Radio continuum observations at 1.4 , 4.8 and 8.6 GHz of the two Planetary Nebulae ( PNe ) in the Sagittarius dwarf galaxy reveal the elongated shape of Wray 16-423 and the extreme compactness of He 2-436 .
It is confirmed that He 2-436 is subject to local dust extinction .

Photoionization models for both PNe are obtained from two different codes , allowing theoretical uncertainties to be assessed .
Wray 16-423 , excited by a star of effective temperature 1.07 \times 10 ^ { 5 } K , is an ellipsoidal , matter-bounded nebula , except for a denser sector of solid angle 15 \% .
He 2-436 , excited by a 7 \times 10 ^ { 4 } K star , includes two radiation-bounded shells , with the very dense , low-mass , incomplete , inner shell possibly corresponding to a transitory event .
The continuum jump at the He ^ { + } limit ( \lambda 22.8nm ) agrees with NLTE model stellar atmospheres , despite the Wolf-Rayet nature of the stars .
Both stars are on the same ( H-burning ) evolutionary track of initial mass ( 1.2 \pm 0.1 ) M _ { \odot } and may be twins , with the PN ejection of Wray 16-423 having occured \sim 1500 years before He 2-436 .

The PN abundances re-inforce the common origin of the parent stars , indicating almost identical depletions with respect to solar for O , Ne , Mg , S , Cl , Ar , and K ( -0.55 \pm 0.07 dex ) , and strong overabundances for carbon , particularly in He 2-436 .
He \textsc { i } lines consistently point to large identical overabundances for helium in both PNe .
An excess nitrogen makes Wray 16-423 nearly a Type I PN .

These PNe provide a means to calibrate both metallicity and age of the stellar population of Sagittarius .
They confirm that the youngest , most metal-rich population has an age of 5Gyr and a metallicity of [ Fe/H ] = -0.55 , in agreement with the slope of the red giant branch .