Magnetic massive stars as progenitors of "heavy" stellar-mass black holes


Petit, V. (1), Keszthelyi, Z. (2,3), MacInnis, R. (1), Cohen, D. H. (4), Townsend, R. H. D. (5), Wade, G. A. (2), Thomas, S. L. (1), Owocki, S. P. (6), Puls, J. (7), ud-Doula, A. (8)

1- Department of Physics and Space Sciences, Florida Institute of Technology;
2- Department of Physics, Royal Military College of Canada;
3- Department of Physics, Engineering Physics and Astronomy, Queen's University;
4- Department of Physics and Astronomy, Swarthmore College;
5- Department of Astronomy, University of Wisconsin-Madison;
6- Department of Physics and Astronomy, University of Delaware;
7- LMU Munich, Universitats-Sternwarte, Scheinerstr;
8- Penn State Worthington Scranton

The groundbreaking detection of gravitational waves produced by the inspiralling and coalescence of the black hole (BH) binary GW150914 confirms the existence of "heavy" stellar-mass BHs with masses >25 Msun. Initial modelling of the system by Abbott et al. (2016a) supposes that the formation of black holes with such large masses from the evolution of single massive stars is only feasible if the wind mass-loss rates of the progenitors were greatly reduced relative to the mass-loss rates of massive stars in the Galaxy, concluding that heavy BHs must form in low-metallicity (Z < 0.25-0.5 Zsun) environments. However, strong surface magnetic fields also provide a powerful mechanism for modifying mass loss and rotation of massive stars, independent of environmental metallicity (ud-Doula & Owocki 2002; ud-Doula et al. 2008). In this paper we explore the hypothesis that some heavy BHs, with masses >25 Msun such as those inferred to compose GW150914, could be the natural end-point of evolution of magnetic massive stars in a solar-metallicity environment. Using the MESA code, we developed a new grid of single, non-rotating, solar metallicity evolutionary models for initial ZAMS masses from 40-80 Msun that include, for the first time, the quenching of the mass loss due to a realistic dipolar surface magnetic field. The new models predict TAMS masses that are significantly greater than those from equivalent non-magnetic models, reducing the total mass lost by a strongly magnetized 80 Msun star during its main sequence evolution by 20 Msun. This corresponds approximately to the mass loss reduction expected from an environment with metallicity Z = 1/30 Zsun.

Reference: MNRAS in press
Status: Manuscript has been accepted

Weblink: https://arxiv.org/abs/1611.08964

Comments:

Email: vpetit@udel.edu