Evolutionary Population Synthesis for Binary Stellar Population at High Spectral Resolution: Integrated Spectral Energy Distributions and Absorption-feature Indices

Using EPS we present high resolution (0.3 \AA, HRes) ISEDs from 3000 to 7000 \AA and Lick/IDS absorption-line indices, for an extensive set of instantaneous burst binary stellar populations (BSPs) with binary interactions. The ages of the BSPs are in the range 1 - 15 Gyr and the metallicities are in the range 0.004 - 0.03. This HRes synthesis results can satisfy the needs of modern spectroscopic galaxy surveys, and are available on request. By comparing the synthetic continuum of BSPs at high and low resolution (LRes) we show that there is a good agreement for Z=0.02 and a tolerable disagreement for non-solar metallicity. The strength of the Balmer lines at HRes is greater than that at LRes for all metallicities. The comparison of Lick/IDS absorption-line indices at LRes and HRes, both of which are obtained by the fitting functions (FFs), shows that the discrepancies in all indices except for TiO_1 and TiO_2 are insignificant for BSPs with Z=0.004 and Z=0.02. The HRes Ca4227, Fe5015 and Mg_b indices are redder than the corresponding LRes one for BSPs with Z=0.01 and Z=0.03, this effect lowers the derived age and metallicity of the BSP. The high resolution Mg_1, Fe5709 and Fe5782 indices are bluer than those at LRes, it raises the age and metallicity. The discrepancy in these six indices is greater for BSPs with Z=0.03 in comparison to Z=0.01. At HRes we compare the Lick/IDS spectral absorption indices obtained by using the FFs with those measured directly from the synthetic spectra, and see that Ca4455, Fe4668, Mg_b and Na D indices obtained by the use of the FFs are redder for all metallicities, Fe5709 is redder at Z=0.03 and becomes to be bluer at Z=0.01 and 0.004, and other indices are bluer for all metallicities than the corresponding values measured directly from the synthetic spectra.Comment: 11 pages, 10 figures, to be published in MNRA

A library of high resolution Kurucz spectra in the wavelength range 3000 - 10000 AA

We present a library of 6410 synthetic spectra with resolution Lambda/dLambda = 250,000 based on the revised Kurucz 1993 model atmospheres. The library covers the wavelength range 3000 - 10,000 AA with 54 values of effective temperature in the range 5250 - 50,000 K, 11 values of log surface gravity between 0.0 and 5.0 and 19 metallicities in the range -5.0 to 1.0. We find that, with a few caveats, the library compares well with both the original 20 AA Kurucz spectra and also with observed spectra. The library is intended for use in population synthesis and physical parameterisation of stellar spectra. We assess the suitability of the library for these tasks.Comment: 10 pages, 6 figures, to be published in MNRA

European mobility of United Kingdom educated graduates. Who stays, who goes?

Official figures from the Home Office show an increase in mobility of the highly-skilled from the United Kingdom (UK) to other European countries. This paper analyses the social composition of intra-European mobile graduates from the UK in the context of recent political developments (Bologna-Process, European Higher Education Area). Using quantitative and qualitative data from a longitudinal study of students and its follow-up study, the paper compares the social composition and current activity of intra-European mobile graduates with those remaining in the UK. Personal and higher education-related variables together with the current type of employment were significant for the distinction between intra-European mobile graduates and ‘UK stayers’. UK-educated mobile graduates were identified as ‘Eurostars’, who come from high social classes or studied at high tariff higher education institutions. Mobility was identified as one way for UK-educated graduates to avoid employment in non-graduate jobs and add further value to their undergraduate degrees

Uncertainties in the production of p nuclei in massive stars obtained from Monte Carlo variations

T. Rauscher, N. Nishimura, R. Hirschi, G. Cescutti, A. St. J. Murphy and A. Heger, ‘Uncertainties in the production of p nuclei in massive stars obtained from Monte Carlo variations’, MNRAS Vol 463( 4 ): 4153-4166, first published online on 8 September 2016, the version of record is available online via doi:10.1093/mnras/stw2266 © 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.Nuclear uncertainties in the production of $p$ nuclei in massive stars have been quantified in a Monte Carlo procedure. Bespoke temperature-dependent uncertainties were assigned to different types of reactions involving nuclei from Fe to Bi. Their simultaneous impact was studied in postprocessing explosive trajectories for three different stellar models. It was found that the grid of mass zones in the model of a 25 $M_\odot$ star, which is widely used for investigations of $p$ nucleosynthesis, is too crude to properly resolve the detailed temperature changes required for describing the production of $p$ nuclei. Using models with finer grids for 15 $M_\odot$ and 25 $M_\odot$ stars with initial solar metallicity, it was found that most of the production uncertainties introduced by nuclear reaction uncertainties are smaller than a factor of two. Since a large number of rates were varied at the same time in the Monte Carlo procedure, possible cancellation effects of several uncertainties could be taken into account. Key rates were identified for each $p$ nucleus, which provide the dominant contribution to the production uncertainty. These key rates were found by examining correlations between rate variations and resulting abundance changes. This method is superior to studying flow patterns, especially when the flows are complex, and to individual, sequential variation of a few rates.Peer reviewedFinal Published versio

