Astronomy and Astrophysics – Astrophysics – Solar and Stellar Astrophysics
Scientific paper
2012-04-16
Astronomy and Astrophysics
Astrophysics
Solar and Stellar Astrophysics
13 pages, 5 tables. In submitting to Astrophysics
Scientific paper
The existence of convective and turbulent motions and the evolution of stellar magnetic fields give rise to existence of temperature fluctuations in stellar atmospheres. We observe the time and surface averaged radiation fluxes from the stars. The usual photosphere models do not take into account the temperature fluctuations and only present the distribution of the mean temperature into surface layers of stars. We investigate how the temperature fluctuations change the stellar spectra in continuum. The degree of fluctuations (the ratio of mean temperature fluctuation to the mean temperature) is supposed to be small. We discuss the procedure of calculation of the star spectrum, which takes into account the temperature fluctuations. As a first step we use the usual model of a photosphere without fluctuations. The observed spectrum is presented as a part depending on mean temperature and the additional part proportional to quadratic value of fluctuation degree. It is shown that the additional part in Wien's region of spectrum can be evaluated directly from wave length dependence of observed spectrum. This part depends on the first and second wavelength derivatives near the observed wavelength. It can be also derived from known models of photospheres. Our estimations show that the temperature dependence of absorption factors is very important by calculation of continuum spectra corrections. As the examples we present these estimations for some stars from Pulkovo spectrophotometric catalog and for the Sun. The influence of temperature fluctuations on color indices is also investigated. The problem how estimate the degree of fluctuations from statistical investigation of weakly variable stars and the stars of the same spectral type with almost equal luminosities is also discussed.
Alekseeva G. A.
Novikov Victor
Silant'ev N. A.
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