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 Tools annual

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 Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

The gamma-ray emission in broad-line blazars is generally explained asinverse Compton (IC) radiation of relativistic electrons in the jet scatteringoptical-UV photons from the Broad Line Region (BLR), the so-called BLR ExternalCompton scenario. We test this scenario on the Fermi gamma-ray spectra of 106broad-line blazars detected with the highest significance or largest BLR, bylooking for cut-off signatures at high energies compatible with gamma-gammainteractions with BLR photons. We do not find evidence for the expected BLRabsorption. For 2/3 of the sources, we can exclude any significant absorption($\tau_{max}<1$), while for the remaining 1/3 the possible absorption isconstrained to be 1.5-2 orders of magnitude lower than expected. This resultholds also dividing the spectra in high and low-flux states, and for powerfulblazars with large BLR. Only 1 object out of 10 seems compatible withsubstantial attenuation ($\tau_{max}>5$). We conclude that for 9 out of 10objects, the jet does not interact with BLR photons. Gamma-rays seem eitherproduced outside the BLR most of the time, or the BLR is ~100x larger thangiven by reverberation mapping. This means that i) External Compton on BLRphotons is disfavoured as the main gamma-ray mechanism, vs IC on IR photonsfrom the torus or synchrotron self-Compton; ii) the Fermi gamma-ray spectrum ismostly intrinsic, determined by the interaction of the particle distributionwith the seed-photons spectrum; iii) without suppression by the BLR, broad-lineblazars can become copious emitters above 100 GeV, as demonstrated by 3C454.3.We expect the CTA sky to be much richer of broad-line blazars than previouslythought.

On the origin of gamma rays in Fermi blazars: beyond the broad line region