Detection of highly ionized silicon in the planetary nebulae NGC 6302 and NGC 6537

Observations of two high-excitation helium-rich PNs are reported, showing Si VI and Si VII near-IR forbidden line emission from NGC 6302 and forbidden Si VI line emission from NGC 6537. The fluxes observed from NGC 6302 are 3.8 X 10 to the -11 ergs/sq cm sec for the forbidden Si VI line at 1.96 microns and 4.3 X 10 to the -11 ergs/ sq cm sec for the forbidden Si VII line at 2.48 microns. Abundances for Si (5+) and Si (6+) are derived and the central star temperatures are estimated using the abundance ratio. It is found that NGC 6302 probably has the hottest central star of any planetary that has been observed.