# TeVPA 2018

27-31 August 2018
LVH, Luisenstraße 58, 10117 Berlin
Europe/Berlin timezone
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# Contribution Poster (A0 portrait)

LVH, Luisenstraße 58, 10117 Berlin -
Gamma-rays

# Hadronic processes in structured jets of Cygnus X-1

## Speakers

• Mr. Dimitrios KANTZAS

## Abstract content

Cygnus X-1 is the first Galactic source confirmed to host a black hole and has been observed since then across the whole electromagnetic spectrum. Recently, it was also detected in the 0.1-10 GeV band by Fermi/LAT and possibly detected at low significance by MAGIC during a flare. The source's non-thermal radiation is thought to originate from the relativistic jets launched by the black hole because of the flat radio spectrum and of the orbital-period dependence found in the high energy light curve. The processes that lead to this non-thermal emission are still debated, with both leptonic and hadronic deemed to be viable. The latter scenario requires protons to be accelerated up to hundreds of TeV by some natural mechanism. These particles can collide with other protons ejected by the companion star in the form of stellar wind or with the photons produced by the companion. These interactions lead to particle cascades and produce secondary electrons, $\gamma$-rays and neutrinos. In this work, we use for the first time a multi-zone, jet model parameterizing the magnetohydrodynamical profile, together with a self-consistent secondary cascade and radiation calculation, and apply it to the best yet simultaneous dataset of Cygnus X-1 in the hard state. We discuss which scenario, hadronic or leptonic, best describes the dataset, as well as some of the uncertainties in understanding the role of secondary electrons in the spectrum.