How photon astronomy affects searches for continuous gravitational waves

Due to their computational limitations, searches for continuous gravitational waves (GW) are significantly more sensitive when informed by observational photon astronomy and theoretical astrophysics. Indirect upper limits on GW emission inferred from photon astronomy indicate which objects are more interesting for GW searches, and also set sensitivity milestones which GW searches need to beat to be considered GW astronomy. How GW results are interpreted depends on previous indirect limits and the theory of astrophysical GW emission mechanisms. I describe the interplay between these issues for the four types of continuous GWs searches, and show how photon astronomers can help the growing field of GW astronomy now and in the near future.