Robert Izzard's Pages of Astronomical Happiness


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  Papers • Papers of 2006
Population nucleosynthesis in single and binary stars. I. Model
R.G. Izzard, ; L.M. Dray; A.I. Karakas; M. Lugaro; C.A. Tout
Astronomy and Astrophysics, Volume 460, Issue 2, December III 2006, pp.565-572
We present a synthetic algorithm to rapidly calculate nucleosynthetic yields from populations of single and binary stars for use in population synthesis, globular cluster and Galactic chemical evolution simulations. Even though this algorithm operates about 107 times faster than full evolution and nucleosynthesis calculations, agreement with such models is good. We extend the single star model to include prescriptions of binary star interactions.
Evolution in the surface abundance-mass plane for a binary with initial conditions M1=7 M, M2=5 M, P=40 days, Z=0.02, the primary is black, the secondary is grey.
Galactic Sodium from AGB Stars
R.G. Izzard, B.K. Gibson and R.J. Stancliffe 2006
Why Galaxies Care About AGB Stars: Their Importance as Actors and Probes. ASP Conference Series, Vol. 378
Sodium abundance ([Na/Fe]) as a function of iron abundance ([Fe/H]) in the solar neighbourhood for a variety of Chemical Evolution models against the observations.
Galactic chemical evolution (GCE) models which include sodium from type II supernovae (SNe) alone underestimate the abundance of sodium in the interstellar medium by a factor of 2 to 3 over about 3 dex in metallicity and predict a flat behavior in the evolution of [Na/Fe] at super-solar metallicities. Conversely, recent observations of stars with [Fe/H]˜+0.4 suggest that [Na/Fe] increases at high metallicity. We have combined stellar evolution models of asymptotic giant branch (AGB) and Wolf-Rayet (WR) stars with the latest SN yields in an attempt to resolve these problems dots and have created many more.
Window To The Stars
R.G. Izzard and E. Glebbeek
We present Window To The Stars, a graphical user interface to the popular TWIN single/binary stellar evolution code, for novices, students and professional astrophysicists. It removes the drudgery associated with the traditional approach to running the code, while maintaining the power, output quality and flexibility a modern stellar evolutionist requires. It is currently being used for cutting edge research and interactive teaching.
See also the Window To The Stars website.
An example of a Kippenhahn-style diagram plotted with Window To The Stars
New Astronomy, Volume 12, Issue 2, p. 161-163
Synthetic Super AGB Stars
Izzard and Poelarends
We describe our first attempt at modelling nucleosynthesis in massive AGB stars which have undergone core carbon burning, the super-AGB stars. We fit a synthetic model to detailed stellar evolution models in the mass range 9< M/M<11.5 (Z=0.02), and extrapolate these fits to the end of the AGB. We determine the number of thermal pulses and AGB lifetime as a function of mass and mass-loss prescription. Our preliminary nucleosynthesis calculations show that, for a reasonable mass-loss rate, the effect of hot-bottom burning in super-AGB stars on the integrated yield of a stellar population is not large. There are many uncertainties, such as mass-loss and convective overshooting, which prevent accurate yield calculations. However, as potential progenitors of electron-capture supernovae, these stars may contribute 7% of non-type-Ia supernovae.
Memorie della Societa Astronomica Italiana, v.77, p.840
Population Synthesis of s-process element enhanced stars: Constraining the C13 efficiency
Bonacic, Izzard, Lugaro and Pols
Memorie della Societa Astronomica Italiana, v.77, p.879
Software Provides Window To The Stars
R.G. Izzard and E. Glebbeek
Robert Izzard and Evert Glebbeek demonstrate the working of their user-friendly stellar modelling tool, Window to the Stars.
Astronomy & Geophysics, Volume 47, Issue 4, pp. 4.28-4.29
Carbon-enhanced metal-poor stars - effects of binary evolution at low metallicity
O.R. Pols and R.G. Izzard
Stellar Evolution at Low Metallicity: Mass Loss, Explosions, Cosmology ASP Conference Series, Vol. 353, Proceedings of the Conference Held 15-19 August, 2005 in Tartu, Estonia
NIC 2006 proceedings (NeNa/MgAl)
R.G. Izzard, M. Lugaro, C. Iliadis and A.I. Karakas
Proceedings of the International Symposium on Nuclear Astrophysics - Nuclei in the Cosmos - IX. 25-30 June 2006, CERN., p.38.1
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