[Triumf-seminars] TRIUMF Colloquium today at 14:00

[TRIUMF Seminars]

Date/Time: Wed 2014-04-02 at 14:00

Location:  Auditorium          

Speaker:   Robert Izzard (U. Bonn)

Title:     The Origin of the Elements and the Critical Role of Binary Stars

Abstract: In a few millenia of recorded history, mankind has made great strides in its understanding of the Universe. We now know that the Big Bang created almost all visible matter as just two elements, hydrogen and helium, which were later turned into carbon, oxygen, iron and the 90+ other chemical elements by nucleosynthesis in stars. Many of these stars are gravitationally bound as close binary systems which may evolve quite differently to single stars leading to exotic phenomena such as thermonuclear novae and gamma-ray bursts. Binaries are also crucial to galactic chemical evolution, particularly through type Ia supernovae which make most of the iron in the Universe. Furthermore, ancient binary stars preserve the chemistry of their long-dead companion and offer unique insight into nucleosynthesis when our galaxy was young.

By comparing statistical models of binary star populations with observations, we can pin down the uncertainties in stellar astrophysics models. For example, chemically peculiar stars, such as carbon-enhanced metal-poor and barium stars, are difficult to reproduce both in number and binary orbital properties with conventional stellar models. Much of my recent work has involved statistically testing new theories of mass transfer and orbital interactions to explain these and other unusual binary stars. Statistical methods are also predictive and I will report on new calculations of a binary-star source of the most contemptuous element in the Universe: lithium. Canonical Galactic chemical evolution models of lithium make too little by a factor of three. Mass ejection from binary stars offers an alternative, hitherto ignored, source of lithium which helps to solve this problem but creates a few more along the way.

Refreshments to appear 15 minutes before the start.

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General TRIUMF seminar information available at http://www.triumf.ca/home/upcoming-events/about-seminars-lectures