1: Yi, Demarque, Kim, Lee, Ree, Lejeune, &Barnes 2001, ApJS, 136, 417
Paper 2: Kim, Demarque, Yi, & Alexander 2002, ApJS, 143, 499
Paper 3: Yi, Kim, & Demarque 2003, ApJS, 144, 259
Paper 4: Demarque, Woo, Kim, & Yi 2004, ApJS, 155, 667
Read News on updates!
New version 2 Isochrones and
interpolator (in Z, age, [a/Fe]).
(23 dec 02) Isochrones and
Download the Green et al. colour table.
Download the Lejeune et al. colour table.
Download the database of the Y2
We have constructed a new set of isochrones, called the Y2 Isochrones, that represent an update of the Revised
Yale Isochrones (RYI), using improved opacities and equations of state. Helium diffusion and convective core
overshoot have also been taken into consideration. This first set of isochrones (Paper 1) was for the scaled solar
mixture. Now the completing sets (for twice and four-times a-enhanced) are released through Paper 2. Two
additional significant features of these isochrones are that (1) the stellar models start their evolution from the
pre-main sequence birthline instead of from the zero-age main sequence, and (2) the color transformation has been
performed using both the latest table of Lejeune et al., and the older, but now modified, Green et al.table.
The isochrones have performed well under the tests conducted thus far. The reduction in the age of the Galactic
globular clusters caused by this update in stellar models alone (assuming [a/Fe]=0.3) is approximately 20-25%
relative to RYI-based studies. When post-RGB evolutionary stages are included, we find that the ages of globular
clusters derived from integrated colors are consistent with the isochrone fitting ages (Paper 1).