SIMBAD references

2005ApJ...620..948S - Astrophys. J., 620, 948-960 (2005/February-3)

A starfish preplanetary nebula: IRAS 19024+0044.

SAHAI R., SANCHEZ CONTRERAS C. and MORRIS M.

Abstract (from CDS):

Using the Hubble Space Telescope, we have imaged the OH/IR star IRAS 19024+0044 (I19024) at 0.6, 0.8, 1.1, and 1.6 µm, as part of our surveys of candidate preplanetary nebulae. The images show a multipolar nebula of size ∼3".7x2".3, with at least six elongated lobes emanating from the center of the nebula. Two of the lobes show limb-brightened tips having point-symmetric structure with respect to the expected location of the central star. The central region shows two dark bands southwest and northeast of a central shallow maximum that may be either two inclined dusty toroidal structures or the dense parts of a single wide, inhomogeneous, toroid. A very faint, surface brightness-limited, diffuse halo surrounds the lobes. Long-slit/echelle optical spectroscopy obtained at the Mount Palomar and Keck observatories shows a spatially compact source of Hα emission; the Hα line shows a strong, narrow, central core with very broad (±1000 km/s), weak wings, and a narrower blueshifted absorption feature signifying the presence of a ∼100 km/s outflow. The spectrum is characterized by a strong, relatively featureless, continuum and lacks the strong forbidden emission lines characteristic of planetary nebulae, confirming that IRAS 19024 is a preplanetary nebula; the spectral type for the central star, although uncertain, is most likely early G. Interferometric observations of the CO J=1-0 line emission with the Owens Valley Radio Interferometer show a marginally resolved molecular envelope (size 5".5x4".4) with an expansion velocity of 13 km/s, resulting from the asymptotic giant granch (AGB) progenitor's dense, slow wind. We derive a kinematic distance of 3.5 kpc to I19024, based on its radial velocity. The bolometric flux is 7.3x10–9 ergs/s/cm2, and the luminosity 2850 L. The relatively low luminosity of I19024, in comparison with stellar evolutionary models, indicates that the initial mass of its central star was ∼1-1.5 M. The lobes, which appear to be hollow structures with dense walls, have a total mass greater than or equal to about 0.02 M. The dusty tori in the center have masses of a few times 10–3 M. The faint halo has a power-law radial surface brightness profile with an exponent of about -3 and most likely represents the remnant spherical circumstellar envelope formed as a result of constant mass loss during the AGB phase over the past several thousand years. From the CO data we infer a molecular mass ≳0.025 Mand an expansion age ≲2870 yr, giving a mass-loss rate ≳10–5 M/yr. The far-infrared fluxes of I19024 indicate the presence of a large mass of cool dust in the nebula; from a simple model we infer the presence of ``cool'' (109 K) and ``warm'' (280 K) components of dust mass 5.7x10–4 and 1.5x10–7 M. We discuss our results for I19024 in the light of past and current ideas for the dramatic transformation of the morphology and kinematics of mass-ejecta as AGB stars evolve into planetary nebulae.

Abstract Copyright:

Journal keyword(s): Stars: Circumstellar Matter - ISM: refection nebulae - ISM: Planetary Nebulae: General - Stars: AGB and Post-AGB - Stars: Individual: Alphanumeric: IRAS 19024+0044 - Stars: Mass Loss

CDS comments: Peak P = 2MASS J19050205+0048508

Simbad objects: 17

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2021.07.25-09:28:08

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