We present the photometric and spectroscopic evolution of supernova (SN) 2019cad during the first ∼100 d 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 ∼8 d, while the r-band peak occurred ∼15 d post-explosion. A second and more prominent peak is reached in all bands at ∼45 d past explosion, followed by a fast decline from ∼60 d. During the first 30 d, the spectra of SN 2019cad show the typical features of a Type Ic SN, however, after 40 d, a blue continuum with prominent lines of Si ii λ6355 and C ii λ6580 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⊙, and an explosion energy of 3.5 × 1051 erg. The light-curve morphology can be reproduced either by a double-peaked 56Ni distribution with an external component of 0.041 M⊙, and an internal component of 0.3 M⊙ or a double-peaked 56Ni distribution plus magnetar model (P ∼ 11 ms and B ∼ 26 × 1014 G). If SN 2019cad were to suffer from significant host reddening (which cannot be ruled out), the 56Ni model would require extreme values, while the magnetar model would still be feasible.

中文翻译：

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双峰 Ic 型超新星 2019cad：另一个类似 SN 2005bf 的天体

我们展示了超新星 (SN) 2019cad 在爆炸后的前 100 天内的光度和光谱演化。基于光曲线形态，我们发现 SN 2019cad 类似于双峰 Ib/c 型 SN 2005bf 和 Ic 型 PTF11mnb。与这两个天体不同的是，SN 2019cad 还在较红的波段中显示了初始峰值。对 g 波段光曲线的检查表明，在 ∼8 d 内达到初始峰值，而 r 波段峰值出现在爆炸后 ∼15 d。在爆炸后约 45 d 时，所有波段都达到第二个更突出的峰值，随后从 约 60 d 快速下降。在前 30 天，SN 2019cad 的光谱显示出 Ic SN 的典型特征，然而，在 40 天后，再次观察到具有 Si ii λ6355 和 C ii λ6580 突出线的蓝色连续谱。将辐射热曲线与流体动力学模型进行比较，我们发现 SN 2019cad 与 11 M⊙ 的前 SN 质量和 3.5 × 1051 erg 的爆炸能量一致。可以通过外部分量为 0.041 M⊙、内部分量为 0.3 M⊙ 的双峰 56Ni 分布或双峰 56Ni 分布加磁星模型（P ∼ 11 ms 和 B ～ 26 × 1014 G)。如果 SN 2019cad 遭受显着的宿主变红（不能排除），56Ni 模型将需要极值，而磁星模型仍然可行。0.3 M⊙ 的内部分量或双峰 56Ni 分布加磁星模型（P ∼ 11 ms 和 B ∼ 26 × 1014 G）。如果 SN 2019cad 遭受显着的宿主变红（不能排除），56Ni 模型将需要极值，而磁星模型仍然可行。0.3 M⊙ 的内部分量或双峰 56Ni 分布加磁星模型（P ∼ 11 ms 和 B ∼ 26 × 1014 G）。如果 SN 2019cad 遭受显着的宿主变红（不能排除），56Ni 模型将需要极值，而磁星模型仍然可行。