Related papers: The Classification of M1-78
Why 80% of planetary nebulae are not spherical is not yet understood. The Binary Hypothesis states that a companion to the progenitor of the central star of a planetary nebula is required to shape the nebula and even for a planetary nebula…
Many ultracompact HII regions exhibit a cometary morphology in radio continuum emission. In such regions, a young massive star is probably ablating, through its ultraviolet radiation, the molecular cloud clump that spawned it. On one side…
There is no quantitative theory to explain why a high 80% of all planetary nebulae are non-spherical. The Binary Hypothesis states that a companion to the progenitor of a central star of planetary nebula is required to shape the nebula and…
Extensive photoionization model grids for single star HII regions using a variety of recent state-of-the-art stellar atmosphere models have been computed with the main aim of constraining/testing their predicted ionizing spectra against…
The Orion Nebula is one of the most frequently observed nearby (<1 kiloparsec) star forming regions and, consequently, the subject of a large bibliography of observations and interpretation. The summary in this chapter is bounded spatially…
Many more supernova remnants (SNRs) are now known in external galaxies than in the Milky Way. Most of these SNRs have been identified using narrow-band imaging, separating SNRs from HII regions on the basis of [SII]:H-alpha ratios that are…
A high quality, medium-resolution K-band spectrum has been obtained of the ultracompact HII region G29.96-0.02 with the Very Large Telescope (VLT). The slit was positioned along the symmetry axis of the cometary shaped nebula. Besides the…
This chapter reviews progress in the field of massive star formation. It focuses on evidence for accretion and current models that invoke high accretion rates. In particular it is noted that high accretion rates will cause the massive young…
The study of planetary nebulae provides important constraints for many aspects of stellar and Galactic evolution. Hen 2-108 is a poorly known planetary nebula with a slight elliptical morphology and a peculiar central star (CS), which has…
We present a detailed study of the stellar and orbital parameters of the post-common envelope binary central star of the planetary nebula Ou~5. Low-resolution spectra obtained during the primary eclipse -- to our knowledge the first…
The direct detection of a stellar system that explodes as a Type Ia supernova (SN Ia) has not yet been successful. Various indirect methods have been used to investigate SN Ia progenitor systems but none have produced conclusive results. A…
A number of late [WC] stars have unique infrared properties, not found among the non-[WC] planetary nebulae, and together define a class of IR-[WC] stars. They have unusual IRAS colours, resembling stars in the earliest post-AGB evolution…
The origin of the abundance discrepancy in nebulae is one of the key problems in the physics of photoionized nebulae. In this work we have analized a sample of Galactic and extragalactic H II regions where the abundance discrepancy have…
A detailed examination of new high quality radio catalogues (e.g. Cornish) in combination with available mid-infrared (MIR) satellite imagery (e.g. Glimpse) has allowed us to find 70 new planetary nebula (PN) candidates based on existing…
Photoionized nebulae comprise basically HII regions and planetary nebulae, and their abundances give important clues on the nucleosynthesis and chemical evolution of their host galaxies. There is presently a large amount of data on these…
Bipolar planetary nebulae (PNe) are thought to result from binary star interactions and, indeed, tens of binary central stars of PNe have been found, in particular using photometric time-series that allow detecting post-common envelope…
The LMC is ideal for studying the co-evolution of planetary nebulae (PNe) and their central stars, in that the debilitating uncertainties of the Galactic PN distance scale and selection biases from attenuation by interstellar dust do not…
The transition from Asymptotic Giant Branch star to Planetary Nebula is short-lived and mysterious. Though it lasts only a few thousand years, it is thought to be the time when the asymmetries observed in subsequent phases arise. During…
We present deep spectrophotometry for a sample of 8 PNe and 12 HII regions in the irregular galaxy NGC 3109, to analyze the chemical composition of both types of nebulae. We present line intensities and the physical conditions and the…
Helium star--compact object binaries, and helium star--neutron star binaries in particular, are widely believed to be the progenitors of the observed double neutron star systems. In these, the second neutron star is presumed to be the…