The Evolution of Supermassive Population III Stars

Abstract

Supermassive primordial stars forming in atomically-cooled halos at $z\sim 15-20$ are currently thought to be the progenitors of the earliest quasars in the Universe. In this picture, the star evolves under accretion rates of $0.1-1$ $M_{\odot }$ yr${}^{-1}$ until the general relativistic instability triggers its collapse to a black hole at masses of $\sim 10^5$ $M_{\odot }$. However, the ability of the accretion flow to sustain such high rates depends crucially on the photospheric properties of the accreting star, because its ionising radiation could reduce or even halt accretion. Here we present new models of supermassive Population III protostars accreting at rates $0.001-10$ $M_{\odot }$ yr${}^{-1}$, computed with the GENEVA stellar evolution code including general relativistic corrections to the internal structure. We use the polytropic stability criterion to estimate the mass at which the collapse occurs, which has been shown to give a lower limit of the actual mass at collapse in recent hydrodynamic simulations. We find that at accretion rates higher than $0.001$ $M_{\odot }$ yr${}^{-1}$ the stars evolve as red, cool supergiants with surface temperatures below $10^4$ K towards masses $>10^5$ $M_{\odot }$, and become blue and hot, with surface temperatures above $10^5$ K, only for rates $\lesssim 0.001$ $M_{\odot }$ yr${}^{-1}$. Compared to previous studies, our results extend the range of masses and accretion rates at which the ionising feedback remains weak, reinforcing the case for direct collapse as the origin of the first quasars.

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Cited by in corpus (17)

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• On the Rotation of Supermassive Stars
• On the Detection of Supermassive Primordial Stars
• Maximally accreting supermassive stars: a fundamental limit imposed by hydrostatic equilibrium
• Fragmentation inside atomic cooling haloes exposed to Lyman-Werner radiation
• Finding Direct-Collapse Black Holes at Birth
• On the Detection of Supermassive Primordial Stars. II. Blue Supergiants
• The Final Fate of Supermassive $M\sim 5\times 10^4{M}_{\odot }$ Pop III Stars: Explosion or Collapse?
• The effects of a background potential in star cluster evolution: a delay in the relaxation time-scale and runaway collision processes
• Spectral properties and detectability of supermassive stars in protoglobular clusters at high redshift
• Gravitational stability and fragmentation condition for discs around accreting supermassive stars
• Magnetic braking of supermassive stars through winds
• Intermittent fragmentation and statistical variations during gas collapse in magnetised atomic cooling haloes
• Growth of massive black holes at high-z via accretion predominantly driven by magnetic outflows
• Maximally Rotating Supermassive Stars at the Onset of Collapse: Effects of Gas Pressure