The radio-quiet quasar SDSS J1536+0441 shows two broad-line emission systems that Boroson & Lauer interpret as a candidate binary black-hole system with a separation of 0.1 pc ( 0.02 mas ) .
From new VLA imaging at 8.5 GHz , two faint sources , separated by 0.97″ ( 5.1 kpc ) , have been discovered within the quasar ’ s optical localization region .
Each radio source is unresolved , with a diameter of less than 0.37″ ( 1.9 kpc ) .
A double radio structure is seen in some other radio-quiet quasars , and the double may be energized here by the candidate 0.1-pc binary black-hole system .
Alternatively , the radio emission may arise from a binary system of quasars with a projected separation of 5.1 kpc , and the two quasars may produce the two observed broad-line emission systems .
Binary active galactic nuclei with a kpc scale separation are known from radio and X-ray observations , and a few such system are expected in the Boroson & Lauer sample based on the observed clustering of quasars down to the 10 kpc scale .
Future observations designed to distinguish between the 0.1 pc and 5 kpc scales for the binary system are suggested .