Double white dwarfs (DWDs) in the Laser Interferometer Space Antenna (LISA) band are major Galactic gravitational-wave sources, yet the standard isolated-binary picture is incomplete: a substantial fraction of tight DWD progenitors may reside in hierarchical triples. Triple evolution can therefore alter both the production rate and the parameter distributions of LISA DWDs. Using the multiple stellar evolution (MSE) code, we study how the adiabatic mass-loss model (Ge model) and the SCATTER formalism for triple common-envelope evolution affect triple-channel LISA DWD formation. Our main model (model 1) evolves ${10}^5$ triples adopting both ingredients. Three additional triple control models, each with ${10}^4$ triples, vary the mass-transfer stability criterion to the original MSE polytropic model, remove the SCATTER formalism, or adopt low metallicity ($Z=0.001$). We also evolve ${10}^6$ isolated binaries with the same binary-evolution framework to provide a binary-channel reference. Systems classified as dynamically unstable under the polytropic model can instead undergo stable Roche-lobe overflow under the Ge model. This sustained mass transfer modifies the donor envelope, reduces its binding energy, and helps the subsequent common-envelope phase form a close DWD rather than a merger. The Ge model increases the triple-channel LISA DWD yield by about 60% relative to the polytropic model, whereas the SCATTER formalism changes the integrated yield by only about 3%. After residence-time weighting, triples contribute about $1.3\times {10}^7$ LISA-band DWDs, including $1.4\times {10}^4$ individually resolvable systems. In the combined triple-plus-binary normalization, the binary channel contributes $3.1\times {10}^6$ LISA-band DWDs and $4.7\times {10}^3$ individually resolvable systems. These values are the binary share of the combined population, not the binary-only Galactic estimate. The main triple model has a flatter, higher-$q$ mass-ratio distribution than the polytropic-model triple populations, is dominated by He-CO and He-He binaries, and produces rare eccentric systems only when a tertiary star remains bound.

Close

PrevNext

View figure in article

• Formation & evolution of stars & galaxies
• Gravitational wave sources
• Gravitational waves
• Stars
• Numerical simulations in gravitation & astrophysics