Disk wind in young binaries and the origin of the cyclic activity of young stars |
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| Authors: | V P Grinin L V Tambovtseva N Ya Sotnikova |
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| Institution: | (1) Pulkovo Astronomical Observatory, Russian Academy of Sciences, Pulkovskoe shosse 65, St. Petersburg, 196140, Russia;(2) Sobolev Astronomical Institute, St. Petersburg State University, Universitetskii pr. 28, St. Petersburg, 198504, Russia;(3) Crimean Astrophysical Observatory, pos. Nauchnyi, Crimea, Ukraine |
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| Abstract: | We present the results of our numerical simulations of the cyclic brightness modulation in young binary systems with eccentric orbits and low-mass secondary components. We suggest that the binary components accrete matter from the remnants of the protostellar cloud, with the main accretor (according to current models) being the low-mass component. The brightness variations of the primary are attributable to the periodic extinction variations on the line of sight caused by the disk wind from the secondary and by the common envelope produced by this wind. The distribution of matter in the envelope was calculated in the ballistic approximation. When calculating the optical effects produced by the dust component of the disk wind, we adopted the dust-to-gas mass ratio of 1:100 characteristic of the interstellar medium and the optical parameters of the circumstellar dust typical of young stars. Our calculations show that the theoretical light curves for binaries with elliptical orbits exhibit a wider variety of shapes than those for binaries with circular orbits. In this case, the parameters of the photometric minima (their depth, duration, and shape of the light curve) depend not only on the disk-wind parameters and the orbital inclination of the binary to the line of sight, but also on the longitude of the periastron. We investigate the modulation of the scattered radiation from the common envelope with orbital phase in the single-scattering approximation. The modulation amplitude is shown to be at a maximum when the system is seen edge-on and to be also nonzero in binaries seen pole-on. We discuss possible applications of the theory to young stellar objects. In particular, several model light curves have been found to be similar to those of candidate FU Orionis stars (FUORs). |
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| Keywords: | stars— young binaries accretion disk wind activity cycles UXORs |
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