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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Spectroscopic characterization of a sample of metal-poor solar-type stars from the HARPS planet search program. Precise spectroscopic parameters and mass estimationStellar metallicity strongly correlates with the presence of planets and their properties. To check for new correlations between stars and the existence of an orbiting planet, we determine precise stellar parameters for a sample of metal-poor solar-type stars. This sample was observed with the HARPS spectrograph and is part of a program to searchSousa, S. G. et al.
Fecha de publicación:
22011 -
Searching for the Signatures of Terrestrial Planets in Solar AnalogsWe present a fully differential chemical abundance analysis using very high resolution (λ/δλ >~ 85, 000) and very high signal-to-noise (S/N ~800 on average) HARPS and UVES spectra of 7 solar twins and 95 solar analogs, of which 24 are planet hosts and 71 are stars without detected planets. The whole sample of solar analogs provides very accurateGonzález-Hernández, J. I. et al.
Fecha de publicación:
92010 -
Overabundance of α-elements in exoplanet-hosting starsWe present the results for a chemical abundance analysis between planet-hosting and stars without planets for 12 refractory elements for a total of 1111 nearby FGK dwarf stars observed within the context of the HARPS GTO programs. Of these stars, 109 are known to harbour high-mass planetary companions and 26 stars are hosting exclusively NeptuniansAdibekyan, V. Zh. et al.
Fecha de publicación:
72012 -
Measuring Be Depletion in Cool Stars with ExoplanetsWe present new UVES spectra of a sample of 14 mostly cool unevolved stars with planetary companions with the aim of studying possible differences in Be abundance with respect to stars without detected planets. We determine Be abundances for these stars that show an increase in Be depletion as we move to lower temperatures. We carry out aDelgado Mena, E. et al.
Fecha de publicación:
22011 -
Low Mg/Si Planetary Host Stars and Their Mg-depleted Terrestrial PlanetsSimulations have shown that a diverse range of extrasolar terrestrial planet bulk compositions are likely to exist based on the observed variations in host star elemental abundances. Based on recent studies, it is expected that a significant proportion of host stars may have Mg/Si ratios below 1. Here we examine this previously neglected group ofCarter-Bond, Jade C. et al.
Fecha de publicación:
32012 -
Higher depletion of lithium in planet host stars: no age and mass effectRecent observational work by Israelian et al. has shown that sun-like planet host stars in the temperature range 700 K Teff 5850 K have lithium abundances that are significantly lower than those observed for “single” field stars. In this letter we use stellar evolutionary models to show that differences in stellar mass and age are not responsibleSousa, S. G. et al.
Fecha de publicación:
32010 -
Fluorine abundances in dwarf stars of the solar neighbourhoodContext. In spite of many observational efforts to characterize the chemical evolution of our Galaxy, not much is known about the origin of fluorine (F). Models suggest that the F found in the Galaxy might have been produced mainly in three different ways, namely, Type II supernovae, asymptotic giant branch nucleosynthesis, or in the core of WolfRecio-Blanco, A. et al.
Fecha de publicación:
22012 -
Enhanced lithium depletion in Sun-like stars with orbiting planetsThe surface abundance of lithium on the Sun is 140 times less than the protosolar value, yet the temperature at the base of the surface convective zone is not hot enough to burn-and hence deplete-Li (refs 2, 3). A large range of Li abundances is observed in solar-type stars of the same age, mass and metallicity as the Sun, but such a range isIsraelian, Garik et al.
Fecha de publicación:
112009 -
Cosmology: The lithium problemThe theory that predicts how the lightest elements formed after the Big Bang has hitherto failed to explain the amount of cosmic lithium. The detection of interstellar lithium beyond the Milky Way gives this theory a boost. See Article p.121Israelian, G.
Fecha de publicación:
92012 -
Chemical Clues on the Formation of Planetary Systems: C/O Versus Mg/Si for HARPS GTO SampleTheoretical studies suggest that C/O and Mg/Si are the most important elemental ratios in determining the mineralogy of terrestrial planets. The C/O ratio controls the distribution of Si among carbide and oxide species, while Mg/Si gives information about the silicate mineralogy. We present a detailed and uniform study of C, O, Mg, and SiDelgado-Mena, E. et al.
