# Overview

This is a README file for the MESA Isochrones and Stellar Tracks (MIST) models v0.30. The evolutionary tracks are computed using the publicly available stellar evolution package Modules for Experiments in Stellar Astrophysics (MESA v7503; Paxton et al. 2011, 2013, 2015), and the isochrones are generated using Aaron Dotter’s publicly available iso package on github (https://github.com/dotbot2000/iso). The input physics, general overview of the models, and comparisons with observations are described extensively in Paper I (Choi et al. 2016). The isochrone construction procedure is explained in detail in Paper 0 (Dotter 2016). The user is strongly encouraged to read Papers 0 and I, and refer to the MESA papers for additional information.

There are three types of models offered: the equivalent evolutionary point (EEP) tracks, theoretical isochrones, and observed isochrones. The EEP tracks are processed versions of the raw MESA evolutionary track files (or “history files” in MESA-speak). These EEP tracks, resampled from regular time coordinates to uniform “EEP coordinates,” are much smaller in size compared to the raw MESA files but are still able to describe the evolutionary history with sufficient detail. For consistency, we retain the column header names used in MESA in the EEP files (see Table I in README_HEADERS file for a list of column header names and descriptions). Theoretical isochrones are generated from a grid of EEP tracks, and also use the same column header names. Observed isochrones are transformations of theoretical isochrones via a set of bolometric corrections that are largely based on a new grid of stellar atmosphere and synthetic spectra created with the ATLAS12/SYNTHE 1D atmosphere codes (Kurucz 1970, 1993; Conroy et al. in prep.). The ATLAS12/SYNTHE spectra are supplemented with synthetic spectra for H-rich WDs from Koester (2010) and a set of blackbody spectra at the highest temperatures ($$T_{\rm eff} \geq 2\times10^5$$ K). The list of available filters can be found in Table II of the README_HEADERS file.

# Tarballs

## Models

We provide separate tarballs of EEP tracks and isochrones (theoretical and observed) at every metallicity grid point we have computed. There are XXX tracks (from 0.1 to $$300~M_{\odot}$$) in the EEP tarball. We interpolated new EEP tracks for masses where the original stellar evolution calculation did not run to completion due to computational problems. There is an ASCII file with a list of interpolated EEPs included in every EEP tarball. The default set of ages in the isochrone tarball ranges from $$\log \rm Age = 5.0$$ to $$\log \rm Age = 10.3$$ with $$\Delta \log \rm Age = 0.05$$.

For additional masses (EEP tracks) and ages (isochrones), as well as observed isochrones with extinction, we refer the user to the web interpolator.

## “Other Stuff”

In addition to tarballs of ready-to-use EEP tracks and isochrones, we also provide everything necessary should any user wish to run his/her own set of models with MESA v7503. They include MESA inlists, run_star_extras.f, a grid of photosphere and $$\tau=100$$ boundary condition tables computed from ATLAS12/SYNTHE, and a number of modified routines. For more information on getting started with MESA, we recommend browsing through http://mesa.sourceforge.net/starting.html.

# Web Interpolated Models

We offer web interpolation tools for both EEP tracks and isochrones.

## Interpolated EEP Tracks

The user must specify the metallicity [Fe/H] and initial mass in order to retrieve an EEP track. Note that the metallicity here refers to the initial bulk metallicity, which generally is NOT equal to the surface metallicity a later time in the course of star’s lifetime due to processes such as mixing, diffusion, and mass loss.

In addition to the option to interpolate both a single EEP track, the user may also request a series of EEP tracks at fixed [Fe/H] and different initial masses and vice versa. Finally, choose between the standard outputs (age, initial mass, current mass, effective temperature, luminosity, radius, surface gravity, surface and central $$^1$$H, $$^4$$He, $$^{12}$$C, and $$^{16}$$O abundances, mass loss rate, and evolutionary phase) and extended outputs (everything listed in Table I in README_HEADERS).

## Interpolated Isochrones

The user has the option to choose between the linear and logarithmic scales for age. There are three input options for the age: a single isochrone, a series of isochrones within an age range with a desired time interval, and an arbitrary list of ages. Next, the user must specify the composition, either as [Fe/H] or $$Z$$. Note that $$Z$$ here refers to the initial bulk metallicity, and $$Z_{\odot}$$ (again, the initial solar metallicity) is assumed to be 0.0142 following Asplund et al. (2009). Currently, we only offer solar-scaled abundances. The next set of models will comprise of non-solar-scaled abundance models, including $$\alpha$$-enhanced models.

Finally, the user must choose the output format by checking as many boxes as desired. The currently available list of filters can be found in Table II in README_HEADERS. The bolometric corrections include a range of extinction values, as characterized by both $$A_V$$ and $$R_V$$,following the extinction curve of Cardelli et al. (1989).