Quasi-periodic oscillations of GHz-band polarization in a black hole

Abstract

Relativistic jets from accreting black holes radiate non-thermal emission which is highly variable in different time scales. Previous studies on black holes of different mass scales, including supermassive and stellar-mass black holes, only report flux quasi-periodic oscillations in radio, optical, X-ray and gamma-ray bands. No quasi-periodic variations in polarization have yet been detected in any black hole systems. Here, we report a detection of GHz-band radio polarization oscillations in GRS 1915+105, which harbors a fast-spinning stellar-mass black hole with a relativistic jet. Our observations show that during the increasing phase of radio emission, linear polarization and flux exhibit similar oscillation periods of 17 and 33 seconds, and their variation patterns anti-correlate with each other. These rare, short-period oscillations in both polarization and flux would be important to understand instabilities and special dynamics in magnetized relativistic jets.