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Stars of spectral types O and B produce neutron stars (NSs) after supernova explosions. Most of NSs are strongly magnetised including normal radio pulsars with $B \propto 10^{12}$ G and magnetars with $B\propto 10^{14}$ G. A fraction of 7-12 per cent of massive stars are also magnetised with $B\propto 10^3$ G and some are weakly magnetised with $B\propto 1$ G. It was suggested that magnetic fields of NSs could be the fossil remnants of magnetic fields of their progenitors. This work is dedicated to study this hypothesis. First, we gather all modern precise measurements of surface magnetic fields in O, B and A stars. Second, we estimate parameters for log-normal distribution of magnetic fields in B stars and found $\mu_B = 2.83\pm 0.1$ $\log_{10}$ (G), $\sigma_B=0.65\pm 0.09$ for strongly magnetised and $\mu_B = 0.14\pm 0.5$ $\log_{10}$ (G), $\sigma=0.7_{-0.27}^{+0.57}$ for weakly magnetised. Third, we assume that the magnetic field of pulsars and magnetars have $2.7$ DEX difference in magnetic fields and magnetars represent 10 per cent of all young NSs and run population synthesis. We found that it is impossible to simultaneously reproduce pulsars and magnetars populations if the difference in their magnetic fields is 2.7 DEX. Therefore, we conclude that the simple fossil origin of the magnetic field is not viable for NSs., Comment: 23 pages, accepted for publication in MNRAS on 19 April 2021

Studies of the magnetic fields of Herbig Ae/Be (HAeBe) stars can aid in understanding how the magnetic fields of AB stars of intermediate mass are created and evolve. It has been shown that the magnetic fields and magnetic fluxes of HAeBe stars before they emerge on the main sequence are significantly lower than for their successors, main sequence AB stars. In order to explain this mystery, the effect of accretion on Herbig stars and their magnetic fields is studied. Evidence is found in favor of the assumption that in magnetic HAeBe stars with a higher rate of accretion the magnetic fields are lower on the average. However, since the accretion rates fall off exponentially with the age of a star, even if it should be confirmed, this effect cannot fully explain the discontinuous increase in the magnetic fields and magnetic fluxes when HAeBe stars enter the main sequence.

The results of observations at high temporal resolution (∆T~4 min) of the B0.5V star e Per A on the 2-m telescope of the Terskol Observatory are reported. Regular components of variations in line profiles with periods 1.5-18 hours are recorded. Evidence of irregular variations in line profiles on time scales of minutes is detected. The nature of these variations is discussed.

—This study continues the investigation of the super-fast variability of line profiles in the spectra of stars of early spectral classes performed in 2017 and 2018. We investigated the variability of line profiles in the spectra of OBA stars with the SCORPIO multi-mode focal reducer at the 6-m SAO RAS telescope (BTA). Short-period regular variations of the H and He lines were detected in the spectra of the chemically peculiar A0Vp star α2 CVn with periods ranging from approximately 30 to 135 minutes. Using the windowed Fourier transform let us detect the transient quasi-regular variations in the Balmer-line profiles with periods of 3–6 minutes. We discuss a possible origin of fast spectral variations.

—In the paper the possibility of the presence of a non-thermal component described by a power law spectrum in the X-ray spectra of OB stars is investigated. The low-resolution spectra of 101 OB stars obtained using the EPIC camera on the XMM satellite are analyzed. It is concluded that the contribution of the non-thermal component of X-ray emission can be significant and even determining for the stars similar to γ Cas. The inclusion of the non-thermal component in the model X-ray spectra reduces the temperature of the thermal components of the X-ray plasma of such stars down to typical for OB stars values. The contribution of the non-thermal component can also be significant for binary stars with colliding stellar winds and for Of?p stars.

