The stellar wind as a key to the understanding of the spectral activity of IN Com

We present long-term spectral observations (R = 20000) of IN Com in the region of the H_α, H_β, and He I 5876 lines. One distinguishing characteristic of the stellar spectrum is the presence in the H_α line of an extended two-component emission with limits up to ±400 km/s. Emission parameters show the rotation modulation with the stellar rotation period and a significant variability on the long-term scale. Similar emissions are also observed in the H_β and He I 5876 lines. Our results allow us to conclude that observational emission profiles are formed in an optically thin hot gas. This is a result of the presence of a circumstellar gas disk around IN Com. Its size does not exceed several stellar radii. The material for the disk is supported by the stellar wind from IN Com. The detected variability of H_α-emission parameters shows a clear connection with the photopolarimetric activity of the star. This fact allows us to associate the long-term spectral variability with cycles of stellar activity of IN Com.     

Time-variability analysis of the Hα, He i and Na i D lines in the T Tauri star LkHα 264

We present a time-series analysis of quasi-simultaneous high-resolution profiles of the Hα, He i (λ5876 Å) and Na i D lines for the highly active T Tauri star LkHα 264.
Our data include repeated observations on time-scales ranging from approximately 1 d down to less than 1 h, at two different epochs. For the three lines we have analysed the time variability of the equivalent width and of the profile, using in this case both the normalized variance and correlation matrix analysis.
The behaviours of the equivalent widths of the He i and Na i lines on time-scales of the order of 1 d were found to correlate well. The correlation is more conspicuous when the level of variability of the lines is more dramatic. We conclude that there is a common region of formation for these lines, very close to the star. However, the Hα equivalent width follows such behaviour only when the He i and Na i D lines are less variable.
In terms of profile variations, He i and Na i differ from Hα. The He i and Na i D variations occur coherently over the entire profile, independently of the time-scales, although there are indications that such behaviour may break down for time-scales shorter than ≈20 min. In contrast, the variability of Hα occurs mainly on the blue side of the line. Variations on short time-scales seem to be associated with a secondary blue emission peak. Variations on time-scales of 1 d are linked to two weak blueshifted absorptions. These absorptions occur in an outer region and their behaviour can be understood in terms of an optical depth effect.
We conclude that the Hα line is formed in two distinct regions. The inner region, which is not too distinct from the one producing the He i and Na i D lines, is highly sensitive to the level of activity. The outer and more extended region dominates the contribution to the flux in Hα when the general level of stellar activity is high.     

Large-scale variability in the profiles of Hα and Hβ in the spectrum of the Herbig B8e star MWC 419 and a model interpretation of it

Spectroscopic data taken with a moderate resolution spectrograph in the region of the Hα and Hβ lines are presented for the Herbig B8e star MWC 419. The spectroscopic observations were accompanied by broad band BVR photometric measurements. The observations reveal a variability in the line profiles that is typical of Herbig Ae/Be stars with signs of a strong stellar wind. The greatest changes are observed in the region of the absorption components of the line profiles, which convert the profile from a type P CygII to P CygIII, as well as in the intensities of the central emission components. A model technique is used for quantitative interpretation of this variability and it shows that the P Cyg profile conversion of the absorption component can be explained in terms of a stellar wind model in which its distribution over latitude varies on a time scale of a few days. __________ Translated from Astrofizika, Vol. 50, No. 2, pp. 259–280 (May 2007).     

Structure of the inner region of the accretion disk of the Herbig Ae star CQ Tau based on long-term monitoring data

Results from simultaneous spectral and photometric monitoring of the Herbig Ae star CQ Tau in the neighborhood of the Hα and resonance sodium doublet Na I D lines are presented. It is shown that the inner structure of the accretion disk of CQ Tau is nonuniform and consists of two regions with quite different kinematic characteristics. Region I is characterized by relative stability and a smooth long-term variation in the velocity of the gas along the line of sight. Region II is distinguished by the highest velocities and a variability in their maximum values over time scales from a few days to 700 days. The dust clouds which produse the star’s brightness minima may also be the source of cold gas and contribute to the observed spectral variability. We assume that region I of the disk coincides with the accretion disk of the star. The kinematic differences in region II may be caused by dissipation of circumstellar dust clouds which, moving in elongated orbits, are able to approach the star quite closely. __________ Translated from Astrofizika, Vol. 50, No. 1, pp. 39–55 (February 2007).     

