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Published January 2021 | Accepted Version + Published
Journal Article Open

A new lepto-hadronic model applied to the first simultaneous multiwavelength data set for Cygnus X–1


Cygnus X–1 is the first Galactic source confirmed to host an accreting black hole. It has been detected across the entire electromagnetic spectrum from radio to GeV gamma-rays. The source's radio through mid-infrared radiation is thought to originate from the relativistic jets. The observed high degree of linear polarization in the MeV X-rays suggests that the relativistic jets dominate in this regime as well, whereas a hot accretion flow dominates the soft X-ray band. The origin of the GeV non-thermal emission is still debated, with both leptonic and hadronic scenarios deemed to be viable. In this work, we present results from a new semi-analytical, multizone jet model applied to the broad-band spectral energy distribution of Cygnus X–1 for both leptonic and hadronic scenarios. We try to break this degeneracy by fitting the first-ever high-quality, simultaneous multiwavelength data set obtained from the CHOCBOX campaign (Cygnus X–1 Hard state Observations of a Complete Binary Orbit in X-rays). Our model parametrizes dynamical properties, such as the jet velocity profile, the magnetic field, and the energy density. Moreover, the model combines these dynamical properties with a self-consistent radiative transfer calculation including secondary cascades, both of leptonic and hadronic origin. We conclude that sensitive TeV gamma-ray telescopes like Cherenkov Telescope Array (CTA) will definitively answer the question of whether hadronic processes occur inside the relativistic jets of Cygnus X–1.

Additional Information

© 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model). Accepted 2020 October 20. Received 2020 October 16; in original form 2020 March 3. Published: 29 October 2020. We would like to thank the reviewer for the very helpful comments on improving the original manuscript. DK would like to thank Maria Petropoulou for fruitful discussions, and Ping Zhou and Thomas Russell for useful comments on the manuscript. DK, SM, ML, and AC were supported by the Netherlands Organisation for Scientific Research (NWO) VICI grant (no. 639.043.513). VG is supported through the Margarete von Wrangell fellowship by the ESF and the Ministry of Science, Research and the Arts Baden-Württemberg. JCAM-J is the recipient of an Australian Research Council Future Fellowship (FT140101082), funded by the Australian government. This work is based on observations carried out under the project number W15BQ with the IRAM NOEMA Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). This research made use of ASTROPY (http://www.astropy.org) a community-developed core PYTHON package for Astronomy (Astropy Collaboration et al. 2013; Price-Whelan et al. 2018), MATPLOTLIB (Hunter 2007), NUMPY (Oliphant 2006), SCIPY (Virtanen et al. 2020), ISIS functions (ISISscripts) provided by ECAP/Remeis observatory and MIT (http://www.sternwarte.unierlangen.de/isis/), and the CTA instrument response functions provided by the CTA Consortium and Observatory, see http://www.cta-observatory.org/science/cta-performance/ (version prod3b-v2) for more details. Data Availability: The data underlying this article are available in Zenodo, at https://dx.doi.org/10.5281/zenodo.4126910.

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Published - staa3349.pdf

Accepted Version - 2010.08501.pdf


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August 20, 2023
October 20, 2023