Bibliographic Details
| Title: |
Lepton acceleration in the vicinity of the event horizon: High-energy and Very-high-energy emissions from rotating black holes with various masses |
| Authors: |
Hirotani, Kouichi, Pu, Hung-Yi, Lin, Lupin Chun-Che, Chang, Hsiang-Kuang, Inoue, Makoto, Kong, Albert K. H, Matsushita, Satoki, Tam, Pak-Hin T. |
| Publication Year: |
2016 |
| Collection: |
Astrophysics |
| Subject Terms: |
Astrophysics - High Energy Astrophysical Phenomena |
| More Details: |
We investigate the electrostatic acceleration of electrons and positrons in the vicinity of the event horizon, applying the pulsar outer-gap model to black hole magnetospheres. During a low accretion phase, the radiatively inefficient accretion flow (RIAF) cannot emit enough MeV photons that are needed to sustain the force-free magnetosphere via two-photon collisions. In such a charge-starved region (or a gap), an electric field arises along the magnetic field lines to accelerate electrons and positrons into ultra-relativistic energies. These relativistic leptons emit copious gamma-rays via curvature and inverse-Compton (IC) processes. Some of such gamma-rays collide with the submillimeter-IR photons emitted from the RIAF to materialize as pairs, which polarize to partially screen the original acceleration electric field. It is found that the gap gamma-ray luminosity increases with decreasing accretion rate. However, if the accretion rate decreases too much, the diminished RIAF soft photon field can no longer sustain a stationary pair production within the gap. As long as a stationary gap is formed, the magnetosphere becomes force-free outside the gap by the cascaded pairs, irrespective of the BH mass. If a nearby stellar-mass black hole (BH) is in quiescence, or if a galactic intermediate-mass BH is in a very low accretion state, its curvature and IC emissions are found to be detectable with Fermi/LAT and imaging atmospheric Cherenkov telescopes (IACT). If a low-luminosity active galactic nucleus is located within a few tens of Mpc, the IC emission from its super-massive BH is marginally detectable with IACT.
Comment: 17 pages, 28 figures; accepted for publication in ApJ |
| Document Type: |
Working Paper |
| DOI: |
10.3847/1538-4357/833/2/142 |
| Access URL: |
http://arxiv.org/abs/1610.07819 |
| Accession Number: |
edsarx.1610.07819 |
| Database: |
arXiv |
