|Fluorine in carbon-enhanced metal-poor stars: a binary scenario|
|M. Lugaro, S. E. de Mink, R. G. Izzard, S. W. Campbell, A. I. Karakas, S. Cristallo, O. R. Pols, J. C. Lattanzio, O. Straniero, R. Gallino, T. C. Beers|
|A super-solar fluorine abundance was observed in the carbon-enhanced metal-poor (CEMP) star HE 1305+0132 ([F/Fe]=+2.90, [Fe/H]=-2.5). We propose that this observation can be explained using a binary model of mass transfer from an asymptotic giant branch (AGB) star companion.
||Fluorine vs (Carbon+Nitrogen) for HE 1305+0132 vs that in our models.
|Astronomy and Astrophysics, Volume 484, Issue 3, 2008, pp.L27-L30|
|Gamma-Ray Bursts from tidally spun-up Wolf-Rayet stars?|
|R. G. Detmers, N. Langer, Ph. Podsiadlowski, R.G. Izzard|
|The outcome of the evolutionary calculations for helium star-compact object binaries with two different mass-loss rates.
||The collapsar model requires rapidly rotating Wolf-Rayet stars as progenitors of long gamma-ray bursts. However, Galactic Wolf-Rayet stars rapidly lose angular momentum due to their intense stellar winds. We find that the simple scenario - i.e., the Wolf-Rayet star being tidally spun up and producing a collapsar - does not occur at solar metallicity and may only occur with low probability at low metallicity.
|Astronomy and Astrophysics, Volume 484, Issue 3, 2008, pp.831-839|
|The effect of massive binaries on stellar populations and supernova progenitors|
|J. J. Eldridge, R. G. Izzard and C. A. Tout. |
|We have calculated a large set of detailed binary models and tested them against observed stellar populations to compare the number of blue/red supergiants and Wolf-Rayet stars at different metallicities. We have also estimated the relative rate of type Ib/c to type II supernovae. We find, with an interacting binary fraction of about two thirds, that we obtain better agreement between our models and observations than with single stars.
||Supernova type Ib/c to type II ratio for single vs binary stars and compared to observations for our models and those of the Geneva group.
|Massive Stars as Cosmic Engines, Proceedings of IAU Symposium 250, pp.179-184|
|The Mysterious R Stars|
|R. G. Izzard, C. S. Jeffery, J. Lattanzio|
|The R stars are a rare class of K-type giant carbon stars. Canonical stellar evolutionary theory cannot explain their existence, yet they have been observed for more than a century. The early-R stars, the warmest in the R class, are enhanced in 12C, 13C and 14N relative to the Sun, but not in s-processes elements or oxygen, and are all single stars. We test the idea that binary mergers lead to the formation of the early-R stars by a comparison of binary population synthesis model results with observations. |
|Proceedings of the IXth Torino Workshop on AGB Stars, Perugia, 2008|
|Modelling the evolution and nucleosynthesis of carbon-enhanced metal-poor stars|
|O. R. Pols, R. G. Izzard, M. Lugaro, S. E. de Mink|
|We present the results of binary population simulations of carbon-enhanced metal-poor (CEMP) stars. We show that nitrogen and fluorine are useful tracers of the origin of CEMP stars, and conclude that the observed paucity of very nitrogen-rich stars puts strong constraints on possible modifications of the initial mass function at low metallicity. The large number fraction of CEMP stars may instead require much more efficient dredge-up from low-metallicity asymptotic giant branch stars. |
|The Art of Modeling (sic) Stars in the 21st Century, Proceedings of IAU Symposium 252|