No Pulsar Wind Nebula in the Southern Blowout Region of the Cygnus Loop

Abstract We report on optical observations of the Katsuda et al. candidate X-ray pulsar and pulsar wind nebula in the Cygnus Loop supernova remnant. We determine that the point source suggested to be a pulsar is actually the nucleus of a Seyfert 1 galaxy at redshift z = 0.2080, while the diffuse X-ray source, which is displaced by 2.′6 from the point source, is a cluster of galaxies at z = 0.223. We also analyze an archival follow-up XMM-Newton observation of this field, the results of which support our extragalactic identifications. Thus, a long expected neutron star remnant of the Cygnus Loop explosion remains elusive.