1,721,288 research outputs found
Isotopic Anomalies in Cr, Fe and Ni from ``s'' Processing in AGB Stars
No full textThe Fe group nuclei ^54Cr, ^58Fe, and ^64Ni are readily produced in AGB stars during "s" processing. These nuclides do not require SNe production. ..
VizieR Online Data Catalog: Infrared photometry of mass-losing AGB stars (Guandalini+, 2008)
No full textTables 11 and 12 present the data of the "Sub-sample D" discussed in the paper. In particular, Table 11 shows for each source the different denominations, the coordinates, spectral type, variability type and period. Instead, photometric fluxes in near- and mid-infrared, apparent bolometric magnitudes and an indication if the star is Intrinsic or Extrinsic are reported in Table 12. (2 data files). ..
Review and new concepts for neutron-capture measurements of astrophysical interest
No full textThe idea of slow-neutron capture nucleosynthesis formulated in 1957 triggered a tremendous experimental effort in different laboratories worldwide to measure the relevant nuclear physics input quantities, namely () cross sections over the stellar temperature range (from few eV up to several hundred keV) for most of the isotopes involved from Fe up to Bi. A brief historical review focused on total energy detectors will be presented to illustrate how, advances in instrumentation have led, over the years, to the assessment and discovery of many new aspects of -process nucleosynthesis and to the progressive refinement of theoretical models of stellar evolution. A summary will be presented on current efforts to develop new detection concepts, such as the Total-Energy Detector with -ray imaging capability (i-TED). The latter is based on the simultaneous combination of Compton imaging with neutron time-of-flight (TOF) techniques, in order to achieve a superior level of sensitivity and selectivity in the measurement of stellar neutron capture rates...
Ninth Torino Workshop on Evolution and Nucleosynthesis in AGB Stars and IIND Perugia Workshop on Nuclear Astrophysics
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Isotopic Abundances in Presolar SiC Grains accounted by s-Processing from MHD-induced Mixing in low mass AGB stars
No full textIn the past, the observational evidence that s-process elements from Sr to Pb are produced by stars ascending the so-called Asymptotic Giant Branch (or AGB) could not be explained by self-consistent models, forcing researchers to extensive parameterisations. The crucial point is to understand how protons can be injected from the envelope into the He-rich layers, yielding to the formation of C-13 and then the activation of the C-13(alpha,n)O-16 reaction. In the last decade, some physically-based mixing mechanisms have been considered to solve this problem. Nowadays, a big step forward in s-process studies would be to understand what is among the suggested ones the physical model better accounts for the observational constrains. In this paper we analyse a model where the C-13 forms as a feedback of MHD processes in the stellar plasma. We compare results of nucleosynthesis models for low mass AGB stars (M<3M(circle dot)), developed from the MHD scenario, with the record of isotopic abundance ratios of s-elements in presolar SiC grains, which were shown to offer precise constraints on the C-13 reservoir. We find that n-captures driven by magnetically-induced mixing can well account for the SiC data and that this is due to the fact that our C-13 distribution fullfills the above constraints rather accurately. We show comparisons between model predictions and measurements for isotopes of Sr, Zr, Ba, Mo and Ru as representative examples of light and heavy s-elements
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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