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Paper: Helium Core Flash and Tip of RedGiant Branch Distances
Volume: 167, Harmonizing Cosmic Distance Scales in a Post-Hipparcos Era
Page: 161
Authors: Madore, Barry F.; Freedman, Wendy L.
Abstract: Theory suggests and observations confirm that the tip of the first-ascent red giant branch can be used as an accurate and precise distance indicator for all galaxies displaying a measurable population of low-metallicty stars. The bolometric luminosity at which the helium core flash is triggered in low-mass stars is well understood to be largely independent of the mass and/or the chemical composition of the layers surrounding the degenerate He core. The bolometric luminosity at core flash is then expected to be a standard candle of relatively high stellar luminosity and having low dispersion. Empirical evidence suggest that, for a wide range of atmospheric metallicities, the emergent I-band flux shares the low dispersion in luminosity predicted by theory. The early history of using the brightest stars in globular clusters as distance indicators is reviewed and contrasted with the modern, tip of the red giant branch (TRGB) method currently being employed extensively in the determination of extragalactic distances. Recent applications of the TRGB method are also reviewed. Finally, comparisons are made with the Cepheid distance scale, and prospects for future applications are outlined.
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