Department of Physics and Astronomy, FI-20014 University of Turku, Finland.
Space Research Institute (IKI) of the Russian Academy of Sciences, 117997 Moscow, Russia.
Science. 2022 Feb 25;375(6583):874-876. doi: 10.1126/science.abl4679. Epub 2022 Feb 24.
The observational signatures of black holes in x-ray binary systems depend on their masses, spins, accretion rate, and the misalignment angle between the black hole spin and the orbital angular momentum. We present optical polarimetric observations of the black hole x-ray binary MAXI J1820+070, from which we constrain the position angle of the binary orbital. Combining this with previous determinations of the relativistic jet orientation, which traces the black hole spin, and the inclination of the orbit, we determine a lower limit of 40° on the spin-orbit misalignment angle. The misalignment must originate from either the binary evolution or black hole formation stages. If other x-ray binaries have similarly large misalignments, these would bias measurements of black hole masses and spins from x-ray observations.
X 射线双星系统中黑洞的观测特征取决于它们的质量、自旋、吸积率以及黑洞自旋和轨道角动量之间的不吻合角度。我们呈现了对黑洞 X 射线双星 MAXI J1820+070 的光学偏振观测结果，从中我们约束了双星轨道的位置角。将这与之前确定的反映黑洞自旋的相对论喷流方向以及轨道倾斜度相结合，我们确定了自旋-轨道不吻合角度的下限为 40°。这种不吻合必须源自双星演化或黑洞形成阶段。如果其他 X 射线双星具有类似的大不吻合度，这将使通过 X 射线观测测量黑洞质量和自旋的结果产生偏差。
