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dc.contributor.authorAbdalla, Hassan
dc.contributor.authorBöttcher, Markus
dc.date.accessioned2019-04-29T06:10:25Z
dc.date.available2019-04-29T06:10:25Z
dc.date.issued2017
dc.identifier.citationAbdalla, H. & Böttcher, M. 2017. Why the universe is unexpectedly transparent to very high energy gamma rays. 5th Annual Conference on High Energy Astrophysics in Southern Africa (HEASA), 4-6 Oct 2017, University of the Witwatersrand (Wits), South Africa. Proceedings of science, 319: Article no 28. [https://doi.org/10.22323/1.319.0028]en_US
dc.identifier.issn1824-8039 (Online)
dc.identifier.urihttp://hdl.handle.net/10394/32273
dc.identifier.urihttps://pos.sissa.it/319/028/pdf
dc.identifier.urihttps://doi.org/10.22323/1.319.0028
dc.description.abstractRecent observations of distant gamma ray sources indicate that the universe may be more transparent to VHE-gamma-rays than expected. In this paper we study the reduction of the EBL gamma-gamma opacity due to the existence of underdense regions along the line of sight to VHE gamma-ray sources and the possibility of a Lorentz Invariance Violation (LIV) signature. Therefore, we study whether one or both of these effects could be suitable to explain the spectral hardening observed in a few VHE gamma-ray sources. We found that, although the cosmic opacity for VHE gamma rays with energy more than 10 TeV can be strongly reduced, the spectral hardening feature observed in some VHE gamma-ray blazars with energy from 300 GeV up to few TeVs (e.g. PKS 1424+240) still remains puzzlingen_US
dc.language.isoenen_US
dc.publisherSissa Medialaben_US
dc.titleWhy the universe is unexpectedly transparent to very high energy gamma raysen_US
dc.typePresentationen_US
dc.contributor.researchID26598973 - Abdalla, Hassan
dc.contributor.researchID24420530 - Böttcher, Markus


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