  Next generation gravitational wave detectors will start taking data in the
near future. Here we discuss the chances to detect the continuous emission from
r-mode oscillations in compact stars and study which properties of compact
stars we can infer from such novel data. In particular we show that the
combination of the gravitational wave data with electromagnetic multi-messenger
observations could give us detailed insight into compact star properties,
ranging from precise mass-radius measurements to the determination of the
equation of state and the phase structure of dense matter.
