Caltech-NRAO Stripe 82 Survey (CNSS). IV. The Birth of Radio-loud Quasar 013815+00

TL;DR

This paper reports the first observation of a quasar transitioning from radio-quiet to radio-loud, linked to increased accretion activity, marking the birth of a new radio-loud active galactic nucleus with a compact, evolving jet.

Contribution

It presents the first detection of a rapid radio mode transition in a quasar, providing insights into the birth of radio-loud AGNs and their early jet development.

Findings

Detected a rapid transition from radio-quiet to radio-loud in quasar 013815+00

Observed spectral and morphological properties indicating a GPS phase

Predicted slow development of the jet due to short-term activity

Abstract

It is believed that the gas accretion onto the supermassive black holes (SMBHs) is the main process of powering its luminous emission, which occurs in optical, UV and X-ray regimes and less frequently in radio waves. The observational fact that only a few percent of quasars are radio-loud is still an unresolved issue concerning the understanding of the active galactic nucleus (AGN) population. Here we present a detection of a rapid transition from the radio-quiet to the radio-loud mode in quasar 013815+00 (z=0.94) which coincides with changes of its UV-optical continuum and the low ionization MgII broadline. We interpret this as an enhancement of accretion onto a central black hole of mass about 10^9 solar masses. As a consequence a new radio-loud AGN was born. Its spectral and morphological properties indicate that it went through the short gigahertz-peaked spectrum (GPS) phase at the beginning of its activity and has now stabilized its flux density at the level of a few mJy. The radio morphology of 013815+00 is very compact and we predict that with such short-term jet activity its development will be very slow. The observed luminosity changes of the accretion disk are shorter than the lifetime of the new radio phase in 013815+00.