Grants related:
General
Several spectroscopic analyses of stars with planets have recently been carried out. One of the most remarkable results is that planet-harbouring stars are on average more metal-rich than solar-type disc stars. Two main explanations have been suggested to link this metallicity excess with the presence of planets. The first of these, the “self-enrichement” hypothesis, attributes the origin of the observed overabundance of metals to the accretion of large amounts of metal-rich H- and He-depleted rocky planetesimal materials on to the star. The opposite view, the “primordial” hypothesis, considers the metallicity enhancement to be caused by the high metal content of the protoplanetary cloud from which the planetary system formed. Light elements may give fundamental information about the mixing, diffusion and angular momentum history of exoplanets hosts, as well as stellar activity caused by interaction with. Studies of Be, Li and the isotopic could give evidences to distinguish between different planet formation theories. Evidences of pollution have been found in HD82943 by Israelian et al.(2001, Nature, 411, 163; 2003, A&A, 405, 753).
The “self-enrichement” scenario should lead to a relative overabundance of refractories, such as Si, Mg, Ca, Ti and the iron-group elements, compared to volatiles, such as CNO, S and Zn. Differents spectroscopic studies of Fe (Santos et al. 2001, A&A, 373, 1019; 2003, A&A, 398, 363; 2004, A&A, 415, 1153) and other elements (Bodaghee et al 2003, A&A, 404, 715; Ecuvillon, Israelian, Santos et al. 2004, A&A, 418, 703; 2004, A&A, 426, 619) have been completed.
The spectroscopic analisis of metal rich stars can also give us a valuable information about yields of chemical elements produced by supernovae during the last 10 Gyr. An alternative method to investigate products of supernova explosions is by studying secondary stars in Low Mass X-ray binary systems (LMXB). The secondary stars in LMXBs have survived the supernova explosions and could have captured a part of the matter ejected during the explosion. This material can be mixed in the convection zone in a way that the final surface abundanced will be altered. Thus, a study of abundance anomalies in the atmospheres of these stars can provide us an information about nucleosynthesis and evolution of massive stars and also about supernova explosions. This new idea was applied for the first time by Israelian et al. (1999, Nature 401, 142) in the spectroscopic study of GRO J1655-40 (Nova Scorpii 1994), a LMXB with a black hole which has the most reliable mass determination. The analysis has shown that the abundances of O, Mg, Si and S are from 6 to 10 times larger compared with the Sun. These results were considered as the evidence that a supernova explosion took place and created the black hole in the system where the low mass secondary star could not produce these elements
Members
Results
- The planet-metallicity correlation is reviewed showing that the metallicity distribution of stars hosting low-mass planets (below 30 M⊕) is indistinguishable from that from the solar neighborhood sample in terms of metallicity distribution.
- We found that 3D 6Li/7Li corrections are always negative, showing that 1D LTE analysis can significantly overestimate the presence of 6Li (up to 4.9% points) in the atmospheres of solar-like dwarf stars. Although 3D NLTE spectral synthesis implies an extensive computational effort, the results can be made accessible with parametric tools like the ones presented by us
- We have analyzed the behaviour of chemical abundances of Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd, and Eu in the large and homogeneous HARPS-GTO planet search sample.We compared the [X/Fe] ratios of such elements in different metallicity bins and we find that planet hosts present higher abundances of Zn for [Fe/H] < -0.1 dex.
- We found that 100% of planetary sample in HARPS-GTO present C/O < 0.8. 86% of stars with high-mass companions present 0.8 > C/O > 0.4, while 14% present C/O values lower than 0.4. Regarding Mg/Si, all stars with low-mass planetary companion showed values between one and two, while 85% of the high-mass companion sample does.
Scientific activity
Related publications
-
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.
Advertised on:
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.
Advertised on:
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.
Advertised on:
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.
Advertised on:
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.
Advertised on:
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.
Advertised on:
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.
Advertised on:
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.
Advertised on:
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.
Advertised on:
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.
Advertised on:
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.
Advertised on:
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.
Advertised on:
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.
Advertised on:
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.
Advertised on:
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.
Advertised on:
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.
Advertised on:
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.
Advertised on:
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.
Advertised on:
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.
Advertised on:
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.
Advertised on:
92011
