The Variability of OH Maser Lines of the Stars: R Crt, W Hya and RT Vir

Details The Variability of OH Maser Lines of the Stars: R Crt, W Hya and RT Vir The Variability of OH Maser Lines of the Stars: R Crt, W Hya and RT Vir

Oct 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001phdt.........2b&link_type=abstract

Torun Centre for Astronomy PhD Thesis, 175 p. (in Polish)

Astronomy and Astrophysics

Astronomy

Masers, Masers: Polarisation, Stars: Variable, Stars: Agb, Circumstellar Matter

Scientific paper

The results of analysis of long time observations of OH ground state main maser lines towards three SR stars are presented. About dozen year period of observations (14 years for R Crt and RT Vir, a nd 10 years for W Hya) is comparable to the gas travel time across OH maser shell. All observations have been done with the Nançay Radio Telescope between 1982 and 1996. The temporal changes of maser line intensities were considered. The period analysis of variability were made and presented in details. The presence of long-period changes, subperiods and sudden activities has been demonstrated in flux plots. The phase lags between redshifted and blueshifted line features were measured. The radio and optical light curves were compared for W Hya. The variability indices across whole spectra for scrutinised stars were also calculated. The radial velocity drift of line components was measured. I have presented the examples of the velocity changes up to 2 km/s for time interval from a few month to 10 years. The 1667 MHz to 1665 MHz flux ratio has been analysed and discussed. Some examples of narrowing and rebroadening of spectral lines in flared features which depict changes of maser saturation degree were given. The tangential amplified components were also measured, analised and discussed. Long-term variations of fractional circular polarisation degree for many components across spectra were presented. Their analysis shows nonperiodical short-term local variations and global long time changes of polarisation for measured components. The measurements and comparison of linear and circular polarisation degree where made for the last two years of observations. The most interesting result is the anticorrelation between degrees of linear and circular net polarisations for RT Vir. All measurements show multicomponent and very complicated, dynamic picture of the OH envelopes in scrutinised variable stars. Some results suggest presence of thin and turbulent OH envelopes where maser action are sustained in a few blobs. The polarimetric properties suggest a globally ordered magnetic field with complicated local structure. This PhD thesis contains three principal parts: 1. the background of maser emission in late type stars envelopes; 2. presentation of the data and results of multi-parameter measurements; 3. discussion of obtained results with compact summary. The appendixes are: the complete atlas of spectra used; maser emission and polarimetry theory; description of numerical methods used in data analysis.

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