1,721,337 research outputs found
The effect of diffusion on the red giant luminosity function 'bump'
No full textThis paper investigates the effect of microscopic diffusion of helium and heavy elements on the location of the red giant branch (RGB) luminosity function bump in Population II stellar models. To this aim, updated evolutionary models taking into account diffusion from the main sequence until the zero-age horizontal branch (ZAHB) are computed. The observational luminosity difference between the RGB bump and the ZAHB (Delta V-hb(bump)), as collected for a sample of Galactic globular clusters, is compared with the corresponding theoretical values obtained by adopting both canonical and diffusive models. We find that the effect of diffusion, even if slightly improving the agreement between observations and theory, is negligible with respect to the observational uncertainties. In any case, the theoretical predictions for Delta V-hb(bump) models with and without diffusion appear in agreement with the observational results within the estimated errors. Thus canonical models can be still safely adopted, at least until much more accurate observational data become available
A Practical Account of Designing a Support Tool for an Educational Experience
No full textThe aims of any educational program are, in principle, always independent of the technological means used in their actual implementation. Modern technology-smartphones, applications, wearable devices, communication means-has proven to be a helpful ally in improving the delivery of educational programs. However, we argue, the outcomes of an educational program strongly depend on its delivery. In this paper, we present an application developed to support an innovative teaching program with the primary objective of increasing students' awareness of their careers, goals, and lifestyle. We discuss the design methodology we employed in the development of our application, with the aim of investigating how to successfully design a tool that supports and enhances the objective of a generic educational program
The true nature of HE 0057-5959, the most metal-poor, Li-rich star
No full textThe Li-rich stars are a class of rare objects with a surface lithium abundance, A(Li), that exceeds that of other stars in the same evolutionary stage. The origin of these stars is still debated, and valuable routes to look at include the Cameron-Fowler mechanism, a mass-Transfer process in a binary system, or the engulfment of rocky planets or brown dwarfs. Metal-poor ([Fe/H
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