New results of magnetic field measurements for BP Tau

We present measurements of the longitudinal magnetic field component B _‖ of the young star BP Tau in the He I 5876 emission line formation region, i.e., in the accretion flow near the stellar surface. The values obtained (?1.7 kG and ?1.0 kG in 2000 and 2001, respectively) agree with the results of similar measurements by other authors. At the same time, we show that the previously obtained field strength at the magnetic pole, B _p, and the inclination of the magnetic axis to the rotation axis, β, are untrustworthy. In our opinion, based on the B _‖ measurements available to date, it is not possible to conclude whether the star’s magnetic field is a dipole one or has a more complex configuration and to solve the question of whether this field is stationary. However, we argue that at least in the He I 5876 line formation region, the star’s magnetic field is not stationary and can be restructured in a time of the order of several hours. Nonstationary small-scale magnetic fields of active regions on the stellar surface and/or magnetospheric field line reconnection due to the twisting of these field lines as the star rotates could be responsible for the short-term magnetic field variability. It seems highly likely that there are no strictly periodic variations in brightness and emission line profiles in BP Tau due to the irregular restructuring of the star’s magnetic field.     

Spectral variability of IL cephei

The results of six years of spectroscopic studies of the Herbig Be star IL Cep (HD216629) are reported. Various spectral parameters of the Hα and Hβ emission lines and those of the He I λ 5876 Å absorption feature are found for the first time to have exhibited slow variations in 2006–2011 and to have reached their extrema in 2009–2010. The Na I D1 and D2 lines reproduce, in a weaker form, the Hα radialvelocity variations. It is suggested that the variations found in the spectrum of the star may be due to the presence of additional bodies in the system.     

Structure of the inner regions of the circumstellar gas envelopes of young hot stars. I. The isolated Ae Herbig star WW Vul

Results of simultaneous spectral and photometric monitoring of the Ae Herbig star WW Vul in the neighborhoods of the Ha line and the sodium NaI D resonance doublet are reported. It is shown that the spectral variability of the star is caused mainly by the anisotropic disk wind, whose high velocity component forms in the inner region of the accretion disk. The circumstellar gas in footpoint of the wind shows the variability of the density and velocity, that is in good agreement with the results of modeling of an accretion and outflows around young stars controlled by the stellar and/or disk magnetic field. An analysis of the variability of the parameters of the Ha emission line also showed that the density of the gas in the inner region of the accretion disk varies over a time scale exceeding 10 years. __________ Translated from Astrofizika, Vol. 49, No. 2, pp. 171–185 (May 2006).     

Spectral observations of the novalike star TT Ari. II

Results from a spectral study of one of the brightest cataclysmic variables, the star TT Ari, are presented. They are generally in good agreement with previous observations, but there are some differences. The luminosity of the star, as well as the equivalent widths of emission lines, reveal variations that are probably periodic in character. Emission from the star in the CIV 5801Å and 5812 Å lines is observed for the first time. The observed variations in the symmetry of the broad absorption Balmer series (beginning with Hβ) may be a consequence of the appearance of a P Cyg line profile. The Hα line manifests a P Cyg profile consisting of two components corresponding to 600 and 1900 km/s. The average of the ratio EWHα/EWHβ indicates that the formation of these lines may be explained, at least partially, in terms of a simple photoionization-recombination model. __________ Translated from Astrofizika, Vol. 51, No. 3, pp. 445–460 (August 2008).     

