The giant haloes of NGC 6543 and 6826.
Walsh, J. R.; Clegg, R. E. S.; Middlemass, D.
United Kingdom, Netherlands
Abstract
Long-slit spectra at several positions on the large faint haloes of NGC 6543 and 6826 were obtained using IPC spectrograph and CCD detectors. It is shown that the halo emission is thermal in origin, and that the forbidden O III electron temperature is higher in each halo than in its central nebula. Halo electron temperature values of 14,700 K for NGC 6543 and 13,000 K for NGC 6826 are found. Photoionization models cannot completely reproduce the properties of the haloes. The results suggest that the hot fast stellar wind in NGC 6543 has escaped beyond the central nebula and shocked the filamentary halo.