Constraints on the cosmological coupling of black holes from Gaia

Understand

Recent work has suggested that black holes (BHs) could be cosmologically coupled to the accelerated expansion of the universe, potentially becoming a candidate for dark energy.

• This would imply BH mass growth following the cosmological expansion, with the masses of individual BHs growing as $M_{\rm BH}\propto (1+z)^3$.
• In this letter, we discuss the binary systems Gaia BH1 and Gaia BH2, which contain $\sim 9\,M_{\odot}$ BHs orbited by $\sim 1\,M_{\odot}$ stars in widely-separated orbits.
• The ages of both systems can be constrained by the properties of the luminous stars.