ChETEC


Chemical Elements as Tracers of the Evolution of the Cosmos

Lithium in the Universe: to Be or not to Be? (Working Group Meeting)

Among all the chemical species present in the Universe, lithium is unique for being the protagonist in several astrophysical contexts, spanning all epochs, from the Big Bang to the present day, and extending over distances from our Sun to remote regions in the Milky Way system and beyond. Lithium is currently at the centre of two highly debated mysteries that catch the attention of astrophysicists. The expected primordial value of 7Li is a factor of 3 higher than measured in warm halo dwarf stars. This discrepancy is normally referred to as the cosmological lithium problem. Since the present lithium abundance as measured in meteorites or in young stars is A(Li)=3.3, a Galactic source is required. The identification of such sources is referred to as the Galactic lithium problem.
  • Lithium in the Universe: to Be or not to Be? (Working Group Meeting)
  • 2019-11-18T00:00:00+01:00
  • 2019-11-22T23:59:59+01:00
  • Among all the chemical species present in the Universe, lithium is unique for being the protagonist in several astrophysical contexts, spanning all epochs, from the Big Bang to the present day, and extending over distances from our Sun to remote regions in the Milky Way system and beyond. Lithium is currently at the centre of two highly debated mysteries that catch the attention of astrophysicists. The expected primordial value of 7Li is a factor of 3 higher than measured in warm halo dwarf stars. This discrepancy is normally referred to as the cosmological lithium problem. Since the present lithium abundance as measured in meteorites or in young stars is A(Li)=3.3, a Galactic source is required. The identification of such sources is referred to as the Galactic lithium problem.
  • When 18 Nov, 2019 to 22 Nov, 2019 (Europe/Paris / UTC100)
  • Where The Observatory of Rome, Monte Porzio Catone, Italy
  • Contact Name
  • Attendees INVITED SPEAKERS - Jerome Bouvier, Sergio Cristallo, Franca D’Antona, Barry Davids, Brian Fields, Anibal Garcia-Hernandez, Nadege Lagarde, Karin Lind, Jordi Jose, Francesca Matteucci, Jorge Melendez, Paolo Molaro, Cyril Pitrou, Rafael Rebolo, Matthias Steffen, Aaron Steinhauer, Rodolfo Smiljanic, Bruce Twarog - SOC - Gabriele Cescutti, Alain Coc, Constantin Deliyannis, Margarita Hernanz, Christian Iliaidis, Andreas Korn (co-chair), Karin Lind, Ana Palacios, Paolo Ventura (co-chair), Maria Rosa Zapatero-Osorio - LOC - Giuliana Giobbi (chair), Marco Castellani, Flavia Dell'Agli, Marcella Di Criscienzo, Maria Lugaro, Ester Marini, Vincenzo Testa - For an updated list of the participants: https://lithiumintheuniverse.wixsite.com/lithium2019/partecipants
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Scientific rationale

Among all the chemical species present in the Universe, lithium is unique for being the protagonist in several astrophysical contexts, spanning all epochs, from the Big Bang to the present day, and extending over distances from our Sun to remote regions in the Milky Way system and beyond.

   Lithium is currently at the centre of two highly debated mysteries that catch the attention of astrophysicists. 7Li is the heaviest nucleus produced in significant amounts during the Big Bang. Primordial 7Li production can be estimated in the framework of standard primordial nucleosynthesis; the expected primordial value is A(Li)=2.6, which is a factor of about 3 higher than measured in warm halo dwarf stars. This discrepancy is normally referred to as the cosmological lithium problem.  Since the present lithium abundance as measured in meteorites or in young stars is A(Li)=3.3, a Galactic source is required to account for the increase from 2.6. The identification of such sources is referred to as the Galactic lithium problem.

   These open issues have stimulated several lines of research focusing on the identification of the mechanisms potentially able to alter the lithium content within stars, either via the activation of nuclear channels involving lithium or by mixing mechanisms which provoke significant variations in the surface lithium abundance. In parallel, there have been many studies on the nuclear reactions involving lithium, in an attempt of reconciling the results from Big Bang nucleosynthesis modelling with the observational evidence.

   On the purely stellar side, a fragile element that burns at a temperature of 2.5 MK encountered at the base of the convective envelope of low-mass stars, lithium is slowly depleted during the star’s evolution along the Main Sequence, with the possible exception of stars on the Spite plateau. Beyond this secular trend, the depletion rate is extremely sensitive to temperature and lithium abundances and thus provides an excellent probe to transport processes at work in stellar interiors. Indirect diagnostics of internal processes are therefore extremely valuable at all phases of stellar evolution, and the surface lithium abundance is readily accessible through the 670.8 nm photospheric resonance doublet present in the optical spectra of cool dwarfs. Over the past decades, this has motivated thorough investigations of the connection between lithium and rotation and/or magnetic activity in solar-type stars at various stages of evolution.

   Cluster observations have taken a critical role in disentangling the impact of the multitude of factors that can influence the lithium abundance of a given star. Crucially, ages and mass estimates can be derived for individual hotter, higher mass stars with known metallicity and reddening, for cooler dwarfs the age and distance can be extracted observationally from the sample of hotter stars within the same cluster.  Furthermore, the analysis of lithium abundances in Globular Cluster stars has proven to be a potentially important source of information to understand how atomic diffusion alters surface lithium and how multiple populations formed and evolved in these structures.

   The scope of the meeting is to gather scientists active in the above-mentioned fields to stimulate open discussions on the many questions we still have. This conference is particularly timely because the last years have witnessed a significant improvement in the capability of major nuclear physics facilities, that will soon allow a high-quality description of the nuclear reactions involving lithium and beryllium. Furthermore, a growing body of observational data of lithium in cluster stars will soon be available, such as the WYIN open cluster survey. Furthermore, there is considerable development of 3D and NLTE modelling and their application to large spectroscopic data sets, which, while being computationally demanding, will allow determinations of lithium abundances with much higher fidelity than until now.