Fecha de publicación:
122010 -
Chemical abundances of 451 stars from the HARPS GTO planet search program. Thin disc, thick disc, and planetsWe present a uniform study of the chemical abundances of 12 elements (Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Na, Mg, and Al) derived from the spectra of 451 stars observed as part of one of the HARPS GTO planet search programs. Sixty eight of these are planet-bearing stars. The main goals of our work are: i) the investigation of possible differencesNeves, V. et al.
Fecha de publicación:
42009 -
Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program. Galactic stellar populations and planetsContext. We performed a uniform and detailed abundance analysis of 12 refractory elements (Na, Mg, Al, Si, Ca, Ti, Cr, Ni, Co, Sc, Mn, and V) for a sample of 1111 FGK dwarf stars from the HARPS GTO planet search program. Of these stars, 109 are known to harbor giant planetary companions and 26 stars are exclusively hosting Neptunians and superAdibekyan, V. Zh. et al.
Fecha de publicación:
92012 -
Beryllium abundances in stars with planets. Extending the sampleContext. Chemical abundances of light elements such as beryllium in planet-host stars allow us to study the planet formation scenarios and/or investigate possible surface pollution processes. Aims: We present here an extension of previous beryllium abundance studies. The complete sample consists of 70 stars that host planets and 30 stars withoutGálvez-Ortiz, M. C. et al.
Fecha de publicación:
62011 -
Be Abundances in Cool Main-sequence Stars with ExoplanetsWe present new Ultraviolet and Visual Echelle Spectrograph (UVES) spectra of a sample of 15 cool unevolved stars with and without detected planetary companions. Together with previous determinations, we study Be depletion and possible differences in Be abundances between the two groups of stars. We obtain a final sample of 89 and 40 stars with andDelgado Mena, E. et al.
Fecha de publicación:
22012 -
An effective temperature calibration for solar type stars using equivalent width ratios. A fast and easy spectroscopic temperature estimationAims: Precise determination of the stellar effective temperature of solar type stars is extremely important for astrophysics. We present an effective temperature calibration for FGK dwarf stars using the line equivalent width ratios of spectral absorption lines. Methods: We used the automatic code ARES to measure the equivalent width for severalSousa, S. G. et al.
Fecha de publicación:
32010 -
A search for naphthalene in diffuse interstellar cloudsWe have obtained high-resolution optical spectroscopy of 10 reddened O-type stars with Ultraviolet and Visual Echelle Spectrograph at Very Large Telescope to search for interstellar bands of the naphthalene cation (C10H8+) in the intervening clouds. No absorption features were detected near the laboratory strongest band of this cation at 6707 ÅIglesias-Groth, S. et al.
Fecha de publicación:
32012 -
A new α-enhanced super-solar metallicity populationWe performed a uniform and detailed analysis of 1112 high-resolution spectra of FGK dwarfs obtained with the HARPS spectrograph at the ESO 3.6 m telescope (La Silla, Chile). Most stars have effective temperatures 4700 K ≤ Teff ≤ 6300 K and lie in the metallicity range of -1.39 ≤ [Fe/H] ≤ 0.55. Our main goal is to investigate whether there are anyAdibekyan, V. Zh. et al.
Fecha de publicación:
112011 -
A homogeneous spectroscopic analysis of host stars of transiting planetsContext: The analysis of transiting extra-solar planets provides an enormous amount of information about the formation and evolution of planetary systems. A precise knowledge of the host stars is necessary to derive the planetary properties accurately. The properties of the host stars, especially their chemical composition, are also of interest inAmmler-von Eiff, M. et al.
Fecha de publicación:
112009 -
On the mass of the neutron star in Cyg X-2We present new high-resolution spectroscopy of the low-mass X-ray binary Cyg X-2, which enables us to refine the orbital solution and rotational broadening of the donor star. In contrast with Elebert et al., we find a good agreement with results reported in Casares et al. We measure P = 9.84450 +/- 0.00019 d, K2 = 86.5 +/- 1.2 kms-1 and V sini = 33Casares, J. et al.
Fecha de publicación:
22010 -
Chemical Abundances of the Secondary Star in the Black Hole X-Ray Binary V404 CygniWe present a chemical abundance analysis of the secondary star in the black hole binary V404 Cygni, using Keck I/High Resolution Spectrometer. We adopt a χ2-minimization procedure to derive the stellar parameters, taking into account any possible veiling from the accretion disk. With these parameters we determine the atmospheric abundances of O, NaGonzález-Hernández, J. I. et al.
Fecha de publicación:
92011
