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Showing 1 to 20 of 26 for “"planetary nebulae"”.
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Local Extinctions for Planetary Nebulae
Made available in DSpace on 2014-12-14T05:15:28Z (GMT). No. of bitstreams: 1 7708977.pdf: 6128946 bytes, checksum: 96a303b573cca8583e508b0d8fb3d2e4 (MD5) Previous issue date: 1976
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Population Discrimination Among Planetary Nebulae
Made available in DSpace on 2014-12-09T18:33:59Z (GMT). No. of bitstreams: 1 6808092.pdf: 3154378 bytes, checksum: 4222944d29d2612abb1cafac0f157c8f (MD5) Previous issue date: 1967
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Small-scale structures in planetary nebulae
Two planetary nebulae (PNe) were studied in order to investigate small scale molecular structures in planetary nebulae, the survival of which affects the structure and composition of the interstellar medium (ISM) from which the next generation of stars is born. Molecular hydrogen (H[subscript 2]) …
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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 …
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Interstellar Dust and Distances to Planetary Nebulae
Made available in DSpace on 2014-12-10T23:45:12Z (GMT). No. of bitstreams: 1 7219872.pdf: 3519216 bytes, checksum: f7ecce761bb4c7dc9bfcbe0d059e9d55 (MD5) Previous issue date: 1972
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Hot planetary nebulae nuclei and related objects
The hottest central stars found in planetary nebulae excite the O VI atomic transition in their atmospheres. Presumably the central stars of all planetary nebulae become O VI stars during some phase of their evolution. Observational studies show that all post-asymptotic giant branch (P-AGB) stars …
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Chemical abundances in planetary nebulae in NGG 6822
… an investigation of the optical spectra of five planetary nebulae and two H II regions are presented. The nebulae, located in NGC 6822, a Local Group Irregular Galaxy at a distance of .557 Mpcs, were examined using the Richey-Cretien spectrograph and the Silicon Intensified (SIT) Vidicon, on the …
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Spectrophotometry of Bowen resonance fluorescence lines in three planetary nebulae
… fluorescence mechanism of OIII in three planetary nebulae: NGC 6210, 7027, and 7662. It utilizes the best spectra to date of this phenomena in the wavelength range of 3100 A-3850 A. The data are presented in the form of flux ratios relative to the strong 3444.1 A line and compared to …
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SALT and TESS monitoring of central stars of planetary nebulae
Planetary Nebulae (PNe) are the product of Asymptotic Giant Branch (AGB) evolution. Evolved from Solar-like intermediate mass stars (0.8 – 8M), they have a hot, radiating core that ionizes the gas of the expelled envelope, producing a glowing nebula. The core eventually evolves into a white dwarf …
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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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In search of binary Wolf-Rayet central stars of planetary nebulae
Planetary Nebulae (PNe) are circumstellar gas envelopes ejected during Asymptotic Giant Branch (AGB) phase of the stars between 1M࿉ to 8M࿉. In around 3000 galactic PNe, 10 to 20 % are known to host a Wolf-Rayet type central star ([WR] CSPN). These [WR] CSPNe are known to be very hydrogen deficient …
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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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Post-common-envelope binary central stars of Planetary Nebulae in the OGLE-IV survey
Planetary Nebulae (PNe) are defined as the ionized shells of circumstellar gas ejected through an intense stellar wind at the end of the star's life. PNe come in different shapes, from spherical to highly complex, non-spherical shapes. Mass loss in AGB stars is presumed as the shaping mechanism but …
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Identifying binary central stars of planetary nebulae with Kepler K2 campaign 11 photometric data
A large majority of planetary nebulae (PNe) are non-spherical, and many have complex structures; these are unlikely to be created trivially by a single central star. The Binary Hypothesis proposes that the complex morphologies of most non-spherical PNe are caused by interactions between their …
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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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Molecular Line Studies of Circumstellar Envelopes
… central stars which may be young or forming planetary nebulae.
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Following Carbon's Evolutionary Path: From Nucleosynthesis to the Solar System
… observations of circumstellar envelopes (CSEs), planetary nebulae (PNe), molecular clouds and comets. The 12C/13C isotope ratio was measured in Galactic molecular clouds using the CN isotopologs. A gradient of 12CN/13CN was determined to be 12C/13C = 6.01 DGC +12.28, where DGC is distance from …
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