Subvenciones relacionadas:
General
La espectroscopía de estrellas nos permite determinar las propiedades y composiciones químicas de las mismas. A partir de esta información para estrellas de diferente edad en la Vía Láctea es posible reconstruir la evolución química de la Galaxia, así como el origen de los elementos más pesados que el boro, forjados principalmente en los interiores estelares. También es posible estudiar la formación estelar, y la de la propia Galaxia, a través de la huella que deja el potencial Galáctico en las órbitas de las estrellas, y de las distribuciones de masa, edad y la abundancia de elementos pesados.
La obtención de espectros con alta resolución espectral, apropiados para estudios de la composición química, requiere instrumentación sofisticada y eficiente. Esto es especialmente cierto en investigaciones en las que se necesitan extensas muestras de estrellas, que exigen observar cientos, o incluso miles de fuentes de forma simultánea. El procesado y análisis de los datos debe ser automatizado para ser igualmente eficiente.
La interpretación de los espectros se basa en modelos físicos de las atmósferas de las estrellas, de donde se escapa la luz que observamos. Los ingredientes fundamentales para la construcción de estos modelos son la dinámica de fluidos, y las propiedades de los átomos, iones y moléculas, especialmente en lo que se refiere a sus interacciones con la radiación que proviene del interior estelar. Una vez que se tiene un modelo plausible, es posible calcular de forma detallada cómo se propaga la radiación a través de la atmósfera estelar, y el espectro emergente, para, de forma iterativa, compararlo con las observaciones y refinar el modelo.
Este Proyecto incluye tres diferentes frentes de investigación:
- La mejora de los modelos de atmósfera y las simulaciones de espectros estelares.
- El desarrollo de herramientas para la obtención, reducción y el análisis de observaciones espectroscópicas, y en particular para la determinación de abundancias químicas en estrellas.
- El diseño, preparación, y ejecución de estudios espectroscópicos de estrellas con el fin de entender a) los aspectos más relevantes de la física de las atmósferas estelares, b) la formación y evolución de las estrellas, c) el origen de los elementos químicos y d) la formación, estructura y evolución química de la Vía Láctea.
Miembros
Resultados
- Completar la instalación y pruebas de HORuS en GTC
- Descubrir dos nuevas estrellas con abundancias de hierro inferiores a 100.000 veces el valor solar
- Completar la clasificación de los espectros de APOGEE con K-means
- Publicar una colección completa de espectros modelo para estrellas O a M
- Identificar la huella de la difusión química en las atmósferas de estrellas del cúmulo M67
Actividad científica
Publicaciones relacionadas
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Back to the Lithium Plateau with the [Fe/H] < -6 Star J0023+0307We present an analysis of the Ultraviolet and Visual Echelle Spectrograph (UVES) high-resolution spectroscopic observations at the 8.2 m Very Large Telescope of J0023+0307, a main-sequence extremely iron-poor dwarf star. We are unable to detect iron lines in the spectrum but derive [Fe/H] -6.1 from the Ca II resonance lines assuming [Ca/Fe] ≥ 0.40Aguado, D. S. et al.
Fecha de publicación:
42019 -
Exploring circumstellar effects on the lithium and calcium abundances in massive Galactic O-rich AGB starsContext. We previously explored the circumstellar effects on Rb and Zr abundances in a sample (21) of massive Galactic O-rich asymptotic giant branch (AGB) stars. Here we are interested in clarifying the role of the extended atmosphere in the case of Li and Ca. Li is an important indicator of hot bottom burning while the total Ca abundances inPérez-Mesa, V. et al.
Fecha de publicación:
32019 -
Chemical Abundances of Main-sequence, Turnoff, Subgiant, and Red Giant Stars from APOGEE Spectra. II. Atomic Diffusion in M67 StarsChemical abundances for 15 elements (C, N, O, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, and Ni) are presented for 83 stellar members of the 4 Gyr old solar-metallicity open cluster M67. The sample contains stars spanning a wide range of evolutionary phases, from G dwarfs to red clump stars. The abundances were derived from near-IR (λ1.5–1.7 μm)Souto, D. et al.
