Measuring mass transfer of AM CVn binaries with a space-based gravitational wave detector

The formation mechanism of AM CVn binary has not been well understood yet. Accurate measurements of the mass transfer rate can help to determine the formation mechanism. But unfortunately such observation by electromagnetic means is quite challenging. One possible formation channel of AM CVn binary is a semi-detached white dwarf binary. Such system emits strong gravitational wave radiation which could be measured by the future space-based detectors. We can simultaneously extract the mass transfer rate and the orbital period from the gravitational wave signal. We employ a post-Keperian waveform model of gravitational wave and carry out a Fisher analysis to estimate the measurement accuracy of mass transfer rate through gravitational wave detection. Special attention is paid to the observed sources in Gaia Data Release 2. We found that we can accurately measure the mass transfer rate for those systems. Comparing to electromagnetic observations, gravitational wave detection improves the accuracy more than one order. Our results imply that the gravitational wave detection will help much in understanding the formation mechanism of AM CVn binaries.