Anisotropic illumination of a circumbinary disk in the presence of a low-mass companion

Abstract

The model of an young star with a protoplanetary disk and a low-mass companion (q ≤ 0.1), which is moving on a circular orbit, inclined to the disk plane, is considered. The hydrodynamic models of such a system were calculated by SPH method. It was shown the distortions in the disk, caused by the orbital motion of the companion, lead to the strong dependence of illumination conditions of the disk on the azimuth (because of extinction between the star and the disk surface) and, therefore, it leads to the appearance of large-scale asymmetry in images of disks. The calculations showed the dependence of the illumination on the azimuth was stronger in the central part of the disk than on the periphery. Bright and dark domains are located not symmetry with respect to the line of nodes. The sizes and locations of the domains are depended on the model parameters as well as on the phase of the orbital period. The bright and dark domains do not follow the companion, but they make small amplitude oscillations with respect to some direction. The properties of the model, which were written above, open new opportunities of searching low-mass companions in the vicinity of young stars. The stars with protoplanetary disks, which are observed face-on or under the small inclination angle i, are the best ones for this purpose.

Variable Dynamics in the Inner Disk of HD 135344B Revealed with Multi-epoch Scattered Light Imaging∗

“…An extended low-density atmosphere could be supported by the magnetic field of the inner disk which may explain a large near-infrared excess and possible shadowing (Turner et al 2014). Alternatively, the central star could drive a wind from the circumplanetary disk of a planetary companion (Tambovtseva et al 2006) or disk perturbations by a companion on an inclined orbit may also cause an asymmetric illumination of the disk (Demidova et al 2013). Three-dimensional radiation nonideal magnetohydrodynamical simulations show turbulent velocities in the inner disk up to 10% of the sound speed and a nonaxisymmetric shadow on the outer disk cast by a dead zone-induced vortex (Flock et al 2017).…”

Infrared variability from circumbinary disc temperature modulations

“…Depending on how the fluctuations in temperature along the disc wall propagate outward, radiative transfer could strengthen or diminish the amplitude of light curve variations. Demidova et al (2013) found that the radius to which illumination asymmetries created by shadows of small mass companion can be observed depends on the viscosity of the disc. Asymmetries are more quickly reduced in low viscosity or "cold" discs but such asymmetries only extend out a small fraction of the total disc.…”

“…A binary star system can be embedded in a circumbinary disc (e.g., Jensen et al 2007;Ireland & Kraus 2008;Nagel et al 2012;Biller et al 2012;Takakuwa et al 2013;Gillen et al 2014). Periodic broad-band photometric variations could constrain the location or shape of the circumbinary disc edge (Nagel et al 2010(Nagel et al , 2012, infer the presence of a low mass companion (Demidova et al 2013;Maíz Apellániz et al 2015) or discover a circumbinary or circumsecondary disc (Rattenbury et al 2015). As studies increase light curve quality, the number of data points, and the wavelength coverage, it may become possible to differentiate between different variability mechanisms using light curve morphology and colour.…”

On the origin of the azimuthal asymmetry in pole-on protoplanetary disks: The case of LkHα 101

“…In the models with a low-mass companion (q < 0.01), a matter-free ring is formed near the orbital radius of the companion instead of the gap (de Val-Borro et al 2007). If the companion's orbit is inclined relative to the plane of the circumbinary disk, than the matter captured by the companion from the circumbinary disk forms a disk around the binary's primary component whose plane is inclined both relative to the plane of the outer disk and relative to the orbital plane of the companion (Larwood et al 1996;Papaloizou & Terquem 1995;Grinin et al 2010;Demidova et al 2013;Xiang-Gruess & Papaloizou 2013). It can be seen from Fig.…”