High Energy Emission from a
Black Hole (Charge-Starving) Gap
MeV photons emit from the black hole accretion flow may colliding each other and materialize as electron-positron pairs in the black hole magnetosphere. At very low accretion rate, when the resulting pair number density becomes less than the Goldreich-Julian charge, a charge-starving region appears in the magnetosphere. Such gap arises around the null-charge surface, where the field angular velocity equals to the spacetime dragging velocity.
The deviation from the Goldreich-Julian charge can result in a strong electric field along the field line, accelerating electrons and positrons and emit gamma-rays via curvature and inverse Compton processes. The gap may arise only intermittently, causing TeV flares
- Hirotani & Pu, 2016 “Energetic Gamma Radiation from Rapidly Rotating Black Holes” (ADS)
- Hirotani, Pu et al., 2016 “Lepton Acceleration in the Vicinity of the Event Horizon: High-Energy and Very-High-Energy Emissions from Rotating Black Holes with Various Masses” ( ADS)
- Hirotani, Pu et al. 2017 “Lepton acceleration in the vicinity of the event horizon: Very-high-energy emissions from super-massive black holes”
- Lin, Pu, Hirotani et al., 2017 “Searching For High Energy, Horizon-Scale Emissions from Galactic Black Hole Transients During Quiescence”
A black hole magnetosphere with monopole-like field configuration at different black hole spin. The Null-charge surface is shown by the red line, while the separation surface (which separates inflow and outflow region, as described here) is shown by blue dots.