Numerical simulations of the interacting galaxies in the NGC 520/UGC 957 system are presented. Two sets of models were produced to investigate the postulated three-galaxy system of two colliding disk galaxies within NGC 520 and the dwarf galaxy UGC 957. The first set of models simulated a dwarf perturbing one-disk galaxy, which tested the

Approximate carbon abundances and C-12/C-13 isotope ratios are obtained for 70 M giant stars from intermediate-resolution spectrophotometry of the CO bands near 2.3 microns. A low mean carbon abundance (C/H = -0.64 + or - 0.29) is obtained, suggesting that standard mixing is insufficient to explain atmospheric abundances in M giants. HR 8795

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