Daily variability at milli-arcsecond scales in the radio quiet NLSy1 Mrk 110

TL;DR

This study presents the first evidence of rapid radio variability at milli-arcsecond scales in the radio-quiet NLSy1 galaxy Mrk 110, indicating a compact emission region likely from a jet or corona.

Contribution

It demonstrates milli-arcsecond scale radio variability in a radio-quiet AGN, providing new insights into the origin of radio emission in such sources.

Findings

Radio variability observed at 5 GHz on days to weeks scales.

Emission region size estimated to be smaller than ~180 Schwarzschild radii.

Radio and X-ray variability suggest jet or outflowing corona origin.

Abstract

The origin of radio emission in the majority of Active Galactic Nuclei (AGN) is still poorly understood. Various competing mechanisms are likely involved in the production of radio emission and precise diagnostic tools are needed to disentangle them, of which variability is among the most powerful. For the first time, we show evidence for significant radio variability at 5 GHz at milli-arcsecond scales on days to weeks time scales in the highly accreting and extremely radio-quiet (RQ) Narrow Line Seyfert 1 (NLSy1) Mrk110. The simultaneous Swift/XRT light curve indicates stronger soft than hard X-ray variability. The short-term radio variability suggests that the GHz emitting region has a size smaller than ~180 Schwarzschild radii. The high brightness temperature and the radio and X-ray variability rule out a star-formation and a disc wind origin. Synchrotron emission from a low-power jet and/or an outflowing corona is then favoured.