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Article overview
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Gravitational Light Bending Prevents $gammagamma$ Absorption in Gravitational Lenses | | Markus Boettcher
; Hannes Thiersen
; | | Date: |
5 Sep 2016 | | Abstract: | The magnification effect due to gravitational lensing enhances the chances of
detecting moderate-redshift ($z sim 1$) sources in very-high-energy (VHE; $E >
100$ GeV) $gamma$-rays by ground-based Atmospheric Cherenkov Telescope
facilities. It has been shown in previous work that this prospect is not
hampered by potential $gamma-gamma$ absorption effects by the intervening
(lensing) galaxy, nor by any individual star within the intervening galaxy. In
this paper, we expand this study to simulate the light-bending effect of a
realistic ensemble of stars. We first demonstrate that, for realistic
parameters of the galaxy’s star field, it is extremely unlikely (probability
$lesssim 10^{-6}$) that the direct line of sight between the $gamma$-ray
source and the observer passes by any star in the field close enough to be
subject to significant $gammagamma$ absorption. Our simulations then focus on
the rare cases where $gammagamma$ absorption by (at least) one individual
star might be non-negligible. We show that gravitational light bending will
have the effect of avoiding the $gamma-gamma$ absorption spheres around
massive stars in the intervening galaxy. This confirms previous results by
Barnacka et al. and re-inforces arguments in favour of VHE $gamma$-ray
observations of lensed moderate-redshift blazars to extend the redshift range
of objects detected in VHE $gamma$-rays, and to probe the location of the
$gamma$-ray emission region in those blazars. | | Source: | arXiv, 1609.1179 | | Services: | Forum | Review | PDF | Favorites | |
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