Lionel Siess Homepage : WWWTools

COMPUTATION OF ISOCHRONES

This program allows you to compute any isochrone and/or the ZAMS position for pre-main and main sequence stars.

To proceed, select the metallicity and mass tracks and then specify the age . The results will be displayed on the screen and can be saved by typing Alt + S. They include the stellar mass, age, radius, luminosity, and effective temperature as well as some colors.

To convert the effective temperatures resulting from our models to colors, you have the choice to use the conversion table presented in Kenyon and Hartmann (1995, Astrophys. J. Suppl. Series 101, 117) or the one compiled by Siess et al. (1997, Astron. Astrophys. 324, 556). Note that in the latter case, only the B,V,R and I magnitudes are available. The colors are expressed in the Cousins system.

When the selected age for the isochrone is greater than the age of the last computed model, we take this last value in our files. This is indicated by flag = 1 (0 by default). When the colors are extrapolated out of the tables, this is indicated by check = 1 (0 by default).

Reference to be mentioned:
Siess L., Dufour E., Forestini M. 2000, A&A, 358, 593 PDF

Metallicity

Stellar models

Select the mass tracks that will be used to compute the isochrones

Isochrone

Start counting time from the birthline yes no

The birthline was computed with a mass accretion rate of $\dot M = 10^{-5} M_\odot yr^{-1}$
(see my PhD for details)

Compute ZAMS or early-MS

Compute the ZAMS (defined as the time, after deuterium burning, when the nuclear luminosity provides at least 99% of the total stellar luminosity, i.e. when Lnucl > 0.99 L)

compute the early MS (defined as the time, when the star settles on the main sequence after the CN cycle has reached its equilibrium (this only affects stars with M>~1.2 Msun)

Compute isochrones : Enter the age (in year)

When the age is out of range (e.g. a very large age for a massive star), the displayed value corresponds to the last value computed in the stellar model. This is indicated by flag = 1 (flag = 0 when the value is found).

Output

Additional information wanted yes no

surface abundances of light elements (He, Li, Be, B)
central conditions (central temperature, density, degeneracy)
internal structure (size, mass of the burning region, convective envelope, moments of inertia)
energetics (luminosity associated to nuclear/gravothermal sources)

Conversion Table

Siess et al. (1997) Kenyon and Hartmann (1995)

Please note

if you want information in the K, J, H or L band you MUST use the Kenyon and Hartmann (1995) compilation.
the Siess et al. (1997) conversion table only provides the B, V, R and I magnitudes.