We report observations of NGC 6334N, Ml7 5W, W 51 and DR2l(OH) in the J = 4→3 transition of HCN at 354GHz. These results are combined with previously obtained J=1→0HCN data to determine molecular abundances X(HCN) ˜4 × 10-11 -4 × 10-12, and characteristic line excitation zone densities n(H2)˜106 cm-3. These results are at variance with previous

Thirty Seyfert galaxies have been studied for bright sources. The photometry is reported and three of the more unusual galaxies (Mrk 705, Mrk 817, and Mrk 1095) are individually discussed. It is confirmed that infrared emission in excess of the stellar contribution is commonplace in Seyfert galaxies. Attention is drawn to the J-K colors of the

Observations of the 1400-1800 A region in late A type stars are presented, which were obtained using the IUE satellite at low and high resolution. The calibrated energy distribution is derived and presents a large variation with wavelength in the spectral range due to Si I photoionization discontinuities. Emission lines formed in the transition

Spectra from IUE of 6 main sequence and near main sequence stars from classes A5 to G8, between 2700 A and 2900 A wavelength are described. In toto, some 250 absorption lines are identified. Observed differences in those atomic and ionic multiplets present in each spectrum are shown to be due either to the regular progression in spectral class, or

This paper presents an alternative procedure which extracts spectra from IUE low resolution images. The -by-line image is scanned perpendicularly to the direction of dispersion . The resulting cross-cuts are then fitted with a known-form analytical function, which consists of a linear base-line describing the background plus as many bands as there

A model is given for constructing artificial integrated spectral lines which allows the inclusion of all effects relevant to the synthesis of these lines by numerical methods. Among the effects included are noise, limb darkening, the centre-to-limb variation of the shapes and wavelength positions of the spectral line profiles, different laws of the