| Issue |
A&A
Volume 670, February 2023
|
|
|---|---|---|
| Article Number | L6 | |
| Number of page(s) | 4 | |
| Section | Letters to the Editor | |
| DOI | https://doi.org/10.1051/0004-6361/202245332 | |
| Published online | 30 January 2023 | |
Letter to the Editor
Limits on the non-thermal emission of the WR–WR system Apep
Institut für Astro- und Teilchenphysik, Leopold-Franzens-Universität Innsbruck, 6020 Innsbruck, Austria
e-mail: guillem.marti-devesa@uibk.ac.at
Received:
31
October
2022
Accepted:
16
December
2022
Colliding-wind binaries (CWBs) constitute an emerging class of γ-ray sources powered by strong, dense winds in massive stellar systems. The most powerful of them are those binaries hosting a Wolf-Rayet (WR) star. Following the recent discovery of Apep – the closest known Galactic WR–WR binary – we discuss the non-detection of its putative high-energy emission by the Fermi Large Area Telescope (Fermi-LAT) in this Letter. The limits reported in the GeV regime can be used to set a lower limit on the magnetic field pressure density within the shocked wind-collision region (WCR), and to exclude Apep as a bright γ-ray emitting binary. Given that this WR–WR system is the most luminous CWB identified until now at radio wavelengths, this result proves unambiguously that non-thermal synchrotron emission is not a suitable identifier for the subset of γ-ray emitters in this class of particle accelerators. Rather, Apep could be an interesting case of study for magnetic field amplification in shocked stellar winds.
Key words: gamma rays: general / binaries: general / stars: individual: Apep / radiation mechanisms: non-thermal
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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