Probing AGN with spectropolarimetry: accretion disc and SMBH parameters

ABSTRACT The interaction of a supermassive black hole with the matter of an accretion disc in the presence of a magnetic field is the key mechanism of energy release in active galactic nuclei. However, determining the physical parameters of this system, such as the spin and mass of the black hole, the shape and parameters of the rotation of the accretion disc, and the geometry of the magnetic field in the accretion disc is a complex and not completely solved problem. We have previously shown, based on our numerical models, that these estimates can be obtained from just three parameters: the black hole mass, bolometric luminosity, and optical polarization. In this paper, we estimate the accretion disc and black hole parameters for a sample of 14 type 1 Seyfert galaxies. Using the spectropolarimetric data obtained by us, we selected only those objects in which the polarization of optical radiation is generated mainly by the mechanism in the accretion disc. Despite the small statistics, our results for such a sample are consistent with our previous conclusions and show a discrepancy between the disc magnetic field parameters and the classical Shakura–Sunyaev disc model.

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