The results of ultrahigh-time-resolution ( $$\Delta T\sim 12$$ s) observations of the B1 Iab supergiant $$\rho$$ Leo with the 1.25-m telescope at the Crimean Astronomical Station of the SAI MSU are presented. Regular line profile variations with periods of 15–30 min have been revealed. Significant changes in the average line profiles on time intervals of 1–3 days have been detected. Evidence for the existence of short-period line profile variations on time scales of 15–25 min is provided. The nature of the short-period line profile variations is discussed. The possibility of studying the fast variations in the profiles of broad lines (mostly the Balmer hydrogen and He I lines) using low-resolution spectrographs with $$R=1000{-}2000$$ at 1–2-m telescopes is pointed out.

Magnetic-field measurements for Herbig Ae/Be stars are analyzed to determine the distribution functions of root-mean-squared magnetic field strengths $$\mathcal{B}$$ (in G) and magnetic fluxes Φ (in G cm2) for Herbig stars with measured magnetic field. The $$\mathcal{B}$$ and Φ values are approximated by log-normal functions with the means equal to 〈log $$\mathcal{B}$$ 〉 = 2.0 and log 〈Φ Φ〉 = 25.5, respectively, and with the widths of $${\rm{log}}(\sigma)_\mathcal{B}=0.3$$ dex and log(σΦ) = 0.4 dex, respectively. The inferred distribution widths are close to the typical values for main-sequence (MS) AB-type stars, whereas the mean logarithms of magnetic fields and magnetic fluxes proved to be significantly (by up to one order of magnitude) lower than the corresponding values for MS stars (2.5 and 26.4, respectively). The origin of these differences and the evolution of magnetic fields for intermediate-mass pre-MS stars are discussed.

High-resolution spectroscopic data for the binary system HD83058 located in the OB association Sco-Cen are presented. The observations were made at the ESO and Sierra Armazones (Chile) observatories over 3 seasons: in March 1998, in 2007-2009, and in May 2013. A total of 41 spectra of the object were obtained. An analysis of the radial velocities of the lines from both system component yielded the orbital elements and an orbital period of P = 2.3650804 ± 0.0000034 days was found. Using a model of stellar atmospheres we separated the spectra of the two components and found their parameters to be Teff = 25700 ± 400 K, logg = 4.27 ± 0.05, and Teff = 19200 ± 600 K, logg = 4.03 ± 0.20 for components A and B, respectively. We confirmed the presence of moving local features in the profiles of the SiIII lines in the spectrum of component A which may be associated either with pulsation activity of the star or with the rotation of spot-like inhomogeneities on its surface. We found that the lines in the spectrum of component B have another type of variability in which the width and depth of almost all the atmospheric lines change in opposite phase on individual dates. It was found that the system is substantially asynchronous. We assume that the desynchronization of the system may arise from gravitational interactions of the system with a third body, since the density of stars within the OB association must be much higher than usual.

This work is a continuation of the studies of the ultrafast variability of line profiles in the spectra of early-type stars. Line profile variations (LPVs) in the spectrum a chemically peculiar A0Vp star $\alpha^2\,$CVn are investigated using the January 6, 2020 observations carried out with the 6-meter BTA telescope at Special Astrophysical observatory (SAO) of the Russian Academy of Sciences (RAS) equipped with the MSS spectrograph. Regular short-term periodic variations of the H$_\beta$, Fe\,II, and Cr\,II lines were detected with periods ranging from $\sim\!$4 to $\sim\!$140 minutes. The magnetic field of the star was determined for all observations. The average measured longitudinal magnetic field component over the entire duration of observations is about $\approx$600\,G, which is close to the value expected from the well-known magnetic field phase curve., Comment: 11 pages, 8 figures

This study continues our investigation of the super-fast variability of line profiles in the spectra of early-type stars. We have investigated the line-profile variability in spectra of OBA-stars with the SCORPIO multi-mode focal reducer mounted at the 6-m SAO RAS telescope. Regular short-period variations of the H and He lines in the spectra of the B1I star ρ Leo were detected with periods ranging from 2 to 90 minutes, as well as irregular line-profile variations on time intervals less than 1 minute. A possible origin of rapid spectral variations is discussed.

