Examinando por Autor "Ernandes, H."
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Ítem A MUSE study of the inner bulge globular cluster Terzan 9: A fossil record in the Galaxy(2019-12) Ernandes, H.; Dias, B.; Barbuy, B; Kamann, S.; Ortolani, S.; Cantelli, E; Bica, E.; Rossi, L; Ortolani, S; Cantelli, E.; Bica, E; Rossi, LContext. Moderately metal-poor inner bulge globular clusters are relics of a generation of long-lived stars that formed in the early Galaxy. Terzan 9, projected at 4°.12 from the Galactic center, is among the most central globular clusters in the Milky Way, showing an orbit which remains confined to the inner 1 kpc. Aims. Our aim is the derivation of the cluster's metallicity, together with an accurate measurement of the mean radial velocity. In the literature, metallicities in the range between-2.0 < [Fe/H] < -1.0 have been estimated for Terzan 9 based on color-magnitude diagrams and CaII triplet (CaT) lines. Methods. Given its compactness, Terzan 9 was observed using the Multi Unit Spectroscopic Explorer (MUSE) at the Very Large Telescope. The extraction of spectra from several hundreds of individual stars allowed us to derive their radial velocities, metallicities, and [Mg/Fe]. The spectra obtained with MUSE were analysed through full spectrum fitting using the ETOILE code. Results. We obtained a mean metallicity of [Fe/H] ≈ -1.10 ±0.15, a heliocentric radial velocity of vhr = 58.1 ± 1.1 km s-1, and a magnesium-To-iron [Mg/Fe] = 0.27 ± 0.03. The metallicity-derived character of Terzan 9 sets it among the family of the moderately metal-poor Blue Horizontal Branch clusters HP 1, NGC 6558, and NGC 6522. © ESO 2019.Ítem Abundance analysis of APOGEE spectra for 58 metal-poor stars from the bulge spheroid(Oxford University Press, 2022-12-01) Razera, R.; Barbuy, B.; Moura, T.C.; Ernandes, H.; Pérez Villegas, A.; Souza, S.O.; Chiappini, C.; Queiroz, A.B.A.; Anders, F.; Fernández Trincado, J.G.; Friaça, A.C.S.; Cunha, K.; Smith, V.V.; Santiago, B.X.; Schiavon, R.P.; Valentini, M.; Minniti, D.; Schultheis, M.; Geisler, D.; Sobeck, J.; Placco, V.M.; Zoccali, M.The central part of the Galaxy hosts a multitude of stellar populations, including the spheroidal bulge stars, stars moved to the bulge through secular evolution of the bar, inner halo, inner thick disc, inner thin disc, as well as debris from past accretion events. We identified a sample of 58 candidate stars belonging to the stellar population of the spheroidal bulge, and analyse their abundances. The present calculations of Mg, Ca, and Si lines are in agreement with the ASPCAP abundances, whereas abundances of C, N, O, and Ce are re-examined. We find normal α-element enhancements in oxygen, similar to magnesium, Si, and Ca abundances, which are typical of other bulge stars surveyed in the optical in Baade's Window. The enhancement of [O/Fe] in these stars suggests that they do not belong to accreted debris. No spread in N abundances is found, and none of the sample stars is N-rich, indicating that these stars are not second generation stars originated in globular clusters. Ce instead is enhanced in the sample stars, which points to an s-process origin such as due to enrichment from early generations of massive fast rotating stars, the so-called spinstars. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.Ítem Gemini/Phoenix H -band analysis of the globular cluster AL 3(EDP Sciences, 2021-04-01) Barbuy, B.; Ernandes, H.; Souza, S. O.; Razera, R.; Moura, T.; Meléndez, J.; Pérez-Villegas, A.; Zoccali, M.; Minniti, D.; Dias, B.; Ortolani, S.; Bica, E.Context. The globular cluster AL 3 is old and located in the inner bulge. Three individual stars were observed with the Phoenix spectrograph at the Gemini South telescope. The wavelength region contains prominent lines of CN, OH, and CO, allowing the derivation of C, N, and O abundances of cool stars. Aims. We aim to derive C, N, O abundances of three stars in the bulge globular cluster AL 3, and additionally in stars of NGC 6558 and HP 1. The spectra of AL 3 allows us to derive the cluster's radial velocity. Methods. For AL 3, we applied a new code to analyse its colour-magnitude diagram. Synthetic spectra were computed and compared to observed spectra for the three clusters. Results. We present a detailed identification of lines in the spectral region centred at 15 555 Å, covering the wavelength range 15 525-15 590 Å. C, N, and O abundances are tentatively derived for the sample stars.