Inferring supernova IIb/Ib/Ic ejecta properties from light curves and spectra: correlations from radiative-transfer models

We present 1D non-local thermodynamic equilibrium time-dependent radiative-transfer simulations for a large grid of supernovae (SNe) IIb/Ib/Ic that result from the terminal explosion of the mass donor in a close-binary system. Our sample covers ejecta masses M-e of 1.7-5.2 M-aS (TM), kinetic energies E-kin of 0.6-5.0 x 10(51) erg, and Ni-56 masses of 0.05-0.30 M-aS (TM). We find a strong correlation between the Ni-56 mass and the photometric properties at maximum, and between the rise time to bolometric maximum and the post-maximum decline rate. We confirm the small scatter in (V - R) at 10 d past R-band maximum. The quantity is comparable to the Doppler velocity measured from He i 5875 at maximum in SNe IIb/Ib, although some scatter arises from the uncertain level of chemical mixing. The O i 7772 line may be used for SNe Ic, but the correspondence deteriorates with higher ejecta mass/energy. We identify a temporal reversal of the Doppler velocity at maximum absorption in the similar to 1.05 mu m feature in all models. The reversal is due to He i alone and could serve as a test for the presence of helium in SNe Ic. Because of variations in composition and ionization, the ejecta opacity shows substantial variations with both velocity and time. This is in part the origin of the offset between our model light curves and the predictions from the Arnett model.