Recent XMM-Newton observations of the B2 type star rho Oph A indicated a periodicity of 1.205d, which was ascribed to rotational modulation. Since variability of X-ray emission in massive stars is frequently the signature of a magnetic field, we investigated whether the presence of a magnetic field can indeed be invoked to explain the observed X-ray peculiarity. Two FORS2 spectropolarimetric observations in different rotation phases revealed the presence of a negative (_all=-419+-101G) and positive (_all=538+-69G) longitudinal magnetic field, respectively. We estimate a lower limit for the dipole strength as B_d = 1.9+-0.2kG. Our calculations of the Kepler and Alfven radii imply the presence of a centrifugally supported, magnetically confined plasma around rho Oph A. The study of the spectral variability indicates a behaviour similar to that observed in typical magnetic early-type Bp stars., Comment: 7 pages, 1 table, 5 figures, accepted for publication in AN

A significant fraction of high-mass X-ray binaries are supergiant fast X-ray transients (SFXTs). The prime model for the physics governing their X-ray behaviour suggests that the winds of donor OB supergiants are magnetized. To investigate if magnetic fields are indeed present in the optical counterparts of such systems, we acquired low-resolution spectropolarimetric observations of the two optically brightest SFXTs, IGR J08408-4503 and IGR J11215-5952 with the ESO FORS2 instrument during two different observing runs. No field detection at a significance level of 3sigma was achieved for IGR J08408-4503. For IGR J11215-5952, we obtain 3.2sigma and 3.8sigma detections (_hydr = -978+-308G and _hydr = 416+-110G) on two different nights in 2016. These results indicate that the model involving the interaction of a magnetized stellar wind with the neutron star magnetosphere can indeed be considered to characterize the behaviour of SFXTs. We detected long-term spectral variability in IGR J11215-5952, while for IGR J08408-4503 we find an indication of the presence of short-term variability on a time scale of minutes., Comment: 5 pages, 1 table, 7 figures, accepted for publication in MNRAS

A longitudinal magnetic field with a strength of 5.2kG was recently detected in CPD -62 2124, which has a fractional main-sequence lifetime of about 60%. Strongly magnetic early-B type chemically peculiar stars in an advanced evolutionary state are of special interest to understand the evolution of the angular momentum and spin-down timescales in the presence of a global magnetic field. We exploited 17 FORS2 low-resolution spectropolarimetric observations and 844 ASAS3 photometric measurements for the determination of the rotation period, pulsations, and the magnetic field geometry of the star. We calculated periodograms and applied phenomenological models of photometric, spectral and spectropolarimetric variability. We found that all quantities studied, specifically equivalent widths, the mean longitudinal magnetic field , and the flux in the V filter, vary with the same period P = 2.628d, which was identified as the rotation period. The observed variations can be fully explained by a rigidly rotating main-sequence star with an uneven distribution of chemical elements, photometric spots, and a stable, nearly dipolar magnetic field with a polar field strength of about 21kG, frozen into the body of the star. The magnetic field of CPD -62 2124 is tilted to the rotation axis by beta=28+-7deg, while the inclination of the rotation axis towards the line of sight is only i=20+-5deg. In the acquired FORS2 spectra, we detect short-term line profile variations indicating the presence of beta Cephei type pulsations. As of today, no other pulsating star of this type is known to possess such a strong magnetic field., Comment: 9 pages, 3 tables, 9 figures, accepted for publication in MNRAS

We present first results of spectroscopic observations of transiting exoplanets in the Special Astrophysical Observatory of the Russian Academy of Sciences with the Main Stellar Spectrograph of the 6-m BTA telescope. For the exoplanetWASP-32b, we detected a significant variation of intensity and equivalent width in the Hα spectral line of the parent star at the time of a transit. The equivalent width of the line during transit is by 8–10% larger than outside the planet passage. Residual intensity in the core of the line reveals the following tendency: the line is by 10–15% deeper inside transit than outside it. Observations with the long-slit spectrograph of the Crimean Astrophysical Observatory at the 2.6-m ZTSh telescope also showed a transit event in the Hα line, although, with a smaller amplitude and shape inverted in relation to the data from the 6-m telescope. While in the observations with the BTA the Hα line becomes deeper during the transit, in the ZTSh observations, the residual intensity of the Hα line decreases during the transit. Reducing and analysis of the archive data of WASP-32b observations with the HARPS spectrograph also confirm the Hα line modulation at the time of the transit. The observed data give evidence of the envelope in WASP-32b filling the Roche lobe and a comet-like tail of changing geometry and orientation relative to the observer. These changes determine different depths and shapes of the Hα spectral line at the time of transits.

