2006PASP..118.1528L

Because of the similarity of the primary star of HS 1136+6646 to the planetary nebula central star BE Ursae Majoris, we performed wide-field imaging of the former with an Hα filter. No nebulosity was detected. On the other hand, the point-spread function of the star appears extended. A partially resolved red component is detected in an image from the five-band Sloan Digital Sky Survey. Most importantly, a companion is easily resolved in a Hubble Space Telescope acquisition image from the published Space Telescope Imaging Spectrograph observations. A companion to the precataclysmic binary is present at a separation of 1".349 at a position angle of 54°.4. Evidence indicates that it is likely of spectral type K. We cannot demonstrate conclusively that this component has common proper motion with the close binary. However, the similar apparent z magnitudes and spectral types of HS 1136+6646B and the resolved component make it likely that we have, in reality, a hierarchical triple system. In any case, the presence of this component needs to be taken into account in future ground-based studies.