This article describes a fiber optic system contrived to perform spectral imaging of extended objects. It consists of two fiber bundles mounted simultaneously on the spectrograph, which allow one to change the spatial and spectral resolution without any modification in the spectrograph's configuration. At the focal plane, the 61 fibers of each

In a previous work (Paper I of this series), we presented a procedure for computing the temperature distribution in a stellar atmosphere under the constraint of radiative equilibrium. This scheme, which answers the major requirements of simplicity and computational speed, is based on the choice of proper iteration factors that allow a quick

A large, international program of ground-based optical spectroscopy and photometry of the variable Seyfert 1 galaxy NGC 5548 undertaken in support of an IUE monitoring campaign is described. This contribution presents the data base and describes the methods used to correct for systematic differences between spectra from different sources. Optical

Three spiral galaxies with warped disks have been observed; NGC 4013, NGC 4565, and NGC 6504. There is a clear wavelength dependence in the warp's curve, the bluest colors presenting greater distortion. These differences cannot be due to extinction. A larger warp in the young population of stars can be clearly and directly appreciated in the NGC

The direct correlation between effective radius Re and corresponding surface brightness mu-e, found for early-type galaxies by Kormendy (1977) and later confirmed by several studies, is reexamined using a homogeneous photometric data base relative to a luminosity-limited sample of 33 E and SO Virgo cluster galaxies. Contrary to previous belief, but

Spectroscopic observations of the dwarf nova IR Gem in the range 4000-7000 A, covering a whole orbital period, are presented. The dates of the observations (February 3-6, 1987) were at the end of the decline from an outburst and the beginning of quiescence. Evidence of phase related variations in H-alpha equivalent width is found, showing a maximum