Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5486717 | Astroparticle Physics | 2017 | 6 Pages |
Abstract
In the extragalactic sky, microquasars and ultra-luminous X-ray sources (ULXs) are known as energetic compact objects locating at off-nucleus positions in galaxies. Some of these objects are associated with expanding bubbles with a velocity of 80-250 kmsâ1. We investigate the shock acceleration of particles in those expanding nebulae. The nebulae having fast expansion velocity â³120kmsâ1 are able to accelerate cosmic rays up to â¼100 TeV. If 10% of the shock kinetic energy goes into particle acceleration, powerful nebulae such as the microquasar S26 in NGC 7793 would emit gamma rays up to several tens TeV with a photon index of â¼2. These nebulae will be good targets for future Cherenkov Telescope Array observations given its sensitivity and angular resolution. They would also contribute to â¼7% of the unresolved cosmic gamma-ray background radiation at ⥠0.1âGeV. In contrast, particle acceleration in slowly expanding nebulae â²120kmsâ1 would be less efficient due to ion-neutral collisions and result in softer spectra at â³ 10 GeV.
Related Topics
Physical Sciences and Engineering
Physics and Astronomy
Astronomy and Astrophysics
Authors
Yoshiyuki Inoue, Shiu-Hang Lee, Yasuyuki T. Tanaka, Shogo B. Kobayashi,