Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 13 of 13 for “"central stars"”.
-
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 …
-
SALT and TESS monitoring of central stars of planetary nebulae
… 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 (WD), following the WD cooling track. Complex, aspherical morphologies are …
-
In search of binary Wolf-Rayet central stars of planetary nebulae
… 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 (H-deficient), the mechanism behind which is not clearly …
-
Dust disks around hot white dwarfs and central stars of planetary nebulae
… their WDs, and a large 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 …
-
Study of binary central stars of planetary nebulae with GALEX and corollary optical surveys.
… 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 complex morphologies. In …
-
Post-common-envelope binary central stars of Planetary Nebulae in the OGLE-IV survey
… complex, non-spherical shapes. Mass loss in AGB stars is presumed as the shaping mechanism but how it results in different PNe morphologies is still unclear. Binary central stars that have undergone common envelope evolution are thought to be a possible solution to this longstanding problem. …
-
Identifying binary central stars of planetary nebulae with Kepler K2 campaign 11 photometric data
… 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 central stars and companions, with some unknown percentage in close binary systems. In this study, a …
-
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 …
-
Probing Late Stages of Stellar Evolution with Gaia-selected Planetary Nebulae
… 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 that low and intermediate mass stars experience towards the ends of their lives before becoming white dwarfs. The thesis has …
-
Molecular Line Studies of Circumstellar Envelopes
… envelopes commonly found around highly evolved stars. Most of the objects observed are M or N giants and are typically long-period variables. We also observed some objects with hotter central stars which may be young or forming planetary nebulae.
-
The formation of enhanced, low-ionization emission in galactic halos
… in NGC 891 and the Galaxy indicates that OB stars, and the central stars of planetary nebulae dominate the excitation of their DIMs. Photoionization models require local DIM electron densities of order unity to reproduce the observed emission characteristics of the high-$\vert z\vert$ gas. …
-
Star Cluster Formation and Galactic Assembly: from instrumentation, to observations and simulations
… differential abundance analysis of 15 red giant stars in the potential cluster siblings, NGC 288 and 362. Both clusters show sta- tistically significant dispersion in both iron and heavy elements, seemingly at odds with the current classifications of GCs. The dynamical evolution of GCs is probed …
-
Star Cluster Formation and Galactic Assembly: from instrumentation, to observations and simulations
… differential abundance analysis of 15 red giant stars in the potential cluster siblings, NGC 288 and 362. Both clusters show sta- tistically significant dispersion in both iron and heavy elements, seemingly at odds with the current classifications of GCs. The dynamical evolution of GCs is probed …