Y2 Isochrones

  • The 3rd version of Y2 isochrone set is available now!
  • Download the 3rd version Y2
    When downloaded, ungzipped and untared, an interpolation program together with the isochrones can be found.
    This is for interpolation in Y, [a/Fe], Z, and age.

  • Download the evolutionary tracks of the Y2 3rd version
    The first announcement of the 3rd version has been;
    Yi, S. K., Kim, Y. -C., Demarque, P., Lee, Y. W., Han, S.-I. and Kim, D. G. `The Y2 Isochrones getting an extra dimension' (2008) The Art of Modelling Stars in the 21st Century, IAU Symposium 252, held 6-11 April 2008 at Sanya, China, 413 -- 416

    The HB tracks (Han, S.-I. et al. 2009) will be on-line soon.
    We acknowledge the significant contribution of J. S. Na, S. -I. Han, and D. G. Kim, to this 3rd version.

    The coverage of the 3rd version of Y2

    Z [a/Fe]=0.0, [a/Fe]=0.3, [a/Fe]=0.6
    dY/dZ=1.5 dY/dZ=2.0 dY/dZ=2.5 dY/dZ=3.0
    0.00001 O O O O
    0.0001 O O O O
    0.0004 O O O O
    0.001 O O O O
    0.004 O O O O
    0.007 O O O O
    0.01 O O O O
    0.02 O O O O
    0.04 O O O O
    0.06   O O O
    0.08   O O O

    Y = dY/dZ * Z + Yp, for Yp=0.23

  • For a wider Y range, download this seperate set ,

    The coverage of this seperate set

    Z [a/Fe]=0.3
    Yp=0.23 Yp=0.28 Yp=0.33 Yp=0.38 Yp=0.43
    0.00001 O O O O O
    0.0001 O O O O O
    0.0004 O O O O O
    0.001 O O O O O
    0.004 O O O O O
    0.007 O O O O O
    0.01 O O O O O
    0.02 O O O O O
    0.04 O        
    0.06 O        
    0.08 O        

    Y = dY/dZ * Z + Yp, for dY/dZ=2.0

  • Take a look at the updates in the Yale page!
  • Paper 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

  • 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).

  • Read An old news on updates
  • Try our Simple population synthesis
  • Download New version 2 (Paper 4) Isochrones and interpolator (in Z, age, [a/Fe]). Bug fixed!(22/09/2003)
  • Download the Green et al. colour table.
  • Download the Lejeune et al. colour table.
  • Are you interested in the database of the Y2 evolutionary tracks?
  • Do you want try our other sites? US site at Yale, Asian site at Yonsei, European site at Oxford