Magnetic braking of supermassive stars through winds

Abstract

Supermassive stars (SMSs) are candidates for being progenitors of supermassive quasars at high redshifts. However, their formation process requires strong mechanisms that would be able to extract the angular momentum of the gas that the SMSs accrete. We investigate under which conditions the magnetic coupling between an accreting SMS and its winds can remove enough angular momentum for accretion to proceed from a Keplerian disc. We numerically computed the rotational properties of accreting SMSs that rotate at the $\Omega \Gamma$-limit and estimated the magnetic field that is required to maintain the rotation velocity at this limit using prescriptions from magnetohydrodynamical simulations of stellar winds. We find that a magnetic field of 10 kG at the stellar surface is required to satisfy the constraints on stellar rotation from the $\Omega \Gamma$-limit. Magnetic coupling between the envelope of SMSs and their winds could allow for SMS formation by accretion from a Keplerian disc, provided the magnetic field is at the upper end of present-day observed stellar fields. Such fields are consistent with primordial origins.

References in corpus (14)

• A luminous quasar at a redshift of z = 7.085
• An ultra-luminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30
• Stellar magnetism: empirical trends with age and rotation
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: II. The Effects of Field-Aligned Rotation
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: III. Angular Momentum Loss and Rotational Spindown
• The Evolution of Supermassive Population III Stars
• Formation of massive protostars in atomic cooling haloes
• The Final Fates of Accreting Supermassive Stars
• The Magnetic Fields at the Surface of Active Single G-K Giants
• Formation of primordial supermassive stars by burst accretion
• On the Rotation of Supermassive Stars
• On the Detection of Supermassive Primordial Stars
• Do Stellar Winds Prevent the Formation of Supermassive Stars by Accretion?
• Primordial protostars accreting beyond the $\Omega \Gamma$-limit: radiation effect around the star-disk boundary

Cited by in corpus (11)

• Turbulent Cold Flows Gave Birth to the First Quasars
• The effects of surface fossil magnetic fields on massive star evolution: II. Implementation of magnetic braking in MESA and implications for the evolution of surface rotation in OB stars
• On the Evolution of Supermassive Primordial Stars in Cosmological Flows
• Maximally accreting supermassive stars: a fundamental limit imposed by hydrostatic equilibrium
• Direct collapse of exceptionally heavy black holes in the merger-driven scenario
• On the Detection of Supermassive Primordial Stars. II. Blue Supergiants
• Spectral properties and detectability of supermassive stars in protoglobular clusters at high redshift
• General-relativistic instability in rapidly accreting supermassive stars: the impact of rotation
• General-relativistic instability in hylotropic supermassive stars
• First emergence of cold accretion and supermassive star formation in the early universe
• Magnetohydrodynamic simulation assessment of a potential near-ultraviolet early ingress in WASP-189b