Circumstellar medium around rotating massive stars at solar metallicity

¹ Astrophysics group, EPSAM, Keele University, Lennard-Jones Labs, Keele, ST5 5BG UK
e-mail: c.georgy@keele.ac.uk
² École Normale Supérieure, Lyon, CRAL, UMR CNRS 5574, Université de Lyon, 69364 Lyon Cedex 07, France
³ Ioffe Physical Technical Institute of the Russian Academy of Sciences, 194021 Saint Petersburg, Russia
⁴ Laboratoire Univers et Particules de Montpellier, Université Montpellier 2, CNRS/IN2P3, CC 72, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France
⁵ CSCS − Swiss National Supercomputing Centre, via Trevano 131, 6900 Lugano, Switzerland

Received: 2 February 2013
Accepted: 4 September 2013

Abstract

Aims. Observations show nebulae around some massive stars but not around others. If observed, their chemical composition is far from homogeneous. Our goal is to put these observational features into the context of the evolution of massive stars and their circumstellar medium (CSM) and, more generally, to quantify the role of massive stars for the chemical and dynamical evolution of the ISM.

Methods. Using the A-MAZE code, we perform 2d-axisymmetric hydrodynamical simulations of the evolution of the CSM, shaped by stellar winds, for a whole grid of massive stellar models from 15 to 120 M_⊙ and following the stellar evolution from the zero-age main-sequence to the time of supernova explosion. In addition to the usual quantities, we also follow five chemical species: H, He, C, N, and O.

Results. We show how various quantities evolve as a function of time: size of the bubble, position of the wind termination shock, chemical composition of the bubble, etc. The chemical composition of the bubble changes considerably compared to the initial composition, particularly during the red-supergiant (RSG) and Wolf-Rayet (WR) phases. In some extreme cases, the inner region of the bubble can be completely depleted in hydrogen and nitrogen, and is mainly composed of carbon, helium, and oxygen. We argue why the bubble typically expands at a lower rate than predicted by self-similarity theory. In particular, the size of the bubble is very sensitive to the density of the ISM, decreasing by a factor of ~2.5 for each additional dex in ISM density. The bubble size also decreases with the metallicity of the central star, because low-metallicity stars have weaker winds. Our models qualitatively fit the observations of WR ejecta nebulae.