A radio parallax to the black hole X-ray binary MAXI J1820+070

Understand

Using the Very Long Baseline Array and the European Very Long Baseline Interferometry Network we have made a precise measurement of the radio parallax of the black hole X-ray binary MAXI\,J1820+070, providing a model-independent distance to the source.

• Our parallax measurement of ($0.348\pm0.033$) mas for MAXI J1820+070 translates to a distance of ($2.96\pm0.33$) kpc.
• This distance implies that the source reached ($15\pm3)\%$ of the Eddington luminosity at the peak of its outburst.
• Further, we use this distance to refine previous estimates of the jet inclination angle, jet velocity and the mass of the black hole in MAXI J1820+070 to be ($63\pm3)^{\circ}$, ($0.89\pm0.09)c$ and ($9.2\pm1.3) M_{\odot}$, respectively.