Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 0711.0683

Ciao? Adios!

Andreas Korn
View original source ↗Read source document ↗Export metadata ↓

Abstract

At the "New Horizons in Globular Cluster Astronomy" conference (Padova, June 2002), two members of the VLT globular cluster team presented different views on the importance of heavy-element sedimentation in Population II stars: "The lack of evidence for depletion of Fe and Li in the atmospheres of globular cluster subgiants led some people to suspect that, for unknown reasons, Population II stars are not affected by this mechanism." (Castellani 2003) and "There should be some mechanism that prevents sedimentation." (Gratton 2003). In this review, I will argue that the scepticism behind both these statements is justified. We recently revisited the results on sedimentation in NGC 6397 stars presented by Gratton et al. (2001) using higher-quality VLT/FLAMES-UVES data (Korn et al. 2006, 2007). Element-specific abundance trends were identified which agree with atomic-diffusion predictions, if turbulent mixing below the convective envelope is accounted for in a parametrized way. Have we thus detected signatures of Atomic Diffusion in Old Stars (ADiOS)? Or are these trends mere artefacts of Conspiring Inaccuracies in Abundance Observations (CIAO)?

Explore related subjects

astro-ph

Keep this discovery

BibTeXRIS

Andreas Korn. 2007-11-05. Ciao? Adios!. https://arxiv.org/abs/0711.0683

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2009

Solar system tests do not rule out 1/R gravity

We argue that Solar system tests do not rule out 1/R gravity at least due to the reason addressed in Phys. Rev. D 74 (2006) 121501 [astro-ph/0610483] (ref. [1]) and subsequent published papers. Ref. [1] has not only modified the Einstein-Hilbert action but also has changed the boundary conditions since they altered the equations of motion. In Einstein-Hilbert action equations are second order, so the fall off of the fields suffices to single out a unique solution. In 1/R gravity the equations are fourth order, so we should impose additional boundary conditions. Perhaps the boundary condition we must impose is that the abrupt change in the second derivative of the metric near the surface of the Sun remains intact by adding `1/R' corrections to the equations of motion. The solution of 1/R gravity with this boundary condition remains consistent with the solar system tests. Ref. [1] assumes that as soon as they perturbatively modified the equations then the Ricci scalar becomes smooth on the surface of the Sun. This assumption is simply wrong because the boundary conditions and equations of motions are two different entities.

astro-ph↗
arXiv2009

Gamma-ray luminosity function of Gamma-ray bright AGNs

Detection of Gamma-ray emission from a class of active galactic nuclei (viz blazars), has been one of the important findings from the Compton Gamma Ray Observatory (CGRO). However, their Gamma-ray luminosity function has not been well determined. Few attempts have been made in earlier works, where BL Lacs and Flat Spectrum Radio Quasars (FSRQs) have been considered as a single source class. In this paper we investigated the evolution and Gamma-ray luminosity function of FSRQs and BL Lacs separately. Our investigation indicates no evolution for BL Lacs, however FSRQs show significant evolution. Pure luminosity evolution is assumed for FSRQs and exponential and power law evolution models are examined. Due to the small number of sources, the low luminosity end index of the luminosity function for FSRQs is constrained with upper limit. BL Lac luminosity function shows no signature of break. As a consistency check, the model source distributions deriving from these luminosity functions show no significant departure from the observed source distributions.

astro-ph↗
arXiv2009

Multi-Scale Morphological Analysis of SDSS DR5 Survey using the Metric Space Technique

Following novel development and adaptation of the Metric Space Technique (MST), a multi-scale morphological analysis of the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5) was performed. The technique was adapted to perform a space-scale morphological analysis by filtering the galaxy point distributions with a smoothing Gaussian function, thus giving quantitative structural information on all size scales between 5 and 250 Mpc. The analysis was performed on a dozen slices of a volume of space containing many newly measured galaxies from the SDSS DR5 survey. Using the MST, observational data were compared to galaxy samples taken from N-body simulations with current best estimates of cosmological parameters and from random catalogs. By using the maximal ranking method among MST output functions we also develop a way to quantify the overall similarity of the observed samples with the simulated samples.

astro-ph↗