The observed emission-line ratios of the extended emission-line regions of Cen A and 3C 227 are compared with the theoretical results from photoionization...

High signal-to-noise spectra of the H-beta region of eight radio-loud quasars are presented in an investigation seeking evidence for the emission of this line...

The evolutionary scenario concerning the production and the cooling of He white dwarfs is revisited and discussed. We show that, for a given star metallicity...

A large fraction of Type Ia supernova (SN Ia) observations over the next decade will be in the near-infrared (NIR), at wavelengths beyond the reach of the...

The effect of a spiral-like perturbation in the orbits of an axisymmetric galactic potential is studied using surfaces of section. It is found that the...

Observations in the 100-1000-micron band and the instruments used to obtain them are discussed in contributions to the Submillimeter Wave Astronomy Conference...

Using the H-II region H-alpha emission detected in high-resolution long slit spectra of the normal spiral NGC 6946 out to 6 kpc from the center, and along 8...

BVRI surface photometry is presented for the interacting galaxy pair Arp 86 (NGC 7753-7752). Deep high-resolution images were obtained in order to study the...

Near-infrared, optical, and ultraviolet quasi-simultaneous observations of 11 BL Lacertae objects are reported. For all but one source the dereddened spectral...