Non-thermal emission processes in massive binaries

Becker, M. De

doi:10.1007/s00159-007-0005-2

Cited by 98 publications

(92 citation statements)

References 109 publications

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“…However, the reverse is not true; i.e., (many) massive binaries exist that show no signature of colliding winds. In fact, nonthermal radio emission is a rare feature (fewer than 40 cases in our Galaxy, see De Becker 2007;Benaglia 2010), and recent X-ray surveys have shown that most binaries are not significantly overluminous at high energies (Nazé 2009). Understanding why it is so will improve our knowledge of both collision mechanisms and stellar wind properties since such emissions heavily depend on them.…”

Section: Introductionmentioning

confidence: 94%

The 2.35 year itch of Cygnus OB2 #9

Nazé

Mahy

Damerdji

et al. 2012

A&A

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Context. Nonthermal radio emission in massive stars is expected to arise in wind-wind collisions occurring inside a binary system. One such case, the O-type star Cyg OB2 #9, was proven to be a binary only four years ago, but the orbital parameters remained uncertain. The periastron passage of 2011 was the first one to be observable under good conditions since the discovery of binarity. Aims. In this context, we have organized a large monitoring campaign to refine the orbital solution and to study the wind-wind collision.Methods. This paper presents the analysis of optical spectroscopic data, as well as of a dedicated X-ray monitoring performed with Swift and XMM-Newton. Results. In light of our refined orbital solution, Cyg OB2 #9 appears as a massive O+O binary with a long period and high eccentricity; its components (O5-5.5I for the primary and O3-4III for the secondary) have similar masses and similar luminosities. The new data also provide the first evidence that a wind-wind collision is present in the system. In the optical domain, the broad Hα line varies, displaying enhanced absorption and emission components at periastron. X-ray observations yield the unambiguous signature of an adiabatic collision, because as the stars approach periastron, the X-ray luminosity closely follows the 1/D variation expected in that case. The X-ray spectrum appears, however, slightly softer at periastron, which is probably related to winds colliding at slightly lower speeds at that time. Conclusions. It is the first time that such a variation has been detected in O+O systems, and the first case where the wind-wind collision is found to remain adiabatic even at periastron passage.

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Section: Introductionmentioning

confidence: 94%

The 2.35 year itch of Cygnus OB2 #9

Nazé

Mahy

Damerdji

et al. 2012

A&A

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“…The models were aimed to describe the symbiotic systems and gamma-ray binaries, and also binary systems with O-type and Wolf-Rayet stars including the enigmatic object in η-Carinae. The colliding wind binaries were long known to be sources of non-thermal radio emission Eichler and Usov (1993), Dougherty et al (2005), Pittard and Dougherty (2006), De Becker (2007) and the catalog of colliding wind binaries with non-thermal particle acceleration compiled by De Becker and Raucq (2013) contains 43 objects.…”

Section: Colliding Wind Binariesmentioning

confidence: 99%

Nonthermal particles and photons in starburst regions and superbubbles

Bykov

2014

Astron Astrophys Rev

118

102

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Starforming factories in galaxies produce compact clusters and loose associations of young massive stars. Fast radiation-driven winds and supernovae input their huge kinetic power into the interstellar medium in the form of highly supersonic and superalfvenic outflows. Apart from gas heating, collisionless relaxation of fast plasma outflows results in fluctuating magnetic fields and energetic particles. The energetic particles comprise a long-lived component which may contain a sizeable fraction of the kinetic energy released by the winds and supernova ejecta and thus modify the magnetohydrodynamic flows in the systems. We present a concise review of observational data and models of nonthermal emission from starburst galaxies, superbubbles, and compact clusters of massive stars. Efficient mechanisms of particle acceleration and amplification of fluctuating magnetic fields with a wide dynamical range in starburst regions are discussed. Sources of cosmic rays, neutrinos and multi-wavelength nonthermal emission associated with starburst regions including potential galactic "PeVatrons" are reviewed in the global galactic ecology context.

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“…Second, in a number of cases non-thermal emission is observed (e.g. Dougherty & Williams 2000;van Loo 2005;De Becker et al 2006;van Loo et al 2006van Loo et al , 2008De Becker 2007;Nazé et al 2008;Montes et al 2009;Blomme et al 2010;A&A 570, A10 (2014) A prime example that fits into this class of X-ray and nonthermal radio emitting massive binary is the O+O-star system Cyg OB2#9 (van Loo et al 2008;Nazé et al 2008Nazé et al , 2010Volpi et al 2011). Our recent campaign to study this object has so far consisted of an analysis of optical and X-ray data by Nazé et al (2012b), and radio observations by Blomme et al (2013), which have refined the orbital solution and provided initial estimates for the stellar parameters − see Tables 1 and 2.…”

Section: Introductionmentioning

confidence: 99%

The 2.35 year itch of Cygnus OB2 #9

Parkin

Pittard

Nazé

et al. 2014

A&A

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Context. The wind-wind collision in a massive star binary system leads to the generation of high temperature shocks that emit at X-ray wavelengths and, if particle acceleration is effective, may exhibit non-thermal radio emission. Cyg OB2#9 is one of a small number of massive star binary systems in this class. Aims. X-ray and radio data recently acquired as part of a project to study Cyg OB2#9 are used to constrain physical models of the binary system, providing in-depth knowledge about the wind-wind collision and the thermal, and non-thermal, emission arising from the shocks. Methods. We use a 3D, adaptive mesh refinement simulation (including wind acceleration, radiative cooling, and the orbital motion of the stars) to model the gas dynamics of the wind-wind collision. The simulation output is used as the basis for radiative transfer calculations considering the thermal X-ray emission and the thermal/non-thermal radio emission. Results. The flow dynamics in the simulation show that wind acceleration (between the stars) is inhibited at all orbital phases by the opposing star's radiation field, reducing pre-shock velocities below terminal velocities. To obtain good agreement with the X-ray observations, our initial mass-loss rate estimates require a down-shift by a factor of ∼7.7 to 6.5 × 10 −7 M yr −1 and 7.5 × 10 −7 M yr −1 for the primary and secondary star, respectively. Furthermore, the low gas densities and high shock velocities in Cyg OB2 #9 are suggestive of unequal electron and ion temperatures, and the X-ray analysis indicates that an immediately post-shock electron-ion temperature ratio of 0.1 is also required. The radio emission is dominated by non-thermal synchrotron emission. A parameter space exploration provides evidence against models assuming equipartition between magnetic and relativistic energy densities. However, fits of comparable quality can be attained with models having stark contrasts in the ratio of magnetic-to-relativistic energy densities. Both X-ray and radio lightcurves are largely insensitive to viewing angle. The variations in X-ray emission with orbital phase can be traced back to an inverse relation with binary separation and pre-shock velocity. The radio emission also scales with pre-shock velocity and binary separation, but to positive powers (i.e. not inversely). The radio models also reveal a subtle effect whereby inverse Compton cooling leads to an increase in emissivity as a result of the synchrotron characteristic frequency being significantly reduced. Finally, using the results of the radio analysis, we estimate the surface magnetic field strengths to be ≈0.3−52 G.

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Non-thermal emission processes in massive binaries

Cited by 98 publications

References 109 publications

The 2.35 year itch of Cygnus OB2 #9

The 2.35 year itch of Cygnus OB2 #9

Nonthermal particles and photons in starburst regions and superbubbles

The 2.35 year itch of Cygnus OB2 #9

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