The Lick/SDSS Library. I. Synthetic Index Definition and Calibration

Franchini, M.; Morossi, C.; Marcantonio, P. Di; Malagnini, M. L.; Chávez, M.

doi:10.1088/0004-637x/719/1/240

Cited by 23 publications

(66 citation statements)

References 36 publications

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“…The proposed method differs from current methods which rely on a synthetic grid to model out the effects of the stellar parameters (e.g. Thomas, Maraston & Bender 2003;Franchini et al 2010Franchini et al , 2011. The advantage of our method is that we can use the spectrum alone to estimate the [α/Fe] with relatively little effect from the uncertainties in the stellar parameters provided they are within the stellar parameter range defined in Section 3.4 below.…”

Section: Spectral-index Methods (Sim)mentioning

confidence: 99%

On the relative ages of the α-rich and α-poor stellar populations in the Galactic halo

Hawkins

Jofré

Gilmore

et al. 2014

Monthly Notices of the Royal Astronomical Society

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We study the ages of α-rich and α-poor stars in the halo using a sample of F and G dwarfs from the Sloan Digital Sky Survey (SDSS). To separate stars based on [α/Fe], we have developed a new semi-empirical spectral-index based method and applied it to the low-resolution, moderate signal-to-noise SDSS spectra. The method can be used to estimate the [α/Fe] directly providing a new and widely applicable way to estimate [α/Fe] from low-resolution spectra. We measured the main-sequence turnoff temperature and combined it with the metallicities and a set of isochrones to estimate the age of the α-rich and α-poor populations in our sample. We found all stars appear to be older than 8 Gyr confirming the idea that the Galactic halo was formed very early on. A bifurcation appears in the age-metallicity relation such that in the low metallicity regime the α-rich and α-poor populations are coeval while in the high metallicity regime the α-rich population is older than the α-poor population. Our results indicate the α-rich halo population, which has shallow age-metallicity relation, was formed in a rapid event with high star formation, while the α-poor stars were formed in an environment with a slower chemical evolution timescale.

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Section: Spectral-index Methods (Sim)mentioning

confidence: 99%

On the relative ages of the α-rich and α-poor stellar populations in the Galactic halo

Hawkins

Jofré

Gilmore

et al. 2014

Monthly Notices of the Royal Astronomical Society

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“…The adoption of different selection criteria, however, leads to different samples of candidate thick-and thin-disc stars (e.g. Bensby et al 2003Bensby et al , 2014Franchini et al 2020). In particular, with regard to 7 Li evolution, Bensby & Lind (2018) caution that the chemical selection may cause a contamination of the thick-disc sample with thin-disc members, especially at higher metallicities, which may lead to a spurious trend of increasing 7 Li abundance with metallicity for the thick disc.…”

Section: Sanity Check On Membership and Accreted Starsmentioning

confidence: 99%

The Gaia-ESO Survey: Galactic evolution of lithium from iDR6

Romano¹,

Magrini

Randich

et al. 2021

A&A

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Context. After more than 50 years, astronomical research still struggles to reconstruct the history of lithium enrichment in the Galaxy and to establish the relative importance of the various 7Li sources in enriching the interstellar medium (ISM) with this fragile element. Aims. To better trace the evolution of lithium in the Milky Way discs, we exploit the unique characteristics of a sample of open clusters (OCs) and field stars for which high-precision 7Li abundances and stellar parameters are homogeneously derived by the Gaia-ESO Survey (GES). Methods. We derive possibly un-depleted 7Li abundances for 26 OCs and star forming regions with ages from young (∼3 Myr) to old (∼4.5 Gyr), spanning a large range of galactocentric distances, 5 < RGC/kpc < 15, which allows us to reconstruct the local late Galactic evolution of lithium as well as its current abundance gradient along the disc. Field stars are added to look further back in time and to constrain 7Li evolution in other Galactic components. The data are then compared to theoretical tracks from chemical evolution models that implement different 7Li forges. Results. Thanks to the homogeneity of the GES analysis, we can combine the maximum average 7Li abundances derived for the clusters with 7Li measurements in field stars. We find that the upper envelope of the 7Li abundances measured in field stars of nearly solar metallicities (−0.3 < [Fe/H]/dex < +0.3) traces very well the level of lithium enrichment attained by the ISM as inferred from observations of cluster stars in the same metallicity range. We confirm previous findings that the abundance of 7Li in the solar neighbourhood does not decrease at super-solar metallicity. The comparison of the data with the chemical evolution model predictions favours a scenario in which the majority of the 7Li abundance in meteorites comes from novae. Current data also seem to suggest that the nova rate flattens out at later times. This requirement might have implications for the masses of the white dwarf nova progenitors and deserves further investigation. Neutrino-induced reactions taking place in core-collapse supernovae also produce some fresh lithium. This likely makes a negligible contribution to the meteoritic abundance, but could be responsible for a mild increase in the 7Li abundance in the ISM of low-metallicity systems that would counterbalance the astration processes.

