Studying the Power Sources Behind Type Ic Supernovae

TL;DR

This work develops and applies a fast, analytic-light-curve framework (SNLC) to dissect the energy sources powering Type Ic-BL supernovae. By simulating a broad grid of progenitor masses, ejecta velocities, nickel masses and distributions, and incorporating four energy sources (Ni decay, external shocks, magnetar/pulsar injection, and fallback), the authors find that Ni decay alone cannot reproduce Ic-BL peak features and that shock interactions with a clumpy wind or shell can dominate the peak, with mixed models offering a wide range of light-curve shapes. The results indicate that early-time light curves are best explained by shock heating while late-time emission is more Ni-decay–driven, though full disentanglement requires multi-band, spectral, and late-time data. The study highlights degeneracies between opacity, mass, and velocity, and emphasizes the need for multi-dimensional modeling and spectra to robustly constrain explosion mechanisms for Ic-BL supernovae.

Abstract

Astrophysical transients can be powered by a broad range of energy sources including shock-heating (internal and external shocks), decay of radioactive isotopes, and long-lived central engines (magnetar and fallback). The dominant energy source for astrophysical transients depends on the nature of the explosive engine and its progenitor. To model all transients, light-curve codes must include all of these energy sources. Here we present a supernova light-curve code implementing analytic source models to compare the role of different energy sources in these transients. To demonstrate the utility of this code, we conduct an extensive study of type Ic broad-line supernovae. A diverse set of energy sources have been linked to Ic broad-line supernovae making them an excellent candidate for this light-curve code. In this paper, we explore which features of the explosion (mass, velocity, etc.) affect the type Ic supernovae light-curves, focusing on shock-interaction and radioactive decay energy sources. Although the explosion properties under both energy sources can be tuned to match the peak emission, matching the light-curve evolution in many Ic broad-line supernovae requires fine-tuned conditions. We find that shock interactions in the stellar wind are likely to be the dominant energy source at peak for these supernovae.

Figures (16)

• Figure 1: Initial velocity and temperature profiles for a sampling of our models. We maintain the same profile as the M25aE7.42 from 2018ApJ...856...63F and scale up the velocity. The temperature scales with the density (mass) and velocity to mimic internal shock-heating.
• Figure 2: Temperature profiles at 0, 1, 2, and 5 days for two nickel powered simulations. The rapid cooling from expansion occurs in the first day. The position of the strong temperature gradient (enclosed mass of 0.3 M$_\odot$ for the $f_{\rm mix}=1$ case and $\sim 1$,M$_\odot$ for the $f_{\rm mix}=0.25$ case) shows the rough position of the $^{56}$Ni decay. With time, this energy begins to diffuse to the photosphere.
• Figure 3: Photospheric properties for the ni0.2f1m1 models varying $f_{\rm vel}$ from 1 to 8. The black line stops when the photosphere has reached the center of the star.
• Figure 4: Bolometric light-curves for a subset of $f_{\rm vel} = 1.0$ models using two different values for $f_{\rm mass} (0.5, 1.0)$ and 3 different mixing parameters: $f_{\rm mix} = 1, 0.25, 0.1$. For $f_{\rm mix} = 1$, the $^{56}$Ni is located in the innermost ejecta. For the $f_{\rm mass} = 0.5, f_{\rm mix}=0.1$ model, it is nearly mixed out to the outer edge. The inset plot shows the same data without the logarithmic y-axis.
• Figure 5: Bolometric light-curves for heavily mixed nickel powered models with four different velocity models: $f_{\rm vel} = 1,2,4 {\rm \, and }\, 8$. As the velocity increases, the light-curve peaks earlier, but is dimmer. The inset plot shows the same data without the logarithmic y-axis.