The delayed-detonation explosion mechanism applied to a Chandrasekhar-mass white dwarf offers a very attractive model to explain the inferred characteristics of Type Ia supernovae (SNe Ia). The resulting ejecta are chemically stratified, have the same mass and roughly the same asymptotic kinetic energy, but exhibit a range in 56Ni mass. We investigate the contemporaneous photometric and spectroscopic properties of a sequence of delayed-detonation models, characterized by 56Ni masses between 0.18 and 0.81 Msun. Starting at 1d after explosion, we perform the full non-LTE, time-dependent radiative transfer with the code CMFGEN, with an accurate treatment of line blanketing, and compare our results to SNe Ia at bolometric maximum. Despite the 1D treatment, our approach delivers an excellent agreement to observations. We recover the range of SN Ia luminosities, colours, and spectral characteristics from the near-UV to 1 micron, for standard as well as low-luminosity 91bg-like SNe Ia. Our models predict an increase in rise time to peak with increasing 56Ni mass, from ~15 to ~21d, yield peak bolometric luminosities that match Arnett's rule to within 10%, and reproduce the much smaller scatter in near-IR magnitudes compared to the optical. We reproduce the morphology of individual spectral features, the stiff dependence of the R(Si) spectroscopic ratio on 56Ni mass, and the onset of blanketing from TiII/ScII in low-luminosity SNe Ia with a 56Ni mass <0.3 Msun. We find that ionization effects, which often dominate over abundance variations, can produce high-velocity features in CaII lines, even in 1D. Distinguishing between different SN Ia explosion mechanisms is a considerable challenge but the results presented here provide additional support to the viability of the delayed-detonation model.
The full paper is available here: arXiv, ADS
The maximum-light spectra of the DDC model series can be downloaded here: SNIa_DDC_series_B13.tgz (174K). This also includes the hydro grid (velocity, density) and abundance profiles for 56Ni, Ni, Si, and O within 20-60 s from explosion.
The optical and NIR passbands used to compute UBVRIJHKs magnitudes are available here: optnir_passbands.tgz.