Issue |
A&A
Volume 581, September 2015
|
|
---|---|---|
Article Number | A27 | |
Number of page(s) | 19 | |
Section | Astrophysical processes | |
DOI | https://doi.org/10.1051/0004-6361/201425394 | |
Published online | 27 August 2015 |
Modelling the high-energy emission from gamma-ray binaries using numerical relativistic hydrodynamics⋆
1 Univ. Grenoble Alpes, IPAG, 38000 Grenoble, France
e-mail: Guillaume.Dubus@obs.ujf-grenoble.fr
2 CNRS, IPAG, 38000 Grenoble, France
3 Department of Physics, University of Wisconsin-Milwaukee, Milwaukee WI 53201, USA
4 Laboratoire AIM, CEA/DSM–CNRS–Université Paris 7, Irfu/Service d’Astrophysique, CEA-Saclay, 91191 Gif-sur-Yvette, France
Received: 24 November 2014
Accepted: 12 May 2015
Context. Detailed modelling of the high-energy emission from gamma-ray binaries has been propounded as a path to pulsar wind physics.
Aims. Fulfilling this ambition requires a coherent model of the flow and its emission in the region where the pulsar wind interacts with the stellar wind of its companion.
Methods. We have developed a code that follows the evolution and emission of electrons in the shocked pulsar wind based on inputs from a relativistic hydrodynamical simulation. The code is used to model the well-documented spectral energy distribution and orbital modulations from LS 5039.
Results. The pulsar wind is fully confined by a bow shock and a back shock. The particles are distributed into a narrow Maxwellian, emitting mostly GeV photons, and a power law radiating very efficiently over a broad energy range from X-rays to TeV gamma rays. Most of the emission arises from the apex of the bow shock. Doppler boosting shapes the X-ray and very high energy (VHE) lightcurves, constraining the system inclination to i ≈ 35°. There is tension between the hard VHE spectrum and the level of X-ray to MeV emission, which requires differing magnetic field intensities that are hard to achieve with constant magnetisation σ and Lorentz factor Γp of the pulsar wind. Our best compromise implies σ ≈ 1 and Γp ≈ 5 × 103, so respectively higher and lower than the typical values in pulsar wind nebulae.
Conclusions. The high value of σ derived here, where the wind is confined close to the pulsar, supports the classical picture that has pulsar winds highly magnetised at launch. However, such magnetisations will require that further investigations are based on relativistic MHD simulations.
Key words: radiation mechanisms: non-thermal / stars: individual: LS 5039 / stars: winds, outflows / gamma rays: general / X-rays: binaries / methods: numerical
Movies associated to Figs. A.1−A.4 are available in electronic form at http://www.aanda.org
© ESO, 2015
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.