CAOSP abstracts, Volume: 55, No.: 3, year: 2025

Abstract: To date, a large number of variable stars have been classified as eclipsing binaries. Large photometric surveys such as Kepler, TESS or Plato are finding thousands of new candidates. However, only a few have been studied in detail. Moreover, photometric data provide no information about the masses of stars, which is the key information about the system. Spectroscopic observations and radial-velocity measurements are required for this purpose. Therefore, ground-based spectroscopy is a useful supplementary source of data for large photometric surveys. Additionally, a few interesting phenomena can be discovered using radial velocity curves, which are hardly detectable on the light curve. Binary orbits could be significantly eccentric, the system could have an unusually low mass ratio, or it would not have to be binary at all. Here, we present some interesting systems observed using the OES spectrograph attached at the Perek 2-meter telescope in Ondřejov together with their light curves obtained by the TESS mission.