Rotating massive stars: Pre-SN models and stellar yields at solar metallicity

Abstract

We present a new set of stellar yields obtained from rotating stellar models at solar metallicity covering the massive star range (9-120 M⊙). The stellar models were calculated with the latest version of the Geneva stellar evolution code described in [Hirschi, R., Meynet, G., & Maeder, A. 2004, astro-ph/0406552, accepted for publication in A&A]. Evolution and nucleosynthesis are in general followed up to Silicon burning. The contributions from stellar winds and from supernova explosions to the stellar yields were calculated separately. The two contributions were then added to compute the total stellar yields [Hirschi, R., Meynet, G., & Maeder, A. 2004, "Yields of rotating stars at solar metallicity", submitted to A&A]. The effects of rotation on pre-supernova models are significant between 15 and 30 M⊙. Above 20 M⊙, rotation may change the radius or colour of the supernova progenitors (blue instead of red supergiant) and the supernova type (IIb or Ib instead of II). Rotation increases the α and CO core sizes by a factor ∼ 1.5. Thus, rotation increases the yields for heavy elements and in particular for carbon and oxygen by a factor 1.5-2.5. Rotating models produce larger yields for 12C and 16O in the mass range between 9 and about 35 M⊙ compared to the 1992 calculations [Maeder, A. 1992, A&A, 264, 105]. For Wolf-Rayet stars (M ≳ 30 M⊙), the pre-supernova structures are mostly affected by the intensities of the stellar winds and less by rotation [Meynet, G. & Maeder, A. 2003, A&A, 404, 975]. In this mass range, rotation increases the yields of helium and other hydrogen burning products but does not significantly affect the yields of elements produced in more advanced evolutionary stages. Note that the final masses of the most massive stellar models (∼ 120 M⊙) are similar to the final masses of less massive stars (∼ 40 M⊙) due to the use of revised mass loss rates from Nugis and Lamers 2000 [Nugis, T. & Lamers, H. J. G. L. M. 2000, A&A, 360, 227]. The most massive stars are therefore also expected to form black holes. © 2005 Elsevier B.V. All rights reserved.