Axion Emissivity from the Conversion of a Neutron Star into a Strange   Star
  The conversion of neutron matter into strange matter in a neutron star occurs through the non-leptonic weak-interaction process. We study the energy loss of the neutron star by the emission of axions in that process. Owing to that process, the neutron star will liberate the energy which can in no way be negligible as an axion burst. 
In-Saeng Suh and Chul H. Lee