On the geometrical and kinematic structure of the postnova shell of HR Delphini

The present observational results demonstrate the power of high resolution slit spectroscopy in revealing subarcsec-domain kinematic and geometrical structures in emission nebulae. The emission line structure of the postnova, HR Del, leads to the construction of a detailed expanding shell model, as well as a determination of distance independently from other observations. Pronounced clumping appears to dominate the internal structure of HE Del's polar caps and of the equatorial ring, whose physical conditions appear to be different from those in the caps and to change with a different time scale.