相关论文: Close binary central stars and the abundance discr…

We show that there are strong links between certain types of asymmetrical Planetary Nebulae (PNe) and symbiotic stars. Symbiotics are binaries and several have extended optical nebulae all of which are asymmetrical and ~-40% are bipolar.…

I propose that the relatively high eccentricity found in some tidally strongly interacting binary systems, where the mass-losing star is an evolved giant star, e.g., an asymptotic giant branch star, is caused by an enhanced mass loss rate…

Recent analyses of nebular spectra have resulted in discrepant abundances from CNO forbidden and recombination lines. We consider independent methods of determining ion abundances for emission nebulae, comparing ion emission measures with…

When comparing nebular electron densities derived from collisionally excited lines (CELs) to those estimated using the emission measure, significant discrepancies are common. The standard solution is to view nebulae as aggregates of dense…

This paper is the fourth and final report on a project designed to study carbon abundances in a sample of planetary nebulae representing a broad range in progenitor mass and metallicity. We present newly acquired optical spectrophotometric…

Promising methods for studying galaxy evolution rely on optical emission line width measurements to compare intermediate-redshift objects to galaxies with equivalent masses at the present epoch. However, emission lines can be misleading. We…

A recent spectroscopic analysis of central stars of planetary nebulae (CSPNe) claims that the sample includes five CSPNe with masses very close to the Chandrasekhar limit of white dwarfs. This claim should be verified or discarded from the…

Considerable effort has been applied towards understanding the precise shaping mechanisms responsible for the diverse range of morphologies exhibited by planetary nebulae (PNe). A binary companion is increasingly gaining support as a…

In this brief invited review, I will attempt to summarise some of the key areas of interest in the study of central stars of planetary nebulae which (probably) won't be covered by other speakers' proceedings. The main focus will,…

The Galactic centre and its surrounding space are important in studying galaxy-scale evolution, and stellar populations therein are expected to have imprints of the long-term evolution. Interstellar extinction, however, severely limits…

Shaping axi-symmetric planetary nebulae is easier if a companion interacts with a primary at the top of the asymptotic giant branch. To determine the impact of binarity on planetary nebula formation and shaping, we need to determine the…

Recent numerical work by Wilson, Mathews, and Marronetti [J. R. Wilson, G. J. Mathews and P. Marronetti, Phys. Rev. D 54, 1317 (1996)] on the coalescence of massive binary neutron stars shows a striking instability as the stars come close…

We present preliminary results obtained from the analysis of very deep echelle spectra of a dozen planetary nebulae with [WC] or weak emission lines (wels) central stars. The computed abundance discrepancy factors (ADFs) are moderate, with…

In this work, a review is given of some recent results and problems involved in the determination of chemical abundances of galactic planetary nebulae, particularly regarding disk and bulge objects.

New observations and derived chemical abundances are reported for a sample of 57 bulge planetary nebulae (PN). Together with our previous results, a total of over a hundred objects have been analyzed, which constitute one of the largest…

In this review we present a brief discussion on the observational evidence in favor of the presence of temperature variations, and conclude that many planetary nebulae show spatial temperature variations that are larger than those predicted…

The existence of strange quark stars has been proposed many years ago. More recently, the possible co-existence of a first family composed of "normal" neutron stars with a second family of strange quark stars has been proposed as a solution…

We present long-slit spectroscopy and imaging data obtained with FORS2 on the Very Large Telescope of 13 optically selected type 2 quasars at z~0.3-0.6 from the original sample of Zakamska et al. (2003). The sample is likely to be affected…

We present a spectroscopic investigation of 25 objects previously reported as possible Planetary Nebulae (PNe) in recent catalogs to obtain their physical properties and to establish their true nature. We found 11 objects showing intense…

The formation of massive stars is one of the major unsolved problems in stellar astrophysics. However, only few if any of these are found as single stars, on average massive stars have more than one companion. Many of them are born in dense…