Thorne-Żytkow object

A Thorne-Żytkow object (TZO or TŻO) is a theoretical star type consisting of a giant star with a neutron star as its core. One could result from a neutron star colliding with a red giant or supergiant; if the two come into contact, drag could eventually bring the neutron star to the center after some time with the neutron star within the giant star's envelope, orbiting the giant star's core. Alternately, this could happen when a neutron star is swallowed during a binary companion's expansion into such a giant star. It is assumed such a TZO would be a phase, perhaps leading to a more conventional neutron star with an accretion disk. A number of candidates exist, among them the star HV 2112 identified as such in 2014.