C, S, Zn and Cu abundances in planet-harbouring stars

Ecuvillon, A.; Israelian, G.; Santos, N. C.; Mayor, M.; Villar, V.; Bihain, G.

doi:10.1051/0004-6361:20041136

Cited by 103 publications

(115 citation statements)

References 38 publications

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“…Our [C/Fe] determinations for dwarfs are somewhat lower than in other works (Ecuvillon et al 2004b;Gonzalez & Laws 2000;Reddy et al 2003). We found that the Sun is slightly overabundant in carbon compared to other dwarfs in the same metallicity range, which is the opposite situation found by those A71, page 6 of 13 authors.…”

Section: Resultscontrasting

confidence: 83%

Homogeneous photospheric parameters and C abundances in G and K nearby stars with and without planets

Silva

Milone

Reddy

2010

A&A

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Aims. We present a determination of photospheric parameters and carbon abundances for a sample of 172 G and K dwarf, subgiant, and giant stars with and without detected planets in the solar neighbourhood. The analysis was based on high signal-to-noise ratio and high resolution spectra observed with the ELODIE spectrograph (Haute Provence Observatory, France) and for which the observational data were publicly available. We intend to contribute precise and homogeneous C abundances in studies that compare the behaviour of light elements in stars with and without planets. This will bring new arguments to the discussion of possible anomalies that have been suggested and will contribute to a better understanding of different planetary formation process. Methods. The photospheric parameters were computed through the excitation potential, equivalent widths, and ionisation equilibrium of iron lines selected in the spectra. Carbon abundances were derived from spectral synthesis applied to prominent molecular head bands of C 2 Swan (λ5128 and λ5165) and to a C atomic line (λ5380.3). Careful attention was drawn to carry out this homogeneous procedure and to compute the internal uncertainties. [Fe/H] shows no difference in the behaviour of planet-host stars in comparison with stars for which no planet was detected, for both dwarf and giant subsamples. This result agrees with the hypothesis of a primordial origin for the chemical abundances presently observed instead of self-enrichment during the planetary system formation and evolution. Additionally, giant stars are clearly depleted in [C/Fe] (by about 0.14 dex) when compared with dwarfs, which is probably related to evolution-induced mixing of H-burning products in the envelope of evolved stars. Subgiant stars, although in small number, seem to follow the same C abundance distribution as dwarfs. We also analysed the kinematics of the sample stars that in their majority are members of the Galaxy's thin disc. Finally, comparisons with other analogue studies were performed and showed good agreement within the uncertainties. Results. The distribution of [C/Fe] as a function of

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Section: Resultscontrasting

confidence: 83%

Homogeneous photospheric parameters and C abundances in G and K nearby stars with and without planets

Silva

Milone

Reddy

2010

A&A

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“…τ Boo was noted as a metal-rich star according to the criterion [Fe/H] > 0.2. Subsequently, the high metallicity of our target was confirmed by several accurate abundance analyses, the most recent performed by Ecuvillon et al (2004b), Valenti & Fischer (2005), Takeda & Honda (2005), Gilli et al (2006), Luck &Heiter (2006), andTakeda (2007).…”

Section: Photospheric Abundancesmentioning

confidence: 56%

Photospheric and coronal abundances in solar-type stars: the peculiar case ofτ Bootis

