| Authors Affiliation: | 1 Manipal Centre for Natural Sciences, Centre of Excellence, Manipal Academy of Higher Education, Manipal, Karnataka - 576104, India
2 National Centre for Radio Astrophysics (NCRA) - Tata Institute of Fundamental Research (TIFR), S. P. Pune University Campus, Ganeshkhind Pune 411007, India
3 Núcleo de Astrofı́sica, Universidade Cidade de São Paulo, R. Galvão Bueno 868, Liberdade, São Paulo, SP, 01506-000, Brazil
4 Purdue University, West Lafayette IN, USA |
| Abstract : | Now it is well established that the mergers are essential part of the galaxy evolution process. As a
natural consequence, the presence of supermassive binary black holes (BBH) should be common in
galaxies. However, few definite cases of supermassive BBHs with parsec scale separation are
known till date. Confirmation of two supermassive black holes in any given binary system needs
multiple direct and indirect observational evidence. We have identified a supermassive BBH
candidate in the radio galaxy J1328+2752. We performed Very Long Baseline eArray (VLBA),
European Very Long Baseline Interferometry (VLBI) Network (EVN) and 3.6m Devasthal Optical
Telescope (DOT) follow-up observations of this candidate to investigate its central system. Within
3.5 years of our previous observations, the central parsec scale radio structure of J1328+2752 has
changed from a double to a single component and its flux density has increased by a factor of three.
The multi-frequency radio data shows a spectral turnover at ~3 GHz for this component. While, the
super-resolved VLBA spectral index image does indicate the presence of two components at a
separation of ∼ 4.2 parsec. The kinematic jet precession model applied to the kilo parsec scales jets
of J1328+2752 indicates that if it is a BBH, the accretion disk of the primary black hole is not
coplanar with the binary system orbit making its jet precess under the effect of the torque produced
by the secondary black hole. Its optical emission lines are double-peaked with average velocity
separation ∼ 235 km/s. New DOT observation indicates that there is no significant change in
optical line profiles and intensities over the past few years. The radio structure, the flux density
enhancement and spectral shape can potentially be consistent both with the signature of a young
Gigahertz peaked spectrum (GPS) source or a BBH at the center of this target. |
