MG15 - Talk detail

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We discuss the effects of electric charging on the equilibrium configurations of magnetized, rotating fluid tori around black holes of different mass. In the context of gaseous/dusty tori in galactic nuclei, the central black hole dominates the gravitational field and it remains electrically neutral, while the surrounding material acquires some electric charge and exhibits non-negligible self-gravitational effect on the torus structure. The structure of the torus is influenced by the balance between the gravitational and electromagnetic forces. By comparison with previous works we show that the conditions of existence of these configurations can be diverse. Similar effects occur also in the context of stellar-mass black holes, where a massive torus can form as a remnant of a tidally disrupted companion.

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Super-Massive Black Holes reside in galactic nuclei, where they exhibit episodic bright flares due to accretion events. Taking into account relativistic effects, namely, the boosting and lensing of X-ray flares, we further examine the possibility to constrain the mass of the SMBH from the predicted profiles of the observed light curves. To this end, we have studied four bright flares from Sagittarius A*, which exhibit an asymmetric shape consistent with a combination of two intrinsically separate peaks that occur with a specific time delay with respect to each other. We thus proposed that an interplay of relativistic effects could be responsible for the shape of the observed light curves and we tested the reliability of the method (further details: Karssen et al. 2017, arXiv:1709.09896).

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Session

Accepted

Yes

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Time

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Abstract

We study the modulation of the observed radiation flux and the associated changes in the polarization degree and angle that are predicted by the orbiting spot model for flares from accreting black holes. The geometric shape of the emission region influences the resulting model light curves, namely, the emission region of a spiral shape can be distinguished from a simpler geometry of a small orbiting spot. We further explore this scheme for the observed flares from the supermassive black hole in the context of Galactic center (Sgr A*). Our code simulates the light curves for a wide range of parameters. The energy dependence of the changing degree and angle of polarization should allow us to discriminate between the cases of a rotating vs. non-rotating black hole.

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