Profiles of the Hα and Hβ lines in the spectra of B and Be stars in the diffuse stellar cluster h/χ Persei

High dispersion CCD spectra are used to study the profiles of the Hα and Hβ lines of 48 stars in early spectral classes in the young diffuse binary cluster h/χ Per. In addition, moderate resolution spectra of 15 B and Be stars were taken over the interval 4400–4960 Å. One or, possibly, two new Be stars are discovered. The major parameters of the Hα line are measured for the observed B and Be stars. The spectra over 4400–4960 Å are used to estimate T_eff, logg, and υsin i. No traces of emission are detected in the Hα line profiles for 28 of the stars and emission is observed in the Hα line for 20. During our observations an absorption profile of the Hα line was observed for some of the stars, such as Oo146, Oo566, Oo922, and Oo1268, although they have previously been identified as Be stars. A significant long-term variability of the Hα line is discovered for the Be stars Oo1161 and Oo2242. Oo2371 manifests a variability in its faint emission spectrum which is typical of close binary systems that include a Be star. __________ Translated from Astrofizika, Vol. 51, No. 2, pp. 305–319 (May 2008).     

Line variability in the spectrum of supergiant α Cam

CCD spectra taken with the PFES and CEGS echelle spectrographs attached to the 6-m Special Astrophysical Observatory (Russian Academy of Sciences) telescope and the 2-m Shamakha Astrophysical Observatory (National Academy of Sciences of Azerbaijan) telescope, respectively, were used to study the line-profile variations in the spectrum of the hot supergiant α Cam. No fast (≤1.5 h) line-profile and radial-velocity variations were found. Some of the systematic effects that cause spurious variability are considered. The Hα-profile variability appears symmetric relative to the radial velocity of the star’s center of mass and is attributable to variable blueshifted and redshifted emission and/or absorption components superimposed on a variable photospheric profile. The Hα line shows evidence of a large-scale mass ejection from the stellar surface, which is also traceable in other spectral lines. The He II 4686 line exhibits an inverse P Cyg profile, while the red wing of the He I 5876 line shows weak and variable emission. The fast (on characteristic time scales of shorter than an hour) variability of the He II 4686 profile that was previously revealed by our observations (Kholtygin et al. 2000) is called into question. A comparison of the observational data on the variability of ultraviolet and optical line profiles for the supergiant αCam suggests that nonradial motions are mainly responsible for the radial-velocity and line-profile variability.     

Disk wind and magnetospheric accretion in emission from the Herbig Ae star MWC 480

The young Herbig Ae star MWC 480 (HD 31648) is one of the comprehensively spectroscopically studied stars in the ultraviolet, optical, and infrared spectral ranges. Using non-LTE modeling of its hydrogen spectrum, we have calculated the contribution to the hydrogen emission from such important regions of the circumstellar environment as the disk wind and the magnetosphere. We have used our own observations of the stellar spectrum performed with the 2.4-m telescope at the Thai National Observatory to quantitatively check our theoretical calculations. In addition, all of the visible and infrared spectra available in the literature have been used for a qualitative comparison. The modeling results have revealed a significant role of the magneto-centrifugal disk wind in the formation of atomic hydrogen emission. The cause of the emission line variability in the spectrum ofMWC 480 is discussed.     

Photographic spectrophotometry of selected bright B and Be Stars

Coudé spectra taken in the red region of 49 bright B and Be stars were examined for the behaviour of Hα and the He I λλ 5876 and 6678 line profiles. 51 per cent of the stars were found to show Hα emission to some degree and 22 per cent showed helium emission. Evidence is presented for the existence of drastic changes in the line profile and the radial velocity in some of the stars on a time scale of fractions of a day. Visiting Astronomer, Kitt Peak National Observatory and Cerro Tololo Inter-American Observatory, operated by the Association of Universities for Research in Astronomy, under contract with the National Science Foundation.     

Influence of stellar wind on the long-term variability of the Hα emission line. The case of the Herbig Ae-star HD 31648

The results of high-resolution long-term spectral monitoring in the region of the emission Ha line of the Herbig Ae star HD 31648 are reported. The variability in the observed profile is shown to be caused mainly by a change in the parameters of outflowing circumstellar gas over a time scale of about 3 years. __________ Translated from Astrofizika, Vol. 49, No. 1, pp. 81–90 (February 2006).     

