Prominence threads are expected to be cold plasma condensations in a long magnetic tube. Because of this density inhomogeneity along the magnetic field, the ratio of the fundamental transverse mode period to twice that of its first overtone, P 1/2P 2, must differ from 1. We investigate the dependence of this ratio on the equilibrium parameters of

The aim of a data reduction process is to minimize the influence of data acquisition imperfections on the estimation of the desired astronomical quantity. For this purpose, one must perform appropriate manipulations with data and calibration frames. In addition, random-error frames (computed from first principles: expected statistical distribution

We present results of an optical and near-infrared (IR) 1.8 deg2 survey in the Pleiades open cluster to search for substellar objects. From optical I-band images from the CFHT and J-band images from the 3.5 m CAHA Telescope, we identify 18 faint and very red L brown dwarf candidates, with I> 20.9 and I-J> 3.2. The follow-up observations of nine

Proper motions in penumbra have been measured using local correlation tracking techniques in a high spatial resolution series of images (˜0.12 arcsec). Assuming these motions to trace true plasma motions, we have detected converging flows that arrange the plasma in long narrow filaments mostly placed along dark penumbral filaments. These converging

We present a long-term project to study the characteristics and evolution of current star-forming galaxies at different redshifts. Our results support the idea that the higher Star Formation Density measured at redshift z=0.24 is due to an increase of the density of bursting galaxies and not to an intrinsic change on overall galaxy properties.

In this poster we present statistical properties of a sample of Hii regions in the spiral galaxies NGC 4254, NGC 4321, NGC 5194, NGC 5248, NGC 5350 and NGC 6951. We have constructed catalogues of H ii regions using Hα and Hβ line images. In these catalogues we show Hα fluxes corrected for extinction, Hβ fluxes corrected for stellar absorption and