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Showing 1 to 20 of 43 for “"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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Pulsar wind nebulae at high energies
Pulsar wind nebulae (PWNe) are the most abundant TeV gamma-ray emitters in the Milky Way. The radiative emission of these objects is powered by fast-rotating pulsars, which donate parts of their rotational energy into winds of relativistic particles. This thesis presents an in-depth study of the …
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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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A Study of Small Diffuse Nebulae
Made available in DSpace on 2014-12-14T05:15:26Z (GMT). No. of bitstreams: 1 7524364.pdf: 2842813 bytes, checksum: a0f750abcab66ffd593aef15e9285c88 (MD5) Previous issue date: 1975
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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
… 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 4-meter …
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Study of fullerene-based molecular nanostructures in planetary nebulae
… by focusing our study on Galactic planetary nebulae (PNe). First, we present a detailed diffuse interstellar band (DIB) radial velocity analysis and a complete search of diffuse bands towards three PNe (Tc 1, M 1-20, and IC 418) containing fullerenes. In particular, some DIBs are found to be …
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Level Populations of Hydrogen and Helium in Gaseous Nebulae
Made available in DSpace on 2014-12-09T18:34:00Z (GMT). No. of bitstreams: 1 6812149.pdf: 2993666 bytes, checksum: d54cbfe248806376971f2d9b61694202 (MD5) Previous issue date: 1968
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Spectrophotometry of Bowen resonance fluorescence lines in three planetary nebulae
… 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 expectations …
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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
… 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 important phase …
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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
… of which are still central stars of planetary nebulae (CSPNs). We have therefore used archival Spitzer IRAC and MIPS observations of PNe to search for CSPNs with excess IR emission, and found five additional IR excesses likely originating from dust disks. For some of these CSPNs, we have …
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Photoionization of Se Ions for the Determination of Elemental Abundances in Astrophysical Nebulae
Absolute single photoionization cross section measurements are presented for Se+ ,Se2+, Se3+ and Se5+. These measurements were performed at undulator beamline 10.0.1 of the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory using the merged-beams technique. All ions except Se5+ …
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Study of binary central stars of planetary nebulae with GALEX and corollary optical surveys.
Planetary Nebulae (PNe) are the descendants of low- and intermediate-mass stars (0.8--8.0 M☉). The shape of the PN takes place at some point between the asymptotic giant branch (AGB) and the white dwarf (WD) stellar phases. Among the astrophysical phenomena, the PNe shows an impressive variety of …
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Prospecting for elements: Galactic halo planetary nebulae abundances and Virgo spiral galaxy color profiles.
Near-infrared Virgo cluster spiral colors. Near-infrared (NIR) surface photometry in J (1.2$\mu$m), H (1.6$\mu$m) and K (2.2$\mu$m) have been obtained for a sample of Virgo cluster spirals; NGC4321, NGC4303, NGC4571, NGC4689, and NGC4254 which span a large range in HI deficiency. The spirals range …
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