Detection of eccentric close-binary supermassive black holes with incomplete interferometric data
Abstract
Context. Recent studies have proposed that General Relativity Analysis via VLT InTerferometrY upgrade (GRAVITY+) on board the Very Large Telescope Interferometer (VLTI) is able to trace the circular orbit of the subparsec (≲0.1 pc) close-binary supermassive black holes (CB-SMBHs) by measuring the photo-centre variation of the hot dust emission. However, the CB-SMBHs orbit may become highly eccentric throughout the evolution of these objects, and the orbital period may be far longer than the observational time baseline.
Aims: We investigate the problem of detecting the CB-SMBH with hot dust emission and high eccentricity (eCB-SMBH, e = 0.5) when the observed time baselines of their astrometric data and radial velocities are considerably shorter than the orbital period.
Methods: The parameter space of the Keplerian model of the eCB-SMBH is large for exploratory purposes. We therefore applied the Bayesian method to fit orbital elements of the eCB-SMBH to combine radial velocity and astrometric data covering a small fraction of the orbital period.
Results: We estimate that a number of potential eCB-SMBH systems within reach of GRAVITY+ will be similar to the number of planned circular targets. We show that using observational time baselines that cover ≳10% of the orbit increases the possibility of determining the period, eccentricity, and total mass of an eCB-SMBH. When the observational time baseline becomes too short (~5%), the quality of the retrieved eCB-SMBH parameters degrades. We also illustrate how interferometry may be used to estimate the photo-centre at the eCB-SMBH emission line, which could be relevant for GRAVITY+ successors. Even if the astrometric signal for eCB-SMBH systems is reduced by a factor of √(1 - e2) compared to circular ones, we find that the hot dust emission of eCB-SMBHs can be traced by GRAVITY+ at the elementary level.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- July 2022
- DOI:
- 10.1051/0004-6361/202243419
- arXiv:
- arXiv:2205.12783
- Bibcode:
- 2022A&A...663A..99K
- Keywords:
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- galaxies: active;
- quasars: supermassive black holes;
- techniques: interferometric;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- accepted for publication in the journal Astronomy &