We present an analysis of the UV ( IUE ) spectra of the central stars of Hb7 and Sp3 .
Comparison with the IUE spectrum of the standard star HD 93205 leads to a spectral classification of O3V for these stars , with an effective temperature of 50 , 000 K. From the P-Cygni profiles of CIV ( 1550Å ) , we derive stellar wind velocities and mass loss rates of - 1317 kms ^ { -1 } \pm 300 kms ^ { -1 } and 2.9X10 ^ { -8 } M _ { \odot } yr ^ { -1 } and - 1603 kms ^ { -1 } \pm 400 kms ^ { -1 } and 7X10 ^ { -9 } M _ { \odot } yr ^ { -1 } for Hb7 and Sp3 respectively .
From all the available data , we reconstruct the spectral energy distribution of Hb7 and Sp3 .