Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSPHERE/SHINE reveals concentric rings in the debris disk of HIP 73145
47
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The debris disk of HIP73145 has been detected in scattered light in the near-IR, and at far-IR wavelengths before, but no substructure has been seen so far. Detection of such substructures in combination with detailed modeling can hint at the presence of perturbing planetary bodies, or reveal other mechanisms acting to replenish gas and dust reservoirs and forming structures such as spirals or rings. We obtained multiwavelength images with SPHERE in the near-IR in the H2 and H3 bands with the IRDIS camera and a 0.95-1.35 micron spectral cube with the IFS. Data were acquired in pupil-tracking mode, thus allowing for angular differential imaging. The SPHERE standard suite of angular differential imaging algorithms was applied. ALMA Band 6 observations complement the SPHERE data. We detect a bright ring of scattered light plus more structures inside, at least one of them forming a secondary, concentric ring with the first. This is the first detection of this disk in total-intensity scattered light. A second object is detected in the field at high contrast but concluded to be a background star. Forward modeling yields information on the primary parameters of the disk and confirms that the detected substructures are not due to the data analysis approach, which sometimes leads to spurious structures. We detect a series of concentric rings in the disk around HIP73145. This is one of the rare cases where multiple components are necessary to fit the SED and are also detected in scattered light. The presence of such ring structures somewhat questions the nature of the object as a pure debris disk, but the gas and dust content would presumably offer sufficient explanations for such structures to form.
rate research
Read More
We present Subaru/HiCIAO H-band high-contrast images of the debris disk around HIP 79977, whose pres- ence was recently inferred from an infrared excess. Our images resolve the disk for the first time, allowing characterization of its shape, size, and dust grain properties. We use angular differential imaging (ADI) to reveal the disk geometry in unpolarized light out to a radius of ~2, as well as polarized differential imaging (PDI) to measure the degree of scattering polarization out to ~1.5. In order to strike a favorable balance between suppression of the stellar halo and conservation of disk flux, we explore the application of principal component analysis (PCA) to both ADI and reference star subtraction. This allows accurate forward modeling of the effects of data reduction on simulated disk images, and thus direct comparison with the imaged disk. The resulting best-fit values and well-fitting intervals for the model parameters are a surface brightness power-law slope of S_out = -3.2 [-3.6,-2.9], an inclination of i = 84{deg} [81{deg},86{deg}], a high Henyey-Greenstein forward-scattering parameter of g = 0.45 [0.35, 0.60], and a non-significant disk-star offset of u = 3.0 [-1.5, 7.5] AU = 24 [-13, 61] mas along the line of nodes. Furthermore, the tangential linear polarization along the disk rises from ~10% at 0.5 to ~45% at 1.5. These measurements paint a consistent picture of a disk of dust grains produced by collisional cascades and blown out to larger radii by stellar radiation pressure.
[abridged] Aims. Our Herschel Open Time Key Programme DUNES aims at detecting and characterizing debris disks around nearby, sun-like stars. In addition to the statistical analysis of the data, the detailed study of single objects through spatially resolving the disk and detailed modeling of the data is a main goal of the project. Methods. We obtained the first observations spatially resolving the debris disk around the sun-like star HIP 17439 (HD23484) using the instruments PACS and SPIRE on board the Herschel Space Observatory. Simultaneous multi-wavelength modeling of these data together with ancillary data from the literature is presented. Results. A standard single component disk model fails to reproduce the major axis radial profiles at 70 um, 100 um, and 160 um simultaneously. Moreover, the best-fit parameters derived from such a model suggest a very broad disk extending from few au up to few hundreds of au from the star with a nearly constant surface density which seems physically unlikely. However, the constraints from both the data and our limited theoretical investigation are not strong enough to completely rule out this model. An alternative, more plausible, and better fitting model of the system consists of two rings of dust at approx. 30 au and 90 au, respectively, while the constraints on the parameters of this model are weak due to its complexity and intrinsic degeneracies. Conclusions. The disk is probably composed of at least two components with different spatial locations (but not necessarily detached), while a single, broad disk is possible, but less likely. The two spatially well-separated rings of dust in our best-fit model suggest the presence of at least one high mass planet or several low-mass planets clearing the region between the two rings from planetesimals and dust.