Fecha de publicación:
32019 -
Chemical Cartography with APOGEE: Multi-element Abundance RatiosWe map the trends of elemental abundance ratios across the Galactic disk, spanning R=3{--}15 {kpc} and midplane distance | Z| =0{--}2 {kpc}, for 15 elements in a sample of 20,485 stars measured by the SDSS/APOGEE survey (O, Na, Mg, Al, Si, P, S, K, Ca, V, Cr, Mn, Fe, Co, Ni). Adopting Mg rather than Fe as our reference element, and separating starsWeinberg, D. H. et al.
Fecha de publicación:
32019 -
Ca line formation in late-type stellar atmospheres. I. The model atomContext. Departures from local thermodynamic equilibrium (LTE) distort the calcium abundance derived from stellar spectra in various ways, depending on the lines used and the stellar atmospheric parameters. The collection of atomic data adopted in non-LTE (NLTE) calculations must be sufficiently complete and accurate. Aims: We derive NLTEOsorio, Y. et al.
Fecha de publicación:
32019 -
J-PLUS: The Javalambre Photometric Local Universe SurveyThe Javalambre Photometric Local Universe Survey (J-PLUS ) is an ongoing 12-band photometric optical survey, observing thousands of square degrees of the Northern Hemisphere from the dedicated JAST/T80 telescope at the Observatorio Astrofísico de Javalambre (OAJ). The T80Cam is a camera with a field of view of 2 deg2 mounted on a telescope with aCenarro, A. J. et al.
Fecha de publicación:
22019 -
J-PLUS: Identification of low-metallicity stars with artificial neural networks using SPHINXContext. We present a new methodology for the estimation of stellar atmospheric parameters from narrow- and intermediate-band photometry of the Javalambre Photometric Local Universe Survey (J-PLUS), and propose a method for target pre-selection of low-metallicity stars for follow-up spectroscopic studies. Photometric metallicity estimates for starsWhitten, D. D. et al.
Fecha de publicación:
22019 -
Homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code. I. The northern clustersAims: We seek to provide abundances of a large set of light and neutron-capture elements homogeneously analyzed that cover a wide range of metallicity to constrain globular cluster (GC) formation and evolution models. Methods: We analyzed a large sample of 885 GCs giants from the SDSS IV-Apache Point Observatory Galactic Evolution ExperimentMasseron, T. et al.
Fecha de publicación:
22019 -
Gaia Data Release 2. Properties and validation of the radial velocitiesContext. For Gaia DR2, 280 million spectra collected by the Radial Velocity Spectrometer instrument on board Gaia were processed, and median radial velocities were derived for 9.8 million sources brighter than GRVS = 12 mag. Aims: This paper describes the validation and properties of the median radial velocities published in Gaia DR2. MethodsKatz, D. et al.
Fecha de publicación:
22019 -
Identifying Sagittarius Stream Stars by Their APOGEE Chemical Abundance SignaturesThe SDSS-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey provides precise chemical abundances of 18 chemical elements for ∼176,000 red giant stars distributed over much of the Milky Way Galaxy (MW), and includes observations of the core of the Sagittarius dwarf spheroidal galaxy (Sgr). The APOGEE chemical abundanceHasselquist, S. et al.
Fecha de publicación:
22019 -
Constraining Metallicity-dependent Mixing and Extra Mixing Using [C/N] in Alpha-rich Field GiantsInternal mixing on the giant branch is an important process which affects the evolution of stars and the chemical evolution of the galaxy. While several mechanisms have been proposed to explain this mixing, better empirical constraints are necessary. Here, we use [C/N] abundances in 26,097 evolved stars from the SDSS-IV/APOGEE-2 Data Release 14 toShetrone, M. et al.
