Vol. 600
In section 7. Stellar structure and evolution

A VLT-ULTRACAM study of the fast optical quasi-periodic oscillations in the polar V834 Centauri

In this paper Mouchet and collaborators observed the polar system V834 Cen with the ESO-VLT equipped with the ULTRACAM instrument in a fast timing mode. Observations were taken simultaneously in the r' and u' bands, as well as across the HeII (4686A) emission line, with a temporal resolution of 2 ms. The optical light curves show clear signs of quasi-periodic oscillations (QPO) at a period of ~2 s. The authors interpret the QPOs as originating from cyclotron emission of the accretion column created by the white dwarf magnetic field. The oscillations are not strictly periodic, probably due to the superposition of individual blobs of matter falling on the white dwarf along different magnetic field lines.