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Títol: Analysis of extremely metal-poor stars abundances


Estudiants que han llegit aquest projecte:


Director: GUTIÉRREZ CABELLO, JORDI

Departament: FIS

Títol: Analysis of extremely metal-poor stars abundances

Data inici oferta: 10-02-2023     Data finalització oferta: 10-10-2023



Estudis d'assignació del projecte:
    MU AEROSPACE S&T 21
Tipus: Individual
 
Lloc de realització: EETAC
 
Segon director (UPC): GIL PONS, PILAR
 
Paraules clau:
stellar evolution, supernovae, big bang, very metal poor stars
 
Descripció del contingut i pla d'activitats:
Understanding the origin of the oldest stars in the universe is
crucial to shed light on its early chemical evolution and on the
formation history of the Milky Way.
The oldest stars were either the direct heirs of the Big-Bang
nucleosynthesis (and thus mainly composed of H and He at their
birth), or were born in clouds of primordial (zero metallicity)
material polluted with the ejecta from one or a few stars. Thus
their observational counterparts must be characterised by very
low amounts of iron in their composition. Currently, there is a
debate on whether the first stellar generations (and thus the
first polluters of the interstellar medium) were composed only of
massive stars, or were a combination of intermediate and massive
objects.

We aim to identify the nature of the progenitors of the most
metal-poor stars observed ([Fe/H] ' -2 or Z ' 1e-4).
Specifically, we intend to know whether these stars show the
nucleosynthetic signatures of early supernova explosions of
different types, or of a combination of the ejecta from massive
and intermediate-mass stars.

We compile theoretical nucleosynthetic yields existing in the
literature for intermediate and massive stars. We propose a
scenario in which the theoretical yields of either an
intermediate mass star or a massive star, are mixed within a gas
cloud of primordial matter. Our main assumption is that some of
the currently observed most metal-poor stars were born in this
polluted clouds and thus, their abundances should show the
nucleosynthetic signatures of their parent stars. We intend to
develop a code able to automatically derive abundances from
theoretical nucleosynthetic yields at different degrees of
dilution with primordial material, and subsequently identify
statistically sound matches between the former theoretical
abundances and the surface abundances of metal poor stars of
[Fe/H]' -2. Automatising this process is crucial, given the
increasing number of new theoretical models and observations of
very metal-poor stars presented in the recent literature.

The expected coincidences between the abundances of theoretical
models and observations will give us information related to their
progenitors' initial masses and metallicities. We will be able to
determine, given state-of-the-art of theoretical nucleosynthetic
yields, whether any of the observed stars could be the offspring
of a genuine primordial (Z=0) star.
 
Overview (resum en anglès):
Context: Understanding the origin of the oldest stars in the universe is crucial to shed light on its early chemical evolution and on the formation history of the Milky Way. The oldest stars were either the direct heirs of the Big-Bang nucleosynthesis (and thus mainly composed of H and He at their birth), or were born in clouds of primordial (zero metallicity) material polluted with the ejecta from one or a few stars. Thus their observational counterparts must be characterised by very low amounts of iron in their composition. Currently, there is a debate on whether the first stellar generations (and thus the first polluters of the interstellar medium) were composed only of massive stars, or were a combination of intermediate and massive objects.

Goal: We aim to identify the nature of the progenitors of the most metal-poor stars observed ([Fe/H] ¿ ¿2 or Z ¿ 10¿4). Specifically, we intend to know whether these stars show the nucleosynthetic signatures of early supernova explosions of different types, or of a combination of the ejecta from massive and intermediate-mass stars.

Methods: We compile theoretical nucleosynthetic yields existing in the literature for intermediate and massive stars. We propose a scenario in which the theoretical yields of either an intermediate mass star or a massive star, are mixed within a gas cloud of primordial matter. Our main assumption is that some of the currently observed most metal-poor stars were born in this polluted clouds and thus, their abundances should show the nucleosynthetic signatures of their parent stars. We intend to develop a code able to automatically derive abundances from theoretical nucleosynthetic yields at different degrees of dilution with primordial material, and subsequently identify statistically sound matches between the former theoretical abundances and the surface abundances of metal poor stars of [Fe/H] ¿ ¿2. Automatising this process is crucial, given the increasing number of new theoretical models and observations of very metal-poor stars presented in the recent literature.

Results: The expected coincidences between the abundances of theoretical models and observations will give us information related to their progenitors¿ initial masses and metallicities. We will be able to determine, given state-of-the-art of theoretical nucleosynthetic yields, whether any of the observed stars could be the offspring of a genuine primordial (Z=0) star.


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