A sample of 198 soft X-ray-selected active galactic nuclei (AGN) from the ROSAT International X-ray Optical Survey (RIXOS) is used to investigate the X-ray luminosity function and its evolution. RIXOS, with a flux limit of 3x10^-14 erg s^-1 cm^-2 (0.5 to 2.0 keV), samples a broad range in redshift over 20 deg^2 of sky, and is almost completely

We have studied spectra of the peculiar B[e] star HD 45677. Examination of the Balmer wings enabled us to determine a value of logg=3.9 indicating a possibly luminosity class V. The weak HeI lines together with the SiII 4128 and 4130A doublet indicate a low rotation velocity in the order of 70km/s, which is much lower than the previously claimed

A method for ``time/frequency'' analysis is shortly described, with a discussion of its limitations in time and frequency resolution, and in sensitivity to noise in the signal. This is then applied to observational data. The data used are the luminosity measurements of the IPHIR experiment, and the velocity measurements performed at the

In this paper we present new chemo-spectro-photometric models of elliptical galaxies in which infall of primordial gas is allowed to occur. They aim to simulate the collapse of a galaxy made of two components, i.e. luminous material and dark matter. The mass of the dark component is assumed to be constant in time, whereas that of the luminous

A systematic structuring of magnetic fields over scales much smaller than the mean free path of photospheric photons may be responsible for the observed asymmetrical Stokes profiles. We explore this possibility by deriving the radiative transfer equation for microstructured magnetic atmospheres (the MISMA approximation). This equation is

We show that the alteration between intervals of cyclic activity and grand minima like the Maunder minimum in the 17th century, which is characteristic for the long-term variation of the solar activity, can be described as on-off intermittency arising in a dymano driven by the instability of magnetic flux tubes in the overshoot layer below the