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In this work we report new high quality spectroscopic data for a sample of PNe in the SMC, aiming to derive physical parameters and chemical abundances, in particular to settle the question concerning the oxygen discrepancy found for type I planetaries with respect to stars and HII regions.
In this work we analyze the beryllium-iron chemical diagram from the point of view of non-LTE effects. Be abundances were re-calculated by considering non-LTE corrections in ionization equilibrium (logg) and Fe abundances ([Fe/H]). These corrections seem do not affect the linear relation between Be-Fe for metal-poor stars already found in the literature for LTE derived abundances.
We have obtained a large sample of PN with accurately determined helium abundances, as well as abundances of several heavy elements. The nebulae are located in the solar neighbourhood, in the galactic bulge, disk and anticentre, and in the Magellanic Clouds. The abundances are analyzed both in terms of the nucleosynthesis of intermediate mass stars and the chemical evolution of the host galaxies. In particular, correlations between the He/H ratio and the abundances of N and O are used as constraints of the nucleosynthetic processes occurring in the progenitor stars.
Planetary nebulae (PN) are favourite objects in the study of stellar populations both in the Galaxy and in other objects as well, due to their high brightness and the considerable range in their kinematic properties and chemical composition. In this work, we take into account available data samples of PN in Local Group galaxies and compare the derived information from different objects, particularly regarding their chemical composition, space distribution, kinematics, and the PN luminosity function.
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