We have recently discovered a supermassive binary black hole system with a projected separation between the two black holes of 7.3 parsecs in the radio galaxy 0402+379 ( 15 ) .
This is the most compact supermassive binary black hole pair yet imaged by more than two orders of magnitude .
We present Global VLBI observations at 1.3464 GHz of this radio galaxy , taken to improve the quality of the HI data .
Two absorption lines are found toward the southern jet of the source , one redshifted by 370 \pm 10 km s ^ { -1 } and the other blueshifted by 700 \pm 10 km s ^ { -1 } with respect to the systemic velocity of the source , which , along with the results obtained for the opacity distribution over the source , suggests the presence of two mass clumps rotating around the central region of the source .
We propose a model consisting of a geometrically thick disk , of which we only see a couple of clumps , that reproduces the velocities measured from the HI absorption profiles .
These clumps rotate in circular Keplerian orbits around an axis that crosses one of the supermassive black holes of the binary system in 0402+379 .
We find an upper limit for the inclination angle of the twin jets of the source to the line of sight of \theta = 66 ^ { \circ } , which , according to the proposed model , implies a lower limit on the central mass of \sim 7 \times 10 ^ { 8 } M _ { \odot } and a lower limit for the scale height of the thick disk of \sim 12 pc .