Transition disks correspond to a short stage between the young protoplanetary phase and older debris phase. Along this evolutionary sequence, the gas component disappears leaving room for a dust-dominated environment where already-formed planets signpost their gravitational perturbations. We endeavor to study the very inner region of the well-known and complex debris, but still gas-rich disk, around HD 141569A using the exquisite high-contrast capability of SPHERE at the VLT. Recent near-infrared (IR) images suggest a relatively depleted cavity within ~200 au, while former mid-IR data indicate the presence of dust at separations shorter than ~100 au. We obtained multi-wavelength images in the near-IR in J, H2, H3 and Ks bands with the IRDIS camera and a 0.95-1.35 micrometers spectral data cube with the IFS. Data were acquired in pupil-tracking mode, thus allowing for angular differential imaging. We discovered several new structures inside 1, of which the most prominent is a bright ring with sharp edges (semi-major axis: 0.4) featuring a strong north-south brightness asymmetry. Other faint structures are also detected from 0.4 to 1 in the form of concentric ringlets and at least one spiral arm. Finally, the VISIR data at 8.6 micrometers suggests the presence of an additional dust population closer in. Besides, we do not detect companions more massive than 1-3 mass of Jupiter. The performance of SPHERE allows us to resolve the extended dust component, which was previously detected at thermal and visible wavelengths, into very complex patterns with strong asymmetries ; the nature of these asymmetries remains to be understood. Scenarios involving shepherding by planets or dust-gas interactions will have to be tested against these observations.
We present observations of the known edge-on debris disk around HIP 79977 (HD 146897, F star in Upper Sco, 123 pc), taken with the ZIMPOL differential polarimeter of the SPHERE instrument in the Very Broad Band filter ($lambda_c=735$ nm, $Deltalambda=290$ nm) with a spatial resolution of about 25 mas. We measure the polarization flux along and perpendicular to the disk spine of the highly inclined disk for projected separations between 0.2 (25 AU) and 1.6 (200 AU) and investigate the diagnostic potential of such data with model simulations. The polarized flux contrast ratio for the disk is $F_{pol}/F_ast= (5.5 pm 0.9) 10^{-4}$. The surface brightness reaches a maximum of 16.2 mag arcsec$^{-2}$ at a separation of $0.2-0.5$ along the disk spine with a maximum surface brightness contrast of 7.64 mag arcsec$^{-2}$. The polarized flux has a minimum near the star $<0.2$ because no or only little polarization is produced by forward or backward scattering in the disk section lying in front of or behind the star. The data are modeled as a circular dust belt with an inclination $i=85(pm 1.5)^circ$ and a radius between $r_0$ = 60 AU and 90 AU. The radial density dependence is described by $(r/r_0)^{alpha}$ with a steep power law index $alpha=5$ inside $r_0$ and a more shallow index $alpha=-2.5$ outside $r_0$. The scattering asymmetry factor lies between $g$ = 0.2 and 0.6 adopting a scattering angle-dependence for the fractional polarization as for Rayleigh scattering. Our data are qualitatively very similar to the case of AU Mic and they confirm that edge-on debris disks have a polarization minimum at a position near the star and a maximum near the projected separation of the main debris belt. The comparison of the polarized flux contrast ratio $F_{pol}/F_{ast}$ with the fractional infrared excess provides strong constraints on the scattering albedo of the dust.
Context: Vertically hydrostatic protoplanetary disk models are based on the assumption that the main heating source, stellar irradiation, does not vary much with time. However, it is known that accreting young stars are variable sources of radiation. This is particularly evident for outbursting sources such as EX Lupi and FU Orionis stars. Aim: We investigate how such outbursts affect the vertical structure of the outer regions of the protoplanetary disk, in particular their appearance in scattered light at optical and near-infrared wavelengths. Methods: We employ the 3D FARGOCA radiation-hydrodynamics code, in polar coordinates, to compute the time-dependent behavior of the axisymmetric disk structure. The outbursting inner disk region is not included explicitly. Instead, its luminosity is added to the stellar luminosity and is thus included in the irradiation of the outer disk regions. For time snapshots of interest we insert the density structure into the RADMC-3D radiative transfer code and compute the appearance of the disk at optical/near-infrared wavelengths. Results: We find that, depending on the amplitude of the outbursts, the vertical structure of the disk can become highly dynamic, featuring circular surface waves of considerable amplitude. These hills and valleys on the disks surface show up in the scattered light images as bright and dark concentric rings. Initially these rings are small and act as standing waves, but they subsequently lead to outward propagating waves, like the waves produced by a stone thrown into a pond. These waves continue long after the actual outburst has died out. Conclusions: We propose that some of the multi-ringed structures seen in optical/infrared images of several protoplanetary disks may have their origin in outbursts that occurred decades or centuries ago.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
