Issue |
A&A
Volume 673, May 2023
|
|
---|---|---|
Article Number | L10 | |
Number of page(s) | 4 | |
Section | Letters to the Editor | |
DOI | https://doi.org/10.1051/0004-6361/202346350 | |
Published online | 12 May 2023 |
Letter to the Editor
Constraints on the cosmological coupling of black holes from Gaia
1
Max Planck Institute for Astronomy, Knigstuhl 17, 69117 Heidelberg, Germany
e-mail: andrae@mpia-hd.mpg.de
2
Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
Received:
8
March
2023
Accepted:
2
May
2023
Recent work has suggested that black holes (BHs) could be cosmologically coupled to the accelerated expansion of the Universe, potentially becoming a candidate for origin of dark energy. This would imply that BH mass growth follows cosmological expansion, with the masses of individual BHs growing as MBH ∝ (1 + z)3. In this Letter, we discuss the binary systems Gaia BH1 and Gaia BH2, which contain ∼9 M⊙ BHs orbited by ∼1 M⊙ stars in widely separated orbits. The ages of both systems can be constrained by the properties of the luminous stars. If BH masses are indeed growing as (1 + z)3, the masses of both BHs at formation would have been significantly smaller than today. We find a 77% probability that the mass of the BH in Gaia BH2 would have been below 2.2 M⊙ at formation. This is below the classical Tolman–Oppenheimer–Volkov limit, though it is not yet clear whether or not BHs subject to cosmological coupling should obey this limit. For Gaia BH1, the same probability is 70%. This analysis is consistent with results from two BHs in the globular cluster NGC 3201, but unlike the NGC 3201 BHs, the Gaia BHs have well-constrained inclinations and therefore firm upper mass limits. The discovery of more BHs in binary systems with Gaia astrometry in the coming years will allow us to test the cosmological coupling hypothesis decisively.
Key words: black hole physics / stars: black holes
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Open access funding provided by Max Planck Society.
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