobe. No evidence of a third body in the system could be found in the observed spectra.

We analyzed 62 high-resolution spectra of 30 Galactic Field RR Lyrae-type stars with the aim of deriving their atmospheric parameters (Teff, , Vt), metallicity ([Fe/H]), radial velocities, and NLTE abundances of oxygen and sodium. We found that there is no clear anti-correlation between [O/Fe] and [Na/Fe] as is seen in globular clusters. On this basis, we conclude that the majority of field RR Lyrae-type stars should hardly be considered to be remnants of the dissolution of globular clusters.

We have performed analysis of a large amount of the fields RR Lyr type stars spectra with the aim to derive NLTE oxygen and sodium abundances in our program stars. Fundamental parameters (T-eff, log g, V-t) and metallicity were found using the method of the fitting between synthetic and observed spectra using the SME program which was developed by N. Piskunov and J. A. Valenti. As a result of this analysis anticorrelation between oxygen (O/H) and sodium (Na/H) abundances was found.

Spectroscopic and photometric data for the two rapidly rotating members of the α Persei cluster He 373 and AP 225 are analyzed. Improved estimates have been obtained for the projected equatorial rotation velocities: v sin i = 164 km/s for He 323 and v sin i = 129 km/s for AP 225. Multi-band photometric mapping is used to map the spot distributions on the surfaces of the two stars. The fractional spotted areas S and mean temperature difference ΔT between the unspotted photosphere and the spots are estimated (S = 7% and ΔT = 1000 K for He 373; S = 9% and ΔT = 800 K for AP 225). The H α line profiles of both stars have variable emission components whose widths are used to deduce the presence of extended regions of emission reaching the corotation radius.