Twin Peaks: SN 2021uvy and SN 2022hgk in the Landscape of Double-peaked Stripped Envelope Supernovae

Year: 2025 DOI: 10.1088/1538-3873/ae02c6

In recent years, a class of stripped-envelope supernovae (SESNe) has emerged that show two distinct peaks in their light curves, where the first peak cannot be attributed to shock cooling emission. Such peculiar supernovae are often studied individually, explained by invoking some combination of powering mechanisms. However, they have seldom been discussed in the broader context of double-peaked SESNe. In this paper, we attempt to form a picture of the landscape of double-peaked SESNe and their powering mechanisms by adding two more objects—SN 2021uvy and SN 2022hgk. SN 2021uvy is a broad and luminous SN Ib with an unusually long rise of the first peak and constant color evolution with rising photospheric temperature during the second peak. Although its first peak is similar to that of SN 2019stc, their second peaks differ in properties, making it unique among double-peaked objects. SN 2022hgk shows striking photometric similarity to SN 2019cad and spectroscopic similarity to SN 2005bf, both of which have been suggested to be powered by a double-nickel distribution in their ejecta. We analyze their light curves and colors, compare them with a sample of other double-peaked published supernovae for which we have additional data, and analyze the light curve parameters of the sample. We observe a correlation (p-value ∼ 0.025) between the peak absolute magnitudes of the first and second peaks. The sample shows variety in the photometric and spectroscopic properties, and thus no single definitive powering mechanism applies to the whole sample. However, sub-groups of similarity exist that can be explained by mechanisms like the double-nickel distribution, magnetar central engine, interaction, and fallback accretion. We also map out the duration between the peaks (Δt²¹) versus the difference between peak absolute magnitudes (ΔM²¹) as a phase-space that could potentially delineate the most promising powering mechanisms for the double-peaked SESNe.