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Black Hole lightning due to Particle acceleration at Subhorizon Scales.
Author/s: MAGIC collaboration + M. Kadler, R. Schulz, E. Ros, U. Bach, F. Krauß, J. Wilms
Reference: DOI:10.1126/science.1256183 | Link
Figure caption: Scenario for the magnetospheric origin of the gamma-rays: A maximally rotating black hole with event horizon rg (black sphere) accretes plasma from the center of the galaxy IC 310. In the apple-shaped ergosphere (blue) extending to 2rg in the equatorial plane, Poynting flux is generated by the frame-dragging effect. The rotation of the black hole induces a chargeseparated magnetosphere (red) with polar vacuum gap regions (yellow). In the gaps, the electric field of the magnetosphere has a component parallel to the magnetic field accelerating particles to ultra-relativistic energies. Inverse-Compton scattering and copious pair production due to interactions with low-energy termal photons from the plasma accreted by the black hole leads to the observed gamma rays.
Supermassive black holes with masses of millions to billions of solar masses are commonly found in the centers of galaxies. Astronomers seek to image jet formation using radio interferometry but still suffer from insufficient angular resolution. An alternative method to resolve small structures is to measure the time variability of their emission. Here we report on gamma-ray observations of the radio galaxy IC 310 obtained with the MAGIC telescopes, revealing variability with doubling time scales faster than 4.8 min. Causality constrains the size of the emission region to be smaller than 20% of the gravitational radius of its central black hole. We suggest that the emission is associated with pulsar-like particle acceleration by the electric field across a magnetospheric gap at the base of the radio jet.