INTEGRAL-ISGRI observations of the Cygnus OB2 region

Becker, M. De; Rauw, Grégor; Pittard, J. M.; Sana, H.; Stevens, I. R.; Romero, Gustavo E.

doi:10.1051/0004-6361:20077734

Cited by 14 publications

(18 citation statements)

References 33 publications

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“…Our assumptions could lead to an overestimation of the real value of the total luminosity, but a value of ∼6 × 10 32 erg s −1 , an order of magnitude below the De Becker et al (2007) flux upper limit, would render the low-mass population of importance in searches for emission from specific suspected sources of hard X-rays, such as the unidentified γ-ray source 3EG 2033+4118, the unidentified TeV source TeV J2032+4130, and massive colliding-wind binaries.…”

Section: Discussionmentioning

confidence: 91%

“…Based on the power-law spectrum and slope estimate by Isola et al (2007), we expect the corresponding estimate for the 20-60 keV range to be a factor 1.8 higher. Moreover, the upper limit of the fluxes for the undetected stars was estimated by De Becker et al (2007) within a PSF of 12 . Using the King profile describing the projected spatial distribution of starlight from the association found by Knödlseder (2000), the ratio between the flux in the whole association area (radius ∼60 ) to that in the 3EG J20033+4188 region is 6.6.…”

Section: Discussionmentioning

confidence: 99%

“…Motivated by the detection of nonthermal radio emission from early-type stars in the nearby massive Cygnus OB2 association (d = 1.7 kpc, Massey & Thompson 1991), De Becker et al (2007) have recently used an extensive set of observations obtained by the International Gamma-Ray Laboratory (INTEGRAL) IBIS instrument to search for hard X-ray emission from some of the more prominent radio sources. The nonthermal radio emission from these stars is thought to arise from a relativistic population of electrons accelerated by diffusive shock acceleration in their interacting stellar winds (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Hard X-ray flux from low-mass stars in the Cygnus OB2 association

Caramazza

Drake²,

Micela

et al. 2009

A&A

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Context. The Cygnus OB2 association, the central engine of the Cygnus X star-forming region, is the subject of an extensive INTEGRAL Key Project that will accumulate 6Ms of observations. Analysis of 2Ms of observations by De Becker and co-workers provides the most sensitive limit yet obtained on hard X-ray emission from the cluster. Aims. We investigate the X-ray emission in the 20-40 keV band expected from the flaring low-mass stellar population in Cygnus OB2. We discuss whether such emission needs to be considered in the interpretation of existing and future X-ray observations of the region, and whether such observations might provide insight into the high-energy processes on low-mass pre-main sequence stars. Methods. The total hard X-ray flux from low-mass stars is estimated by assuming the observed soft X-ray emission stems from a superposition of flares. We further assume the ratio of hard X-ray to soft X-ray emission is described by a scaling found for solar flares by Isola and co-workers. Results. We estimate the low-mass stellar hard X-ray flux in the 20-40 keV band to lie in the range ∼2 × 10 31 −6 × 10 32 erg s −1 and discuss some potential biases that might affect this result. Conclusions. Hard X-ray emission could lie at a level not much below the current observed flux upper limits for Cygnus OB2. If this emission could be detected, it would provide insight into the hard X-ray production of large flares on pre-main sequence stars. We highlight the penetrating power of hard X-rays from low-mass stellar populations as a possible pointer to our Galaxy's hidden star-forming clusters and super-clusters using more sensitive observations from future missions.

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Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hard X-ray flux from low-mass stars in the Cygnus OB2 association

Caramazza

Drake²,

Micela

et al. 2009

A&A

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“…A recent detailed investigtion of this system with XMM-Newton revealed a strong soft X-ray emission dominated by the colliding-winds, with significant variations phase-locked with the orbit [7]. The investigation of a large set of INTEGRAL-ISGRI data led to upper limits for the putative hard X-ray emission from this system [5]. With some assumptions on the hard-X-ray flux due to IC scattering, synthetic Simbol-X spectra have been produced, and suggest promising results.…”

Section: The Contribution Of Simbol-x In This Investigationmentioning

confidence: 96%

Non-thermal Processes in Colliding-wind Massive Binaries: the Contribution of Simbol-X to a Multiwavelength Investigation

Becker¹,

Blomme²,

Micela³

et al. 2009

AIP Conference Proceedings

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Abstract. Several colliding-wind massive binaries are known to be non-thermal emitters in the radio domain. This constitutes strong evidence for the fact that an efficient particle acceleration process is at work in these objects. The acceleration mechanism is most probably the Diffusive Shock Acceleration (DSA) process in the presence of strong hydrodynamic shocks due to the colliding-winds. In order to investigate the physics of this particle acceleration, we initiated a multiwavelength campaign covering a large part of the electromagnetic spectrum. In this context, the detailed study of the hard X-ray emission from these sources in the SIMBOL-X bandpass constitutes a crucial element in order to probe this still poorly known topic of astrophysics. It should be noted that colliding-wind massive binaries should be considered as very valuable targets for the investigation of particle acceleration in a similar way as supernova remnants, but in a different region of the parameter space.

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“…The hard X-ray component, more directly sensitive to the variable symbiotic activity, is the manifestation of those nonthermal emission processes (such as synchrotron) which once again prove the key-role played by shocks in accelerating relativistic particles responsible for the bulk of emission at hν >10 (De Becker et al 2007). …”

Section: From 2001 Up To Datementioning

confidence: 99%

The symbiotic system CH Cygni: An analysis of the shocked nebulae at different epochs

Contini¹,

Angeloni

Rafanelli

2009

Astron Nachr

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Context. We analyse the line and continuum spectra of the symbiotic system CH Cygni. Aims. To show that the colliding-wind model is valid to explain this symbiotic star at different phases. Methods. Peculiar observed features such as flickering, radio variation, X-ray emission, as well as the distribution of the nebulae and shells throughout the system are investigated by modelling the spectra at different epochs. The models account consistently for shock and photoionization and are constrained by absolute fluxes. Results. We find that the reverse shock between the stars leads to the broad lines observed during the active phases, as well as to radio and hard X-ray emission, while the expanding shock is invoked to explain the data during the transition phases.

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INTEGRAL-ISGRI observations of the Cygnus OB2 region

Cited by 14 publications

References 33 publications

Hard X-ray flux from low-mass stars in the Cygnus OB2 association

Hard X-ray flux from low-mass stars in the Cygnus OB2 association

Non-thermal Processes in Colliding-wind Massive Binaries: the Contribution of Simbol-X to a Multiwavelength Investigation

The symbiotic system CH Cygni: An analysis of the shocked nebulae at different epochs

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