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Existence of intrinsic correlations among physical parameters of Type Iax supernovae

Ascertain whether statistically robust correlations exist between (i) the V-band peak absolute magnitude and the photospheric velocity and (ii) the V-band decline-rate parameter Δm15(V) and the photospheric velocity for Type Iax supernovae, overcoming previous limitations from small samples and outliers.

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Background

Unlike normal SNe Ia, Type Iax supernovae do not follow the Phillips relation, prompting searches for alternative empirical correlations that could organize their diversity or serve as diagnostics of the explosion physics. Prior efforts examined relationships such as peak V-band luminosity versus photospheric velocity and Δm15(V) versus photospheric velocity.

However, small sample sizes and notable outliers (e.g., SNe 2009ku and 2014ck) have prevented firm conclusions. Establishing or refuting these correlations would meaningfully constrain models of the Iax subclass and clarify whether their physical properties vary along systematic trends.

References

Previously, there have been attempts to find such pairs of correlated parameters, such as the absolute magnitude of the peak in the V band and the photospheric velocity, or the $\Delta m_{15}(V)$ parameter and the photospheric velocity (, ). These studies, however, could not unambiguously determine the existence of such correlations due to the limited sample size and the existence of outliers, such as SNe 2009ku \citep{SN2009ku}, or 2014ck \citep{SN14ck-Iax-relations-2}.

— SN 2022xlp: The second-known well-observed, intermediate-luminosity Iax supernova (2509.07717 - Bánhidi et al., 9 Sep 2025) in Section 1 (Introduction)