We present infrared photometry of the Galactic bulge X-ray binary systems GX 13+1 and GX 17+2 obtained in 1997 July and August using OSIRIS on the 1.8 m Perkins Telescope at Lowell Observatory. GX 13+1 clearly varies over ~0.6 mag in the K band. Our light curve suggests a modulation on a timescale of ~20 days, which is in agreement with previously

We investigate the diagnostic potential of polarimetric measurements with filtergraph instruments. Numerical simulations are used to explore the possibility of inferring the magnetic field vector, its filling factor, and the thermodynamics of model atmospheres when only a few wavelength measurements are available. The simulations assume the

We analyze images of BL Lacertae objects obtained with the Hubble Space Telescope WFPC2 and the F814W filter. The nine objects cover a redshift range of 0.19 to 0.997. The relatively deep images are sufficient to detect galaxies at least one magnitude below MI* (-21.4) and in most cases to three magnitudes below M*. Galaxy enhancement over the

Our HST WFPC2 survey of 110 BL Lac objects, from six complete X-ray-, radio-, and optically-selected catalogs, probes the host galaxies of low-luminosity radio sources in the redshift range /0

Line intensities, visual extinction, abundances and ionization hardness parameter for HII regions in two spiral galaxies are presented. The following galaxies have been observed: NGC 5457 and NGC 4395. In NGC 5457 have been obtained data for 338 regions. In NGC 4395 have been obtained data for 158 regions. For each region position, visual

For decades, the grand-design SAB spiral galaxy NGC 5248 has been postulated to host a short bar of semimajor axis 22" (1.6 kpc). From dynamical and morphological arguments, however, we argue that its spiral structure is being driven by a large-scale bar whose corotation radius lies at ~115" (8.6 kpc). Our estimate is based partially on a deep R