文章基本信息

标题：Maximally accreting supermassive stars: a fundamental limit imposed by hydrostatic equilibrium
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作者：L. Haemmerlé ; G. Meynet ; L. Mayer 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2019
卷号：632
页码：1-5
DOI：10.1051/0004-6361/201936716
语种：English
出版社：EDP Sciences
摘要：Context.Major mergers of gas-rich galaxies provide promising conditions for the formation of supermassive black holes (SMBHs; ≳105 M⊙) by direct collapse because they can trigger mass inflows as high as 104 − 105 M⊙yr−1on sub-parsec scales. However, the channel of SMBH formation in this case, either dark collapse (direct collapse without prior stellar phase) or supermassive star (SMS; ≳104 M⊙), remains unknown.Aims.Here, we investigate the limit in accretion rate up to which stars can maintain hydrostatic equilibrium.Methods.We compute hydrostatic models of SMSs accreting at 1–1000 M⊙yr−1, and estimate the departures from equilibrium a posteriori by taking into account the finite speed of sound.Results.We find that stars accreting above the atomic cooling limit (≳10 M⊙yr−1) can only maintain hydrostatic equilibrium once they are supermassive. In this case, they evolve adiabatically with a hylotropic structure, that is, entropy is locally conserved and scales with the square root of the mass coordinate.Conclusions.Our results imply that stars can only become supermassive by accretion at the rates of atomically cooled haloes (∼0.1 − 10 M⊙yr−1). Once they are supermassive, larger rates are possible.
关键词：enstars: massiveearly Universequasars: supermassive black holesaccretionaccretion disks