Detectability of the IIb–Ib age offset with Hα-based environmental diagnostics

Determine whether Hα-based environmental age diagnostics can robustly recover the modest median explosion-age offset between Type IIb and Type Ib core-collapse supernovae predicted by binary population synthesis models, or whether such small differences are effectively absorbed by the systematic uncertainties inherent to Hα-based methods.

Background

The study finds that Type Ic supernova environments are systematically younger than those of Types II(P), IIb, and Ib, while the latter three show no significant separation in environmental age based on local Hα luminosity.

Binary population synthesis (e.g., Souropanis et al. 2025) predicts a modest shift in the median explosion ages between Type IIb and Type Ib supernovae at roughly solar metallicity. The authors argue that Hα-based age indicators may be sensitive to clear differences (such as for Type Ic) but may struggle to resolve smaller offsets among Types IIb and Ib.

This raises a specific unresolved question: whether Hα-based environmental age diagnostics can detect the small predicted IIb–Ib age offset, or if methodological systematics (e.g., chance alignment, ionizing-photon leakage, star-formation history complexities) mask such differences.