The lithium isotope ratio in the metal-poor halo star G271-162 from VLT/UVES observations

A high resolution (R = 110.000), very high S/N (>600) spectrum of the metal-poor turnoff star G271-162 has been obtained in connection with the commissioning of UVES at VLT/Kueyen. Using both 1D hydrostatic and 3D hydrodynamical model atmospheres, the lithium isotope ratio has been estimated from the LiI 670.8 nm line by means of spectral synthesis. The necessary stellar line broadening (1D: macroturbulence + rotation, 3D: rotation) has been determined from unblended KI, CaI and FeI lines. The 3D line profiles agree very well with the observed profiles, including the characteristic line asymmetries. Both the 1D and 3D analyses reveal a possible detection of 6Li in G271-162, 6Li/7Li = 0.02 +-0.01 (one sigma). It is discussed if the smaller amount of 6Li in G271-162 than in the similar halo star HD84937 could be due to differences in stellar mass and/or metallicity or whether it may reflect an intrinsic scatter of the Li isotope ratio in the ISM at a given metallicity.Comment: 5 pages with 6 figures. Accepted as a letter in A&

The First Galaxies: Clues from Element Abundances

It has recently become possible to measure directly the abundances of several chemical elements in a variety of environments at redshifts up to z = 5. In this review I summarise the latest observations of Lyman break galaxies, damped Lyman alpha systems and the Lyman alpha forest with a view to uncovering any clues which these data may offer to the first episodes of star formation. The picture which is emerging is one where the universe at z = 3 already included many of the components of today's galaxies--even at these early times we see evidence for Populations I and II stars, while the `smoking gun' for Population III objects may be hidden in the chemical composition of the lowest density regions of the IGM, yet to be deciphered.Comment: 15 pages, LaTex, 8 Postscript Figures. To appear in the Philosophical Transactions of The Royal Society, Series

Si and Mn Abundances in Damped Lya Systems with Low Dust Content

We have measured the abundances of Zn, Si, Mn, Cr, Fe, and Ni in three damped Lyman alpha systems at redshifts z < 1 from high resolution echelle spectra of QSOs recorded with the Keck I telescope. In all three cases the abundances of Cr, Fe, and Ni relative to Zn indicate low levels of dust depletions. We propose that when the proportion of refractory elements locked up in dust grains is less than about 50 percent, it is plausible to assume an approximately uniform level of depletion for all grain constituents and, by applying a small dust correction, recover the intrisic abundances of Si and Mn. We use this approach on a small sample of damped systems for which it is appropriate, with the aim of comparing the metallicity dependence of the ratios [Si/Fe] and [Mn/Fe] with analogous measurements in Milky Way stars. The main conclusion is that the relative abundances of both elements in distant galaxies are broadly in line with expectations based on Galactic data. Si displays a mild enhancement at low metallicities, as expected for an alpha-capture element, but there are also examples of near-solar [Si/Fe] at [Fe/H] < -1. The underabundance of Mn at low metallicities is possibly even more pronounced than that in metal-poor stars, and no absorption system has yet been found where [Mn/Fe] is solar. The heterogeneous chemical properties of damped Lyman alpha systems, evident even from this limited set of measurements, provide further support for the conclusion from imaging studies that a varied population of galaxies gives rise to this class of QSO absorbers.Comment: 29 pages, LaTex, 7 Postscript Figures. Accepted for Publication in the Astrophysical Journa

High-precision abundances of elements in Kepler LEGACY stars. Verification of trends with stellar age

HARPS-N spectra with S/N > 250 and MARCS model atmospheres were used to derive abundances of C, O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, and Y in ten stars from the Kepler LEGACY sample (including the binary pair 16 Cyg A and B) selected to have metallicities in the range -0.15 < [Fe/H] < +0.15 and ages between 1 and 7 Gyr. Stellar gravities were obtained from seismic data and effective temperatures were determined by comparing non-LTE iron abundances derived from FeI and FeII lines. Available non-LTE corrections were also applied when deriving abundances of the other elements. The results support the [X/Fe]-age relations previously found for solar twins. [Mg/Fe], [Al/Fe], and [Zn/Fe] decrease by ~0.1 dex over the lifetime of the Galactic thin disk due to delayed contribution of iron from Type Ia supernovae relative to prompt production of Mg, Al, and Zn in Type II supernovae. [Y/Mg] and [Y/Al], on the other hand, increase by ~0.3 dex, which can be explained by an increasing contribution of s-process elements from low-mass AGB stars as time goes on. The trends of [C/Fe] and [O/Fe] are more complicated due to variations of the ratio between refractory and volatile elements among stars of similar age. Two stars with about the same age as the Sun show very different trends of [X/H] as a function of elemental condensation temperature Tc and for 16 Cyg, the two components have an abundance difference, which increases with Tc. These anomalies may be connected to planet-star interactions.Comment: 13 pages with 7 figures. Accepted for publication in A&

The lithium isotope ratio in the metal-poor halo star G271-162 from VLT/UVES observations

