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Register a new userImaging the disc rim and a moving close-in companion candidate in the pre-transitional disc of V1247 Orionis
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V1247 Orionis harbours a pre-transitional disc with a partially cleared gap. Earlier interferometric and polarimetric observations revealed strong asymmetries both in the gap region and in the outer disc. The presence of a companion was inferred to explain these asymmetric structures and the ongoing disc clearing. Using an extensive set of multi-wavelength and multi-epoch observations we aimed to identify the origin of the previously detected asymmetries. We have observed V1247 Ori at three epochs spanning $sim678$ days using sparse aperture masking interferometry with Keck/NIRC2 and VLT/NACO. In addition, we search for signs of accretion through VLT/SPHERE-ZIMPOL spectral differential imaging in H$alpha$ and R-band continuum. Our SMA sub-millimetre interferometry in 880 $mu$m continuum and in the CO(3-2) line allows us to constrain the orientation and direction of rotation of the outer disc. We find the L-band emission to be dominated by static features which trace forward-scattered dust emission from the inner edge of the outer disc located to the north-east. In H- and K-band, we see evidence for a companion candidate that moved systematically by 45$^{circ}$ within the first $sim$345 days. The separation of the companion candidate is not well constrained, but the observed position angle change is consistent with Keplerian motion of a body located on a 6 au orbit. From the SMA CO moment map, the location of the disc rim, and the detected orbital motion, we deduced the three-dimensional orientation of the disc. We see no indication of accretion in H$alpha$ and set upper limits for an accreting companion. The measured contrast of the companion candidate in H and K is consistent with an actively accreting protoplanet. Hence, we identify V1247 Ori as a unique laboratory for studying companion-disc interactions and disc clearing.
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The radial drift problem constitutes one of the most fundamental problems in planet formation theory, as it predicts particles to drift into the star before they are able to grow to planetesimal size. Dust-trapping vortices have been proposed as a possible solution to this problem, as they might be able to trap particles over millions of years, allowing them to grow beyond the radial drift barrier. Here, we present ALMA 0.04-resolution imaging of the pre-transitional disk of V1247 Orionis that reveals an asymmetric ring as well as a sharply-confined crescent structure, resembling morphologies seen in theoretical models of vortex formation. The asymmetric ring (at 0.17=54 au separation from the star) and the crescent (at 0.38=120 au) seem smoothly connected through a one-armed spiral arm structure that has been found previously in scattered light. We propose a physical scenario with a planet orbiting at $sim0.3$$approx$100 au, where the one-armed spiral arm detected in polarised light traces the accretion stream feeding the protoplanet. The dynamical influence of the planet clears the gap between the ring and the crescent and triggers two vortices that trap mm-sized particles, namely the crescent and the bright asymmetry seen in the ring. We conducted dedicated hydrodynamics simulations of a disk with an embedded planet, which results in similar spiral-arm morphologies as seen in our scattered light images. At the position of the spiral wake and the crescent we also observe $^{12}$CO (3-2) and H$^{12}$CO$^{+}$ (4-3) excess line emission, likely tracing the increased scale-height in these disk regions.
Pre-transitional disks are protoplanetary disks with a gapped disk structure, potentially indicating the presence of young planets in these systems. In order to explore the structure of these objects and their gap-opening mechanism, we observed the pre-transitional disk V1247 Orionis using the Very Large Telescope Interferometer, the Keck Interferometer, Keck-II, Gemini South, and IRTF. This allows us spatially resolve the AU-scale disk structure from near- to mid-infrared wavelengths (1.5 to 13 {mu}m), tracing material at different temperatures and over a wide range of stellocentric radii. Our observations reveal a narrow, optically-thick inner-disk component (located at 0.18 AU from the star) that is separated from the optically thick outer disk (radii >46 AU), providing unambiguous evidence for the existence of a gap in this pre-transitional disk. Surprisingly, we find that the gap region is filled with significant amounts of optically thin material with a carbon-dominated dust mineralogy. The presence of this optically thin gap material cannot be deduced solely from the spectral energy distribution, yet it is the dominant contributor at mid-infrared wavelengths. Furthermore, using Keck/NIRC2 aperture masking observations in the H, K, and L band, we detect asymmetries in the brightness distribution on scales of about 15-40 AU, i.e. within the gap region. The detected asymmetries are highly significant, yet their amplitude and direction changes with wavelength, which is not consistent with a companion interpretation but indicates an inhomogeneous distribution of the gap material. We interpret this as strong evidence for the presence of complex density structures, possibly reflecting the dynamical interaction of the disk material with sub-stellar mass bodies that are responsible for the gap clearing.
