Shadows and spirals in the protoplanetary disk HD 100453

Abstract

Context. Understanding the diversity of planets requires studying the morphology and physical conditions in the protoplanetary disks in which they form. Aims. We aim to study the structure of the ∼10 Myr old protoplanetary disk HD 100453, to detect features that can trace disk evolution and to understand the mechanisms that drive these features. Methods. We observed HD 100453 in polarized scattered light with SPHERE/VLT at optical (0.6 µm, 0.8 µm) and near-infrared (1.2 µm) wavelengths, reaching an angular resolution of ∼0.02 , and an inner working angle of ∼0.09 . Results. We spatially resolve the disk around HD 100453, and detect polarized scattered light up to ∼0.42 (∼48 au). We detect a cavity, a rim with azimuthal brightness variations at an inclination of ∼38• with respect to our line of sight, two shadows and two symmetric spiral arms. The spiral arms originate near the location of the shadows, close to the semi major axis. We detect a faint feature in the SW that can be interpreted as the scattering surface of the bottom side of the disk, if the disk is tidally truncated by the M-dwarf companion currently seen at a projected distance of ∼119 au. We construct a radiative transfer model that accounts for the main characteristics of the features with an inner and outer disk misaligned by ∼72• . The azimuthal brightness variations along the rim are well reproduced with the scattering phase function of the model. While spirals can be triggered by the tidal interaction with the companion, the close proximity of the spirals to the shadows suggests that the shadows could also play a role. The change in stellar illumination along the rim induces an azimuthal variation of the scale height that can contribute to the brightness variations. Conclusions. Dark regions in polarized images of transition disks are now detected in a handful of disks and often interpreted as shadows due to a misaligned inner disk. However, the origin of such a misalignment in HD 100453, and of the spirals, is still unclear, and might be due to a yet-undetected massive companion inside the cavity, and on an inclined orbit. Observations over a few years will allow us to measure the spiral pattern speed, and determine if the shadows are fixed or moving, which may constrain their origin.

The Orbit of the Companion to HD 100453A: Binary-driven Spiral Arms in a Protoplanetary Disk

“…Using this strategy, Wagner et al (2015) found a disk inclination of ∼34°from face-on. In agreement with this value, Benisty et al (2017) utilized a similar method on their polarimetric data and found a disk inclination of ∼38°from face-on.…”

“…This inner disk is highly misaligned (∼45°-70°) with respect to the plane of the outer disk (and binary), as evidenced by the prominent shadows cast by this feature on the outer disk (Benisty et al 2017;Long et al 2017), similar to the shadows cast by the misaligned inner disk in HD 142527 . The origin of this misalignment is presently unknown, though a possible scenario involves a companion orbiting within the gap and generating the misalignment, similar to the observed configuration of HD 142527 (Close et al 2014).…”

“…Finally, we assume that rotation in the disk is Keplerian and that the disk is in the same plane throughout. While there is a known warp in the inner dust disk (Benisty et al 2017;Long et al 2017), the CO data are not of sufficient resolution to reveal whether the gas follows this same structure. Thus, our simple model mostly reflects the conditions of the outer disk, which contains the majority of disk surface area and (presumably) CO emission.…”

“…Currently, there exist more alternate hypotheses for the generation of these features than sources to test their predictions. Most models include a massive perturbing companion (either a planet or a low-mass star, e.g., Dong et al 2015a andZhu et al 2015); though, notably, some do not require the presence of any companion (e.g., Kama et al 2016;Montesinos et al 2016;Benisty et al 2017).…”

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

“…• ; Benisty et al 2017). This means that the near side of the inner disk is located in SE direction and a possible misalignment will be minor.…”