A Large Stellar Evolution Database for Population Synthesis Studies. I. Scaled Solar Models and Isochrones

Abstract

We present a large and updated stellar evolution database for low-, intermediate-, and high-mass stars in a wide metallicity range, suitable for studying Galactic and extragalactic simple and composite stellar populations using population synthesis techniques. The stellar mass range is between $0.5 and 10 M with a fine mass spacing. The metallicity [Fe/ H] comprises 10 values ranging from À2.27 to 0.40, with a scaled solar metal distribution. The initial He mass fraction ranges from Y ¼ 0:245, for the more metal-poor composition, up to 0.303 for the more metal-rich one, with ÁY =ÁZ $ 1:4. For each adopted chemical composition, the evolutionary models have been computed without (canonical models) and with overshooting from the Schwarzschild boundary of the convective cores during the central H-burning phase. Semiconvection is included in the treatment of core convection during the He-burning phase. The whole set of evolutionary models can be used to compute isochrones in a wide age range, from $30 Myr to $15 Gyr. Both evolutionary models and isochrones are available in several observational planes, employing an updated set of bolometric corrections and color-T eA relations computed for this project. The number of points along the models and the resulting isochrones is selected in such a way that interpolation for intermediate metallicities not contained in the grid is straightforward; a simple quadratic interpolation produces results of sufficient accuracy for population synthesis applications.We compare our isochrones with results from a series of widely used stellar evolution databases and perform some empirical tests for the reliability of our models. Since this work is devoted to scaled solar chemical compositions, we focus our attention on the Galactic disk stellar populations, employing multicolor photometry of unevolved field main-sequence stars with precise Hipparcos parallaxes, well-studied open clusters, and one eclipsing binary system with precise measurements of masses, radii, and [Fe/ H] of both components. We find that the predicted metallicity dependence of the location of the lower, unevolved main sequence in the color magnitude diagram (CMD) appears in satisfactory agreement with empirical data. When comparing our models with CMDs of selected, well-studied, open clusters, once again we were able to properly match the whole observed evolutionary sequences by assuming cluster distance and reddening estimates in satisfactory agreement with empirical evaluations of these quantities. In general, models including overshooting during the H-burning phase provide a better match to the observations, at least for ages below $4 Gyr. At [Fe/ H] around solar and higher ages (i.e., smaller convective cores) before the onset of radiative cores, the selected efficiency of core overshooting may be too high in our model, as well as in various other models in the literature. Since we also provide canonical models, the reader is strongly encouraged to always compare the results from both sets in this critical age range.

VLT/FLAMES spectroscopy of red giant branch stars in the Carina dwarf spheroidal galaxy

“…As a consequence, the accuracy of our ages will be reduced for these stars. For each point on the metallicity grid, we generated isochrones using the Teramo/BaSTI stellar evolutionary models (Pietrinferni et al, 2004(Pietrinferni et al, , 2006 for ages between 1 and 15 Gyr, with a spacing of 0.5 Gyr. Those isochrones which are consistent with the observed colours and magnitudes within the photometric error-bars were then used to build up a probability distribution function for ages.…”

A seismic and gravitationally bound double star observed byKepler

“…comm.). 3 www.oa-teramo.inaf.it/BASTI (Pietrinferni et al 2004). 4 stev.oapd.inaf.it/YZVAR/cgi-bin/form (Bertelli et al 2008).…”

“…The models cover the mass range 0.60 M to 1.60 M in steps of 0.02 M , and initial metal abundances Z in the range 0.001 to 0.040 in steps of 0.001. The helium abundance is presumed to follow the enrichment law Y = 0.245 + 1.450Z (Pietrinferni et al 2004). The mixing length parameter was fixed at its solarcalibrated value of 1.908, with the same physics.…”

Hubble Space Telescope observations of the Kepler-field cluster NGC 6819 – I. The bottom of the white dwarf cooling sequence★

“…BaSTI 3 scaled-solar isochrones for both WD ) and pre-WD (Pietrinferni et al 2004) evolutionary phases, including MS convective-core overshooting, were used to determine both MS TO and WD ages. We considered the available BaSTI (pre-WD and WD) isochrones First we determined the cluster distance modulus from isochrone fitting to the MS.…”