Can Cosmologically Coupled Mass Growth of Black Holes Solve the Mass Gap Problem?

Observations of elliptical galaxies suggest that black holes (BHs) might serve as dark energy candidates, coupled to the expansion of the Universe. According to this hypothesis, the mass of a BH could increase as the Universe expands. BH low-mass X-ray binaries (LMXBs) in the Galactic disk were born...

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Bibliographic Details
Published in:The Astrophysical journal 2023-10, Vol.956 (2), p.128
Main Authors: Gao, Shi-Jie, Li, Xiang-Dong
Format: Article
Language:English
Subjects:
Astrophysics
Black holes
Dark energy
Elliptical galaxies
Evolution
Expanding universe
Galactic disk
Hypotheses
Low-mass x-ray binary stars
Neutron stars
Stellar mass black holes
Universe
X ray binaries
X ray stars
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Summary:Observations of elliptical galaxies suggest that black holes (BHs) might serve as dark energy candidates, coupled to the expansion of the Universe. According to this hypothesis, the mass of a BH could increase as the Universe expands. BH low-mass X-ray binaries (LMXBs) in the Galactic disk were born several gigayears ago, making the coupling effect potentially significant. In this work, we calculate the evolution of BH binaries with a binary population synthesis method to examine the possible influence of cosmologically coupled growth of BHs, if it really exists. The measured masses of the compact objects in LMXBs show a gap around ∼2.5–5 M ⊙ , separating the most-massive neutron stars from the least-massive BHs. Our calculated results indicate that considering the mass growth seems to (partially) account for the mass gap and the formation of compact BH LMXBs, alleviating the challenges in modeling the formation and evolution of BH LMXBs with traditional theory. However, critical observational evidence like the detection of intermediate-mass BH binaries is required to test this hypothesis.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ace890