Applying the metallicity-dependent binary fraction to double white dwarf formation: Implications for LISA

Understand

Short-period double white dwarf (DWD) binaries will be the most prolific source of gravitational waves (GWs) for the Laser Interferometer Space Antenna (LISA).

• DWDs with GW frequencies below $\sim1$ mHz will be the dominant contributor to a stochastic foreground caused by overlapping GW signals.
• Population modeling of Galactic DWDs typically assumes a binary fraction of 50% and a log-uniform Zero Age Main Sequence (ZAMS) orbital period distribution.
• However, recent observations have shown that the binary fraction of close, solar-type stars exhibits a strong anti-correlation with metallicity which modulates the ZAMS orbital period distribution below $10^4$ days.