Variable Radio AGN at High Redshift Identified in the VLA Sky Survey
  As part of an on-going study of radio transients in Epoch 1 (2017-2019) of
the Very Large Array Sky Survey (VLASS), we have discovered a sample of
0.2<z<3.2 active galactic nuclei (AGN) selected in the optical/infrared that
have recently brightened dramatically in the radio. These sources would have
previously been classified as radio-quiet based on upper limits from the Faint
Images of the Radio Sky at Twenty-centimeters (FIRST; 1993-2011) survey;
however, they are now consistent with radio-loud quasars. We present a
quasi-simultaneous, multi-band (1-18 GHz) VLA follow-up campaign of our sample
of AGN with extreme radio variability. We conclude that the radio properties
are most consistent with AGN that have recently launched jets within the past
few decades, potentially making them among the youngest radio AGN known.
