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Evidence for non-th...
Evidence for non-thermal X-ray emission from the double Wolf-Rayet colliding-wind binary Apep
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- Del Palacio, Santiago, 1990 (author)
- Chalmers tekniska högskola,Chalmers University of Technology
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- García, F. (author)
- Instituto Argentino de Radioastronomia
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- De Becker, M. (author)
- Universite de Liège,University of Liège
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- Altamirano, D. (author)
- University of Southampton
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- Bosch-Ramon, V. (author)
- Universitat de Barcelona,University of Barcelona
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- Benaglia, P. (author)
- Instituto Argentino de Radioastronomia
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- Marcote, B. (author)
- JOINT INSTITUTE FOR V.L.B.I. IN EUROPE (J.I.V.E.),Joint Institute for Very Long Baseline Interferometry European Research Infrastructure Consortium (JIVE)
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- Romero, G. E. (author)
- Instituto Argentino de Radioastronomia
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(creator_code:org_t)
- 2023-02-24
- 2023
- English.
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 672
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https://doi.org/10.1...
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Abstract
Subject headings
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- Context. Massive colliding-wind binaries (CWBs) can be non-thermal sources. The emission produced in their wind-collision region (WCR) encodes information of both the shock properties and the relativistic electrons accelerated in them. The recently discovered system Apep, a unique massive system hosting two Wolf-Rayet stars, is the most powerful synchrotron radio emitter among the known CWBs. It is an exciting candidate in which to investigate the non-thermal processes associated with stellar wind shocks. Aims. We intend to break the degeneracy between the relativistic particle population and the magnetic field strength in the WCR of Apep by probing its hard X-ray spectrum, where inverse-Compton (IC) emission is expected to dominate. Methods. We observed Apep with NuSTAR for 60 ks and combined this with a reanalysis of a deep archival XMM-Newton observation to better constrain the X-ray spectrum. We used a non-thermal emission model to derive physical parameters from the results. Results. We detect hard X-ray emission consistent with a power-law component from Apep. This is compatible with IC emission produced in the WCR for a magnetic field of ≈ 105-190 mG, corresponding to a magnetic-to-thermal pressure ratio in the shocks of ≈ 0.007-0.021, and a fraction of ∼1.5 × 10-4 of the total wind kinetic power being transferred to relativistic electrons. Conclusions. The non-thermal emission from a CWB is detected for the first time in radio and at high energies. This allows us to derive the most robust constraints so far for the particle acceleration efficiency and magnetic field intensity in a CWB, reducing the typical uncertainty of a few orders of magnitude to just within a factor of a few. This constitutes an important step forward in our characterisation of the physical properties of CWBs.
Subject headings
- NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
- NATURVETENSKAP -- Fysik -- Fusion, plasma och rymdfysik (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Fusion, Plasma and Space Physics (hsv//eng)
Keyword
- Outflows
- X-rays: stars
- Radiation mechanisms: non-thermal
- Stars: Wolf-Rayet
- Acceleration of particles
- Stars: winds
Publication and Content Type
- art (subject category)
- ref (subject category)
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