StellaR: A Package to Manage Stellar Evolution Tracks and Isochrones

Abstract

We present the R package stellaR, which is designed to access and manipulate publicly available stellar evolutionary tracks and isochrones from the Pisa low-mass database. procedures for extracting important stages in the evolution of a star from the database, for constructing isochrones from stellar tracks and for interpolating among tracks are discussed and demonstrated. Due to the advance in the instrumentation, nowadays astronomers can deal with a huge amount of high-quality observational data. In the last decade impressive improvements of spectroscopic and photometric observational capabilities made available data which stimulated the research in the glob- ular clusters field. theoretical effort of recovering the evolutionary history of the clusters benefits from the computation of extensive databases of stellar tracks and isochrones, such as Pietrinferni et al. (2006); Dotter et al. (2008); Bertelli et al. (2008). We recently computed a large data set of stellar tracks and isochrones, The Pisa low-mass (Dell'Omodarme et al., 2012), with up to date physical and chemical inputs, and made available all the calculations to the astrophysical community at the Centre de Donnees astronomiques de Strasbourg (CDS) 1 , a data center dedicated to the collection and worldwide distribution of astronomical data. In most databases, the management of the information and the extraction of the relevant evolu- tionary properties from libraries of tracks and/or isochrones is the responsibility of the end users. Due to its extensive capabilities of data manipulation and analysis, however, R is an ideal choice for these tasks. Nevertheless R is not yet well known in astrophysics; up to December 2012 only seven astronomical or astrophysical-oriented packages have been published on CRAN (see the CRAN Task View Chemometrics and Computational Physics). package stellaR (Dell'Omodarme and Valle, 2012) is an effort to make available to the astro- physical community a basic tool set with the following capabilities: retrieve the required calculations from CDS; plot the information in a suitable form; construct by interpolation tracks or isochrones of compositions different to the ones available in the database; construct isochrones for age not included in the database; extract relevant evolutionary points from tracks or isochrones. Get stellar evolutionary data Pisa low-mass database contains computations classified according to four parameters: the metallicity z of the star, its initial helium value y, the value of a-enhancement of the heavy elements mixture with respect to the reference mixture and the mixing-length parameter aml used to model external convection efficiency. values of the parameters available in the database can be displayed using the function showComposition(): > showComposition() Mixing-length values: 1.7, 1.8, 1.9 alpha-enhancement values: 0, 1 (i.e. (alpha/Fe) = 0.0 (alpha/Fe) = 0.3) Chemical compositions: z y.1 y.2 y.3 y.4 y.5 y.6 1e-04 0.249 0.25 0.27 0.33 0.38 0.42 2e-04 0.249 0.25 0.27 0.33 0.38 0.42 3e-04 0.249 0.25 0.27 0.33 0.38 0.42 4e-04 0.249 0.25 0.27 0.33 0.38 0.42 5e-04 0.250 0.25 0.27 0.33 0.38 0.42 6e-04 0.250 0.25 0.27 0.33 0.38 0.42 7e-04 0.250 0.25 0.27 0.33 0.38 0.42 8e-04 0.250 0.25 0.27 0.33 0.38 0.42 9e-04 0.250 0.25 0.27 0.33 0.38 0.42 1e-03 0.250 0.25 0.27 0.33 0.38 0.42 1 via anonymous ftp from ftp://cdsarc.u-strasbg.fr or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/