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

Abstract

We present 1-D 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 d , kinetic energies E kin of 0.6-5.0ˆ10 51 erg, and 56 Ni masses of 0.05-0.30 M d . We find a strong correlation between the 56 Ni 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 V m " a 2E kin {M e is comparable to the Doppler velocity measured from He I 5875Å at maximum in SNe IIb/Ib, although some scatter arises from the uncertain level of chemical mixing.The O I 7772Å 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 " 1.05 µm 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 ionisation, 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.

iPTF15dtg: a double-peaked Type Ic supernova from a massive progenitor

“…This is due to the difficulty of completely stripping the He layer with the current evolutionary models of single stars. However, we note that the He fraction of the progenitor stars of SE SNe should not significantly affect the bolometric light curve from the hydrodynamical model, as shown by Dessart et al (2016) with their He-rich and He-poor models from binaries. The parameter of the progenitor star that mainly affects the SN bolometric light curve is its final mass, which we tuned to be ∼12 M .…”

“…The model assumes constant opacity κ, which we set to 0.07 cm 2 g −1 . This value was also used by Cano (2013) and Taddia et al (2015a), since it is appropriate for the electron scattering in H-poor SNe (the assumption of a constant opacity is obviously a limitation of this model, see e.g., Wheeler et al 2015;and Dessart et al 2016). The model also assumes that the 56 Ni is located at the center of the ejecta.…”

Pre-nebular Light Curves of SNe I

“…The energy where this dip occurs depends both on the temperature and density of the supernova ejecta, and the leakage opacity may vary both up and down as the ejecta expand, ranging within the visible bands from below 0.001 cm g r < --), the opacity in Figure 3 shows gaps with values log 2 10 k~-, around and below the LTE temperature of 1 eV. Guided by Pinto & Eastman (2000b), we assume that this property is set by atomic structure and will be qualitatively true for non-LTE distributions of states; see also Dessart et al (2014Dessart et al ( , 2015Dessart et al ( , 2016, who find that their spectra are surprisingly insensitive to the opacity controlling the radiation flow.…”

“…There is no indication of any bumps due to collision of ejecta with circumsupernova matter, as with type Ibn and IIn events. The smoothness of 1D theoretical light curves result from ad hoc "box-car" mixing; simulations without such mixing are not smooth (Pinto & Eastman 2000a;Dessart et al 2015Dessart et al , 2016. Explosions are unstable to 3D mixing, which can leave an imprint on the young supernova remnant as well as the light curve (Arnett & Meakin 2016).…”

“…For these supernovae, we have bolometric (or near bolometric) light curves, so we may minimize issues of frequency-dependent atmospheric physics. This approach, which assumes three-dimensional (3D) incomplete mixing during the explosion (Arnett & Meakin 2016), is thus different from and a natural complement to a 1D, timedependent stellar atmosphere approach, such as those of Blondin et al (2013) and Dessart et al (2015Dessart et al ( , 2016.…”