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