A comprehensive set of simulations of high-velocity collisions between main sequence stars

We report on a very large set of simulations of collisions between two main sequence (MS) stars. These computations were done with the ``Smoothed Particle Hydrodynamics'' method. Realistic stellar structure models for evolved MS stars were used. In order to sample an extended domain of initial parameters space (masses of the stars, relative velocity and impact parameter), more than 15000 simulations were carried out. We considered stellar masses ranging between 0.1 and 75 Msun and relative velocities up to a few thousands km/s. To limit the computational burden, a resolution of 2000-30000 particles per star was used. The primary goal of this study was to build a complete database from which the result of any collision can be interpolated. This allows us to incorporate the effects of stellar collisions with an unprecedented level of realism into dynamical simulations of galactic nuclei and other dense stellar clusters. We make the data describing the initial condition and outcome (mass and energy loss, angle of deflection) of all our simulations freely available on the Internet. We find that the outcome of collisions depends sensitively on the stellar structure and that, in most cases, using polytropic models is inappropriate. Published fitting formulas for the collision outcomes, established from a limited set of collisions, prove of limited use because they do not allow robust extrapolation to other stellar structures or relative velocities.Comment: 45 pages, 44 figures. Modified to reflect the changes in the published version (MNRAS). PDF version with high-res figures at http://obswww.unige.ch/~freitag/papers/article_collisions.pdf, simulation data at http://obswww.unige.ch/~freitag/MODEST_WG4/FB_Collision_Data/, movies at http://obswww.unige.ch/~freitag/collisions/animations/index.htm

Transnational connections, competences and identities: experiences of Chinese international students after their return ‘home’

International students constitute a substantial and growing mobile population globally. However, as yet, the experiences of returnees and the ways in which their overseas studies impact on their identity and professional and personal lives over time have been under-researched areas. In this article we employ concepts from theories of transnationalism as a framework for the analysis of the experiences of Chinese graduate returnees. The empirical basis for the article is a 20-month, two-stage, mixed-method study of 652 Chinese students who returned home for work on completion of their degrees in UK universities over the last 25+ years. Evidence suggests that their journeys of studying abroad and returning home are dynamic and interconnected transnational experiences. Such experiences are avenues for diverse social networks that reinforce a complex cosmopolitan identity and awareness. They are, also, avenues for transnational(ised) new competences, skills and worldviews, which are increasingly valued by the students themselves upon return home. Irrespective of differences in their demographics and backgrounds, studying and living abroad was perceived by most returnees in our research as a profound identity transformating experience. These new connections, competences and identities enabled them to view and live life with a new sense of self at ‘home’ and, as a result, function in ways that continued to distinguish themselves from those around them over time. The findings have implications for higher education institutions and agencies that are concerned with enhancing the quality of university internationalisation. They also have implications for a broadened empirical and conceptual understanding of transnationalism

A rolling stone gathers no moss? The case of mature students in higher education and their plurilingual repertoires

This study diagnoses how the plurilingual repertoires of mature students (MS) in higher education (HE) are constructed throughout their lives. It addresses the main characteristics of MS; the contexts in which they move throughout their lives, and the situations they contact with languages. Data were collected by means of a questionnaire, mostly comprising open-ended questions. The questionnaire was emailed to 485 MS and was filled in by 195 (40.2%). The results highlight the intrinsic relationship between the MS’ life histories and the construction of their plurilingual repertoires. The findings reinforce the relevance of considering the MS’ plurilingual repertoires and life histories in the development of educational linguistic policies in HE.publishe

Introductory programming: a systematic literature review

As computing becomes a mainstream discipline embedded in the school curriculum and acts as an enabler for an increasing range of academic disciplines in higher education, the literature on introductory programming is growing. Although there have been several reviews that focus on specific aspects of introductory programming, there has been no broad overview of the literature exploring recent trends across the breadth of introductory programming. This paper is the report of an ITiCSE working group that conducted a systematic review in order to gain an overview of the introductory programming literature. Partitioning the literature into papers addressing the student, teaching, the curriculum, and assessment, we explore trends, highlight advances in knowledge over the past 15 years, and indicate possible directions for future research

A library of high resolution synthetic stellar spectra from 300nm to 1.8 micron with solar and alpha-enhanced composition

Libraries of stellar spectra are fundamental tools for the study of stellar populations and both empirical and synthetic libraries have been used for this purpose. In this paper, a new library of high resolution synthetic spectra is presented, ranging from the near-ultraviolet (300nm) to the near-infrared (1.8${\rm \mu}$m). The library spans all the stellar types that are relevant to the integrated light of old and intermediate-age stellar populations in the involved spectral region (spectral types F through M and all luminosity classes). The grid was computed for metallicities ranging from [Fe/H] = --2.5 to +0.5, including both solar and $\alpha$-enhanced ([$\alpha$/Fe] = 0.4) chemical compositions. The synthetic spectra are a good match to observations of stars throughout the stellar parameter space encompassed by the library and over the whole spectral region covered by the computations.Comment: A&A, accepted (revised version