We report the results of photometric observations of a number of magnetic white dwarfs in order to search for photometric variability in these stars. These V-band observations revealed significant variability in the classical highly magnetized white dwarf GRW+70◦8247 with a likely period from several days to several dozen days and a half-amplitude of about 0. m 04. Our observations also revealed the variability of the well-known white dwarf GD229. The half amplitude of its photometric variability is equal to about 0. m 005, and the likely period of this degenerate star lies in the 10–20 day interval. This variability is most likely due to the rotation of the stars considered.We also discuss the peculiarities of the photometric variability in a number of other white dwarfs. We present the updated “magnetic field–rotation period” diagram for the white dwarfs.

This paper is the third in our series of papers devoted to the investigation of X-ray emission from OB stars. In our two previous papers, we study the high-resolutionX-ray spectra of 32 O stars and 25 B stars to investigate the correlations between the properties of X-ray emission and stellar parameters.We checked if the X-ray hardness and post-shock plasma temperature grow with increasing stellar magnetic field, mass loss rate and terminal wind velocity. Our previous analysis of high-resolution spectra showed that the correlations are weak or even absent. In the present paper, we analyzed low-resolution X-ray spectra, using model-independent X-ray hardness values for checking the above mentioned dependencies. We establish that X-ray luminosities L X weakly depend on the stellar magnetic field. At the same time, L X ∝ Ṁ 0.5 and L X ∝ E kin 0.5 , where ṁ is the mass loss rate and E kin is the kinetic energy of the wind. The X-ray luminosities decrease with growing magnetic confinement parameter η. We also argue that there is an additional (probably non-thermal) component contributed to the stellar X-ray emission.

Only eleven O-type stars have been confirmed to possess large-scale organized magnetic fields. The presence of a -600G longitudinal magnetic field in the O9.7V star HD54879 with a lower limit of the dipole strength of ~2kG, was discovered a few years ago in the framework of the ESO large program "B-fields in OB stars". Our FORS2 spectropolarimetric observations from 2017 October 4 to 2018 February 21 reveal the presence of short and long-term spectral variability and a gradual magnetic field decrease from about -300G down to about -90G. Surprisingly, we discover on the night of 2018 February 17 a sudden, short-term increase of the magnetic field strength and measure a longitudinal magnetic field of -833G. The inspection of the FORS2 spectrum acquired during the observed magnetic field increase indicates a very strong change in spectral appearance with a significantly lower photospheric temperature and a decrease of the radial velocity by several 10km/s. Different scenarios are discussed in an attempt to interpret our observations. The FORS2 radial velocity measurements indicate that HD54879 is a member of a long-period binary., Comment: 13 pages, 4 tables, 14 figures, accepted for publication in MNRAS

The goal of the present study is the development and testing of a method for spectral detection of the light of host stars reflected from their exoplanets. The presented method is based on the analysis of dynamical spectra, which make it possible to obtain high signal-to-noise residual spectra after host star spectrum deduction. These residual spectra contain information on the light reflected from an exoplanet and on its albedo. The first results of such research for the exoplanet HD 189733b are presented in the paper. We obtained a series of a few dozens moderate-resolution spectra of the host star HD 189733. Individual spectra have a high signal-to-noise ratio (≈700) and cover a considerable part of the complete orbital cycle of the exoplanet. The use of the developed method allowed us to achieve a characteristic contrast of the reflected light detection at a level of 5 × 10−4 from the continuum. Investigation of the dynamic spectra with this characteristic value as a detection threshold has not revealed obvious evidence of the host star light reflected from the planet. Nevertheless, the obtained threshold is high, which demonstrates the necessity of the development of the method for the exoplanet monitoring studies.

