On The Origin of Supernova-less Long Gamma-Ray Bursts

The fraction of long duration gamma ray bursts (GRBs) without an associated bright supernovae (SNe) at small redshifts $(z 4)$, however, favors phase transition of neutron stars to quark stars in high mass X-ray binaries (HMXBs), rather than merger of neutron stars, as the origin of SN-less GRBs.