The Low‐ and Intermediate‐Mass Stellar Population in the Small Magellanic Cloud: The Central Stars of Planetary Nebulae

Abstract

We present a study on the central stars (CSs) of planetary nebulae (PNs) observed in the Small Magellanic Cloud (SMC) with the Space Telescope Imaging Spectrograph (STIS) instrument on board the Hubble Space Telescope (HST). The stellar magnitudes have been measured using broadband photometry, and Zanstra analysis of the nebulae provided the stellar temperatures. From the location of the CSs on the H-R diagram, and by comparing the observed CSs with current models of stellar evolution, we infer the CS masses. We examine closely the possibility of light contamination in the bandpass from an unrecognized stellar companion, and we establish strong constraints on the existence and nature of any binary companion. We find an average mass of 0.63 M☉, which is similar to the mass obtained for a sample of CSs in the LMC (0.65 M☉). However, the SMC and LMC CS mass distributions differ slightly, with the SMC sample lacking an intermediate-mass stellar population (0.65-0.75 M☉). We discuss the significance and possible reasons for the difference between the two mass distributions. In particular, we consider the differences in the star formation history between the clouds and the mass-loss rate dependence on metallicity.