A study of the central stars of planetary nebulae in the magellanic clouds.

The most widely applicable method for the determination of masses for the Central Stars (CSs) of Planetary Nebulae (PNs) consists in comparing their position in the HR diagram to theoretical evolutionary tracks. The main problem is that for Galactic PNs the distance uncertainty dominates the error in the determination of CS luminosities, and, therefore, a set of reliable masses for a sample of CS of PNs has not yet been obtained. We have observed a sample of 35 PNs in the Large Magellanic Cloud (LMC), and 27 PNs in the Small Magellanic Cloud (SMC) with the WFPC2 and STIS instruments on board the Hubble Space Telescope (HST), with the aim of obtaining accurate CS masses. By observing MCs objects, our sample is free from the distance uncertainty that dominates the luminosity determinations of Galactic PNs, and by observing with the HST, we resolve the nebula, and, therefore, detect the CS unambiguously. We have obtained core masses for 16, and 14 CSs in the LMC and SMC respectively, after determining their position in the HR diagram by analyzing medium- and broad-band photometry and using the Zanstra method to calculate the stellar effective temperature. This sample of CS masses is the largest and most reliable set obtained in an extragalactic environment. We find similar average masses in the two galaxies and a hint of a difference in the mass distribution of the two samples. As the immediate precursors of white dwarfs, the study of the mass distribution of CSPNs will help to constrain the initial-to-final mass relation under different metallicity environments.