DT Serpentis: neither a symbiotic star nor a planetary nebula associate
  We present an alternative interpretation for the putative symbiotic star DT Serpentis, and its proposed planetary nebula (PN), recently announced by Munari et al. Our analysis is based on their data combined with additional archival data trawled from Virtual Observatory databases. We show that the star known as DT Ser is not a symbiotic star, and is merely superposed on the newly discovered but unrelated background PN. There is no evidence for any periodic variability for DT Ser as expected for a symbiotic star. We further establish that there is no physical association between DT Ser and the PN, which has a considerably higher extinction, befitting the larger distance we estimate. The significantly different radial velocities of the star and nebula also likely preclude any association. Finally, we show that the mid-infrared source detected by the IRAS and WISE surveys is actually coincident with the PN so there is no evidence for DT Ser being a dusty post-AGB star. 
David J. Frew, Joao Bento, Ivan S. Bojicic and Quentin A. Parker
astro-ph.SR