Astronomy and Astrophysics – Astrophysics
Scientific paper
2008-01-15
Astronomy and Astrophysics
Astrophysics
12 pages, 5 figures. accepted by Astronomy Letters
Scientific paper
10.1007/s11443-008-4002-1
We examine a problem of the dust grains survival in the disk wind in T Tauri stars (TTSs). For consideration we choose the disk wind model described by Garcia et al. (2001), where a gas component of the wind is heated by an ambipolar diffusion up to the temperature of the order of 10$^4$ K. It is shown that the dust grains heating due to collisions with the gas atoms and electrons is inefficient in comparison with heating by the stellar radiation, and thus, dust survives even in the hot wind component. Owing to this, the disk wind may be opaque for the ultraviolet and optical radiation of the star and is capable to absorb its noticeable fraction. Calculations show that at the accretion rate $\dot{M_a} = 10^{-8}-10^{-6} M_\odot$ per year this fraction for TTSs may range from 20% to 40% of a total luminosity of the star correspondingly. This means that the disk wind in TTSs can play the same role as the puffed inner rim considered in the modern models of accretion disks. In Herbig Ae stars (HAEs) inner regions of the disk winds ($r \le 0.5$ AU) are free of dust since there dust grains sublimate under the effect of the radiation of the star. Therefore, in this case a fraction of the absorbed radiation by the disk wind is significantly less, and may be compared with the effect of the "puffed-up inner rim" only at $\dot{M_a} \geq 10^{-6} M_\odot$ yr$^{-1}$. Due to the structural inhomogeneity of the disk wind its optical depth towards an observer may be variable resulting in the photometric activity of the young stars. For the same reason, one can observe moving shadows from the gas and dust streams with the spiral-like structure on the highly resolved circumstellar disk images.
Grinin V. P.
Tambovtseva L. V.
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