Ítem High-resolution abundance analysis of four red giants in the globular cluster NGC 6558(EDP Sciences, 2018-11) Barbuy, B.; Muniz, L.; Ortolani, S.; Ernandes, H.; Dias, B.; Saviane, I.; Kerber, L.; Bica, E.; Pérez-Villegas, A.; Rossi, L.; Held, E.V.Context. NGC 6558 is a bulge globular cluster with a blue horizontal branch (BHB), combined with a metallicity of [Fe/H] â‰-1.0. It is similar to HP 1 and NGC 6522, which could be among the oldest objects in the Galaxy. Element abundances in these clusters could reveal the nature of the first supernovae. Aims. We aim to carry out detailed spectroscopic analysis for four red giants of NGC 6558, in order to derive the abundances of the light elements C, N, O, Na, Al, the α-elements Mg, Si, Ca, Ti, and the heavy elements Y, Ba, and Eu. Methods. High-resolution spectra of four stars with FLAMES-UVES at VLT UT2-Kueyen were analysed. Spectroscopic parameter-derivation was based on excitation and ionization equilibrium of Feâraquo; I and Feâ» II. Results. This analysis results in a metallicity of [Fe/H] =-1.17 ± 0.10 for NGC 6558. We find the expected α-element enhancements in O and Mg with [O/Fe] = +0.40, [Mg/Fe] = +0.33, and low enhancements in Si and Ca. Ti has a moderate enhancement of [Ti/Fe] = +0.22. The r-element Eu appears very enhanced with a mean value of [Eu/Fe] = +0.63. The first peak s-elements Y and Sr are also enhanced, these results have however to be treated with caution, given the uncertainties in the continuum definition; the use of neutral species (Srâraquo; I, Yâ» I), instead of the dominant ionized species is another source of uncertainty. Ba appears to have a solar abundance ratio relative to Fe. Conclusions. NGC 6558 shows an abundance pattern that could be typical of the oldest inner bulge globular clusters, together with the pattern in the similar clusters NGC 6522 and HP 1. They show low abundances of the odd-Z elements Na and Al, and of the explosive nucleosynthesis α-elements Si, Ca, and Ti. The hydrostatic burning α-elements O and Mg are normally enhanced as expected in old stars enriched with yields from core-collapse supernovae, and the iron-peak elements Mn, Cu, Zn show low abundances, which is expected for Mn and Cu, but not for Zn. Finally, the cluster trio NGC 6558, NGC 6522, and HP 1 have relatively high abundances of first-peak heavy elements, variable second-peak element Ba, and the r-element Eu is enhanced. The latter is particularly high in NGC 6558. © 2018 ESO.Ítem High-resolution abundance analysis of red giants in the metal-poor bulge globular cluster HP 1(EDP SCIENCES, 2016-06) Barbuy, B.; Cantelli, E.; Vemado, A.; Ernandes, H.; Ortolani, S.; Saviane, I.; Bica, E.; Minniti, D.; Dias, B.; Momany, Y.; Hill, V.; Zoccali, M.; Siqueira-Mello, C.Context. The globular cluster HP 1 is projected at only 3.̊33 from the Galactic center. Together with its distance, this makes it one of the most central globular clusters in the Milky Way. It has a blue horizontal branch (BHB) and a metallicity of [Fe/H] ≈ −1.0. This means that it probably is one of the oldest objects in the Galaxy. Abundance ratios can reveal the nucleosynthesis pattern of the first stars as well as the early chemical enrichment and early formation of stellar populations. Aims. High-resolution spectra obtained for six stars were analyzed to derive the abundances of the light elements C, N, O, Na, and Al, the alpha-elements Mg, Si, Ca, and Ti, and the heavy elements Sr, Y, Zr, Ba, La, and Eu. Methods. High-resolution spectra of six red giants that are confirmed members of the bulge globular cluster HP 1 were obtained with the 8 m VLT UT2-Kueyen telescope with the UVES spectrograph in FLAMES-UVES configuration. The spectroscopic parameter derivation was based on the excitation and ionization equilibrium of Fe i and Fe ii. Results. We confirm a mean metallicity of [Fe/H] = −1.06 ± 0.10, by adding the two stars that were previously analyzed in HP 1. The alpha-elements O and Mg are enhanced by about +0.3 ≲ [O,Mg/Fe] ≲ +0.5 dex, Si is moderately enhanced with +0.15 ≲ [Si/Fe] ≲ +0.35 dex, while Ca and Ti show lower values of −0.04 ≲ [Ca,Ti/Fe] ≲ +0.28 dex. The r-element Eu is also enhanced with [Eu/Fe] ≈ +0.4, which together with O and Mg is indicative of early enrichment by type II supernovae. Na and Al are low, but it is unclear if Na-O are anticorrelated. The heavy elements are moderately enhanced, with −0.20 < [La/Fe] < +0.43 dex and 0.0 < [Ba/Fe] < +0.75 dex, which is compatible with r-process formation. The spread in Y, Zr, Ba, and La abundances, on the other hand, appears to be compatible with the spinstar scenario or other additional mechanisms such as the weak r-process.