The Intriguing Parsec-Scale Radio Structure in the "Offset AGN" KISSR
  102
  We report the detection of an intriguing parsec-scale radio source in the
"offset AGN" candidate, KISSR 102. The elliptical host galaxy includes two
optical nuclei at a projected separation of 1.54 kpc, N1 and N2, to the
south-east and north-west, respectively. Phase-referenced VLBA observations at
1.5 and 4.9 GHz of this LINER galaxy, have detected double radio components (A
and B) at a projected separation of 4.8 parsec at 1.5 GHz, and another
partially-resolved double radio structure at 4.9 GHz coincident with the
brighter radio component A. These radio detections are confined to the optical
nucleus N1. The brightness temperatures of all the detected radio components
are high, $\gtrsim10^8$ K, consistent with them being components of a radio
AGN. The 1.5-4.9 GHz spectral index is inverted ($\alpha\sim+0.64\pm0.08$) for
component A and steep for component B ($\alpha \lesssim-1.6$). The dramatic
change in the spectral indices of A and B is inconsistent with it being a
typical "core-jet" structure from a single AGN or the mini-lobes of a compact
symmetric object. To be consistent with a "core-jet" structure, the jet in
KISSR 102 would need to be undergoing strong jet-medium interaction with dense
surrounding media resulting in a drastic spectral steepening of the jet.
Alternatively, the results could be consistent with the presence of a
parsec-scale binary radio AGN, which is the end result of a three-body
interaction involving three supermassive black holes in the centre of KISSR
102.
