2026ApJ...999..151F

Type Ia supernovae (SNe Ia), thermonuclear explosions of white dwarfs in binary systems, are widely used as standard candles owing to the empirical width-luminosity relation of their light curves. Recent theoretical and observational studies indicate a diversity of progenitor systems and explosion mechanisms. In the supernova remnant (SNR) phase, the diversity in Fe-Kα centroid energies and line luminosities suggests variations in the underlying explosion mechanisms. X-ray spectra of SNRs, which trace shocked ejecta and the surrounding medium, are crucial diagnostics of progenitor systems and explosion physics. Thanks to recent advances in spectroscopy with XRISM, high-resolution X-ray spectroscopy enables 3D diagnostics, including line-of-sight velocities. In this study, we perform 3D hydrodynamic simulations of SNRs from six Type Ia explosion models: two each of pure deflagration, delayed detonation, and double detonation. Each model is evolved for 1000 yr in a uniform medium, consistently accounting for nonequilibrium ionization. Our efficient numerical scheme enables systematic parameter surveys in full 3D. From these models, we synthesize X-ray spectra with ∼1 eV resolution, exceeding XRISM/Resolve's spectral resolution. This work presents the first calculation of X-ray spectra for Type Ia SNRs derived from 3D hydrodynamic simulations that follow the evolution self-consistently from the SN phase into the SNR phase. Our results show intermodel diversity in the X-ray spectra. Asymmetric, red- and blueshifted line profiles arise from the 3D ejecta distributions. These findings demonstrate that 3D SNR modeling can reproduce the observed diversity of Type Ia SNRs and provide qualitative constraints on progenitor systems and explosion mechanisms.