A jet bent by a stellar wind in the black hole X-ray binary Cygnus X-1

Abstract Jets provide an important channel for kinetic feedback from accreting black holes into their environment, without which models of the formation of large-scale structure in the Universe fail to reproduce the observed properties of galaxies. Hence, an accurate measurement of jet power is critical for understanding black hole growth through accretion and also for quantifying the impact of kinetic feedback. However, the absence of instantaneous jet power measurements has precluded direct comparisons with the accretion luminosity, forcing kinetic feedback models to rely on ad hoc assumptions about how much jet power is released per accreted amount of mass. Here using 18 years of high-resolution radio imaging, we report the detection of stellar wind-induced bending of the jets in the black hole X-ray binary Cygnus X-1. By modelling jet–wind interactions, we determine the current kinetic instantaneous power of the jet to be $${\log }_{10}[{L}_{{\rm{j}}{\rm{e}}{\rm{t}}}\,({{\rm{erg}}\,{\rm{s}}}^{-1})]=37.{3}_{-0.2}^{+0.1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>log</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> </mml:msub> <mml:mo>[</mml:mo> <mml:msub> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mrow> <mml:mrow> <mml:mrow> <mml:mi>j</mml:mi> </mml:mrow> </mml:mrow> <mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> </mml:mrow> </mml:mrow> <mml:mrow> <mml:mrow> <mml:mi>t</mml:mi> </mml:mrow> </mml:mrow> </mml:mrow> </mml:msub> <mml:mspace/> <mml:mo>(</mml:mo> <mml:msup> <mml:mrow> <mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> <mml:mi>r</mml:mi> <mml:mi>g</mml:mi> </mml:mrow> </mml:mrow> <mml:mspace/> <mml:mrow> <mml:mrow> <mml:mi>s</mml:mi> </mml:mrow> </mml:mrow> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> <mml:mo>)</mml:mo> <mml:mo>]</mml:mo> <mml:mo>=</mml:mo> <mml:mn>37.</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.1</mml:mn> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> , comparable with the bolometric X-ray luminosity. This result critically places prevailing assumptions about the energetics of black hole-powered jets in both galaxy formation simulations and in scaling models of black hole accretion on a firm empirical footing.