Stellar-mass black holes on the millimetre Fundamental Plane of black hole accretion

ABSTRACT Recent work revealed the existence of a galaxy ‘millimetre Fundamental Plane of black hole accretion’, a tight correlation between nuclear 1 mm luminosity, intrinsic 2–10 keV X-ray luminosity and supermassive black hole mass, originally discovered for nearby low- and high-luminosity active galactic nuclei. Here we use mm and X-ray data of five X-ray binaries (XRBs) to demonstrate that these stellar-mass black holes also lie on the mm Fundamental Plane, as they do at radio wavelengths. One source for which we have multi-epoch observations shows evidence of deviations from the plane after a state change, suggesting that the plane only applies to XRBs in the hard state, as is true again at radio wavelengths. We show that both advection-dominated accretion flows and compact jet models predict the existence of the plane across the entire range of black hole masses, although these models vary in their ability to accurately predict the XRB black hole masses.