Two data series of disk integrated solar irradiance, taken by the Variability of the solar IRradiance and Gravity Oscillations (VIRGO) experiment on board the Solar and Heliospheric Observatory (SoHO) mission, corresponding to epochs of minimum and maximum solar activity have been analysed in order to study the background signal of the associated

Using GOLF/SOHO data a detailed analysis of the solar background spectrum has been performed at high and low phases of solar activity cycle. The analysis includes not only the non-periodic components of the background power spectrum but also the periodic ones. Apart from the solar activity, other causes produce similar effects in the data

Non-axisymmetric features such as bars drive the dynamical and secular evolution of disk galaxies by exerting gravitational torques which redistribute mass and angular momentum. While most (> 70 %) spirals are barred in the local Universe, early studies of the Hubble Deep Field (HDF) suggest a remarkably low bar fraction ( 20 %) at intermediate

We use the OSUBSGS (Ohio State University Bright Spiral Galaxy Survey, Eskridge et al. 2002) and NIRS0S (Near-IR S0 Survey, Laurikainen et al. 2005) data to study the connection of bars and outer spiral structures. Using near-IR images, the non-axisymmetric gravity perturbation associated with the bar is evaluated at various distances outside the

Bars are prominent features that occur in most disc galaxies and have important dynamical effects on their hosts. This paper describes some of the known properties of bars, illustrating the discussion with images that show the beauty of the galaxies under consideration. The focus of this article is on the evolution of bars and on their influence on

We present a test for the degree of symmetry in the distribution of the Hα brightness along the arms of a sample of spiral galaxies. The test consists of deriving the cross-correlation function of the Hα brightness as a function of curvilinear distance along pairs of opposed arms, after unfolding the arms geometrically. Our results reveal a