A high resolution (lambda /Delta lambda =~ 110 000), very high S/N (>~ 600) spectrum of the metal-poor turnoff star G 271-162 has been obtained in connection with the commissioning of UVES at VLT/Kueyen. Using both 1D hydrostatic and 3D hydrodynamical model atmospheres, the lithium isotope ratio has been estimated from the \ion{Li}{i},670.8 nm line by means of spectral synthesis. The necessary stellar line broadening (1D: macroturbulence + rotation, 3D: rotation) has been determined from unblended \ion{K}{i}, \ion{Ca}{i} and \ion{Fe}{i} lines. The 3D line profiles agree very well with the observed profiles, including the characteristic line asymmetries. Both the 1D and 3D analyses reveal a possible detection of \element[][6]{Li} in G 271-162, element [][6]{Li}/element [][7]{Li} = 0.02+/-0.01 (1sigma ). It is discussed if the smaller amount of \element[][6]{Li} in G 271-162 than in the similar halo star HD 84937 could be due to differences in stellar mass and/or metallicity or whether it may reflect an intrinsic scatter of \element[][6]{Li}/\element[][7]{Li} in the ISM at a given metallicity. Based on public data released from the UVES commissioning at the VLT/Kueyen telescope, ESO, Paranal, Chile

The [Y/Mg] clock works for evolved solar metallicity stars

Previously [Y/Mg] has been proven to be an age indicator for solar twins. Here, we investigate if this relation also holds for helium-core-burning stars of solar metallicity. High resolution and high signal-to-noise ratio (S/N) spectroscopic data of stars in the helium-core-burning phase have been obtained with the FIES spectrograph on the NOT 2.56m telescope and the HIRES spectrograph on the Keck I 10 m telescope. They have been analyzed to determine the chemical abundances of four open clusters with close to solar metallicity; NGC 6811, NGC 6819, M67 and NGC 188. The abundances are derived from equivalent widths of spectral lines using ATLAS9 model atmospheres with parameters determined from the excitation and ionization balance of Fe lines. Results from asteroseismology and binary studies were used as priors on the atmospheric parameters, where especially the $\log g$ is determined to much higher precision than what is possible with spectroscopy. It is confirmed that the four open clusters are close to solar metallicity and they follow the [Y/Mg] vs. age trend previously found for solar twins. The [Y/Mg] vs. age clock also works for giant stars in the helium-core burning phase, which vastly increases the possibilities to estimate the age of stars not only in the solar neighborhood, but in large parts of the Galaxy, due to the brighter nature of evolved stars compared to dwarfs.Comment: 5 pages, 3 figures, accepted for publication as a Letter to A&

The beryllium abundance in the very metal-poor halo star G 64-12 from VLT/UVES observations

We report on a new spectroscopic analysis of the very metal deficient star G 64-12 ([Fe/H]=-3.3), aimed at determining, for the first time, its Be content. The spectra were observed during the Science Verification of UVES, the ESO VLT Ultraviolet and Visible Echelle Spectrograph. The high resolution (~48,000) and high S/N (~130 per pixel) achieved at the wavelengths of the BeII resonance doublet allowed an accurate determination of its abundance: log N(Be/H) = -13.10 +/- 0.15 dex. The Be abundance is significantly higher than expected from previous measurements of Be in stars of similar metallicity (3D and NLTE corrections acting to make a slightly higher value than an LTE analysis). When compared to iron, the high [Be/Fe] ratio thus found may suggest a flattening in the beryllium evolutionary trend at the lowest metallicity end or the presence of dispersion at early epochs of galactic evolution.Comment: Accepted for publication in A&A Letters (LaTeX, 6 pages, 3 eps figures

Continuity of care for children with anorexia nervosa in the Netherlands:A modular perspective

Care provision for children with anorexia nervosa is provided by outpatient care teams in hospitals, but the way these teams are organized differs per hospital and hampers the continuity of care. The aim of this study is to explore the organization and continuity of care for children with anorexia nervosa in the Netherlands by using a modular perspective.We conducted a qualitative, exploratory case study and took the healthcare provision for children with anorexia nervosa, provided by outpatient care teams, as our case. We conducted nine interviews with healthcare professionals involved in outpatient care teams from six hospitals. A thematic analysis was used to analyze the data.The modular perspective offered insights into the work practices and working methods of outpatient care teams. We were able to identify modules (i.e. the separate consultations with the various professionals), and components (i.e. elements of these consultations). In addition, communication mechanisms (interfaces) were identified to facilitate information flow and coordination among healthcare professionals. Our modular perspective revealed gaps and overlap in outpatient care provision, consequently providing opportunities to deal with unnecessary duplications and blind spots.Conclusion: A modular perspective can be applied to explore the organization of outpatient care provision for children with anorexia nervosa. We specifically highlight gaps and overlap in healthcare provision, which in turn leads to recommendations on how to support the three essential parts of continuity of care: informational continuity, relational continuity, and management continuity

Galactic Cosmic Rays from Superbubbles and the Abundances of Lithium, Beryllium, and Boron

In this article we study the galactic evolution of the LiBeB elements within the framework of a detailed model of the chemical evolution of the Galaxy that includes galactic cosmic ray nucleosynthesis by particles accelerated in superbubbles. The chemical composition of the superbubble consists of varying proportions of ISM and freshly supernova synthesized material. The observational trends of 6 LiBeB evolution are nicely reproduced by models in which GCR come from a mixture of 25% of supernova material with 75% of ISM, except for 6 Li, for which maybe an extra source is required at low metallicities. To account for 7 Li evolution several additional sources have been considered (neutrino-induced nucleosynthesis, nova outbursts, C-stars). The model fulfills the energetic requirements for GCR acceleration.Comment: 25 pages, 9 figures. Accepted for publication in the Astrophysical Journa