The Yonsei-Yale Isochrones have been widely used since its birth in 2001. We announce a major upgrade mainly making varieties of helium values available. The recent works on the globular clusters with extreme helium abundances have called for such a need. The new version of the Y2 Isochrones are available for [α/Fe] = 0 through 0.6, δY/δZ = 1.5 through 3.0, and extreme helium abundances (Y = normal 0.05, 0.1, 0.15, 0.2), and for 11 metallicity grids, with full capability of interpolation. The database will be powerful for making population models. Besides, the accuracy of the models on the lower main sequence has been substantially improved. We illustrate the major upgrades and demonstrate the power of the new grids.
|Number of pages||4|
|Journal||Proceedings of the International Astronomical Union|
|Publication status||Published - 2008|
Bibliographical noteFunding Information:
We thank Harvey Richer and Ivan King for sending us their new HST photometry data on NGC 6397. We are grateful to Chul Chung for regenerating the NGC2808 model HRD that suits the format of this paper. This research has been supported by Korea Research Foundation (SKY).
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science