LELUYA at the Asymmetric Planetary Nebulae III Meeting

LELUYA and its first results were presented at the Asymmetric Planetary Nebulae III meeting in Mt. Rainier, Washington, Jul.28 - Aug.01, 2003.

Invited talk by Dejan Vinkovic: "Evidence of Bipolar Structures in Precursors of PNe"

Proceeding paper based on this talk (available from arXiv.org):
"Evidence for bipolar jets in late stages of AGB winds"
Authors: D. Vinkovic, M. Elitzur, K.-H. Hofmann, G. Weigelt
Abstract: "Bipolar expansion at various stages of evolution has been recently observed in a number of AGB stars. The expansion is driven by bipolar jets that emerge late in the evolution of AGB winds. The wind traps the jets, resulting in an expanding, elongated cocoon. Eventually the jets break-out from the confining spherical wind, as recently observed in W43A. This source displays the most advanced evolutionary stage of jets in AGB winds. The earliest example is IRC+10011, where the asymmetry is revealed in high-resolution near-IR imaging. In this source the jets turned on only ~200 years ago, while the spherical wind is ~4000 years old."

LELUYA at the Astrophysics of Dust meeting

LELUYA and its first results were presented at the Astrophysics of Dust meeting in Estes Park, Colorado, 26-30 May 2003.

Abstract of the poster (P1.64, Poster Session I, Monday, 26 May, 2003 19:00 - 21:00):

Bipolar Structures in the Dust Shell of the AGB Star IRC+10011
D. Vinkovic (University of Kentucky) , K.-H. Hofmann (Max-Planck-Institut fuer Radioastronomie), M. Elitzur (University of Kentucky), G. Weigelt (Max-Planck-Institut fuer Radioastronomie)

"Planetary nebulae are largely asymmetric, while their progenitors, AGB winds, are mostly spherically symmetric. This remains one of the fundamental problems of planetary nebulae evolution. High-resolution J-band imaging of IRC+10011, the prototype of high mass-loss rate AGB winds, provides a rare example of shell asymmetry. Interpretation of the observed asymmetry requires a 2D radiative transfer solver that can handle arbitrary axially symmetric dust density configurations. LELUYA (www.leluya.org) is the first such general-purpose code that can provide the exact solution to an arbitrary multi-grain dust distribution around an arbitrary heating source. By employing a new numerical method, the implemented algorithm automatically traces the dust density and optical depth gradients, creating the optimal unstructured triangular grid. The radiative transfer equation, including dust scattering, absorption and emission, is solved without any approximation. Unique to LELUYA is also its ability to self-consistently reshape the sublimation/condensation dust cavity around the source to accomodate for the unisotropic diffuse radiation. We successfully explain the IRC+10011 images and the overall spectral energy distribution. Particularly interesting is the wavelength dependence of the imaged asymmetry, which disappears within a wavelength shift of only 0.5 microns. The asymmetry is produced by an unusual dust density distribution, traced by the J-band imaging. Two bipolar cones with 1/r0.5 density profile are imbedded in the standard 1/r2 dusty wind profile. The cones are still breaking though the 1/r2 wind, suggesting they are a recent episode in the final short superwind phase of AGB evolution before turning into a proto-planetary nebula."

LELUYA at SC2002

LELUYA is presented at the SC2002 conference (November 16-22, 2002) by the exibitor Aggregate (booth #R1659).

LELUYA is one of the users on the Linux supercomputer cluster KLAT2 designed by the Aggregate researchers.

Download the promo-poster of LELUYA: Leluya-poster-SC2002.jpg


The first results from LELUYA will be presented during the 200th Meeting of the American Astronomical Society, 2-6 June 2002, Albuquerque, NM, by Dejan Vinkovic

Session 85. Stars: Disks, Shells and Variability
Oral, Thursday,
June 6, 2002,
2:00-3:30pm, Ballroom A

LELUYA -- the First Exact General 2D Radiative Transfer Solver

Dejan Vinkovic, Moshe Elitzur (University of Kentucky)
Zeljko Ivezic (Princeton University)

"Observations of objects deeply imbedded in dust cannot be studied without exact solution of the multidimensional radiative transfer problem. LELUYA (www.leluya.org) is the first code capable of solving exactly an arbitrary axially symmetric multi-grain dust distribution around a heating source. A newly developed parallel algorithm automatically traces the dust density and optical depth gradients, creating the optimal adaptive grid, which is highly unstructured and triangular. Different grids are created this way for different wavelengths to accommodate the spectral variation of dust opacity. The radiative transfer problem, including dust absorption, emission and scattering, is solved exactly. Applications will be presented for two systems. CIT3 is an evolved star whose image seemed to require an unphysical binary system. I will show that this is an artifact of certain 2D dust geometry around a single star, which includes a non-spherical dust cavity. In young stellar objects, such as AB Aur, LELUYA provides the first tool capable of exact handling of non-spherical geometries, crucial for understanding configurations such as flared disks. "

A talk about LELUYA at the VLA

Dejan Vinkovic will give a talk about LELUYA at the Very Large Array observatory, Socorro, New Mexico.

noon, May 29, 2002


... visit also the poster presentation about disks and halos

Session 71. Stellar Youth: Tomorrow's Degenerates
Display, Thursday, June 6, 2002, 9:20am-4:00pm, SW Exhibit Hall

Disks and Halos in Pre-Main-Sequence Stars

Moshe Elitzur, Dejan Vinkovic (University of Kentucky)
Anatoly,S.Miroshnichenko (University of Toledo)
Zeljko Ivezic (Princeton University)

"The flared disk geometry of Chiang & Goldreich (CG) (ApJ, 490, 368, 1997) is currently the most popular model for the circumstellar dust distribution around pre-main-sequence stars. However, imaging observations suggest that optically thin halos are present through most of the pre-main-sequence phase. The halo provides additional heating of the disk, changes its temperature profile, and dominates the IR excess. Ignoring the halo in the radiative transfer models leads to erroneous interpretation of the dust properties and evolution. So far, the only support for the CG model comes from its successful fitting of spectral energy distributions (SED). However, we show that for every CG model there is a mathematically equivalent disk+halo model with identical SED, therefore it is impossible to distinguish these two geometries without imaging data. We show that in AB Aur, the best-studied Herbig Ae/Be star, the CG-model is inconsistent with imaging observations. In contrast, the theoretical images from a disk+halo model successfully explain the observed images which are large and circularly symmetric at scattering wavelengths but small and elliptical at millimeter wavelengths. We propose a simple test to derive directly from the observed images an objective level of confidence in the applicability of the flared disk hypothesis. "
download the poster (1.1Mb)