The results of kinetic equilibrium modeling for highly ionized atoms in the expanding atmospheres of early-type stars are presented. The influence of these processes on the forbidden-tointercombination line intensity ratio R = f/i for He-like ions (CV, NVI, OVII, etc.) in X-ray spectra is considered. If non-stationarity of the levels is taken into account, the instantaneous value of R m can vary on short time scales (fraction of a second) by nearly three orders of magnitude, compared to the stationary value in an equilibrium plasma. At the same time, the value of this ratio averaged over long time scales (hours and minutes), R a, can vary by 20%, leading to overestimation of the electron number density by up to one to two orders of magnitude.

The study of radiation processes in celestial objects is a fundamental problem in astrophysics. A powerful tool for the solution of this problem is provided by the theory of radiative transfer. One of the founding fathers of modern radiative transfer theory was the prominent full member of the Russian (formerly Soviet) Academy of Sciences Viktor Viktorovich Sobolev.Academician Sobolev was born on 2 September 1915. All his professional life was associated with the Saint Petersburg (formerly Leningrad) State University. From 1948 to 1988 he was the head of the Chair of Astrophysics. He passed away on 7 January 1999 at the age of 83.

Previous circular polarization observations obtained with the ESO FOcal Reducer low dispersion spectrograpgh at the VLT in 2007-2008 revealed the presence of a weak longitudinal magnetic field on the surface of the optical component of the X-ray binary Cyg X-1, which contains a black hole and an O9.7Iab supergiant on a 5.6d orbit. In this contribution we report on recently acquired FORS2 spectropolarimetric observations of Cyg X-1 along with measurements of a few additional high-mass X-ray binaries., Comment: 5 pages, 1 table, 6 figures, to appear in IAU Symposium 346 "High-mass X-ray binaries: illuminating the passage from massive binaries to merging compact objects", 2018 August 27-31, Vienna, Austria

Our recent search for the presence of a magnetic field in the bright early A-type supergiant HD 92207 using FORS 2 in spectropolarimetric mode revealed the presence of a longitudinal magnetic field of the order of a few hundred Gauss. However, the definite confirmation of the magnetic nature of this object remained pending due to the detection of shortterm spectral variability probably affecting the position of line profiles in left- and right-hand polarized spectra. We present new magnetic field measurements of HD 92207 obtained on three different epochs in 2013 and 2014 using FORS 2 in spectropolarimetric mode. A 3σ detection of the mean longitudinal magnetic field using the entire spectrum, 〈Bz〉all = 104 ± 34 G, was achieved in observations obtained in 2014 January. At this epoch, the position of the spectral lines appeared stable. Our analysis of spectral line shapes recorded in opposite circularly polarized light, i.e. in light with opposite sense of rotation, reveals that line profiles in the light polarized in a certain direction appear slightly split. The mechanism causing such a behaviour in the circularly polarized light is currently unknown. Trying to settle the issue of short-term variability, we searched for changes in the spectral line profiles on a time scale of 8–10 min using HARPS polarimetric spectra and on a time scale of 3–4 min using time series obtained with the CORALIE spectrograph. No significant variability was detected on these time scales during the epochs studied. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We present high-resolution spectropolarimetric observations of the spectroscopic binary Chi Dra. Spectral lines in the spectrum of the main component Chi Dra A show variable Zeeman displacement, which confrms earlier suggestions about the presence of a weak magnetic field on the surface of this star. Within about 2 years of time base of our observations, the longitudinal component BL of the magnetic field exhibits variation from -11.5 +/- 2.5 G to +11.1 +/- 2.1 G with a period of about 23 days. Considering the rotational velocity of Chi DraA in the literature and that newly measured in this work, this variability may be explained by the stellar rotation under the assumption that the magnetic field is globally stable. Our new measurements of the radial velocities (RV) in high-resolution I-spectra of Chi Dra A refined the orbital parameters and reveal persistent deviations of RVs from the orbital curve. We suspect that these deviations may be due to the in uence of local magnetically generated spots, pulsations, or a Jupiter-size planet orbiting the system., 5pages, 3figures, accepted for publication in Monthly Notices of the Royal Astronomical Society Letters

