Azerbaijan National Academy of Sciences

Investigation of non-stationary processes taking place in stars;

Non-stationary processes in young stars.

1. Supergiant stars belonging of different luminosity;
2. Wolf-Rayet type stars;
3. Symbiotic stars;
4. T-tau type young stars;
5. Magnetic stars;
6. Close binary stars and novae;
7. Creation of the important programs for the astronomical research.

The spectral observations of stars 89 Her, HD14662, HR7451, HR7495, HR6978 at telescope “Zeiss-2000” of ShAO had been carried out. Determined the chemical composition of these stars and parameters of spectral lines (the equivalentekvivalent width, radial velocity etc.). It was shown that in the spectra of stars 89 Her the absorption component of Ha is shifted to the blue direction of the spectra and emission component always observed in red wing. Sometimes revealed disappearing of line Ha in the spectra of 55 Cyg.

By applying models of Kurucz to spectra of star 89 Her located at high galactic latitude, received at telescope “Zeiss-2000”, the chemical composition and atmospheric parameters of this star were determined. The chemical compositions of supergiant stars located at galactic plane and at high galactic latitudes were determined and comparative analysis of the chemical composition of these stars had been carried out. In chemical composition of star 89 Her and other stars located at high galactic latitudes little iron and a lot of carbon and sulfur were revealed as compared with the other normal super giants of population I. Thus the chemical composition of supergiant stars of spectral type F located at high galactic latitudes and of population I ones are different.

The spectral and photometric observations of Wolf-Rayet (WR) type stars (WR134, WR136, WR138) at telescopes “Zeiss-2000” and “Zeiss-600” of ShAO accordingly had been carried out. Spectral variability of stars WR134, WR136 and short-term (during several minutes) strong (0m.05 and 0m.1) photometric variability of star WR134 were revealed. The strong short-term photometric variability of star WR134 has been detected for the first time. The spectral subtypes of stars WR134 and WR136 which belong to nitric sequence were determined using echelle spectrograms these stars obtained with the aid of telescope “Zeiss-2000” of ShAO. For the spectral classification of these stars the modern classification scheme of WR stars which belong to nitric sequence had been used. The spectral subtypes of these stars was determined as WN6. The dependence of half-widths of emission lines from of their excitation potential was plotted. This dependence is important for the understanding the ionization state of envelope of WR stars.

The comparative analysis of this dependence for the WR stars which belong to different subtypes are important for the understanding the evolutionary properties of these stars.

The joint analyse the results of ivestigations of echelle spectrograms of symbiotic star CH Cyg obtained in 1998-2001 at telescope “Zeiss-2000” of ShAO and published scientific articles in this period concerning to this star give the new scientific results. Variation of absopbtion lines with the period P1=5650d and P2=756d was revealed. These periodic variations it has been explained that the system can be threefold system. The 1350 day periodic variability of radial velosity and other parameters of emission line Ha had been revealed. This period is well agrees with the period found from photometric observations. At 1998 year when within 30 minutes took place the sharp increasing of brightness of CH Cyg, appeared the emission line HeI6678 and when the brightness of star decreased this line disappeared.

The comprehensive analyzing of the spectral observational material with the high resolution obtained in a various stages of photometric activity of the symbiotic star AG Dra, the new scientific results had been received. Using spectral observational material had been obtaining at Cassegrain focus of telescope “Zeiss-2000” of ShAO, during 1983-1987 years, the orbital elements, masses and temperatures of components, temperature and density of envelope existing around AG Dra were calculated. The phenomenological model of star AG Dra explaining its observational properties had been proposed. In June of 1994 (brightness variations of star 2m.9, 2m.2 1m.4, and 0m.6 magnitudes in filters UBVR accordingly, during 18 days) and in August of 1995 (brightness variations of star with the amplitude of ~1 magnitude in filter V) the brightness flash of star AG Dra had been revealed.

The T Tau type stars RY Tau, DR Tau, AB Aur and HD 216629 had been investigated.

Variations of spectral line MgII2800 with the period 23d.26 in the spectra of RY Tau were revealed. In most cases the brightness variations of this star with this period was revealed.

