<i>XMM���Newton</i>observations of the massive colliding wind binary and non-thermal radio emitter Cyg���OB2���#8A [O6If + O5.5III(f)]

Becker, M. De; Rauw, Grégor; Sana, H.; Pollock, A. M. T.; Pittard, J. M.; Blomme, R.; Stevens, I. R.; Loo, S. Van

doi:10.1111/j.1365-2966.2006.10746.x

Cited by 57 publications

(98 citation statements)

References 50 publications

(85 reference statements)

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“…Cyg OB2 #5 and 12 are known to vary, but unfortunately, their variations are not fully explained and predictable (Linder et al 2009;Rauw 2011). The behavior of the collidingwind binary Cyg OB2 #8A is, however, well known (De Becker et al 2006;Blomme et al 2010), and the Swift data are here fully consistent with the XMM-Newton and ASCA data, when taking the errors due to a lower number of counts in the Swift data into account. The rapid brightening of Cyg OB2 #9 near periastron, on timescales of days, may thus well be real.…”

Section: The Spectrasupporting

confidence: 76%

“…γ 2 Vel and WR22 did not show any 1/D variation, despite the changing separation of their components (Rauw et al 2000b;Gosset et al 2009). Cyg OB2 #8A and WR140 deviate from expectations at periastron, since the collisions then become radiative (De Becker et al 2006;Pollock et al 2002;De Becker et al 2012). Hints of the influence of a 1/D relation may have been found in HD 93205 (see Fig.…”

Section: A Wind-wind Collision In Cyg Ob2 #9mentioning

confidence: 99%

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The 2.35 year itch of Cygnus OB2 #9

Nazé

Mahy

Damerdji

et al. 2012

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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: The Spectrasupporting

confidence: 76%

Section: A Wind-wind Collision In Cyg Ob2 #9mentioning

confidence: 99%

The 2.35 year itch of Cygnus OB2 #9

Nazé

Mahy

Damerdji

et al. 2012

A&A

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“…This massive binary with a period of 21.908 d (De Becker et al 2004b) is one of the colliding-wind binaries with the best-constrained stellar, wind, and orbital parameters so far. It has also been intensively investigated in X-rays with a well-studied phase-locked variability (De Becker et al 2006b;Blomme et al 2010) and upper limits on the hard X-ray emission derived from INTEGRAL observations ). The detailed study by Blomme et al (2010) reported on a phasedependent radio light curve and presented some modelling of the non-thermal radio emission from Cyg OB2 #8A.…”

Section: Appendix A: the Cataloguementioning

confidence: 99%

Catalogue of particle-accelerating colliding-wind binaries

Becker

Raucq

2013

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Massive systems made of two or more stars are known to be the site for interesting physical processes -including at least in some cases -particle acceleration. Over the past decade, this topic motivated a particular effort to unveil the properties of these systems and characterize the circumstances responsible for the acceleration of particles and the potential role of pre-supernova massive stars in the production of high energy particles in our Galaxy. Although previous studies on this topic were mostly devoted to processes in general, or to a few individual objects in particular, a unified target-oriented census of particle-accelerating colliding-wind binaries (hereafter PACWBs) does not exist yet. This paper aims at making a general and unified census of these systems, emphasizing their main properties. A general discussion includes energetic considerations along with wind properties in relation with non-thermal emission processes that are likely at work in colliding-wind binaries. Finally, some guidelines for future observational and theoretical studies are drawn.

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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

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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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XMM��Newtonobservations of the massive colliding wind binary and non-thermal radio emitter Cyg��OB2��#8A [O6If + O5.5III(f)]

Cited by 57 publications

References 50 publications

The 2.35 year itch of Cygnus OB2 #9

The 2.35 year itch of Cygnus OB2 #9

Catalogue of particle-accelerating colliding-wind binaries

The 2.35 year itch of Cygnus OB2 #9

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XMM���Newtonobservations of the massive colliding wind binary and non-thermal radio emitter Cyg���OB2���#8A [O6If + O5.5III(f)]

Cited by 57 publications

References 50 publications

The 2.35 year itch of Cygnus OB2 #9

The 2.35 year itch of Cygnus OB2 #9

Catalogue of particle-accelerating colliding-wind binaries

The 2.35 year itch of Cygnus OB2 #9

Contact Info

Product

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XMM��Newtonobservations of the massive colliding wind binary and non-thermal radio emitter Cyg��OB2��#8A [O6If + O5.5III(f)]