arXiv subjects

Garik Israelian

Publications and source records attributed to Garik Israelian.

22 records · Page 2Linked to original sources

arXiv2003

New measurement of the Lithium-6/Lithium-7 isotopic ratio in the extra-solar planet host star HD82943 and line blending in the Li 6708 A region

The presence of possible blends in the spectral region of the Li resonance line at 6708 A in solar-type metal-rich stars is investigated using high resolution and high signal-to-noise spectroscopic observations. Our analysis does not confirm the identification of a weak absorption feature at 6708.025 A with the low excitation TiI line proposed by Reddy et al. (2002). Our spectrum synthesis suggests that the unidentified absorption is most probably produced by a high excitation SiI line originally proposed by Muller et al. (1975). Reanalysis of the Lithium-6/Lithium-7 isotopic ratio in HD82943 was performed by taking the SiI line into account and using new VLT/UVES spectra of HD82943 with a signal-to-noise ratio close to 1000. We confirm the presence of Lithium-6 in the star's atmosphere while the updated value for the isotopic ratio is f(Lithium-6) = 0.05+-0.02.

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arXiv2001

Confirming the Metal-Rich Nature of Stars with Giant Planets

With the goal of confirming the metallicity ``excess'' observed in stars with planetary mass companions, we have conducted a high-precision spectroscopic study of a ``comparison'' sample of dwarfs included in the CORALIE extra-solar planet survey (Santos, Israelian, & Mayor 2001). The targets were chosen following two basic criteria: they make part of a limited volume and they do not present the signature of a planetary host companion. The spectroscopic analysis, done using the very same technique as previous works on the metallicity of stars with planets, permitted a direct and non-biased comparison of the samples. The results have revealed that metallicity plays an impressive role on the giant planet formation. The chemical composition of the molecular cloud is probably the key parameter to form giant planets. Some evidences exist, however, showing the possibility of accretion of matter in the stellar outer convective zone. These conclusions impose serious constraints on the planetary systems formation and evolution models.

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arXiv2001

Sulphur abundance in very metal-poor stars

We have obtained high-resolution high signal-to-noise spectra of the SI near-infrared doublet at 8694 A in eight metal-poor stars with metallicities in the range -0.6 <[Fe/H]< -3.0. Elemental sulphur abundances were derived for six targets and upper limits were set for two of the most metal-poor stars in the sample. The sulphur doublet at 8694.62 A has been detected in three stars (HD19445, HD2665 and HD2796) with [Fe/H]< -1.9. Our observations combined with those available in the literature indicate a monotonic increase of the [S/Fe] ratio as [Fe/H] decreases, reaching values [S/Fe]~0.7-0.8 below [Fe/H]=-2. We discuss plausible scenarios for interpretation of these results.

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arXiv2000

Galactic Evolution of Beryllium and Oxygen

We discuss the early evolution of beryllium and oxygen in our Galaxy by comparing abundances of these elements for halo and disk metal-poor stars. Both, O and Be rise as we go progressively to more metal-rich stars, showing a slope 0.41 +-0.09 ([Be/O] vs [Fe/H]) for stars with [Fe/H] < -1. This relationship provides an observational constraint to the actually proposed Galactic Cosmic Ray theories.

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