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 Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The compact X‐ray binary system Cyg X‐3 has been recently discovered as a source of GeV γ‐rays by the  AGILE  and the  Fermi  satellites. It shows emission features in the GeV γ‐rays similar to other γ‐ray binaries which were also observed in the TeV γ‐rays (LS 5039 and LSI +61 303). The question appears whether Cyg X‐3 can be also detected in the TeV γ‐rays by the Cherenkov telescopes.  Here we discuss this problem in detail based on the anisotropic inverse Compton (IC)  pair cascade model successfully applied to TeV γ‐ray binaries. We calculate the γ‐ray light curves and γ‐ray spectra expected from the cascade process occurring inside the Cyg X‐3 binary system. It is found that the γ‐ray light curves at GeV energies can be consistent with the γ‐ray light curve observed by the  Fermi  for reasonable parameters of the orbit of the injection source of relativistic electrons. Moreover, we show that in such a model the sub‐TeV γ‐ray emission (above 100 GeV) is expected to be below sensitivities of the present Cherenkov telescopes assuming that electrons are accelerated in Cyg X‐3 to TeV energies. The next stage Cherenkov telescopes (MAGIC II, HESS II) should have the energy threshold in the range 20–30 GeV, in order to have a chance to detect the signal from Cyg X‐3. Otherwise, the positive detection of γ‐rays at energies above a few tens of GeV requires a telescope with the sensitivity of  of Crab units. We conclude that detection of sub‐TeV γ‐rays from Cyg X‐3 by on‐ground telescopes has to probably wait for the construction of the Cherenkov Telescope Array.

On the possibility of sub‐TeV ‐ray emission from Cyg X‐3