The magnetic field of CPD -57 3509 was recently detected in the framework of the BOB (B fields in OB stars) collaboration. We acquired low-resolution spectropolarimetric observations of CPD -57 3509 with FORS2 and high-resolution UVES observations randomly distributed over a few months to search for periodicity, to study the magnetic field geometry, and to determine the surface distribution of silicon and helium. We also obtained supplementary photometric observations at a timeline similar to the spectroscopic and spectropolarimetric observations. A period of 6.36d was detected in the measurements of the mean longitudinal magnetic field. A sinusoidal fit to our measurements allowed us to constrain the magnetic field geometry and estimate the dipole strength in the range of 3.9-4.5kG. Our application of the Doppler imaging technique revealed the presence of He I spots located around the magnetic poles, with a strong concentration at the positive pole and a weaker one around the negative pole. In contrast, high concentration Si III spots are located close to the magnetic equator. Further, our analysis of the spectral variability of CPD -57 3509 on short time scales indicates distinct changes in shape and position of line profiles possibly caused by the presence of beta Cep-like pulsations. A small periodic variability in line with the changes of the magnetic field strength is clearly seen in the photometric data., 11 pages, 5 tables, 7 figures, accepted for publication in MNRAS

The standard methods of the magnetic field measurement, based on an analysis of the relation between the Stokes V-parameter and the first derivative of the total line profile intensity, were modified by applying a linear integral operator L to both sides of this relation. As the operator L, the operator of the wavelet transform with DOG-wavelets is used. The key advantage of the proposed method is an effective suppression of the noise contribution to the line profile and the Stokes parameter V. The efficiency of the method has been studied using model line profiles with various noise contributions. To test the proposed method, the spectropolarimetric observations of the A0 star α2 CVn, the Of?p star HD 148937, and the A0 supergiant HD 92207 were used. The longitudinal magnetic field strengths calculated by our method appeared tobe in good agreement with those determined by other methods. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Spectroscopic studies of seven low mass stars in spectral classes F, G, and K are presented. Four of these (HD 1581, HD 10700, HD 17925, and HD 22484) have debris disks and for two of them (HD 22049 and HD 222582(A + B)) planets are observed. Neither a debris disk nor planets have been observed for one the program stars (HD 20766). High resolution spectral observations of the program stars were made at the 2.2-m telescope of the European Southern Observatory (ESO) during 2008 with the FEROS spectrograph (R = 48000, spectral range 3800-9200 Å). The fundamental parameters of the stars are determined, including effective temperature, acceleration of gravity at the stars’ surface, microturbulence velocity, metallicity, and the abundances of volatile and refractory elements in their atmospheres. The positions of all these stars are indicated on a Hertzsprung-Russell diagram. Fil: Rojas, M.. St. Petersburg State University; Rusia Fil: Drake, N. A.. St. Petersburg State University; Rusia. Ministério de Ciencia, Tecnologia e Innovacao. Observatorio Nacional; Brasil Fil: Chavero, Carolina Andrea. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Pereira, C. B.. Universidad Nacional de Cordoba. Observatorio Astronomico de Cordoba; Argentina Fil: Kholtygin, A. F.. St. Petersburg State University; Rusia Fil: Solovyov, D. I.. Russian Academy of Sciences; Rusia

The results of high-resolution spectropolari metric observations (R = 60 000) of the B0.5-type subgiant ɛ PerA are reported. Regular components of line profile variations with the frequencies 3.82–12.99 d−1 are found. A possible relation between the non-radial pulsations of the star and the observed regular variations of the line profiles is shown. A wavelet analysis of the difference of line profiles in the spectrum of ɛ PerA is performed. The amplitude of the wavelet spectrum is found to have two maxima at 10–20 and 50–60 km/s velocity scales. It is suggested that the first maxi mum corresponds to the amplitude of fluctuations in the velocity field of large-scale motions in the non-radially pulsating photosphere of the star, whereas the second maximum is associated with the variation of the half widths of spectral line profiles. An upper limit for the effective magnetic field of the star is inferred.

