GW frequency and strain as a function of time derived from the 3D hydrodynamical simulation of the 1.05 M_⊙ and 0.7 M_⊙ carbon-oxygen white dwarf binary in Pakmor et al. (2022), in which the primary undergoes double detonation. Top panels: Key steps of the double-detonation mechanism. t = −98.8 s is the onset of the mass transfer from the secondary (the visibly larger, fluffier white dwarf) onto the primary (the more compact of the two). t = 0 s is the helium-shell ignition on the primary. At t = 1.3 s the helium detonation wraps around the primary, triggering the detonation of the primary’s carbon-oxygen core. At t = 4.9 s, the carbon detonation completely burns the primary (resulting in a SN Ia) and triggers helium-shell ignition on the secondary. Middle panel: Evolution of GW strain. The A₊^z GW polarisation amplitude is computed based on the output of the hydrodynamical simulation following the Morán-Fraile et al. (2023) method and assuming a distance of 8.2 kpc. The solid black line shows the ‘one-explosion’ model, in which only the primary undergoes double detonation; the dashed line represents the ‘two-explosion’ model, in which the explosion of the primary also triggers a double detonation of the secondary. In both cases, after the SN Ia explosion, the amplitude levels off at a constant value until the end of the simulation, which represents the homogeneous expansion of the supernova ejecta. For comparison, the thick grey-shaded line represents a monochromatic signal of 92 Hz frequency and of equivalent amplitude. The inset shows a zoomed-in view between –0.5 s and 7 s. Bottom panel: Evolution of the GW frequency (solid line) that we computed directly from the binary separation obtained from the hydrodynamical simulation.