Stellar evolution models for Z = 0.0001 to 0.03

Abstract

We have calculated a grid of empirically well tested evolutionary tracks with masses M between 0.5 and 50 M⊙, spaced by approximately 0.1 in log M, and with metallicities Z = 0.0001, 0.0003, 0.001, 0.004, 0.01, 0.02 and 0.03. We use a robust and fast evolution code with a self‐adaptive non‐Lagrangian mesh, which employs the mixing‐length theory but treats convective mixing as a diffusion process, solving simultaneously for the structure and the chemical composition. The hydrogen and helium abundances are chosen as functions of the metallicity: X = 0.76 − 3.0ZY = 0.24 + 2.0Z. Two sets of models were computed, one without and one with a certain amount of enhanced mixing or ‘overshooting’. This amount has been empirically chosen by means of various sensitive tests for overshooting: (1) the luminosity of core helium burning (blue loop) giants of well‐known mass, (2) the width of the main sequence as defined by double‐lined eclipsing binaries with well‐measured masses and radii, and (3) the shape and implied stellar distribution of isochrones of various open clusters. The first two tests have been the subject of previous papers, the third test is discussed in this paper. On the basis of these tests, we recommend the use of the overshooting models for masses above about 1.5M ⊙. We describe here the characteristics of the models, the procedure for constructing isochrones for arbitrary age and metallicity from the models, and the performance of these isochrones for several intermediate‐age and old open clusters. All original models are available in electronic form and we describe the means by which they may be obtained.

Composite spectra: XVII. 12 Comae, a member of the Coma open cluster

“…The above values are in broad agreement with the many published ones based on analyses of F-dwarf members of the Coma Cluster (Nissen 1981;Boesgaard 1987;Boesgaard & Friel 1992;Gratton 2000 and many others), who An isochrone calculated for an age of 0.67×10 9 years since the ZAMS, using the Pols et al (1998) software, is fitted to the (log T eff , log L) positions of the hot and cool components of 12 Comae. A metallicity of Z = 0.012 was adopted, being a median of values published for the metallicity of 31 Vul, the wellfitting surrogate for 12 Com A.…”

“…We compared the components' log T eff , log L positions given in Table 5 with evolutionary tracks computed for appropriate stellar masses using the public routines and models created and described by Pols et al (1998). Overshooting was included, in line with those authors' advice for stars within the range of mass in question here.…”

“…Overshooting was included, in line with those authors' advice for stars within the range of mass in question here. Since the recent evolutionary history of the hotter component is less uncertain than that of the more evolved one, and since one of the objectives of this programme is to determine the masses of The tracks fitted to their (log T eff , log L) points were calculated from publicly available software created by Pols et al (1998). For the reasons explained in the text we calculated the tracks for a slightly reduced metallicity, Z = 0.012.…”

Accretion, ablation and propeller evolution in close millisecond pulsar binary systems

“…Population synthesis calculations that use a non constant value of λ are Voss & Tauris 2003;Podsiadlowski et al 2003;Kiel & Hurley 2006;Kiel et al 2008Kiel et al , 2010Hurley et al 2010). Since its inception bse has been updated to include an algorithm that calculates a value of λ based on comparison to the detailed models of Pols et al (1998), see Kiel & Hurley (2006) and Hurley et al (2010).…”

Exoticism Among the Familiar and Bright

“…Location of the components of o Leo in the l o g i -T e ff plane. The evolutionary tracks, taken from Pols et al (1998), correspond to the stellar masses derived from the astrometric and RV orbit analysis by Hummel et al (2001). The dotted lines indicate the boundaries of the instability strip (from Turcotte et al 2000).…”