SIMBAD references

Infrared spectra taken with the Short Wavelength Spectrometer on board ISO and UV observations with IUE of planetary nebulae BD+30 3639 and NGC 6543 are presented. The extinction derived using infrared lines for BD+30 3639 is E_B–V=0.34, slightly higher than previous determinations. For ∇6 the extinction found from the hydrogen lines is E_B–V=0.07. Infrared, optical and ultraviolet data have been used to derive the physical parameters of the nebula. BD+30 3639 has an average T_e=8500K and N_e=11000cm³. In the case of NGC 6543 a T_e=8200K and N_e=5000cm³ have been found, in agreement with previous determinations. The element abundances have been derived and compared to those found in the Sun and O, B stars. This comparison gives a hint of the mass of the progenitor stars from which they evolved.