Sub-second periodic radio oscillations in a microquasar

TL;DR

This paper reports the detection of transient 5 Hz radio oscillations in the microquasar GRS 1915+105, revealing new rapid variability phenomena in its relativistic jets and circular polarization during these events.

Contribution

It presents the first observation of sub-second radio oscillations at around 5 Hz in a microquasar, expanding understanding of jet variability.

Findings

Detected two instances of ~5 Hz radio oscillations in GRS 1915+105.

Observed circular polarization during the oscillation phases.

Identified these oscillations as transient phenomena in the radio band.

Abstract

Powerful relativistic jets are one of the ubiquitous features of accreting black holes in all scales. GRS 1915+105 is a well-known fast-spinning black-hole X-ray binary with a relativistic jet, termed as a ``microquasar'', as indicated by its superluminal motion of radio emission. It exhibits persistent x-ray activity over the last 30 years, with quasi-periodic oscillations of $\sim 1-10$ Hz and 34 and 67 Hz in the x-ray band. These oscillations likely originate in the inner accretion disk, but other origins have been considered. Radio observations found variable light curves with quasi-periodic flares or oscillations with periods of $\sim 20-50$ minutes. Here we report two instances of $\sim$5 Hz transient periodic oscillation features from the source detected in the 1.05-1.45 GHz radio band that occurred in January 2021 and June 2022, respectively. Circular polarization was also observed during the oscillation phase.