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تسجيل مستخدم جديدExtreme Asymmetry in the Disk of V1247 Ori
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We present the first near-infrared scattered-light detection of the transitional disk around V1247 Ori, which was obtained using high-resolution polarimetric differential imaging observations with Subaru/HiCIAO. Our imaging in the H band reveals the disk morphology at separations of ~0.14-0.86 (54-330 au) from the central star. The polarized intensity (PI) image shows a remarkable arc-like structure toward the southeast of the star, whereas the fainter northwest region does not exhibit any notable features. The shape of the arm is consistent with an arc of 0.28 $pm$ 0.09 in radius (108 au from the star), although the possibility of a spiral arm with a small pitch angle cannot be excluded. V1247 Ori features an exceptionally large azimuthal contrast in scattered, polarized light; the radial peak of the southeastern arc is about three times brighter than the northwestern disk measured at the same distance from the star. Combined with the previous indication of an inhomogeneous density distribution in the gap at $lesssim$46 au, the notable asymmetry in the outer disk suggests the presence of unseen companions and/or planet-forming processes ongoing in the arc.
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Aims: I study new deep (DeltaV ~ 1.20-1.65 mag) occultation events of the delta Scuti, Herbig Ae/Be star V1247 Ori in the Ori OB1 b association. Methods: I use the V-band ASAS light curve of V1247 Ori, which covers the last nine years, together with
photometric data in the near-ultraviolet, visible, near-, and far-infrared taken from the literature. I carry out a periodogram analysis of the cleaned light curve and construct the spectral energy distribution of the star. Results: The star V1247 Ori is interesting for the study of the UX Orionis phenomenon, in which Herbig Ae/Be stars are occulted by their protoplanetary discs, for three reasons: brightness (V ~ 9.85 mag), large infrared excess at 20-100 mum (F_60 ~ 10 Jy), and photometric stability out of occultation (sigma(V) ~ 0.02 mag), which may help to determine the location and spatial structure of the occulting disc clumps.
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 po
ssible 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.
Complex organic molecules (COMs), which are the seeds of prebiotic material and precursors of amino acids and sugars, form in the icy mantles of circumstellar dust grains but cannot be detected remotely unless they are heated and released to the gas
phase. Around solar-mass stars, water and COMs only sublimate in the inner few au of the disk, making them extremely difficult to spatially resolve and study. Sudden increases in the luminosity of the central star will quickly expand the sublimation front (so-called snow line) to larger radii, as seen previously in the FU Ori outburst of the young star V883 Ori. In this paper, we take advantage of the rapid increase in disk temperature of V883 Ori to detect and analyze five different COMs, methanol, acetone, acetonitrile, acetaldehyde, and methyl formate, in spatially-resolved submillimeter observations. The COMs abundances in V883 Ori is in reasonable agreement with cometary values. This result suggests that outbursting young stars can provide a special opportunity to study the ice composition of material directly related to planet formation.
GW Ori is a hierarchical triple system which has a rare circumtriple disk. We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of 1.3 mm dust continuum and 12CO J=2-1 molecular gas emission of the disk. For the first time, we
identify three dust rings in the disk at ~46, 188, and 338 AU, with estimated dust mass of ~70-250 Earth masses, respectively. To our knowledge, the outer ring in GW Ori is the largest dust ring ever found in protoplanetary disks. We use visibility modelling of dust continuum to show that the disk has misaligned parts and the innermost dust ring is eccentric. The disk misalignment is also suggested by the CO kinematics modelling. We interpret these substructures as evidence of ongoing dynamical interactions between the triple stars and the circumtriple disk.
We report the detection of methanol in the disk around the young outbursting star V883 Ori with the Atacama Large Millimeter/submillimeter Array (ALMA). Four transitions are observed with upper level energies ranging between 115 and 459 K. The emissi
on is spatially resolved with the 0.14 beam and follows the Keplerian rotation previously observed for C$^{18}$O. Using a rotational diagram analysis, we find a disk-averaged column density of $sim10^{17}$ cm$^{-2}$ and a rotational temperature of $sim90-100$ K, suggesting that the methanol has thermally desorbed from the dust grains. We derive outer radii between 120 and 140 AU for the different transitions, compared to the 360 AU outer radius for C$^{18}$O. Depending on the exact physical structure of the disk, the methanol emission could originate in the surface layers beyond the water snowline. Alternatively, the bulk of the methanol emission originates inside the water snowline, which can then be as far out as ~100 AU, instead of 42 AU as was previously inferred from the continuum opacity. In addition, these results show that outbursting young stars like V883 Ori are good sources to study the ice composition of planet forming material through thermally desorbed complex molecules, which have proven to be hard to observe in more evolved protoplanetary disks.
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