Maggio

Sanz-Forcada

2011

A&A

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Aims. Chemical abundances in solar-type stars are still a much debated topic in many respects. In particular, planet-hosting stars are known to be metal-rich, but whether or not this peculiarity applies also to the chemical composition of the outer stellar atmospheres is still to be clarified. More in general, coronal and photospheric abundances in late-type stars appear to be different in many cases, but understanding how chemical stratification effects work in stellar atmospheres requires an observational base larger than currently available. Methods. We obtained XMM-Newton high-resolution X-ray spectra of τ Bootis, a well known nearby star with a Jovian-mass close-in planet. We analyzed these data with the aim to perform a detailed line-based emission measure analysis and derive the abundances of individual elements in the corona with two different methods applied independently. We compared the coronal abundances of τ Bootis with published photospheric abundances based on high-resolution optical spectra and with those of other late-type stars with different magnetic activity levels, including the Sun. Results. We find that the two methods provide consistent results within the statistical uncertainties for both the emission measure distribution of the hot plasma and for the coronal abundances, with discrepancies at the 2σ level limited to the amount of plasma at temperatures of 3-4 MK and to the O and Ni abundances. In both cases, the elements for which both coronal and photospheric measurements are available (C, N, O, Si, Fe, and Ni) result systematically less abundant in the corona by a factor 3 or more, with the exception of the coronal Ni abundance which is similar to the photospheric value. Comparison with other late-type stars of similar activity level shows that these coronal/photospheric abundance ratios are peculiar to τ Bootis and possibly related to the characteristic over-metallicity of this planet-hosting star.

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“…The final set of abundances, together with the number of element lines used to derive the abundances and respective errors (denoting the error on the mean) are listed in Table 3. Moreover, we also derived abundances of several volatile elements (C, O, S, and Zn) and heavier elements, following the procedures of Ecuvillon et al (2004) and Bertran de Lis et al (2015). The values allow us to conclude that HD 219828 is a typical thin-disk star from the solar neighbourhood; its [α/Fe] 6 abundance ratios are nearly solar (i.e.…”

Section: Hd 219828: the Starmentioning

confidence: 99%

An extreme planetary system around HD 219828

Santos

Santerne

Faria

et al. 2016

A&A

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Context. With about 2000 extrasolar planets confirmed, the results show that planetary systems have a whole range of unexpected properties. This wide diversity provides fundamental clues to the processes of planet formation and evolution. Aims. We present a full investigation of the HD 219828 system, a bright metal-rich star for which a hot Neptune has previously been detected. Methods. We used a set of HARPS, SOPHIE, and ELODIE radial velocities to search for the existence of orbiting companions to HD 219828. The spectra were used to characterise the star and its chemical abundances, as well as to check for spurious, activity induced signals. A dynamical analysis is also performed to study the stability of the system and to constrain the orbital parameters and planet masses. Results. We announce the discovery of a long period (P = 13.1 yr) massive (m sin i = 15.1 M Jup ) companion (HD 219828 c) in a very eccentric orbit (e = 0.81). The same data confirms the existence of a hot Neptune, HD 219828 b, with a minimum mass of 21 M ⊕ and a period of 3.83 days. The dynamical analysis shows that the system is stable, and that the equilibrium eccentricity of planet b is close to zero. Conclusions. The HD 219828 system is extreme and unique in several aspects. First, ammong all known exoplanet systems it presents an unusually high mass ratio. We also show that systems like HD 219828, with a hot Neptune and a long-period massive companion are more frequent than similar systems with a hot Jupiter instead. This suggests that the formation of hot Neptunes follows a different path than the formation of their hot jovian counterparts. The high mass, long period, and eccentricity of HD 219828 c also make it a good target for Gaia astrometry as well as a potential target for atmospheric characterisation, using direct imaging or high-resolution spectroscopy. Astrometric observations will allow us to derive its real mass and orbital configuration. If a transit of HD 219828 b is detected, we will be able to fully characterise the system, including the relative orbital inclinations. With a clearly known mass, HD 219828 c may become a benchmark object for the range in between giant planets and brown dwarfs.

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C, S, Zn and Cu abundances in planet-harbouring stars

Cited by 103 publications

References 38 publications

Homogeneous photospheric parameters and C abundances in G and K nearby stars with and without planets

Homogeneous photospheric parameters and C abundances in G and K nearby stars with and without planets

Photospheric and coronal abundances in solar-type stars: the peculiar case ofτ Bootis

An extreme planetary system around HD 219828

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