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“…Carbon is measured from the atomic lines (the adopted C i at 5052.144 Å and 5380.325 Å are not affected by strong NLTE; see e.g. Franchini et al 2020), while lithium is measured from the EWs of the resonance doublet at 6708 Å, which is unblended at the high-spectral resolution of HARPS-N. The photospheric abundances of these elements are affected by stellar evolution during the RGB phase because of the first dredge up (FDU).…”

Section: Carbon and Lithiummentioning

confidence: 99%

Stellar Population Astrophysics (SPA) with TNG

Casali

Magrini

Frasca

et al. 2020

A&A

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Context. Open clusters are excellent tracers of the chemical evolution of the Galactic disc. The spatial distribution of their elemental abundances, through the analysis of high-quality and high-resolution spectra, provides insight into the chemical evolution and mechanisms of element nucleosynthesis in regions characterised by different conditions (e.g. star formation efficiency and metallicity). Aims. In the framework of the Stellar Population Astrophysics (SPA) project, we present new observations and spectral analysis of four sparsely studied open clusters located in the solar neighbourhood, namely Collinder 350, Gulliver 51, NGC 7044, and Ruprecht 171. Methods. We exploit the HARPS-N spectrograph at the TNG telescope to acquire high-resolution optical spectra for 15 member stars of four clusters. We derive stellar parameters (Teff, log g, [Fe/H] and ξ) using both the equivalent width (EW) analysis and the spectral fitting technique. We compute elemental abundances for light, α-, iron-peak, and n-capture elements using the EW measurement approach. We investigate the origin of the correlation between metallicity and stellar parameters derived with the EW method for the coolest stars of the sample (Teff < 4300 K). The correlation is likely due to the challenging continuum setting and to a general inaccuracy of model atmospheres used to reproduce the conditions of very cool giant stars. Results. We locate the properties of our clusters in the radial distributions of metallicity and abundance ratios, comparing our results with clusters from the Gaia-ESO and APOGEE surveys. We present the [X/Fe]−[Fe/H] and [X/Fe]−RGC trends for elements in common between the two surveys. Finally, we derive the C and Li abundances as a function of the evolutionary phase and compare them with theoretical models. Conclusions. The SPA survey, with its high-resolution spectra, allows us to fully characterise the chemistry of nearby clusters. With a single set of spectra, we provide chemical abundances for a variety of chemical elements, which are comparable to those obtained in two of the largest surveys combined. The metallicities and abundance ratios of our clusters fit very well in the radial distributions defined by the recent literature, reinforcing the importance of star clusters to outline the spatial distribution of abundances in our Galaxy. Moreover, the abundances of C and Li, modified by stellar evolution during the giant phase, agree with evolutionary prescriptions (rotation-induced mixing) for their masses and metallicities.

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The Lick/SDSS Library. I. Synthetic Index Definition and Calibration

Cited by 23 publications

References 36 publications

On the relative ages of the α-rich and α-poor stellar populations in the Galactic halo

On the relative ages of the α-rich and α-poor stellar populations in the Galactic halo

The Gaia-ESO Survey: Galactic evolution of lithium from iDR6

Stellar Population Astrophysics (SPA) with TNG

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