Overview of non-transient<i>γ</i>-ray binaries and prospects for the Cherenkov Telescope Array

Chernyakova, M.; Malyshev, D.; Paizis, A.; Palombara, N. La; Balbo, Matteo; Walter, R.; Hnatyk, B.; Soelen, B. van; Romano, P.; Munar-Adrover, P.; Vovk, I.; Piano, G.; Capitanio, Fiamma; Falceta‐Gonçalves, D.; Landoni, M.; Luque-Escamilla, Pedro L.; Martı́, Josep; Paredes, J. M.; Ribó, M.; Safi‐Harb, Samar; Saha, L.; Sidoli, L.; Vercellone, S.

doi:10.1051/0004-6361/201936501

Cited by 26 publications

(17 citation statements)

References 199 publications

(223 reference statements)

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“…In future works, it would be mandatory to perform these models with a larger ensemble of particles in order to confirm the obtained results, and more importantly to benchmark upper limit estimates, as well as semi-analytic transport equation calculations for the simulation of nonthermal emission from CWBs. Our results may also be directly compared to the observations in the near future, for example, the Cherenkov Telescope Array (CTA) (Chernyakova et al, 2019).…”

Section: Discussionmentioning

confidence: 94%

Colliding-Wind Binaries as a Source of TeV Cosmic Rays

Kowal

Falceta‐Gonçalves

2021

Front. Astron. Space Sci.

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In addition to gamma-ray binaries which contain a compact object, high-energy and very high–energy gamma rays have also been detected from colliding-wind binaries. The collision of the winds produces two strong shock fronts, one for each wind, both surrounding a shock region of compressed and heated plasma, where particles are accelerated to very high energies. Magnetic field is also amplified in the shocked region on which the acceleration of particles greatly depends. In this work, we performed full three-dimensional magnetohydrodynamic simulations of colliding winds coupled to a code that evolves the kinematics of passive charged test particles subject to the plasma fluctuations. After the run of a large ensemble of test particles with initial thermal distributions, we show that such shocks produce a nonthermal population (nearly 1% of total particles) of few tens of GeVs up to few TeVs, depending on the initial magnetization level of the stellar winds. We were able to determine the loci of fastest acceleration, in the range of MeV/s to GeV/s, to be related to the turbulent plasma with amplified magnetic field of the shock. These results show that colliding-wind binaries are indeed able to produce a significant population of high-energy particles, in relatively short timescales, compared to the dynamical and diffusion timescales.

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Section: Discussionmentioning

confidence: 94%

Colliding-Wind Binaries as a Source of TeV Cosmic Rays

Kowal

Falceta‐Gonçalves

2021

Front. Astron. Space Sci.

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“…Provided that the loosely constrained optical depth is in a reasonable range, the π 0 decay continuum could optimistically be detected even with very short exposure of 1 hour. A detailed study of the η Carinae LC variability and the VHE cut off modulation will allow to probe the geometry of the system, the magnetic field configuration, the location where protons are accelerated and their maximum energy, as well as the distribution of the soft photons in a very complex environment [40]. Finally, the study of η Carinae offers a remarkable opportunity to get a close-up of one of the most massive stars known during the final stage of its evolution, as well as the strong shock wind interactions with its companion.…”

Section: Pos(hepro Vii)043mentioning

confidence: 99%

Gamma rays from $\eta$ Carinae

Balbo¹,

Walter²

2020

Proceedings of High Energy Phenomena in Relativistic Outflows VII — PoS(HEPRO VII)

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The η Carinae binary system is the first γ-ray binary ever observed which does not contain a compact object. It can be considered as a natural laboratory to study particle acceleration and γ-ray emission. Indeed the dense wind of the primary star shocks against the fast light wind coming from the companion star, creating the conditions to accelerate particles up to relativistic energies via Fermi mechanism. These relativistic particles subsequently dissipate energy as nonthermal radiation. Fermi-LAT and H.E.S.S. detections of η Carinae confirm such hypotheses. Hydrodynamic simulations provide a convincing match to the observations if a few percent of the wind mechanical energy dissipated in the shock goes into particle acceleration. The intrinsic π 0 decay spectrum is a complex convolution of the maximum energy, luminosity, particle drift and obscuration. Accelerated particles cool down mainly via inverse-Compton, synchrotron radiation, and proton-proton collisions. High-energy γ rays interact also with the field of anisotropic UV photons emitted by both luminous stars, creating e ± pairs and strongly modifying the observed spectrum. Quick variations of the optical depth are expected along the orbit, due to changes in shape, position, and gas density of the shocked region. Various CTA simulations confirm that flux variability down to few days timescale could be detected above 30 GeV. These variations could disentangle the intrinsic particle spectral cut off from that related to γ-γ opacity and determine the flux of relativistic protons and positrons injected in the interstellar medium, the geometry of the colliding wind region and the magnetic field configuration, as well as the geometrical orientation of the binary system (although not without some assumptions). CTA will also enlighten the nature of the high-energy component, the mechanisms and the percentage of kinetic energy channelled into particle acceleration.

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“…All sources consist of an O or Oe/Be type star with a compact object in the mass range of a neutron star or black hole [see e.g. 1,2]. For two sources, PSR B1259-63 and PSR J2032+4127, pulsed radio and/or gamma-ray emission has been detected, indicating the compact object is a pulsar [3,4].…”

Section: Introductionmentioning

confidence: 99%

Considering the importance of gamma-gamma absorption in gamma-ray binaries

Soelen¹,

Plooy²

2021

Proceedings of High Energy Astrophysics in Southern Africa 2021 — PoS(HEASA2021)

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Gamma-ray binaries are a rare subclass of high mass binary systems, where the non-thermal emission peaks in the gamma-ray regime. Two scenarios have been proposed to explain the production of the emission; in the pulsar wind scenario the compact object is proposed to be a rapidly rotating pulsar, and the emission originates from particle acceleration that occurs at the shock that forms between the pulsar and stellar wind; in the microquasar scenario emission originates from a relativistic jet. In the pulsar wind scenario, the particle acceleration is normally assumed to occur at the apex of the shock, but hydrodynamic simulations have shown that a second shock could occur due to Coriolis forces. Since gamma-gamma absorption will strongly attenuate TeV emission originating from the apex of the shock, this may imply that it originates from this second shock region. We have undertaken a full calculation of the gamma-gamma optical depth around the gamma-ray binary LS 5039, to investigate whether gamma-gamma absorption may introduce observable features that could be used to constrain the location of the gamma-ray production.

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Overview of non-transientγ-ray binaries and prospects for the Cherenkov Telescope Array

Cited by 26 publications

References 199 publications

Colliding-Wind Binaries as a Source of TeV Cosmic Rays

Colliding-Wind Binaries as a Source of TeV Cosmic Rays

Gamma rays from $\eta$ Carinae

Considering the importance of gamma-gamma absorption in gamma-ray binaries

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