Central engine of a gamma-ray blazar resolved through the magnifying glass of gravitational microlensing

Gamma-ray emission from blazars is known to originate from jets emitted by supermassive black holes¹. However, the exact location and size of the γ-ray emitting part of the jets is uncertain^{2, 3, 4,5, 6}. The main difficulty is the very small angular size of these sources, beyond the angular resolution of γ-ray telescopes. Here, we report a measurement of the projected size of the γ-ray jet, revealed by the detection of microlensing in the gravitationally lensed blazar PKS 1830-211. This measurement is consistent with a constraint from the intrinsic variability timescale of the blazar. Our measurement shows that the γ-ray emission originates from the vicinity of the central supermassive black hole. Combining the X-ray and γ-ray data, we use the microlensing effect to constrain the size of the X-ray source. We show that the effect of pair production of γ-rays on X-ray photons does not make the source opaque, owing to the large size of the X-ray emission region.

Website: http://www.arjonline.org/physical-sciences/american-research-journal-of-physics/