FERRE: A Code for Spectroscopic Analysis

FERRE is a data analysis code written in FORTRAN90. It matches models to data, taking a set of observations and identifying the model parameters that best reproduce the data, in a chi-squared sense. Model predictions are to be given as an array whose values are a function of the model parameters, i.e. numerically. FERRE holds this array in memory, or in a direct-access binary file, and interpolates in it to evaluate model predictions. The code returns, in addition to the optimal set of parameters, their uncertainties, covariances, and the corresponding model prediction. The code is used at the core of the APOGEE Stellar Parameters and Chemical Abundances Pipeline, and it is now publicly available.