Evolutionary versus dynamical time scales for the evolution of the central stars of planetary nebulae
The disagreement between evolutionary and dynamical time scales for the evolution of the central stars of planetary nebulae (CSPN) through the H-R diagram is...
We have acquired narrowband imaging of NGC 3587 (the Owl Nebula) in the transitions [O II] λλ3727, 3729, H I λ4861, [O III] λ5007, H I λ6563, [N II] λ6584, [S...
Excitation mechanisms of C II optical permitted lines in ionized nebulae
Context. Carbon is the fourth most abundant element in the universe and its distribution is critical to understanding stellar evolution and nucleosynthesis. In...
Excitation of emission lines by fluorescence and recombination in IC 418
We compare calculated intensities of lines of C II, N I, N II, O I and O II with a published deep spectroscopic survey of IC 418. Our calculations use a self...
Expansion Velocities and Core Masses of Bright Planetary Nebulae in the Virgo Cluster
The line-of-sight velocities and [O III] 5007 Å expansion velocities are measured for 11 planetary nebulae (PNs) in the Virgo Cluster core, at 15 Mpc distance...
Extinction Mapping of the Bipolar Outflow NGC 2346
We have acquired narrowband imaging of NGC 2346 in the transitions H I λ6563 and λ4861 and [O III] λ5007. As a result, we are able to evaluate the variation of...
Extreme nitrogen enrichment in the asymmetrical planetary nebulae M1-75
In the framework of the morphological survey of northern sky planetary nebulae, in progress at the IAC we investigate in detail those nebulae that show...
Faint emission lines in planetary nebulae with a [WC] nucleus
We present first results from the analysis of a sample of 14 planetary nebulae with [WC] nucleus with detected faint carbon and oxygen recombination lines (RLs)...