The jump conditions across a shock front in a thin magnetic flux tube are studied by purely analytical means. Some properties of magnetohydrodynamic shock waves in extended media are shown also to hold in the more complicated case of thin magnetic flux tubes. It is shown that flux tube shock waves are always compressive, thus being accompanied by a

The contrast of the photospheric granulation in the centre of the disk at a wavelength of 500 nm has been determined by means of photographs taken during the solar eclipse of May 30th 1984. After restoration, values of 17.3% and 20.4%, using the sum of two lorentzians to define the instrumental profile, and of 11.7% and 14.3%, using the sum of two

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The authors discuss the nature of S 201 in the light of new optical and infrared observations, in terms of the interaction between an evolved H II region and a nearby molecular cloud. The energetics of the region and the role of star formation in that area are also briefly discussed.

An analysis of the IRAS data for a sample of classical (optically selected) Seyfert galaxies is presented. The IRAS fluxes at 25 micron, 60 micron, and 100 micron are found to be uncorrelated or only very weakly correlated with the UV/Optical continuum flux and the near and mid IR flux at 3.5 and 10 microns. To investigate the possibility that star

The authors present the preliminary results of a search for near-infrared counterparts of compact H II regions and/or H2O masers in the Galactic Plane, probably associated with IRAS sources. J, H, K, L and M photometry of 10 new detections is reported.