We study star formation processes in the disc of the weakly barred grand design spiral galaxy M100 (NGC 4321) from a variety of images tracing recent massive star formation, old and young stars, dust and neutral hydrogen. Differences between arm and interarm regions are specifically studied by decomposing the images into arm and non-arm zones. We

Using the William Herschel Telescope ISIS spectrograph, deep long-slit spectra were obtained of the ionized gas across the blue compact dwarf galaxy I Zw 18 and in an irregular galaxy located 15" to the northwest. Heliocentric radial velocities of H alpha and H beta emission lines were measured over a 50" length spanning the main body of I Zw 18

An international monitoring project, called OJ-94, was set up with the aim of monitoring blazar OJ 287 during the predicted optical outburst (in fall 1994, Sillanpaa et al. 1988ApJ...325..628S) and the predicted secondary outburst (in winter 1995-1996, Sillanpaa et al. 1996A&A...305L..17S). The most prominent features in the OJ 287 light curve

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Far Infrared observations of the Seyfert galaxies NGC 3227, NGC 4051 and NGC 4151 are presented. These are the first data from a complete sample of Seyfert galaxies that is being observed by ISO as part of the ISOPHOT guaranteed time. The new ISO data, in combination with the IRAS data, show that the mid to far IR emission in all three objects can

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