No abstract available

No abstract available

[en] A large discontinuity has been observed in the period of PSR 1641-45. The period of 0.455 s has decreased by about 87 ns corresponding to a fractional change Δ P/P approximately 1.9 x 10^-7. There was a corresponding small increase in the period derivative with Δ (dP/dt)/(dP/dt) approximately 1.6 x 10^-3. (author)

[en] High-velocity features over a velocity range of 180 km s^-1 have now been definitely identified on the profiles of the Hα line from the H II region M17. A photon-counting image tube on the intermediate grating spectrograph of the 3.9 m Anglo-Australian telescope was employed. Many mechanisms for the formation of these high-velocity phenomena and the co-moving H I, molecular/H II large-scale sheets, which have lower velocities, are considered. Flows from ionization fronts moving into (and in one case breaking out from) small globules and large neutral sheets are compared to the large- and small-scale effects of energetic stellar winds. External and internal supernova remnants are also discussed and radiation pressure on embedded dust grains and the ionized gas is not discounted. Motions generated during periods of star formation are also mentioned. (orig.)

[en] We have extended the complex formalism of Bourassa and Kantowski for a transparent gravitational lens to a multilens situation. By using a grid of assumed positions for the cluster center within its measured error box, we have then calculated a range of possible time delays between the two images, A and B. The results indicate a range from 0.03 yr to 1.7 yr, which is somewhat smaller than might have been anticipated

[en] A fluctuation spectrum analysis of single pulse sequences from nine pulsars measured at radio frequencies ranging from 0.43 GHz to 2.7 GHz has been carried out. It is shown that a gradual growth of the quasi-steady component of the pulsar emission with increasing radio frequency is a common feature of these sources. A theoretically predicted radio frequency independence of the P₃ periods is found to hold in both the systematic and the erratic drifters, except for PSR 2016+28 and possibly PSR 2020+28. It is suggested that a slow intensity modulation generated by the quasi-steady component may explain the break frequency found in the modulation index/radio frequency relationship for some pulsars and that the phenomena observed in our data may be directly related to the pulse emission constituents described as the core and the conal emissions. (orig.)

[en] The apparent radii of some HII regions in the galaxies NGC 224, NGC 2403, NGC 300, NGC 598 and NGC 1313 were determined. The size distribution of the apparent radii of the HII regions in these galaxies were studied. Two variants are suggested to determine the distances of these galaxies. The reliability of these variants could be seen by comparison with the distances determined by other methods. (author)

[en] A simple cooling law, based on a recent calculation by Raymond, Cox and Smith, is used to find the temperature in very old supernova remnants. It appears that even after a million years a remnant still contains large regions with very high temperatures. (orig.)

No abstract available

[en] Seven SNR were detected in M31. Their galactic distribution, evolutionary stage, and possible relation to nucleosynthesis are discussed