Y2 Isochrones

  • You can try out the Y2 version 3 !
  • Download the isochrone sets of Y2 version 3
    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.
    The interpolation program has been debuged in May 2018. Please download it again.
  • Download the evolution track sets of Y2 version 3
    This gzipped tared file contains both of the base set and the wider Y set as well as an interpolation program.

    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 C. Na, S. -I. Han, and D. G. Kim, to this 3rd version.

  • The 3rd version Y2 is consisted of 2 sets.
    The base set is for Y = dY/dZ * Z + Yp where dY/dZ = 1.5, 2.0, 2.5, and 3.0, with Yp=0.23
    Thus, the range of Y is narrower in lower Z.
    The extra set for wider range of Y is for Y = dY/dZ * Z + Yp where Yp = 0.23, 0.28, 0.33, 0.38, and 0.43, with dY/dZ=2.0

    The coverage of the base set The coverage of the extra set for wider range of Y
    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
    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 Yp=0.23 Y = dY/dZ * Z + Yp, for dY/dZ=2.0

  • Summary of the input physics
    Grevesse and Noels Solar mixture
    OPAL Rosseland mean Opacities and Ferguson Low temperature opacities
    Bahcall and Pinsonneault Energy generation rates
    Itoh et al. Neutrino loss rate
    Convective core overshoot ~0.2Hp
    Thoul et al. Helium diffusion
    Eddington grey Atmosphere

  • The EEP mapping scheme (Kim, D. G., 2005, MS thesis, Yonsei University)
    EEP mapping scheme
    The 9 Primary EEPs are identified first, and then the secondary EEPs are set in between, in equal spacing.

  • 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 The version 2 (Paper 4) Isochrones and interpolator (in Z, age, [a/Fe]). Bug fixed!(22/09/2003)
    Last modification for gfortran (02/05/2022)
  • 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, and Asian site at Yonsei