We used long duration, high quality, unresolved (Sun-as-a star) observations collected by the ground based network BiSON and by the instruments GOLF and VIRGO on board the ESA/NASA SOHO satellite to search for solar-cycle-related changes in mode characteristics in velocity and continuum intensity for the frequency range between 2.5 mHz

I report observations of unusually strong photospheric and chromospheric velocity oscillations in and near the leading sunspot of NOAA 10781 on 3 July 2005. I investigate an impinging wave as a possible origin of the velocity pattern and the changes of the wave after the passage through the magnetic fields of the sunspot. The wave pattern found

High-resolution spectroscopy in the near-infrared could become the leading method for discovering extra-solar planets around very low mass stars and brown dwarfs. In order to help to achieve an accuracy of ~m s-1, we are developing a gas cell which consists of a mixture of gases whose absorption spectral lines span all over the near-infrared region

Context. The optical ring-like structure detected by Arp (1965) around M 81 (commonly referenced as “Arp's loop”) represents one of the most spectacular features observed in nearby galaxies. Arp's loop is commonly interpreted as a tail resulting from the tidal interaction between M 81 and M 82. However, since its discovery the nature of this

Nuclear disks and rings are frequent galaxy substructures, for a wide range of morphological types [from S0 to Sc, see e.g., 1, 2]. We have investigated the possible minor-merger origin of inner disks and rings in spiral galaxies through collisionless N-body simulations. The models confirm that minor mergers can drive the formation of thin

We investigate the thermodynamical and magnetic properties of a ``dark-cored" fibril seen in the chromospheric Ca II IR line at 854.2 nm to determine the physical process behind its appearance. We analyse a time series of spectropolarimetric observations obtained in the Ca II IR line at 854.2 nm and the photospheric Fe I line at 630.25 nm. We