Fecha de publicación:
22019 -
The Fifteenth Data Release of the Sloan Digital Sky Surveys: First Release of MaNGA-derived Quantities, Data Visualization Tools, and Stellar LibraryTwenty years have passed since first light for the Sloan Digital Sky Survey (SDSS). Here, we release data taken by the fourth phase of SDSS (SDSS-IV) across its first three years of operation (2014 July–2017 July). This is the third data release for SDSS-IV, and the 15th from SDSS (Data Release Fifteen; DR15). New data come from MaNGA—we releaseAguado, D. S. et al.
Fecha de publicación:
22019 -
The Gaia-ESO Survey: impact of extra mixing on C and N abundances of giant starsContext. The Gaia-ESO Public Spectroscopic Survey using FLAMES at the VLT has obtained high-resolution UVES spectra for a large number of giant stars, allowing a determination of the abundances of the key chemical elements carbon and nitrogen at their surface. The surface abundances of these chemical species are known to change in stars duringLagarde, N. et al.
Fecha de publicación:
12019 -
Radial Velocities in the Outermost Disk toward the AnticenterWe measure the mean Galactocentric radial component of the velocity of stars (v R ) in the disk at 8 kpc R 28 kpc in the direction of the anticenter. For this, we use the Apache Point Galactic Evolution Experiment. Furthermore, we compare the result with H I maps along the same line of sight. We find an increase in positive (expansion) v R at R ≈López-Corredoira, M. et al.
Fecha de publicación:
12019 -
The origin of accreted stellar halo populations in the Milky Way using APOGEE, Gaia, and the EAGLE simulationsRecent work indicates that the nearby Galactic halo is dominated by the debris from a major accretion event. We confirm that result from an analysis of APOGEE-DR14 element abundances and Gaia-DR2 kinematics of halo stars. We show that ˜2/3 of nearby halo stars have high orbital eccentricities (e ≳ 0.8), and abundance patterns typical of massiveMackereth, J. Ted et al.
Fecha de publicación:
12019 -
Comprehensive comparison between APOGEE and LAMOST. Radial velocities and atmospheric stellar parametersContext. In the era of massive spectroscopy surveys, automated stellar parameter pipelines and their validation are extremely important for an efficient scientific exploitation of the spectra. Aims: We undertake a critical and comprehensive comparison of the radial velocities and the main stellar atmosphere parameters for stars in common betweenAnguiano, B. et al.
Fecha de publicación:
122018 -
A collection of model stellar spectra for spectral types B to early-MContext. Models of stellar spectra are necessary for interpreting light from individual stars, planets, integrated stellar populations, nebulae, and the interstellar medium. Aims: We provide a comprehensive and homogeneous collection of synthetic spectra for a wide range of atmospheric parameters and chemical compositions. Methods: We compileAllende Prieto, C. et al.
Fecha de publicación:
102018 -
The Origin of the 300 km s‑1 Stream near Segue 1We present a search for new members of the 300 km s‑1 stream (300S) near the dwarf galaxy Segue 1 using wide-field survey data. We identify 11 previously unknown bright stream members in the APOGEE-2 and SEGUE-1 and 2 spectroscopic surveys. Based on the spatial distribution of the high-velocity stars, we confirm for the first time that thisFu, Sal Wanying et al.
Fecha de publicación:
102018 -
The Pristine survey IV: approaching the Galactic metallicity floor with the discovery of an ultra-metal-poor starThe early Universe presented a star formation environment that was almost devoid of heavy elements. The lowest metallicity stars thus provide a unique window into the earliest Galactic stages, but are exceedingly rare and difficult to find. Here, we present the discovery of an ultra-metal-poor star, Pristine_221.8781+9.7844, using narrow-band Ca HStarkenburg, Else et al.
Fecha de publicación:
122018 -
The Gaia-ESO Survey: the origin and evolution of s-process elementsContext. Several works have found an increase of the abundances of the s-process neutron-capture elements in the youngest Galactic stellar populations. These trends provide important constraints on stellar and Galactic evolution and they need to be confirmed with large and statistically significant samples of stars spanning wide age and distanceMagrini, L. et al.
Fecha de publicación:
92018