Observability of characteristic binary-induced structures in circumbinary disks

Abstract

Context. A substantial fraction of protoplanetary disks form around stellar binaries. The binary system generates a time-dependent non-axisymmetric gravitational potential, inducing strong tidal forces on the circumbinary disk. This leads to a change in basic physical properties of the circumbinary disk, which should in turn result in unique structures that are potentially observable with the current generation of instruments. Aims. The goal of this study is to identify these characteristic structures, constrain the physical conditions that cause them, and evaluate the feasibility of observing them in circumbinary disks. Methods. To achieve this, first we perform 2D hydrodynamic simulations. The resulting density distributions are post-processed with a 3D radiative transfer code to generate re-emission and scattered light maps. Based on these distributions, we study the influence of various parameters, such as the mass of the stellar components, mass of the disk, and binary separation on observable features in circumbinary disks. Results. We find that the Atacama Large (sub-)Millimetre Array (ALMA) as well as the European Extremely Large Telescope (E-ELT) are capable of tracing asymmetries in the inner region of circumbinary disks, which are affected most by the binary-disk interaction. Observations at submillimetre/millimetre wavelengths allow the detection of the density waves at the inner rim of the disk and inner cavity. With the E-ELT one can partially resolve the innermost parts of the disk in the infrared wavelength range, including the disk's rim, accretion arms, and potentially the expected circumstellar disks around each of the binary components.

Selected aspects of the analysis of molecular line observations of edge-on circumbinary disks

“…For the current study, we used a single hydrodynamic simulation of this sample, namely a disk with a semimajor axis of a = 30 au and binary masses of M prim = M sec = 1 M , with M prim and M sec as the masses of the primary and secondary components, respectively. As was found by Avramenko et al (2017), these parameters result in particularly large accretion arms and density oscillations. Both factors increase the chances of detecting these features.…”

“…Moreover, since we observe multiple maxima and minima, it is possible to derive the wavelength of the oscillation. As was shown by Avramenko et al (2017), the wavelength of the density wave is connected to the basic parameters of the binary system, such as binary mass and binary separation.…”

“…The wavelength of the oscillation is therefore dependent on the binary period P (see Sect. 3.1 of Avramenko et al 2017). The binary period can be influenced by changing the mass as well as by changing the semimajor axis.…”

“…This was done with the Monte Carlo-based 3D continuum and line radiative transfer code Mol3D (Ober et al 2015). As above, we refer to Avramenko et al (2017) for a full discussion of the radiative transfer simulations. The parameters used in the current study are summarized in Table 2.…”

“…In the case of a disk seen in face-on orientation, the structures resulting from binary-circumbinary disk interactions are expected to be detectable using proper combinations of infrared and sub-millimeter wavelength continuum observations (Avramenko et al 2017;Ruge et al 2015). However, disks inclined edge-on obscure the innermost disk regions at optical to infrared wavelengths.…”