Lorenzo Spina

Spectroscopy - Stellar Composition - Astroarchaeology

Universidade de São Paulo
Instituto de Astronomia, Geofísica e Ciências Atmosféricas

Curriculum Vitae

Professional Profile:

I obtained my PhD in Physics at the University of Florence in 2014. For the time of my doctorate I fulfilled several duties and responsibilities in the framework of the Gaia-ESO Survey. In this context I developed a solid expertise on the analysis of large samples of high-resolution spectra for the derivation of stellar parameters and chemical abundances. In such a large collaboration I also dedicated a great effort to cooperate with other scientific teams. My scientific research as post-doc at the Universidade de São Paulo has been mainly focussed on the high-precision (σ~0.01 dex) chemical analysis of solar-twin stars devoted to the study of the chemical evolution of the Galactic disk and the chemical signatures imprinted by the evolution of planetary systems.


January 2011 — January 2014
PhD in Astronomy
University of Florence (Italy)
Advisors: S. Randich (INAF), F. Palla (INAF)

September 2007 — June 2010
Master degree in Physics
University of Florence (Italy)

September 2004 — January 2008
Bachelor degree in Physics
University of Florence (Italy)


January 2015 — present
Postdoctoral fellow
Universidade de São Paulo, IAG
São Paulo, Brazil

July 2014 — November 2014
Research grant
INAF - Osservatorio Astrofisico di Arcetri
Florence, Italy

September 2009 — January 2010
Research fellow
Space Telescope Science Institute
Baltimore, MD, USA


Research Interests:

  • Chemical evolution of the solar neighbourhood: from the latest stellar formation events to the oldest stars that populate the solar vicinity.
  • Relationship between the architecture of planetary systems and the stellar chemical composition.
  • Planet hunting.
  • Solar twins stars.
  • Open stellar clusters.


Chemical clocks for solar twin stars

The [Y/Mg] and [Y/Al] ratios show very tight correlations with stellar ages. Thus, both these ratios can serve as sensitive age indicators that are completely independent from the classical methods used for age determinations (e.g., isochrones, Li depletion, gyrochronology). Notice that the slightly higher steepness of the [Y/Al] - age relation would provide better constraints on the stellar ages with respect to the [Y/Mg] clock.

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The nucleosynthetic hystory of elements in the Galactic disk

Tight correlations exist between the [X/Fe] ratios and the stellar ages for many elements that we analysed (see figure). We fitted the [X/Fe]-age relation of the light elements (i.e., from C to Zn) using three different models based on a straight line, hyperbolic and two-segmented line functions, respectively. Through a statistical comparison of the results, we demonstrated that most of these species present non-linear or non-monotonic [X/Fe]-age relations. We showed that the hyperbolic model is the most appropriate in fitting the [X/Fe]-ages distribution of most of the light elements. Knowledge of the [X/Fe]-age relations is a gold mine from which we can achieve a great understanding about the processes that governed the formation and evolution of the Milky Way: the nature of the star formation history, the SNe rates, the stellar yields, and the variety of the SNe progenitors, etc.

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Chemical signatures of rocky accretion on a young solar type star

It is likely that during the early evolution of planetary systems part of the rocky material orbiting around the star might have been induced to move into unstable orbits and eventually fall onto the central star. After penetrating into the stellar atmosphere, the rocky mass is rapidly dissolved and mixed with the ambient matter. Thus, a major consequence of such dramatic events is the possible increase of the photospheric metallicity (i.e. the abundance of elements heavier than helium). We identified of a member of the Gamma Velorum cluster(the star 2MASS J08095427-4721419) that is significantly enriched in metals relative to the other members of the same cluster. Our detailed chemical analysis revealed that the overabundance of a given element is correlated with its condensation temperature (see figure). Because of their higher condensation temperature, the refractory elements are thought to be the main components of the solids that accrete onto planets and planetesimals. Most interestingly, the trend between abundance and condensation temperature mirrors the composition seen in planetary material (e.g. meteorites or rocky planets). This suggests that the abundance pattern observed in 2MASS J08095427-4721419 originated from the enrichment subsequent to the ingestion of planetary-mass-sized rocky objects.

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Planet signatures and chemical evolution of the Galactic thin disk

During this chaotic development of the system’s architecture, part of the rocky material orbiting around the star (e.g., cores of gaseous planets, rocky planets, planetesimals, etc...) may be induced to move into unstable orbits and fall onto the central star. On the other hand, other planetary systems can survive without any dramatic mod- ification of their structure. Accordingly to this view, we observed a large range of [X/H]-Tc slope values spanned at all the ages (see figure) by our sample of solar-twins could reflect this variety of fates that the matter in circumstellar disks and the planetary systems can experience.

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