THE TIMESCALE CORRELATION METHOD - DISTANCES TO PLANETARY-NEBULAE WITH HALOS

We present deep narrow-band CCD images of six PNe obtained with the Pa lomar 5 m telescope in the light of [N II] lambda 6584 + H alpha and [ O III] lambda 5007. Several previously undetected structures are found , including faint multiple envelope structures surrounding three of th e targets. The inclusion of these sources with data for other multiple envelope PNe published in the literature permit a statistical evaluat ion of the relationship between PN ''shells'' and the thermal pulses o f the PN nucleus. In this paper, we investigate the dynamical timescal e between successive envelopes, tau(dyn), and the nuclear interpulse t imescale, tau(ip). Our results show that the deviations from the relat ion tau(dyn) = tau(ip) can be explained by the uncertainty m the Shklo vsky distance to individual PNe, which is sigma(dsh)/d(sh) similar to 2. By imposing the constraint that tau(dyn) = tau(ip), we find that it is possible to derive a PN distance indicator, which we name the time scale correlation distance, d(TC). The derivation for d(TC) is indepen dent of ad hoc and often unsupported assumptions inherent to the Shklo vsky method.