Population Boundaries for Galactic White Dwarf Binaries inLISA’s Amplitude‐Frequency Domain

Detached, inspiraling and semi-detached, mass-transferring double white dwarf(DWD) binary systems are both expected to be important sources for the proposedspace-based gravitational-wave detector, LISA. The mass-radius relationship ofindividual white dwarf stars in combination with the constraints imposed byRoche geometries permit us to identify population boundaries for DWD systems inLISA's ``absolute'' amplitude-frequency diagram. With five key populationboundaries in place, we are able to identify four principal populationsub-domains, including one sub-domain that identifies where progenitors of TypeIa supernovae will reside. Given one full year of uninterrupted operation, LISAshould be able to measure the rate at which the gravitational-wave frequency$f$ and, hence, the orbital period is changing in the highest frequencysubpopulation of our Galaxy's DWD systems. We provide a formula by which thedistance to each DWD system in this subpopulation can be determined; inaddition, we show how the masses of the individual white dwarf stars inmass-transferring systems may be calculated.Comment: 23 pages, 3 figures, Accepted for publication in Astrophysical Journa