Alexander B. Men'shchikov

Properties of the close binary and circumbinary torus of the Red Rectangle

New diffraction-limited speckle images of the Red Rectangle in the wavelength range 2.1-3.3 µm with angular resolutions of 44-68 mas (Tuthill et al. 2002) and previous speckle images at 0.7-2.2 µm (Osterbart et al. 1997; Menshchikov et al. 1998) revealed well-resolved bright bipolar outflow lobes and long X-shaped spikes originating deep inside the outflow cavities. This set of high-resolution images stimulated us to reanalyze all infrared observations of the Red Rectangle using our two-dimensional radiative transfer code. The high-resolution images imply a geometrically and optically thick torus-like density distribution with bipolar conical cavities and are inconsistent with the flat disk geometry frequently used to visualize bipolar nebulae. The new detailed modeling, together with estimates of the interstellar extinction in the direction of the Red Rectangle enabled us to more accurately determine one of the key parameters, the distance D ≈ 710pc with model uncertainties of 70pc, which is twice as far as the commonly used estimate of 330pc. The central binary is surrounded by a compact, massive (M ≈ 1.2M⊙), very dense dusty torus with hydrogen densities reaching nH ≈ 2.5 ×10 12 cm −3 (dust-to-gas mass ratiod/� ≈ 0.01). The model implies that most of the dust mass in the dense torus is in very large particles and, on scales of more than an arcsecond, the polar outflow regions are denser than the surrounding medium. The bright component of the spectroscopic binary HD44179 is a post-AGB star with mass M⋆ ≈ 0.57M⊙, luminosity L⋆ ≈ 6000L⊙, and effective temperature T⋆ ≈ 7750K. Based on the orbital elements of the binary, we identify its invisible component with a helium white dwarf with MWD ≈ 0.35M⊙, LWD ∼ 100L⊙, and TWD ∼ 6 ×10 4 K. The hot white dwarf ionizes the low-density bipolar outflow cavities inside the dense torus, producing a small HII region observed at radio wavelengths. We propose an evolutionary scenario for the formation of the Red Rectangle nebula, in which the binary initially had 2.3 and 1.9M⊙ components at a separation of ∼ 130R⊙. The nebula was formed in the ejection of a common envelope after Roche lobe overflow by the present post-AGB star.

Structure and physical properties of the rapidly evolving dusty envelope of IRC + 10216 reconstructed by detailed two-dimensional radiative transfer modeling

We present the first detailed, two-dimensional radiative transfer model of the dusty envelope around the carbon star IRC + 10216. Our goal was to find a self-consistent model of the star and its envelope which takes into account as many observational constraints as possible. The model reproduces very well the entire beam-matched spectral energy distribution of IRC + 10216 from optical to centimeter wavelengths (at several phases of stellar luminosity), observed intensity profiles of the object at 1.25, 2.2, 10.5, 50, 100

Self-consistent Model of the Dusty Torus around HL Tauri

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Diffraction-limited bispectrum speckle interferometry of the nuclear region of the Seyfert galaxy NGC 1068 in the H and K' bands

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Bispectrum speckle interferometry of IRC +10216: The dynamic evolution of the innermost circumstellar environment from 1995 to 2001

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Mid-infrared interferometry of massive young stellar objects I. VLTI and Subaru observations of the enigmatic object M8E-IR

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IRC+10 216 in action: Present episode of intense mass-loss reconstructed by two-dimensional radiative transfer modeling

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Properties of galactic B(e) supergiants V. Two-dimensional radiative transfer model of RY Sct and its dusty disc

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Mid-infrared interferometry of massive young stellar objects

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Near-infrared speckle interferometry and radiative transfer modelling of the carbon star LP Andromedae

bispectrum speckle-interferometry images, and visibilities in