Galactic double white dwarfs (DWD) in close orbits are not only the most numerous and guaranteed gravitational wave (GW) sources for the next generation of space-based interferometers, but are also currently observed electromagnetically. Recently, the Extremely Low Mass white dwarf (WD) survey successfully quintupled the number of such detached tight binaries. The tightest of them, SDSS J065133.33+284423.3 (J0651), has an orbital period of only ~12 min.
Even though tidal signatures in detached WD binaries are readily visible in electromagnetic data (e.g. J0651), the orbital evolution of these systems is typically assumed to be driven by GW-emission alone, calculated for point masses.
In this talk I will discuss a number of important tidal effects in WD binaries. Specifically, I will show how mass estimates based on apsidal precession measurements in eccentric binaries can be upwardly biased if tidal effects are ignored. Moving away from the non-dissipative regime of apsidal precession, I will examine the role of dynamic, non-adiabatic tides in the J0651 system, especially in the context of its measured orbital decay rate being consistent with GW-driven inspiral. I will show how dynamic tides potentially play a key role in explaining this agreement through the anti-resonance locking phenomenon.