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Showing 1 to 10 of 10 for “"Planetary nebula"”.
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The Evolution of Planetary Nebula Nuclei
The evolution of planetary nebula nuclei (PNNs) is examined with the aid of the most recent available stellar evolution calculations and new observations of these objects. Their expected distribution in the log L-log T plane is calculated based upon the stellar evolutionary models of Paczynski, …
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Probing Late Stages of Stellar Evolution with Gaia-selected Planetary Nebulae
… data from the Gaia satellite to study Galactic planetary nebulae. Gaia is a recent ESA mission measuring positions, parallaxes, proper motions, and photometry of nearly two billion stars in the Milky Way. Several thousand of these stars are passing through the planetary nebula phase, an …
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Laboratory and Observational Studies of Transient Molecules at Microwave and Millimeter/Submillimeter Wavelengths
… were also used to conduct a study of the evolved planetary nebula, NGC 7293, or the Helix Nebula. In the Helix, CO, HCO⁺, and H₂CO were observed at several positions offset from the central star to obtain densities and kinetic temperatures throughout the Helix. A map of the HCO⁺ J = 1→ 0 …
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Circumstellar Distribution of Dust Grains Around Proto -Planetary Nebulae: Observational Evidence for Axisymmetry and 2.5-D Radiative Transfer Model Calculations
Proto-planetary nebulae (PPNs) are evolved, intermediate initial mass (0.8--8 solar masses) stars that are in rapid transition from the asymptotic giant branch (AGB) phase into the planetary nebula (PN) phase. Largely spherically symmetric circumstellar dust shells of AGB stars are known to evolve …
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Dust disks around hot white dwarfs and central stars of planetary nebulae
… dust disk around the hot central WD of the Helix planetary nebula (PN), possibly produced by collisions among Kuiper Belt-like objects.To search for more dust disks of the latter type, we have carried out a Spitzer MIPS 24 um survey of 71 hot WDs or pre-WDs, and found nine WDs with excess 24 um …
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Evolution of the Circumstellar Atomic and Molecular Envelopes Around Evolved Stars
… envelope (CSE). For the more evolved protoplanetary nebula (PPN) and planetary nebula (PN) phases, the CSE also chronicles its interaction with fast winds and photodissociating/photoionizing radiation. Most AGB stars lose mass in spherically symmetric outflows, whereas PNe are largely …
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Exploring dark matter locally via a hierarchy of stellar systems
… stellar system we consider is the galactic-wide Planetary Nebula system in the Andromeda galaxy. Along with the galaxy's rotation curve, we use the Planetary Nebulae to constrain dynamical models of the galaxy, with a view to pinning down the parameters of the dark matter halo. We find that the …
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The outbursts and environments of novae
… (i) Nova V458 Vulpeculae and its surrounding planetary nebula; (ii) Detailed nova light curves from the Solar Mass Ejection Imager (SMEI); and (iii) Vl721 Aquilae, an usually fast, luminous, and highly extinguished nova. A brief account is also given of more generalised work on novae in M31, …
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Hydrogen-deficient central stars of planetary nebulae
Central stars of planetary nebulae are low-mass stars on the brink of their final evolution towards white dwarfs. Because of their surface temperature of above 25,000 K their UV radiation ionizes the surrounding material, which was ejected in an earlier phase of their evolution. Such fluorescent …