red giants as clocks

Lars Bildsten (KITP) was in town and gave two talks today. In the first, he talked about super-luminous supernovae, and how they might be powered by the spin-down of the degenerate remnant, when spin-down times and diffusion times become comparable. In the second, he talked about making precise inferences about giant stars from Kepler and COROT photometry. The photometry shows normal modes and mode splittings, which are sensitive to the run of density in the giants; this in turn constrains what fraction of the star has burned to helium. There is a lot of interesting unexplained phenomenology related to the spin of the stellar core, which remains a puzzle. There was much more in the talk as well, but one thing that caught my interest is that some of the modes are exceedingly high in quality factor or coherence. That is, giants look like very good clocks. A discussion broke out at the end about whether or not we could use these clocks to constrain, detect, or measure gravitational radiation. Each star is much worse than a radio pulsar, but there are far, far more of them available for use. Airplane project!

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