Astrophysics and Space Science

, Volume 77, Issue 2, pp 511–520 | Cite as

Circumstellar dust and related phenomena at phase 0.8 in Miras

  • J. Svatoš
  • M. Šolc


SeveralM-type Mira variables (o Cet, RT Cyg) exhibit a sudden polarization increase near phaseP=0.8 of visual light period, whereas the position angle of the linearly polarized component remains almost unchanged. The degree of polarization is observed to be high (∼6%) in the violet and blue region and to decrease slowly toward the infrared. In connection with appearance of the 10 μm band this indicates the presence of circumstellar silicate grains of diameters varying between ∼100 nm and 1 μm.

In dirty silicate particles, i.e. SiO2 + metal ion admixture, the colour centres can be activated by absorbing of energetic photons, which results in increasing imaginary part of the refractive index. As showed by Svat of (1980), this mechanism can explain the polarization rise of light transmitted through a layer of aligned nonspherical dirty silicate glassy grains. From the appearance of the Balmer emission lines in the lower atmospheric layer, SiO maser activity disruption and the other phenomena occuring atP∼0.8 it is concluded, that the source of the activating short wavelength radiation can lie in the ionization front ahead of the expanding shock wave (assumed in the model of Miras atmosphere by Hinkle and Barnes, 1979) and in other eruptive phenomena in Miras. The same mechanism can be effective in Nova outbursts, RS CVn flares and T Tau sudden luminosity variations. The role of magnetic field in the Miras atmosphere is discussed.


Shock Wave Flare Colour Centre Ionization Front Short Wavelength Radiation 
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Copyright information

© D. Reidel Publishing Company 1981

Authors and Affiliations

  • J. Svatoš
    • 1
  • M. Šolc
    • 1
  1. 1.Dept. of Astronomy and AstrophysicsCharles UniversityPragueCzechoslovakia

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