We present 3D hydrodynamical models of the HD142527 protoplanetary disc, a bright and well studied disc that shows spirals and shadows in scattered light around a 100 au gas cavity, a large horseshoe dust structure in mm continuum emission, together with mysterious fast radial flows and streamers seen in gas kinematics. By considering several possible orbits consistent with the observed arc, we show that all of the main observational features can be explained by one mechanism - the interaction between the disc and the observed binary companion. We find that the spirals, shadows and horseshoe are only produced in the correct position angles by a companion on an inclined and eccentric orbit approaching periastron - the red family from Lacour et al. (2016). Dust-gas simulations show radial and azimuthal concentration of dust around the cavity, consistent with the observed horseshoe. The success of this model in the HD142527 disc suggests other mm-bright transition discs showing cavities, spirals and dust asymmetries may also be explained by the interaction with central companions.
Circumstellar discs are expected to be the nursery of planets. Grain growth within such discs is the first step in the planet formation process. The Bok globule CB 26 harbours such a young disc. We present a detailed model of the edge-on circumstellar disc and its envelope in the Bok globule CB 26. The model is based on HST near-infrared maps in the I, J, H, and K bands, OVRO and SMA radio maps at 1.1mm, 1.3mm and 2.7mm, and the spectral energy distribution (SED) from 0.9 microns to 3mm. New photometric and spectroscopic data from the Spitzer Space Telescope and the Caltech Submilimeter Observatory have been obtained and are part of our analysis. Using the self-consistent radiative transfer code MC3D, the model we construct is able to discriminate parameter sets and dust properties of both its parts, namely envelope and disc. We find that the disc has an inner hole with a radius of 45 +/- 5 AU. Based on a dust model including silicate and graphite the maximum grain size needed to reproduce the spectral millimetre index is 2.5 microns. Features seen in the near-infrared images, dominated by scattered light, can be described as a result of a rotating envelope. Successful employment of ISM dust in both the disc and envelope hint that grain growth may not yet play a significant role for the appearance of this system. A larger inner hole gives rise to the assumption that CB 26 is a circumbinary disc.
We present high resolution H-band polarized intensity (PI; FWHM = 0.1: 14 AU) and L-band imaging data (FWHM = 0.11: 15 AU) of the circumstellar disk around the weak-lined T Tauri star PDS 70 in Centaurus at a radial distance of 28 AU (0.2) up to 210 AU (1.5). In both images, a giant inner gap is clearly resolved for the first time, and the radius of the gap is ~70 AU. Our data show that the geometric center of the disk shifts by ~6 AU toward the minor axis. We confirm that the brown dwarf companion candidate to the north of PDS 70 is a background star based on its proper motion. As a result of SED fitting by Monte Carlo radiative transfer modeling, we infer the existence of an optically thick inner disk at a few AU. Combining our observations and modeling, we classify the disk of PDS 70 as a pre-transitional disk. Furthermore, based on the analysis of L-band imaging data, we put an upper limit mass of companions at ~30 to ~50MJ within the gap. Taking account of the presence of the large and sharp gap, we suggest that the gap could be formed by dynamical interactions of sub-stellar companions or multiple unseen giant planets in the gap.
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