Structural peculiarities of circumstellar envelopes of the young A0E herbig stars

Circumstellar peculiarities of the A0-type Herbig stars are analyzed on the basis of high-resolution CCD spectroscopic data, obtained in 1991-1994 at the ESO and the Crimean Astrophysical Observatory (about 250 spectrograms). The results of investigation of the rapid line profile variability in H , H , HeI 5876 and DNa lines are presented for AB Aur, HD 163296, HD 36112 and HD 100546. The conclusion is made that the behaviour of these lines can be explained in the framework of the model containing an equatorially concentrated and azimuthally inhomogeneous stellar wind and an external cool shell occasionally losing matter in the form of infall on to the star.     

Long-Term Spectral Variability of the Herbig Ae-Star HD 179218

The results of high-resolution long-term spectral monitoring of Herbig Ae star HD 179218 in the region of emission H line and the sodium resonance doublet Na I D are presented. The received data show the existence of short-term variability (about 10 days) and long-term wave-like variability of equivalent width EW, intensity of circumstellar (CS) emission I and parameters of H emission profile. The analysis of these data allows us to suppose the existence of the global variability of parameters of accretion disk.     

Integral spectroscopy of the nebula GM 1-29 and the star PV Cep

Integral spectroscopy data for the nebula GM 1-29 and the source star PV Cep obtained on the 2.6-m telescope at the Byurakan Observatory are presented. The structure and kinematics of a collimated emission outflow directed along the axis of the nebula are studied. Changes in the radial velocity and intensity of the absorption component of the nebular Hα line are observed and studied; these are interpreted as a result of an anisotropy in the stellar wind at distances on the order of several stellar radii, where this absorption is formed. __________ Translated from Astrofizika, Vol. 51, No. 3, pp. 461–468 (August 2008).     

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

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.     

Wind dynamics and circumstellar extinction variations in the T Tauri star RY Tau

The wind interaction with the dusty environment of the classical T Tauri star RY Tau has been investigated. During two seasons from 2013 to 2015, we carried out a spectroscopicmonitoring of this star with simultaneous BV R photometry. A correlation between the stellar brightness and the radial velocity of the wind determined from the Hα and Na D line profiles has been found. The irregular stellar brightness variations are shown to be caused by extinction in a dusty disk wind at a distance of about 0.2 AU from the star. We hypothesize that the circumstellar extinction variations result from a cyclic rearrangement of the magnetosphere and coronal mass ejections, which affect the dusty disk wind near the inner boundary of the circumstellar disk.     

Spectral Variability of T Tauri Stars in the Optical

We present the results of time variability analysis of the Hα, He I (λ5876 Å) and Na D (λ5890, 5896 Å) lines in two active T Tauri stars, DL Tau and DR Tau. The aim is the study of time behavior of these lines, during one week, as well as possible correlations among them. The observed profiles of some lines are very complex, often showing characteristics of outflow and accretion.     

Peculiarities of physical property distribution on the surface of CP Star HD182255

The star HD182255 reveals spectral variability in rotation, irregular short-term variability, as well as long-term variations in the spectra. The He and Si abundances vary in antiphase. According to the theory, silicon accumulates in the regions between the poles, where the field lines are horizontal. Hence the observed behavior of He and Si may indicate the presence of magnetic field, where one of the poles passes through the central meridian in phase Φ = 0 as the star rotates. Given a general weakening of He over the entire surface, in Φ = 0 its abundance is higher, which may be linked with the presence of wind from the magnetic pole. The star definitely belongs to the He-w type. The study of the structure of the upper atmosphere based on the hydrogen line profiles shows that it varies over the years. Our estimates of the magnetic field from the Zeeman spectra are within the measurement errors. According to the spectroscopic characteristics the star can be considered weakly magnetic.