Project F

Learning the secret of the elixir of youth: a study of blue stragglers with Gaia

Henri Boffin & Nicola Gentile Fusillo

(email advisors)

Using the Gaia DR3 that will be released just before the start of the Summer programme, we will try to understand what governs the formation in open clusters of the puzzling stars known as "blue strugglers" . Join us in this exciting mining of the new Gaia data release, looking for those stars that shouldn’t exist, and in the process, learn about how couples of stars interact!

The Gaia survey has already led to a revolution in the study of our Milky Way and in stellar evolution. The third data release (DR3), which will come between April and June 2022, will push the potential for discover even further, with its information on binary stars and variability, and the release of many spectra. This is the ideal moment to study the binary content of open clusters, and thereby better understand mass transfer mechanisms in close binaries.

In particular, this will be the opportunity to study a puzzling class of star: the blue stragglers. These stars are too luminous and too blue for the age of the cluster they formed and actually populate  a region of the Hertzsprung-Russell diagram that, according to nominal stellar evolution, should be empty.

Thus, for some reasons, these stars managed to be young again! The cause for this is likely mass transfer in binary systems as the majority of blue stragglers in open clusters are either close binaries with orbital periods of a few days or less, or long period binaries with orbital periods around 1,000 days and a white dwarf companion. The relative proportion of these two flavours of binaries seems to depend on the cluster and one of the aims of this study is to understand what parameters of the open clusters is responsible for this. The Gaia DR3 release, with its identification of many binaries, release of orbits and of light curves of many eclipsing binaries, should bring a completely new light on this and allows us to answer this fundamental question. The release will also provide much additional information on other binaries in the clusters – whether on the main sequence or among the cluster’s white dwarfs – that will also be interesting to study. Finally, given the unexplored DR3, it is likely that in our study of these exotic objects, we will also stumble into some unexpected and exciting systems. Be prepared for surprises! 

#GaiaDR3 #datamining #StellarEvolution #binarystars #BlueStragglers #variability 

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