Effects of the variation of fundamental constants on Population III stellar evolution

¹ Geneva Observatory, University of Geneva, Maillettes 51, 1290 Sauverny, Switzerland e-mail: Sylvia.Ekstrom@unige.ch
² Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), UMR 8609, CNRS/IN2P3 and Université Paris Sud 11, Bâtiment 104, 91405 Orsay Campus, France
³ Physique Nucléaire Théorique et Physique Mathématique, CP 229, Université Libre de Bruxelles (ULB), 1050 Brussels, Belgium
⁴ William I. Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455, USA
⁵ Institut d'Astrophysique de Paris, UMR-7095 du CNRS, Université Pierre et Marie Curie, 98 bis bd Arago, 75014 Paris, France
⁶ Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701, Cape Town, South Africa

Received: 17 November 2009
Accepted: 1 February 2010

Abstract

Aims. A variation of the fundamental constants is expected to affect the thermonuclear rates important for stellar nucleosynthesis. In particular, because of the very low resonant energies of ⁸Be and ¹²C, the triple α process is extremely sensitive to any such variations.

Methods. Using a microscopic model for these nuclei, we derive the sensitivity of the Hoyle state to the nucleon-nucleon potential, thereby allowing for a change in the magnitude of the nuclear interaction. We follow the evolution of 15 and 60  zero-metallicity stellar models, up to the end of core helium burning. These stars are assumed to be representative of the first, Population III stars.

Results. We derive limits on the variation in the magnitude of the nuclear interaction and model dependent limits on the variation of the fine structure constant based on the calculated oxygen and carbon abundances resulting from helium burning. The requirement that some ¹²C and ¹⁶O be present at the end of the helium burning phase allows for permille limits on the change in the nuclear interaction and limits of the order of 10^-5 on the fine structure constant relevant at a cosmological redshift of z ~ 15-20.