Gravitational waves from planets are undetectably small. They do it through gravity directly, as sandworm101 says. You can model it with pure Newtonian gravity

Gravitational waves from planets are undetectably small. They do it through gravity directly, as sandworm101 says. You can model it with pure Newtonian gravity and get resonance effects just fine. See for instance: https://www.youtube.com/watch?v=Qyn64b4LNJ0 https://www.youtube.com/watch?v=Qyn64b4LNJ0