Comparatively analyzing the brightness variations in V band and variation of emission doublet MgII 2800 showed that there are no well-defined correlations between these variations. This observant fact can be connected with that, variability of radial velocity and brightness is caused by various mechanisms. In changes of brightness of a star RY Tau during 1983-2004 years three most probable periods are found out: 22, 14 and 6 years.

The synthetic graphic which well compliant with the annual curve of light is constructed using combination of periods 6 and 14 years. This fact is in favour of idea that the system can be consists of several components. With the aid of the diagram of spectral distribution of energy showed that, an energy source can be the star of spectral class G1-G2 with the temperature of 60000K. The existence of additional source of radiation with the temperature of 30000K had been revealed. The analysis of light curve of star DR Tau, constructed by applying of 28 year observational data, was carried out. It was shown that in spite of 2m brightness variations in filter V in various seasons, the average value of brightness does not change within 10 years. The light curve of this star corresponds to II group, according to of Shamakha classification scheme. The statistical analysing of variations of brightness showed the existence of two more probable values of periodicity P1=5d.8 and P2=7d.4. The periods which had been obtained for the brightness variations das not revealed in variations of spectral lines.

The comprehensive spectral, photometric and magnetic investigations of the magnetic stars HD 112185, HD 189849, HD 124224, HD184905 and HD 137909 belonging to the various type of peculiarity were fulfilled. The new value of periodic variability for the starHD 112185 was found. It has been revealed, that the atmosphere of this star has heterogeneous structure and on its surface more peculiar and comparatively normal areas it is observed at phases j(P)=0.5-0.6 and j(N)=0.30-0.35 accordingly. Using the results of spectral and photometric observations the fundamental parameters (Teff, log g, L, Mv, R) of star HD 112185 had been determined. The parameters of line Ha was determined from the spectrum of stars HD 189849 and HD 137909 obtained after 2006 year, with aid of 2-m telescope ShAO. For the purpose of detection anomalous (peculiar) areas on the surface of both star the results of spectral, photometric and magnetic observations had been used. It was revealed, that on a surface of star HD 137909 more peculiar areas are located around a magnetic pole and this area is observed at phase j(P)=0.15.

The normal areas was observed at phase j(N)=0.6-07. By applying analogous methodology to the star HD 189849 had been revealed that on its surfaces peculiar and normal areas is observed at phases j(P)=0.50-0.60 and j(N)=0.90-1.00 accordingly. The fundamental parameters of the stars HD 189849 and HD 137909 had been determined, obtained following values:

a)Teff(P)=78000K, Teff(N)=78000K, log g=3.75 for the star HD 189849;

b) Teff(P)=80000K, Teff(N)=70000K, log g=4.00 for the star HD 137909.

The analogous investigations had been carried out for the another magnetic star CU Vir.

Some important programs for the astronomical investigations were created:

1.The programme for the solving light transfer equation in the moving medium – RETSLEA

The analytical and numerical solution of light transfer equation is one of difficult problems. Expansion of atmosphere and distribution on frequencies in lines creates difficulty for the analytical solution. Presence the term in the equation taking into account scattering complicates the numerical solution. The method of differential equations of the second order is not correct.

Program RETSLEA created for the solution of given problem allows correct solving the light transfer equation taking into account boundary conditions and using a method of moments.

2.The programme for the solving light transfer equation in spektral lines using method of discrete oordinat – SLP_MDO. One of the methods of solution of light transfer equation is the method discrete ordinates. In this method an integrated member approximates with the sum.

Increasing of number of members for the purpose of high accuracy of approximation and the requirement of boundary conditions for each member creates serious difficulty in program creation. For the purpose of elimination of all these difficulties the program SLP_MDO was created.

3.Light transfer in the envelope – the program Starenvelope.

Presence of a disk or spherical envelope around astrophysical objects is widespread phenomenon. If to a star wind we will consider as envelope it turns out that the astrophysical objects without an envelope are absent. It means that the solving of light transfer equation in envelope is actual. The program Starenvelope was created for this purpose. In this program for the first time calculates the star spectrum and then the spectrum forming in an envelope.

4. Extracting of dates from the astronomical archives and their processing – the program DIPI.

This program was created for the purpose of gathering of astrophysical archive dates and their processing.

5.The programme for the processing observational dates - SpAn