The double-peaked type Ic Supernova 2019cad: another SN 2005bf-like object

TL;DR

SN 2019cad is a double-peaked type Ic supernova with unique red-band initial peak and spectral evolution, modeled by complex nickel distribution or magnetar energy input, providing insights into explosion mechanisms.

Contribution

This study presents detailed photometric and spectroscopic analysis of SN 2019cad, revealing its similarity to SN 2005bf and proposing models involving nickel distribution and magnetar energy.

Findings

SN 2019cad shows a double-peaked light curve with an initial red-band peak.

Spectral features evolve from type Ic to features indicating additional heating after 40 days.

Hydrodynamical models suggest a 11 M$_{\ m\odot}$ progenitor and explosion energy of 3.5×10^{51} erg.

Abstract

We present the photometric and spectroscopic evolution of supernova (SN) 2019cad during the first $\sim100$ days from explosion. Based on the light curve morphology, we find that SN 2019cad resembles the double-peaked type Ib/c SN 2005bf and the type Ic PTF11mnb. Unlike those two objects, SN 2019cad also shows the initial peak in the redder bands. Inspection of the g-band light curve indicates the initial peak is reached in $\sim8$ days, while the r band peak occurred $\sim15$ days post-explosion. A second and more prominent peak is reached in all bands at $\sim45$ days past explosion, followed by and fast decline from $\sim60$ days. During the first 30 days, the spectra of SN 2019cad show the typical features of a type Ic SN, however, after 40 days, a blue continuum with prominent lines of Si II ${\lambda}6355$ and C II ${\lambda}6580$ is observed again. Comparing the bolometric light curve to hydrodynamical models, we find that SN 2019cad is consistent with a pre-SN mass of 11 M$_{\odot}$, and an explosion energy of $3.5\times 10^{51}$ erg. The light curve morphology can be reproduced either by a double-peaked $^{56}$Ni distribution with an external component of 0.041 M$_{\odot}$ and an internal component of 0.3 M$_{\odot}$ or a double-peaked $^{56}$Ni distribution plus magnetar model (P $\sim11$ ms and B $\sim26\times 10^{14}$ G). If SN 2019cad were to suffer from significant host reddening (which cannot be ruled out), the $^{56}$Ni model would require extreme values, while the magnetar model would still be feasible.