Año de inicio
2004
Unidad organizativa
Institución organizadora
Subvenciones relacionadas:
General
Descripción
Recientemente se han llevado a cabo varios análisis espectroscópicos de estrellas con planetas. Uno de los resultados más relevantes ha sido descubrir que las estrellas con planetas son en promedio más metálicas que las estrellas del mismo tipo espectral sin planetas conocidos (Santos, Israelian & Mayor 2001, A&A, 373, 1019; 2004, A&A, 415, 1153). Existen dos hipótesis posibles para relacionar el exceso de metalicidad con la presencia de planetas. La primera es la del “autoenriquecimiento” que atribuye el origen de la sobreabundancia de metales observada en estrellas con planetas a la acreción sobre la estrella madre de grandes cantidades de material planetario rocoso, rico en metales y pobre en elementos como H y He. La hipótesis contraria es la principal y considera que el exceso de metales sea debido al alto contenido en metales de la nube protoplanetaria a partir de la cual se formó el sistema estrella-planeta.
Los elementos ligeros pueden proporcionar información valiosa sobre la mezcla, la difusión y la evolución del momento angular en estrellas con planetas, así como sobre la actividad estelar causada por la interacción con exoplanetas (Santos, Israelian, García López et al. 2004, A&A, 427, 1085; Israelian et al. 2004, A&A, 414, 601). Estudios sobre el berilio, el litio y la razón isotópica 6Li/7Li podrían aportar pruebas para distinguir entre las diferentes teorías de formación planetaria (Sandquist et al. 2002, ApJ, 572, 1012). Israelian et al. encontraron evidencias de la caída de un planeta o de material protoplanetario sobre la estrella HD82943 (2001, Nature, 411, 163; 2003, A&A, 405, 753).
Si el “autoenriquecimiento” fuera el principal responsable del exceso de metalicidad de las estrellas con planetas, eso implicaría una sobreabundancia relativa de elementos refractarios (Si, Mg, Ca, Ti, etc.) respecto a los volátiles (CNO, S y Zn). Se han llevado a cabo varios estudios espectroscópicos del hierro (Santos et al. 2001, A&A, 373, 1019; 2003, A&A, 398, 363; 2004, A&A, 415, 1153) y de otros elementos (Bodaghee et al 2003, A&A, 404, 715; Ecuvillon, Israelian, Santos et al. 2004, A&A, 418, 703; 2004, A&A, 426, 619; 2006, A&A, 445,633; 2006, A&A, 449, 809; Gilli, Israelian, Ecuvillon, et al. 2006, A&A, 449,723).
El análisis espectroscópico de estrellas ricas en metales también proporciona información valiosa sobre las tasas de eyección al medio interestelar de elementos químicos producidos por explosiones de supernova en los últimos 10 mil millones de años. Otro método alternativo para investigar los productos de las explosiones de supernova es el estudio de las estrellas compañeras de los sistemas binarios de rayos X.
Miembros
Investigador principal
Garik
Israelian
Colaboradores
Dr.
M. Mayor
Dr.
N. Santos
Dr.
S. Sousa
Dr.
Elisa Delgado
Dr.
Vardan Adibekyan
Dr.
Cladimir Lipunov
Dr.
Michael Frolov
Dr.
Robin Rees
Resultados
- La correlación planeta-metalicidad se revisa y muestra que la distribución de metalicidad de las estrellas que albergan planetas de baja masa (por debajo de 30 M⊕) es indistinguible de la de la muestra de vecindario solar en términos de distribución de metalicidad.
- Encontramos que las correcciones 3D 6Li / 7Li son siempre negativas, lo que demuestra que el análisis 1D LTE puede sobreestimar significativamente la presencia de 6Li (hasta 4.9% puntos) en las atmósferas de estrellas enanas de tipo solar. Aunque la síntesis espectral NLTE 3D implica un esfuerzo computacional extenso, los resultados pueden hacerse accesibles con herra
- Hemos analizado el comportamiento de las abundancias químicas de Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd y Eu en la muestra de búsqueda de planetas HARPS-GTO grande y homogénea. Comparamos las relaciones [X / Fe] de tales Elementos en diferentes bandejas de metalicidad y encontramos que los anfitriones de los planetas presentan mayores abundancias de Zn para [Fe / H]
- Encontramos que el 100% de la muestra planetaria en HARPS-GTO presenta C / O> 0,4, mientras que el 14% presenta valores de C / O inferiores a 0,4. Con respecto al Mg / Si, todas las estrellas con compañero planetario de baja masa mostraron valores entre uno y dos.
