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Zawartość zarchiwizowana w dniu 2022-12-23

Perturbers and Density Waves in Accretion Disks: the Origin of Cyclical Variability of Pre-Main-Sequence Stars

Cel

The aim of the project is a search of the periodical density waves and streams in accretion disks of young stars, caused by secondary components, including low-mass secondaries such as brown dwarfs and extrasolar protoplanets, as well as the interaction of accretion disks with the stellar magnetospheres. Such waves, streamers, and other periodic effects are predicted by recent theories, but up to now very little is known about them from direct observations. Since they can be a major source of the observed variability of young stars, several monitoring programs will be conducted by participants to detect and study the variability. These programs include multi-band photometric and polarimetric monitoring, as well as high-resolution spectral observations of three groups of young stars. The first group includes the UX Ori type stars (UXORs) whose photometric activity is caused by the variable circumstellar (CS) extinction. The long-term observations of these stars will provide information about the azimuthal distribution of dust in CS disks. The second group includes several classical T Tauri stars (CTTS). Unlike in a UXOR, the CS dust around cooler young stars can survive down to the distances of order of ten stellar radius and can corotate with the stellar magnetosphere. Light variations connected with the presence of dust in the outer layers of stellar magnetosphere have been recently found in AA Tau (Bouvier et al. 1999). The periodic component of the variability of TTS (e. g., in RW Aur, as discovered by Petrov et al. 2001) can be also caused by dynamical modulation of the accretion rate by the binary companion (Artymowicz & Lubow 1996). The third group consists of the young binary stars with the known optical periods. Historical light curves of several such stars will be analysed in order to find the correlations between the light variations and phases of their orbital period. The goal of this part of the project is to understand how the light curves of young binary stars and the properties of their accretion disks depend on the orbital period and eccentricity of orbit. Finally, several UXORs will be observed with 6 m and VLT Interferometer, in order to obtain the high-resolution images. The results of these observations and related theoretical simulations will elucidate the real, complex structure of accretion disks around the young stars, most of which are known to be double or multiple. Detailed hydrodynamical simulations numerical simulation on sophisticated variable-geometry or adaptive meshes will be compared with the new data. The project will act as a springboard for further studies of accretion processes. Especially exciting is the prospect of detecting the low-mass companions and exoplanets via the associated variability. References: Artymowicz P. & Lubow S.H. 1996, ApJ 467, L77 Bouvier J., Chelli A., Allain S. et al. 1999, A&A 349, 619 Petrov P.P. Gahm G., Gameijro J.F. et al. 2001, A&A 369, 993

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Koordynator

Stockholm Observatory
Wkład UE
Brak danych
Adres
Roslagstullsb. 21
SE-10691 Stockholm
Szwecja

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Uczestnicy (4)