Maximally rotating supermassive stars at the onset of collapse: Effects of gas pressure

Kenneth A. Dennison, Thomas W. Baumgarte, Stuart L. Shapiro

Research output: Contribution to journalArticlepeer-review


The ‘direct collapse’ scenario has emerged as a promising evolutionary track for the formation of supermassive black holes early in the Universe. In an idealized version of such a scenario, a uniformly rotating supermassive star spinning at the mass-shedding (Keplerian) limit collapses gravitationally after it reaches a critical configuration. Under the assumption that the gas is dominated by radiation pressure, this critical configuration is characterized by unique values of the dimensionless parameters J/M2 and Rp/M, where J is the angular momentum, Rp the polar radius, and M the mass. Motivated by a previous perturbative treatment, we adopt a fully non-linear approach to evaluate the effects of gas pressure on these dimensionless parameters for a large range of masses. We find that gas pressure has a significant effect on the critical configuration even for stellar masses as large as M ~ 106 MO. We also calibrate two approximate treatments of the gas pressure perturbation in a comparison with the exact treatment, and find that one commonly used approximation in particular results in increasing deviations from the exact treatment as the mass decreases, and the effects of gas pressure increase. The other approximation, however, proves to be quite robust for all masses M >~ 104 MO.

Original languageEnglish (US)
Pages (from-to)4195-4206
Number of pages12
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - Sep 21 2019


  • Black hole physics
  • Equation of state
  • Stars: Population III

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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