A team involved in APOGEE, one of the Sloan Digital Sky Survey III programs, recently announced the discovery of two rare rigidly rotating magnetosphere stars, HD345439 and HD23478. Near-infrared spectra of these objects revealed emission-line behavior identical to that previously discovered in the helium-strong star sigma Ori E, which has a strong magnetic field and rotates fast. A single spectropolarimetric observation of HD345439 with FORS2 at the VLT in 2014 over 88min indicated that HD345439 may host a strong, rapidly varying magnetic field. In this work, we present the results of our spectropolarimetric monitoring of this star with FORS2, which revealed the presence of a strong longitudinal magnetic field dominated by a dipolar component. The analysis of spectral variability indicates an opposite behaviour of He and Si lines, which is usually attributed to differences in the distribution of surface He and Si abundance spots., 5 pages, 1 table, 6 figures, accepted for publication in MNRAS. arXiv admin note: text overlap with arXiv:1702.01063

HD 164492C is a spectroscopic triple stellar system that has been recently detected to possess a strong magnetic field. We have obtained high-resolution spectroscopic and spectropolarimetric observations over a timespan of two years and derived physical, chemical, and magnetic properties for this object. The system is formed by an eccentric close spectroscopic binary (Ca1-Ca2) with a period of 12.5 days, and a massive tertiary Cb. We calculated the orbital parameters of the close pair, reconstructed the spectra of the three components, and determined atmospheric parameters and chemical abundances by spectral synthesis. From spectropolarimetric observations, multi-epoch measurements of the longitudinal magnetic fields were obtained. The magnetic field is strongly variable on timescales of a few days, with a most probable period in the range of 1.4-1.6 days. Star Cb with Teff~25000 K is the apparently fastest rotator and the most massive star of this triple system and has anomalous chemical abundances with a marked overabundance of helium, 0.35+/-0.04 by number. We identified this star as being responsible for the observed magnetic field, although the presence of magnetic fields in the components of the Ca pair cannot be excluded. Star Ca1 with a temperature of about 24000 K presents a normal chemical pattern, while the least massive star Ca2 is a mid-B type star (Teff~15000 K) with an overabundance of silicon. The obtained stellar parameters of the system components suggest a distance of 1.5 kpc and an age of 10-15 Myr., Comment: 15 pages, 5 tables, 12 figures, accepted for publication in MNRAS

Spectroscopic studies of five peculiar stars (CD-65°2893, HD 22229, HD 66812, HD 56523 and HD 31341) with presumed elevated abundances of s-process elements are reported. High spectral resolution observations of these stars made in 2008 at the 2.2-m telescope of the European Southern Observatory (ESO) in Chile with the FEROS spectrograph are analyzed. The evolutionary status of the stars is determined, along with some of their fundamental parameters, such as: effective temperature, acceleration of gravity at their surfaces, microturbulence velocity, metallicity, and the abundance of chemical elements, including s-process elements, in their atmospheres.

We report the results of spectropolarimetric observations of the supergiant ζ Ori A made with 6-m BTA telescope of the SAO RAS. We found regular variations of line profiles in the spectrum of the star with a period of 1–3 hours and point to their possible association with nonradial photospheric pulsations. We also searched for a possible weak magnetic field in ζ Ori A, but observations did not confirm the existence of such a field in the star considered.

We observed the bright O6If(n) supergiant λ Cep in 1997 with the 6-m optical telescope of the Special Astrophysical Observatory and in 2007 with the 1.8-m telescope of the Bohyunsan Optical Astronomy Observatory (South Korea). A total of 90 spectra of the star were acquired, with good time resolution (10 minutes), signal-to-noise ratios 150–300, and spectral resolutions of 45 000–60 000. We detected line-profile variations of H, HeI, and HeII lines. It is suggested that the detected variations are due to non-radial photospheric pulsations and the star’s rotation (rotational profile modulation).

The applications of the spectral analysis methods discovered by Kirchhoff for the investigation of stellar magnetic fields are considered. The statistical properties of the mean magnetic fields for OBA stars have been investigated by analyzing data from two catalogs of magnetic fields. It is shown that the mean effective magnetic field ℬ of a star can be used as a statistically significant characteristic of its magnetic field. The magnetic field distribution functions F(ℬ) have been constructed for B-type and chemically peculiar (CP) stars, which exhibit a power-law dependence on ℬ. A sharp decrease in F(ℬ) in the range of weak magnetic fields has been found. The statistical properties of the magnetic fluxes for main-sequence stars, white dwarfs, and neutron stars are analyzed.

