English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We use the new results of the HEGRA detector on the TeV gamma-ray emissionfrom MKN 501 to set upper limits on the energy density of the cosmic infraredbackground (CIRB). Contrary to previous interpretations of the gamma-rayspectrum of MKN 421 as showing an intergalactic absorption cutoff at 5 TeV, theobserved spectrum of MKN 501 extends beyond 10 TeV and appears to beunattenuated by gamma-gamma collisions with the low-energy  CIRB photons. The upper limits on the CIRB intensity -- derived both assumingan `a priori' shape for the CIRB spectrum and without model-dependentassumptions -- are thus quite strong and come almost in conflict with theobservational evaluations based on deep surveys of extragalactic sources in thenear- and mid-IR. If spectra at TeV energies for extragalactic gamma-raysources like this for MKN 501 will be confirmed with improved statistics, wemay be forced to conclude that the process of gamma-gamma interaction in theintergalactic space is more complex than expected and the average intergalacticmagnetic field extremely weak.Comment: Revised version, 9 pages in AASTEX, 3 figures, text is revised from  the original version, Fig. 2 change

Constraints on the Extragalactic Infrared Background from Gamma-Ray Observations of Markarian 501