TY - JOUR

T1 - Dust in the disk winds from young stars as a source of the circumstellar extinction

AU - Tambovtseva, L. V.

AU - Grinin, V. P.

N1 - Funding Information: We wish to thank A. Königl for useful discussions and valuable advice and the referee for constructive remarks. This work was supported by the “Origin and Evolution of Stars and Galaxies” Program of the Presidium of the Russian Academy of Sciences, INTAS grant no. 03-51-6311, and grant NSh-8542.2006.2.

PY - 2008/4

Y1 - 2008/4

N2 - We consider the problem of dust grain survival in the disk winds from T Tauri and Herbig Ae stars. For our analysis, we have chosen a disk wind model in which the gas component of the wind is heated through ambipolar diffusion to a temperature of ∼104 K. We show that the heating of dust grains through their collisions with gas atoms is inefficient compared to their heating by stellar radiation and, hence, the grains survive even in the hot wind component. As a result, the disk wind can be opaque to the ultraviolet and optical stellar radiation and is capable of absorbing an appreciable fraction of it. Calculations show that the fraction of the wind-absorbed radiation for T Tauri stars can be from 20 to 40% of the total stellar luminosity at an accretion rate a = 10-8-10-6 Myr-1. This means that the disk winds from T Tauri stars can play the same role as the puffed-up inner rim in current accretion disk models. In Herbig Ae stars, the inner layers of the disk wind (r ≤ 0.5 AU) are dust-free, since the dust in this region sublimates under the effect of stellar radiation. Therefore, the fraction of the radiation absorbed by the disk wind in this case is considerably smaller and can be comparable to the effect from the puffed-up inner rim only at an accretion rate of the order of or higher than 10-6M ⊙yr-1. Since the disk wind is structurally inhomogeneous, its optical depth toward the observer can be variable, which should be reflected in the photometric activity of young stars. For the same reason, moving shadows from gas and dust streams with a spiral-like shape can be observed in high-angular-resolution circumstellar disk images.

AB - We consider the problem of dust grain survival in the disk winds from T Tauri and Herbig Ae stars. For our analysis, we have chosen a disk wind model in which the gas component of the wind is heated through ambipolar diffusion to a temperature of ∼104 K. We show that the heating of dust grains through their collisions with gas atoms is inefficient compared to their heating by stellar radiation and, hence, the grains survive even in the hot wind component. As a result, the disk wind can be opaque to the ultraviolet and optical stellar radiation and is capable of absorbing an appreciable fraction of it. Calculations show that the fraction of the wind-absorbed radiation for T Tauri stars can be from 20 to 40% of the total stellar luminosity at an accretion rate a = 10-8-10-6 Myr-1. This means that the disk winds from T Tauri stars can play the same role as the puffed-up inner rim in current accretion disk models. In Herbig Ae stars, the inner layers of the disk wind (r ≤ 0.5 AU) are dust-free, since the dust in this region sublimates under the effect of stellar radiation. Therefore, the fraction of the radiation absorbed by the disk wind in this case is considerably smaller and can be comparable to the effect from the puffed-up inner rim only at an accretion rate of the order of or higher than 10-6M ⊙yr-1. Since the disk wind is structurally inhomogeneous, its optical depth toward the observer can be variable, which should be reflected in the photometric activity of young stars. For the same reason, moving shadows from gas and dust streams with a spiral-like shape can be observed in high-angular-resolution circumstellar disk images.

KW - Accretion

KW - Circumstellar extinction

KW - Disk wind

KW - Young stars

UR - http://www.scopus.com/inward/record.url?scp=42449093779&partnerID=8YFLogxK

U2 - 10.1134/s1063773708040026

DO - 10.1134/s1063773708040026

M3 - Article

AN - SCOPUS:42449093779

VL - 34

SP - 231

EP - 240

JO - Astronomy Letters

JF - Astronomy Letters

SN - 1063-7737

IS - 4

ER -