The tidal precession effect on the gravitational waves from eccentric double white dwarfs*

The tidal effect governs the orbital precession of eccentric binaries at small separations. With the upcoming space-based gravitational wave detector (LISA), we can expect to detect the gravitational wave signals from eccentric double white dwarf systems within our galaxy in the near future. While previous studies mainly focus on the precession effect from the equilibrium component of the tide, we study the full tidal contribution including the dynamical component. In this talk, I will discuss both the resonant and off-resonant dynamical tide precession effects. The former occurs when the orbital frequency or its higher harmonics come near the natural frequency of a pulsation mode of the white dwarf, which can cause a strong precession effect distinct from that of the other contributing factors. We show that these resonant regions can cover about 10% of the frequency space for orbits with close separations. On the other hand, the off-resonant effect causes a small extra orbital precession of up to 20% of the overall amount. This effect degenerates with the uncertainties of the eccentricity within lower mass systems, making it unmeasurable in the gravitational wave signal. For higher mass systems, the radiation reaction effect becomes significant enough to constrain the eccentricity, allowing the measurement of the dynamical tide.