Actividad científica
Publicaciones relacionadas
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82013 -
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62013 -
Very Low Mass Stellar and Substellar Companions to Solar-like Stars from MARVELS. V. A Low Eccentricity Brown Dwarf from the Driest Part of the Desert, MARVELS-6bWe describe the discovery of a likely brown dwarf (BD) companion with a minimum mass of 31.7 ± 2.0 M Jup to GSC 03546-01452 from the MARVELS radial velocity survey, which we designate as MARVELS-6b. For reasonable priors, our analysis gives a probability of 72% that MARVELS-6b has a mass below the hydrogen-burning limit of 0.072 M ☉, and thus it isDe Lee, Nathan et al.
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52013 -
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42013 -
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Volatile and refractory abundances of F- and G-type starsWe present a detailed chemical abundance analysis of a sample of F- and G-type stars. We investigate the possibility that the presence of terrestrial planets could affect the volatile-to-refractory abundance ratios. Stars with and without planets exhibit very similar abundance behaviours, either for solar twins or even when considering the wholeUdry, S. et al.
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22013 -
Very-low-mass Stellar and Substellar Companions to Solar-like Stars from Marvels. III. A Short-period Brown Dwarf Candidate around an Active G0IV SubgiantWe present an eccentric, short-period brown dwarf candidate orbiting the active, slightly evolved subgiant star TYC 2087-00255-1, which has effective temperature T eff = 5903 ± 42 K, surface gravity log (g) = 4.07 ± 0.16 (cgs), and metallicity [Fe/H] = -0.23 ± 0.07. This candidate was discovered using data from the first two years of the MultiZhao, Bo et al.
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12013 -
The Ninth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Baryon Oscillation Spectroscopic SurveyThe Sloan Digital Sky Survey III (SDSS-III) presents the first spectroscopic data from the Baryon Oscillation Spectroscopic Survey (BOSS). This ninth data release (DR9) of the SDSS project includes 535,995 new galaxy spectra (median z ~ 0.52), 102,100 new quasar spectra (median z ~ 2.32), and 90,897 new stellar spectra, along with the dataSheldon, Erin et al.
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122012 -
The hypergiant HR 8752 evolving through the yellow evolutionary voidContext. We study the time history of the yellow hypergiant HR 8752 based on high-resolution spectra (1973-2005), the observed MK spectral classification data, B - V- and V-observations (1918-1996) and yet earlier V-observations (1840-1918). Aims: Our local thermal equilibrium analysis of the spectra yields accurate values of the effectiveNieuwenhuijzen, H. et al.
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Chemically tagging the Hyades Supercluster. A homogeneous sample of F6-K4 kinematically selected northern starsStellar kinematic groups are kinematical coherent groups of stars that might have a common origin. These groups are dispersed throughout the Galaxy over time by the tidal effects of both Galactic rotation and disc heating, although their chemical content remains unchanged. The aim of chemical tagging is to establish that the abundances of everyTabernero, H. M. et al.
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112012 -
Exploring the α-enhancement of metal-poor planet-hosting stars. The Kepler and HARPS samplesRecent studies have shown that at low metallicities Doppler-detected planet-hosting stars tend to have high α-content and to belong to the thick disk. We used the reconnaissance spectra of 87 Kepler planet candidates and data available from the HARPS planet search survey to explore this phenomenon. Using the traditional spectroscopic abundanceAdibekyan, V. Zh. et al.
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112012 -
Chemical abundances of distant extremely metal-poor unevolved starsContext. The old Galactic halo stars hold the fossil record of the interstellar medium chemical composition at the time of their formation. Most of the stars studied so far are relatively near to the Sun, this prompts the study of more distant stars, both to increase the size of the sample and to search for possible variations of abundance patternsBonifacio, P. et al.
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62012 -
TMCalc - a fast code to derive Teff and [Fe/H] for FGK starsWe present a new direct spectroscopic calibration for a fast estimation of the stellar metallicity [Fe/H]. This calibration was computed using a large sample of 451 solar-type stars for which we have precise spectroscopic parameters derived from high quality spectra. The new [Fe/H] calibration is based on weak Fe I lines, which are expected to beSousa, S. G. et al.
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