  It was recently pointed out that very energetic subclasses of supernovae
(SNe), like hypernovae and superluminous SNe, might host ultra-strong magnetic
fields in their core. Such fields may catalyze the production of feebly
interacting particles, changing the predicted emission rates. Here we consider
the case of axion-like particles (ALPs) and show that the predicted large scale
magnetic fields in the core contribute significantly to the ALP production, via
a coherent conversion of thermal photons. Using recent state-of-the-art SN
simulations including magnetohydrodynamics, we find that if ALPs have masses
$m_a \sim {\mathcal O}(10)\, \rm MeV$, their emissivity via magnetic
conversions is over two orders of magnitude larger than previously estimated.
Moreover, the radiative decay of these massive ALPs would lead to a peculiar
delay in the arrival times of the daughter photons. Therefore, high-statistics
gamma-ray satellites can potentially discover MeV ALPs in an unprobed region of
the parameter space and shed light on the magnetohydrodinamical nature of the
SN explosion.
