Stellar wind bubbles of OB stars as Galactic cosmic ray re-accelerators
Cosmic rays are highly energetic messengers propagating in magnetized plasma, which are, possibly but not exclusively, accelerated at astrophysical shocks. Amongst the variety of astrophysical objects presenting shocks, the huge circumstellar stellar wind bubbles forming around very massive stars, a...
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2024 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/361054 |
| Acceso en línea: | http://hdl.handle.net/10261/361054 |
| Access Level: | acceso abierto |
| Palabra clave: | Methods: numerical Radiation mechanisms: non-thermal Stars: massive Cosmic rays ISM: bubbles |
| Sumario: | Cosmic rays are highly energetic messengers propagating in magnetized plasma, which are, possibly but not exclusively, accelerated at astrophysical shocks. Amongst the variety of astrophysical objects presenting shocks, the huge circumstellar stellar wind bubbles forming around very massive stars, are potential non-thermal emitters. We present the 1D magnetohydrodynamical simulation of the evolving magnetized surroundings of a single, OB-type main-sequence 60 M star, which is post-processed to calculate the re-acceleration of pre-existing non-thermal particles of the Galactic cosmic ray background. It is found that the forward shock of such circumstellar bubble can, during the early phase (1 Myr) of its expansion, act as a substantial re-accelerator of pre-existing interstellar cosmic rays. This results in an increasing excess emission flux by a factor of 5, the hadronic component producing γ -rays by π0 decay being more important than those by synchrotron and inverse Compton radiation mechanisms. We propose that this effect is at work in the circumstellar environments of massive stars in general and we conjecture that other nebulae such as the stellar wind bow shocks of runaway massive stars also act as Galactic cosmic ray re-accelerators. Particularly, this study supports the interpretation of the enhanced hadronic emission flux measured from the surroundings of κ Ori as originating from the acceleration of pre-existing particles at the forward shock of its wind bubble. |
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