Magnetar Engines in Broad-lined Type Ic Supernovae and a Unified Picture for Magnetar-powered Stripped-envelope Supernovae

We model the multiband lightcurves of 80 broad-lined Type Ic supernovae (SNe Ic-BL), including 11 associated with long-duration gamma-ray bursts (lGRBs), using a magnetar engine model with 56 Ni decay. The data are all consistent with a magnetar engine, yielding high-quality fits across the sample. The medians with 1 σ regions for key parameters are initial spin period P i ∼ 2.0 3 − 0.95 + 1.81 ms , magnetic field B p ∼ 3.9 7 − 1.42 + 3.07 × 1 0 15 G , ejecta mass M ej ∼ 2.3 0 − 1.01 + 1.46 M ⊙ , and 56 Ni mass M Ni ∼ 0.1 8 − 0.09 + 0.14 M ⊙ , with strong correlations observed for both M ej − P i (anticorrelation) and M Ni − M ej (correlation). Comparing the lGRB-associated and non-lGRB-associated samples using fitting parameters, we find no significant difference, although the lGRB-associated sample is slightly brighter, possibly due to observational bias (dimmer ones overshone by afterglow). Relative to ordinary Type Ic SNe, SNe Ic-BL have similar 56 Ni and ejecta masses, suggesting comparable pre-SN progenitor properties, with differences possibly arising from the presence of a magnetar engine that governs supernova (SN) dynamics. In comparison with other possible magnetar-powered stripped-envelope SNe (SESNe), including Type Ic superluminous SNe (SLSNe Ic) and fast blue optical transients (FBOTs), we confirm a strong universal M ej − P i correlation, indicating a common origin. SNe Ic-BL and SLSNe Ic have similar ejecta mass distributions, typically M ej ≳ 0.5 M ⊙ , while FBOTs mostly lie below this value. Differences between SNe Ic-BL and SLSNe Ic may arise from magnetar properties, with SN Ic-BL magnetars rotating faster and having stronger fields. Moreover, the P i − B p distribution of lGRB magnetars largely overlaps with that of SN Ic-BL magnetars. Motivated by binary simulation results, we propose a unified physical classification and progenitor framework for magnetar-powered SNe and ordinary SESNe.