Self-Shielding of X-rays and Gamma-Rays in Compact Sources

• Main Authors: Illarionov, Andrei F, Krolik, Julian H
• Format: Journal Article
• Language: English
• Published: 29-04-1996
• Subjects: Physics - Astrophysics of Galaxies; Physics - Cosmology and Nongalactic Astrophysics; Physics - Earth and Planetary Astrophysics; Physics - High Energy Astrophysical Phenomena; Physics - Instrumentation and Methods for Astrophysics; Physics - Solar and Stellar Astrophysics
• DOI: 10.48550/arxiv.astro-ph/9604171

It is generally supposed that when the "compactness" $l \equiv L\sigma_T/(r
m_e c^3)$ in photons above the pair-production threshold is large, few
$\gamma$-rays can escape. We demonstrate that even when $l \gg 1$, if the high
energy and low energy photons are produced in geometrically-separated regions,
many of the $\gamma$-rays can, in fact, escape. Pair-production along a thin
surface separating the two sources creates enough Compton optical depth to
deflect most of the low energy photons away from the high energy ones. Those
few low-energy photons which penetrate the shielding surface are reduced in
opacity by advection to large distance and small density, by relativistic
beaming along the inner edge of the surface, and by Compton upscattering to
higher energies inside the surface. The pairs in this surface flow outward
relativistically, forming a structure resembling a pair-dominated mildly
relativistic jet.