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Spectroscopic search for multiple stellar populations in the main sequence of the globular cluster M3
Julio César Mendoza Cervantes
Acceso Abierto
Multiple stellar population
Main sequence
Globular cluster
Spectroscopic index
We present preliminary results on the investigation of the nature of multiple stellar populations in Main Sequence stars (this is, in stars in an evolutionary stage that still preserves their natal chemical composition because they have not yet experienced chemical mixing through deep convection processes) of the Globular Cluster M3 (NGC 5272) by means of a theoretical study using stellar model atmospheres, synthetic spectra and spectroscopic indices. The work is composed of two main parts that include: (i) The calculation of new Opacity Distribution Functions (ODFs) appropriate for the chemical mix observed in evolved stars of globular clusters, and their use in the creation of a new grid of theoretical spectra at very high resolution. (ii) The computation of a set of theoretical absorption line spectroscopic indices and their correlation with the three leading atmospheric parameters: effective temperature, surface gravity and global metallicity (Teff/log 𝚐/[Fe/H]). For the first part we implemented a series of numerical routines within the code DFSYNTHE to calculate the distribution of opacities in agreement with the chemical partitions used by Sbordone et al. (2011) which represent, to some extent, the prototypical elemental abundance combinations of globular clusters with multiple stellar populations. Namely, these partitions were an ⍺-enhanced solar-scaled Reference abundance of [Fe/H] = -1.62 dex (Z = 0:001), compatible with the metallicity of M3 of -1.5 (Harris 1996, 2010 Edition) and a Helium fraction of Y = 0:246 and three other combinations that were labeled as CNONa1Y2, CNONa2Y2 and CNONa1Y4, and incorporate an abundance enhancement of N and Na and depletion of C and O, as well as, for the latter, an enhancement of Helium (Y = 0:400). The newly created ODFs were subsequently implemented as input in the ATLAS9 code to build a grid of 3,472 stellar atmosphere models in a range of effective temperature from 4,300 to 7,000 K, at steps of 100 K, surface gravity log g from 2.0 to 5.0, at steps of 0.1 dex, and the four different chemical compositions from Sbordone et al. (2011).
Instituto Nacional de Astrofísica, Óptica y Electrónica
Tesis de maestría
Público en general
Mendoza Cervantes, J. C., (2017). Spectroscopic search for multiple stellar populations in the main sequence of the globular cluster M3, Tesis de Maestría, Instituto Nacional de Astrofísica, Óptica y Electrónica
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Appears in Collections:Maestría en Astrofísica

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