Whether a member of a multiple (binary) system or not, precise characterization of the stars in terms of fundamental stellar parameters is an absolute must to understand stellar structure and evolution. We analyse and model stellar spectra to derive atmospheric properties such as effective temperature, chemical composition (abundances), gravity, rotational velocity and other possible surface effects (e.g. metallicity caused by diffusion, emission due to a dust shell, ...). Etc.

Figure 1: Comparison of the observed and modeled (red curve) spectra obtained for the binary HD 11190. The disagreement detected at 3935A shows that the components are also Am peculiar.

The goal of asteroseismology is to probe the internal structure of various types of stars by performing a detailed study of their pulsations. To this aim, we observe and study the light and spectral variations of main-sequence pulsating stars over a time-scale of several seasons and/or years. Accurate interpretation of their (complex) frequency spectra is needed. Specific attention is given to pulsating components of binaries since a majority of stars are found to be in binaries and the link between pulsation and binarity still is an open question. We furthermore study the possible interactions between the stellar pulsations and various other phenomena such as chemical composition and magnetic fields.

Cf. Animatie van J. Sorriaux : pulsationgraphe.wmv.

The radio-astronomical station of Humain which is a part of the Royal Observatory of Belgium, is still a privileged site in Belgium with respect to location and environmental light pollution. It is is therefore a suitable site for the construction of a small optical observatory. The aim is to operate a small but well-equipped optical observatory which is dedicated to a few very specific observational programmes. The goal of project "HOACS" is to perform CCD photometric observations of (intrinsic as well as extrinsic) variable stars under sky conditions which are better than those in the region of Brussels, in support of the ongoing astronomical research projects of the Observatory.

Fig. 1.The optical observatory at the radio-astronomy site of the Royal Observatory of Belgium (Dec. 2008)..

Fig. 2. The two light collectors at the radio-astronomy site of the Royal Observatory of Belgium (Oct. 2008)..