Abstract

It is generally believed that Type Ia supernovae are thermonuclear explosions of carbon–oxygen white dwarfs (WDs). However, there is currently no consensus regarding the events leading to the explosion. A binary WD (WD–WD) merger is a possible progenitor of Type Ia supernovae. Space-based gravitational wave (GW) detectors with considerable sensitivity in the decihertz range such as the DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) can observe WD–WD mergers directly. Therefore, access to the decihertz band of GWs would enable multi-messenger observations of Type Ia supernovae to determine their progenitors and explosion mechanism. In this paper, we consider the event rate of WD–WD mergers and the minimum detection range to observe one WD–WD merger per year, using a nearby galaxy catalog and the relation between Ia supernovae and their host galaxies. Furthermore, we calculate DECIGO’s ability to localize WD–WD mergers and to determine the masses of binary mergers. We estimate that a decihertz GW observatory can detect GWs with amplitudes of h ∼ 10⁻²⁰ [Hz^−1/2] at 0.01–0.1 Hz, which is 1000 times higher than the detection limit of DECIGO. Assuming the progenitors of Ia supernovae are merging WD–WD (1 M_⊙ and 0.8 M_⊙), DECIGO is expected to detect 6600 WD–WD mergers within z = 0.08, and identify the host galaxies of such WD–WD mergers within z ∼ 0.065 using GW detections alone.