Two Southern Low Excitation Planetary Nebulae

Within a spectroscopic study of some southern planetary nebulae, we have observed 32 objects. Some of them are symbiotic or suspected symbiotic stars, and one (He 2-61) is evidently not an emission object.

The Probable Low Excitation Planetary Nebula M3-44

The Hα emission object M3-44 was observed photographically and spectroscopically. Photographs were obtained in the visual region, in [0 III] λ5007, and in Hα. The visual image is faint and has almost stellar aspect; the object is not visible in [0 III], but the Hα image is very intense, with a diameter of the order of 5″.

The Magellanic Cloud Supernova Remnants

It was some twenty years ago, at the previous IAU symposium devoted to the Magellanic Clouds, that Mathewson and Healey (1964) announced the discovery of the first supernova remnant (SNR) in the LMC. The method used was to identify a non-thermal radio source with a filamentary optical emission object and this confirmed N49 in the catalogue of Henize (1956) as an SNR and suggested N63 and N132 D as likely candidates.

A Single Star Model for V 1016 Cygni

We present a model of the emission object V1016 Cygni consistent with the current optical, infrared and radio observations. V1016 Cygni is 4.2 ± 1.0 kpc from the sun. It was originally an M star which ejected ∼0.017 M0 at 35 kms"1 over a period of ∼600 years producing a neutral nebula with an r"2 density distribution. This process ceased in 1961.3 ±3.0 when the nebula detached from a remnant hot core (T> 80,000K, R< 1.5 Rg). By 1964 0.1 ± 0.3 the nebula was ionized by the UV radiation from the core, producing the observed emission line spectrum. The infrared energy excess comes from two dust components of M000°K and ∼250°K, which absorb UV photons from the star. The dust is concentrated into clumps which 1) provide high density areas on their inner side, allowing strong [OHI] X4363 to remain; 2) shield the regions on their outer side permitting low excitation lines to be present; 3) explain the observed emission line structure. A stellar wind of 105 km/s helps to keep the centre of the ejected nebula hollow. We suggest V1016 Cygni is an example of a low mass planetary nebula in the formation stage.