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Register a new userTidal Interaction between the UX Tauri Disk A/C System Revealed by ALMA
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Luis A. Zapata
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We present sensitive and high angular resolution ($sim$0.2-0.3$$) (sub)millimeter (230 and 345 GHz) continuum and CO(2$-$1)/CO(3$-$2) line archive observations of the disk star system in UX Tauri carried out with ALMA (The Atacama Large Millimeter/Submillimeter Array). These observations reveal the gas and dusty disk surrounding the young star UX Tauri A with a large signal-to-noise ratio ($>$400 in the continuum and $>$50 in the line), and for the first time is detected the molecular gas emission associated with the disk of UX Tauri C (with a size for the disk of $<$56 au). No (sub)millimeter continuum emission is detected at 5$sigma$-level (0.2 mJy at 0.85 mm) associated with UX Tauri C. For the component UX Tauri C, we estimate a dust disk mass of $leq$ 0.05 M$_oplus$. Additionally, we report a strong tidal disk interaction between both disks UX Tauri A/C, separated 360 au in projected distance. The CO line observations reveal marked spiral arms in the disk of UX Tauri A and an extended redshifted stream of gas associated with the UX Tauri C disk. No spiral arms are observed in the dust continuum emission of UX Tauri A. Assuming a Keplerian rotation we estimate the enclosed masses (disk$+$star) from their radial velocities in 1.4 $pm$ 0.6 M$_odot$ for UX Tauri A, and 70 $pm$ 30 / $sin i$ Jupiter masses for UX Tauri C (the latter coincides with the mass upper limit value for a brown dwarf). The observational evidence presented here lead us to propose that UX Tauri C is having a close approach of a possible wide, evolving and eccentric orbit around the disk of UX Tauri A causing the formation of spiral arms and the stream of molecular gas falling towards UX Tauri C.
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We have observed the Class I protostar L1489 IRS with the Atacama Millimeter/submillimeter Array (ALMA) in Band 6. The C$^{18}$O $J=$2-1 line emission shows flattened and non-axisymmetric structures in the same direction as its velocity gradient due to rotation. We discovered that the C$^{18}$O emission shows dips at a radius of ~200-300 au while the 1.3 mm continuum emission extends smoothly up to r~400 au. At the radius of the C$^{18}$O dips, the rotational axis of the outer portion appears to be tilted by ~15 degrees from that of the inner component. Both the inner and outer components with respect to the C$^{18}$O dips exhibit the $r^{-0.5}$ Keplerian rotation profiles until r~600 au. These results not only indicate that a Keplerian disk extends up to ~600 au but also that the disk is warped. We constructed a three dimensional warped disk model rotating at the Keplerian velocity, and demonstrated that the warped disk model reproduces main observed features in the velocity channel maps and the PV diagrams. Such a warped disk system can form by mass accretion from a misaligned envelope. We also discuss a possible disk evolution scenario based on comparisons of disk radii and masses between Class I and Class II sources.
We present observations of the young multiple system UX Tauri to look for circumstellar disks and for signs of dynamical interactions. We obtained SPHERE/IRDIS deep differential polarization images in the J and H bands. We also used ALMA archival CO data. Large extended spirals are well detected in scattered light coming out of the disk of UX Tau A. The southern spiral forms a bridge between UX Tau A and C. These spirals, including the bridge connecting the two stars, all have a CO (3-2) counterpart seen by ALMA. The disk of UX Tau C is detected in scattered light. It is much smaller than the disk of UX Tau A and has a major axis along a different position angle, suggesting a misalignment. We performed PHANTOM SPH hydrodynamical models to interpret the data. The scattered light spirals, CO emission spirals and velocity patterns of the rotating disks, and the compactness of the disk of UX Tau C all point to a scenario in which UX Tau A has been perturbed very recently (about 1000 years) by the close passage of UX Tau C.
Context: The complex system HD 100453 AB with a ring-like circumprimary disk and two spiral arms, one of which is pointing to the secondary, is a good laboratory to test spiral formation theories. Aims: To quantify the interaction of HD 100453 B with the circumprimary disk. Methods: Using ALMA band 6 dust continuum and CO isotopologue observations we study the HD 100453 AB system with a spatial resolution of 0.09 x 0.17 at 234 GHz. We use SPH simulations and orbital fitting to investigate the tidal influence of the companion on the disk. Results: We resolve the continuum emission around HD 100453 A into a disk between 0.22 and 0.40 with an inclination of 29.5 deg. and a position angle of 151.0 deg., an unresolved inner disk, and excess mm emission cospatial with the northern spiral arm which was previously detected using scattered light observations. We also detect CO emission from 7 au (well within the disk cavity) out to 1.10, i.e., overlapping with HD 100453 B at least in projection. The outer CO disk PA and inclination differ by up to 10 deg. from the values found for the inner CO disk and the dust continuum emission, which we interpret as due to gravitational interaction with HD 100453 B. Both the spatial extent of the CO disk and the detection of mm emission at the same location as the northern spiral arm are in disagreement with the previously proposed near co-planar orbit of HD 100453 B. Conclusions: We conclude that HD 100453 B has an orbit that is significantly misaligned with the circumprimary disk. Because it is unclear whether such an orbit can explain the observed system geometry we highlight an alternative scenario that explains all detected disk features where another, (yet) undetected, low mass close companion within the disk cavity, shepherds a misaligned inner disk whose slowly precessing shadows excite the spiral arms.
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.
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