A possible association of a young pulsar (PSR J0855−4644) with the young Vela supernova remnant RX J0852.0−4622

The recently discovered young supernova remnant (SNR) RX J0852.0−4622 has attracted much interest since its discovery because of the possibility that it may have been generated by the nearest supernova in recent history. We note the presence of two Parkes Multibeam Survey pulsars within the boundary of the remnant. We discuss the properties of the two pulsars and the likelihood of either of them being physically linked to the SNR. We tentatively suggest that, given the current uncertainties in the distance to RX J0852.0−4622, one of these pulsars, the 65-ms period PSR J0855−4644 could indeed be the compact remnant of this supernova explosion. If the pulsar birth site is at the geometrical centre of the nebula, then, for the transverse pulsar velocity to be reasonable, the SNR must be nearby (around 250 pc) and no younger than about 3000 yr old.     

A survey of the unusual motions in M17 with a Fabry-Perot monochromator

The results of the most extensive survey ever undertaken of the profiles of the [Oiii] line over M17 are presented. These were obtained with an optically-contacted, pressure-scanned, single-etalon Fabry-Perot monochromator used on the 74-in. Radcliffe reflector. Some very unusual velocity features have been revealed. Several regions were found to be emitting lines split by motions of 20 km s^?1 whereas others produce lines with three or more separate velocity components which stretch up to ?70 km s^?1 from the mean radial velocity of the nebula. Some speculative explanations for these motions are offered.     

High-speed knots in the hourglass-shaped planetary nebula Hubble 12

We present a detailed kinematical analysis of the young compact hourglass-shaped planetary nebula Hb 12. We performed optical imaging and long-slit spectroscopy of Hb 12 using the Manchester echelle spectrometer with the 2.1-m San Pedro Mártir telescope. We reveal, for the first time, the presence of end caps (or knots) aligned with the bipolar lobes of the planetary nebula shell in a deep [N  ii ]λ6584 image of Hb 12. We measured from our spectroscopy radial velocities of  ∼120 km s⁻¹  for these knots.
We have derived the inclination angle of the hourglass-shaped nebular shell to be ∼65° to the line of sight. It has been suggested that Hb 12's central star system is an eclipsing binary which would imply a binary inclination of at least 80°. However, if the central binary has been the major shaping influence on the nebula, then both nebula and binary would be expected to share a common inclination angle.
Finally, we report the discovery of high-velocity knots with Hubble-type velocities, close to the core of Hb 12, observed in Hα and oriented in the same direction as the end caps. Very different velocities and kinematical ages were calculated for the outer and inner knots showing that they may originate from different outburst events.     

Hi,molecular/Hii shells from 1 to 2000 pc diameter: Wind-driven or supernova remnants?

Deep H+[Nii] photographs of five giant shell-like nebulae in the LMC are compared to 21 cm Hi maps, Schmidt photographs showing the O and B associations and the UV sources from 1200 to 1600 Å. The formation of all shell-like nebulae which do not appear to be supernova remnants and which have diameters between 1 pc and 1900 pc is discussed.     

The expansion of the giant filamentary shell, DEM 171, in the Magellanic Bridge

The giant filamentary shell, DEM 171, is found to be expanding at approximately 37 km s⁻¹. A supernova and stellar wind origin are both explored as possible causes for the expanding shell. A stellar wind origin would imply a mass-loss rate of the order of 10⁻⁵ M_⊙ yr⁻¹, indicating that it could be caused by a Wolf–Rayet star. A number of blue stars are found to lie within the shell and one is identified as a Wolf–Rayet candidate.     

Deep Hα imagery of the Eridanus shells

A deep Hα image of interlocking filamentary arcs of nebulosity has been obtained with a wide-field (≈30° diameter) narrow-band filter camera combined with a charge-coupled device as a detector. The resultant mosaic of images, extending to a galactic latitude of −65°, has been corrected for field distortions and had galactic coordinates superimposed on it to permit accurate correlations with the most recent H  i (21 cm), X-ray (0.75 keV) and FIR ( IRAS 100 μm) maps.
Furthermore, an upper limit of 0.13 arcsec yr⁻¹ to the expansion proper motion of the primary 25° long nebulous arc has been obtained by comparing a recent Hα image obtained with the San Pedro Martir telescope of its filamentary edge with that on a Palomar Observatory Sky Survey E plate obtained in 1951.
It is concluded that these filamentary arcs are the superimposed images of separate shells (driven by supernova explosions and/or stellar winds) rather than the edges of a single 'superbubble' stretching from Barnard's Arc (and the Orion Nebula) to these high galactic latitudes. The proper motion measurement argues against the primary Hα-emitting arc being associated with the giant radio loop (Loop 2) except in extraordinary circumstances.     

A reappraisal of several extensive phenomena of the high galactic latitudes

This is the first of two papers dealing with the extensive high latitude phenomena. The relationships between the diffuse and filamentary gaseous nebulosity, the giant radio loops and the high, medium and low velocity neutral hydrogen are considered in the light of recent observations. The existence of other giant loops is also suggested.A further article (by K.H.E.) will present some very accurate measurements of the radial velocities of the nebulosities in the vicinity of Loop 2. These will be compared to some neutral hydrogen features in that region.     

The motions of the neutral and ionized material in the supermassive Doradus Nebula

A close association between the large scale motions of the neutral and ionized gas in the 30 Doradus Nebular Complex is established. A series ofHi/Hii shells are suggested to explain this phenomenon. The evidence favours a contracting situation, but is not yet conclusive.     

Further observations of the filamentary nebulosity around the cetus Arc (Loop 2)

Previously some filamentary nebulosity was discovered around the outer edge of the Cetus Arc (Loop 2). Some further observations have now been made of this. To determine an upper limit to its proper motion it was photographed again with the Mount Palomar 48-inch Schmidt telescope. Also, to reveal the full extent of this nebulous region, more photographs have been added to the original mosaic and it has been photographed again with a wider field filter camera. No proper motion greater than 0 _. 5/year was detected. However, some further ridges of nebulosity were discovered.A shell model for Loop 2 based on this upper limit to the proper motion of the nebulosity and its similarity to the Cygnus Loop is presented. Some comments on the excitation mechanism of the nebulosity are also made.