We recalculated the distance to 554 galactic Planetary Nebulae (PNe) using the relation between the ionized mass of the nebula μ and the optical thickness parameter τ obtained by Akimkin et al. [1]. We classified these nebulae according to the Peimbert [9] types modified by Quireza et al. [11]. The obtained by us distances to galactic PNe were used to obtain the scale heights h for different subsystem of the Milky Way. Next values if h were estimated: h = 208 ± 10 pc for thin disk objects, h = 600 ± 54 pc for thick disk ones, and h = 1378 ± 180 pc for halo PNe.

We review the interaction in intermediate and high mass stars between their evolution and magnetic and chemical properties. We describe the theory of Ap-star `fossil' fields, before touching on the expected secular diffusive processes which give rise to evolution of the field. We then present recent results from a spectropolarimetric survey of Herbig Ae/Be stars, showing that magnetic fields of the kind seen on the main-sequence already exist during the pre-main sequence phase, in agreement with fossil field theory, and that the origin of the slow rotation of Ap/Bp stars also lies early in the pre-main sequence evolution; we also present results confirming a lack of stars with fields below a few hundred gauss. We then seek which macroscopic motions compete with atomic diffusion in determining the surface abundances of AmFm stars. While turbulent transport and mass loss, in competition with atomic diffusion, are both able to explain observed surface abundances, the interior abundance distribution is different enough to potentially lead to a test using asterosismology. Finally we review progress on the turbulence-driving and mixing processes in stellar radiative zones., Proceedings of IAU GA in Rio, JD4 on Ap stars; 10 pages, 7 figures

The He, C, N, and O abundances in more than 120 planetary nebulae (PNe) of our Galaxy and the Magellanic Clouds have been redetermined by analyzing new PNe observations. The characteristics of PNe obtained by modeling their spectra have been used to compile a new catalog of parameters for Galactic and extragalactic PNe, which is accessible at http://www.astro.spbu.ru/staff/afk/GalChemEvol.html. The errors in the parameters of PNe and their elemental abundances related to inaccuracies in the observational data have been analyzed. The He abundance is determined with an accuracy of 0.06 dex, while the errors in the C, N, and O abundances are 0.1–0.2 dex. Taking into account the inaccuracies in the corrections for the ionization stages of the elements whose lines are absent in the PNe spectra increases the errors in the He abundance to 0.1 dex and in the C, N, and O abundances to 0.2–0.3 dex. The elemental abundances in PNe of various Galactic subsystems and the Magellanic Clouds have been analyzed. This analysis suggests that the Galactic bulge objects are similar to type II PNe in Peimbert’s classification, whose progenitor stars belong to the thin-disk population with ages of at least 4–6 Gyr. A similarity between the elemental abundances in PNe of the Magellanic Clouds and the Galactic halo has been established.

The modern observations of the planetary nebulae (PNe) were used to create a new catalogue of He, C, N, O, Ne, S and some other element abundances for more than 300 Galactic and extragalactic PNe. This catalogue was a start point for studying the star formation history in the Galactic disk. We have found that He, C, N and O abundances in the thin disk PNe are very close to those in bulge PNe. We also established that the abundances of the same elements in the PNe belonging the halo of the Milky Way and the Magellanic Clouds are similar. We have estimated the mean ages of the progenitors of PNe in the thin and thick disks and in the bulge. The evidences in the favor of the suggestion that the formation of the intermediate-mass star began in bulge and only then continued in the thin disk were found.

Diagnostics for the rarefied plasmas in gaseous nebulae are reviewed, beginning with the pioneering papers of V. A. Ambartsumian. These papers, as well as the diagnostic techniques which have been developed on the basis of ideas contained in them, are discussed. Diagnostic techniques for homogeneous, as well as inhomogeneous, plasmas are described.