We present the results of our long-term monitoring of BD +53°2790, the optical counterpart to the X-ray source 4U 2206+54. Unlike previous studies that classify the source as a Be/X-ray binary, we find that its optical and infrared properties differ from those of typical Be stars: the variability of the V/R ratio is not cyclical; there are

Each HDF image consists of a 2.5x2.5arcmin2 Wide Field Pla Camera 2 (WFPC2) pointing. The images were acquired through the broad-band F300W, F450W, F606W and F814W filters. For the present work we have used the publicly available reduced F606W and F814W Version 2 drizzled images with a sampling of 0.04arcsec/pix and a total exposure time of 109050s

The notion that gravitation might lead to a breakdown of standard space-time structure at small distances, and that this might affect the propagation of ordinary particles has led to a program to search for violations of Lorentz invariance as a probe of quantum gravity. Initially it was expected that observable macroscopic effects caused by

We present a study of the ion{H}{i} distribution and dynamics of the nearby spiral galaxy NGC 5055 based on observations with the Westerbork Synthesis Radio Telescope. The gaseous disk of NGC 5055 extends out to about 40 kpc, equal to 3.5 R25, and shows a pronounced warp that starts at the end of the bright optical disk (R25= 11.6 kpc). This very

Local correlation tracking techniques are used to measure proper motions in a series of high angular resolution (~0.1") penumbra images. If these motions trace true plasma motions, then we have detected converging flows that arrange the plasma in long narrow filaments cospatial with dark penumbral filaments. Assuming that these flows are stationary

The stars β Cet, 31 Com, and μ Vel represent the main stages through which late-type giants evolve during their lifetime (the Hertzsprung gap [31 Com], the rapid braking zone [μ Vel], and the core helium burning ``clump'' phase [β Cet]). An analysis of their high-resolution Chandra X-ray spectra reveals similar coronal characteristics in terms of