Origin of the rarity of clear bipolar structures in core-collapse supernovae

Determine why not all core-collapse supernovae exhibit a clear bipolar structure if a progenitor’s natal spin can be inclined to the binary orbital angular momentum and can remain oriented in that direction until core collapse.

Background

As an alternative to late directional rotational accretion, the paper proposes that the progenitor of SN 1987A may have been born with a spin inclined by approximately 45 degrees to the binary angular momentum, with the inner core preserving that orientation until collapse. This could explain the misalignment between SN 1987A’s bipolar Keyhole and its triple-ring system.

The paper leaves unresolved why this type of inclined-spin configuration does not produce similarly clear bipolar structures in all core-collapse supernovae. The question is directly connected to the broader applicability of the proposed explanation and to the diversity of observed core-collapse supernova morphologies.