Context. The planetary nebula luminosity function (PNLF) is a standard candle that comprises a key rung on the extragalactic distance ladder. The method is...
On the nitrogen abundance of fast, low-ionization emission regions: the outer knots of the planetary nebula NGC 7009
We have constructed a 3D photoionization model of a planetary nebula (PN) similar in structure to NGC 7009 with its outer pair of knots (also known as FLIERs -...
On the possible triple central star system of PN SuWt 2: no ménage à trois at the heart of the Wedding Ring
SuWt 2 is a planetary nebula consisting of a bright ring-like waist from which protrude faint extended lobes - a morphology believed to be typical of...
On the post-common-envelope central star of the planetary nebula NGC 2346
The common-envelope phase is one of the most poorly understood phases of (binary) stellar evolution, in spite of its importance in the formation of a wide range...
On the Presence of Metallofullerenes in Fullerene-rich Circumstellar Envelopes
The presence of neutral C 60 fullerenes in circumstellar environments has been firmly established by astronomical observations as well as laboratory experiments...
On the triple-star origin of the planetary nebula Sh 2-71
Recent studies have indicated that triple-star systems may play a role in the formation of an appreciable number of planetary nebulae, however, only one triple...
On the widths of emission lines in spectra of WC9 stars of different kinds
Emission lines in the spectra of WC9 stars have been studied. It is shown that there are clear differences between the spectra of BD + 30 3639 and the central...
Optical and Infrared Observations of the Bipolar Proto-Planetary Nebula Henize 401
Based on optical and near-infrared ground-based spectroscopy and optical and near-infrared Hubble Space Telescope (HST) images, we confirm the classification of...
Orientation of planetary nebulae within the Galaxy
Narrow-band CCD images of 209 axially symmetrical planetary nebulae (PNe) have been examined in order to determine the orientation of their axes within the disc...