Saturday, April 15, 2017 4:24 PM
the launch of the reinvigorated mesastar.org went well, folks are submitting their addons and inlists when asked, and aside from a niggly rendering issue of the home page by firefox 52.0.02, all is going relatively smooth.
i enjoyed reading the paper "the evolution and properties of rotating massive star populations" by jieun choi, charlie conroy, and nell byler. rotation, via the centrigugal force term, changes the shape of the star from spherical to an oblate spheroid shape. regulus in the constellation leo is a good example. when a star is oblate, it has a larger radius at its equator than it does at its poles. as a result, the poles have a higher surface gravity (g = m/r^2) and higher effective temperature and brightness (L = 4 pi r^2 sigma T^4) at the poles than at the equator. the poles aresaid to be "gravity brightened" and the equator "gravity darkened". vega in the constellation lyra is a good example. rotation also can boost the mixing of material by any number of mechanisms, which can feed fresh fuel into the core of the star. this makes the star live longer. this paper uses MESA to examine the impact of rotating massive single stars, at several metallicities, on the ionizing radiation released by a newly born population of such stars (aka "a starburst"). one conclusion from this paper is a large fraction of fast rotating stars can sustain the production of ionizing photons beyond a few millions years (rotating stars have longer lifetimes), which in turn might be relevant for cosmic reionization.