scholarly journals A dynamical and radiation semi-analytical model of pulsar-star colliding winds along the orbit: Application to LS 5039

2020 ◽  
Vol 641 ◽  
pp. A84
Author(s):  
E. Molina ◽  
V. Bosch-Ramon
Keyword(s):  
Analytical Model ◽  
Massive Star ◽  
Gamma Ray ◽  
Orbital Motion ◽  
Three Dimensional ◽  
Particle Accelerators ◽  
Energy Bands ◽  
Nonthermal Radiation ◽  
Wind Structure ◽  
Nonthermal Emission

Context. Gamma-ray binaries are systems that emit nonthermal radiation peaking at energies above 1 MeV. One proposed scenario to explain their emission consists of a pulsar orbiting a massive star, with particle acceleration taking place in shocks produced by the interaction of the stellar and pulsar winds. Aims. We develop a semi-analytical model of the nonthermal emission of the colliding-wind structure, which includes the dynamical effects of orbital motion. We apply the model to a general case and to LS 5039. Methods. The model consists of a one-dimensional emitter, the geometry of which is affected by Coriolis forces owing to orbital motion. Two particle accelerators are considered: one at the two-wind standoff location and the other one at the turnover produced by the Coriolis force. Synchrotron and inverse Compton emission is studied taking into account Doppler boosting and absorption processes associated to the massive star. Results. If both accelerators are provided with the same energy budget, most of the radiation comes from the region of the Coriolis turnover and beyond, up to a few orbital separations from the binary system. Significant orbital changes of the nonthermal emission are predicted in all energy bands. The model allows us to reproduce some of the LS 5039 emission features, but not all of them. In particular, the MeV radiation is probably too high to be explained by our model alone, the GeV flux is recovered but not its modulation, and the radio emission beyond the Coriolis turnover is too low. The predicted system inclination is consistent with the presence of a pulsar in the binary. Conclusions. The model is quite successful in reproducing the overall nonthermal behavior of LS 5039. Some improvements are suggested to better explain the phenomenology observed in this source, such as accounting for particle reacceleration beyond the Coriolis turnover, unshocked pulsar wind emission, and the three-dimensional extension of the emitter.

scholarly journals UNDERSTANDING THE VERY-HIGH-ENERGY EMISSION FROM MICROQUASARS

2009 ◽  
Vol 18 (03) ◽  
pp. 347-387 ◽  
Author(s):  
VALENTÍ BOSCH-RAMON ◽  
DMITRY KHANGULYAN
Keyword(s):  
Energy Range ◽  
Gamma Ray ◽  
High Energy ◽  
Field Energy ◽  
Energy Bands ◽  
Energy Emission ◽  
Nonthermal Emission ◽  
Very High Energy ◽  
High Energy Emission ◽  
Very High

Microquasars are X-ray binaries with relativistic jets. These jets are powerful energy carriers — thought to be fed by accretion — which produce nonthermal emission at different energy bands. The processes behind the bulk of the nonthermal emission in microquasars may be of leptonic (synchrotron and inverse Compton) and hadronic (proton–proton interactions, photomeson production, and photodisintegration) nature. When leptonic, the fast particle cooling would allow one to obtain relevant information about the properties close to the accelerator, like the radiation and the magnetic field energy densities, and the acceleration efficiency. When hadronic, the extreme conditions required in the emitter would have strong implications for the physics of jets and their surroundings. The very-high-energy part of the spectrum, i.e. > 100 GeV, is a good energy range to explore the physics behind the nonthermal radiation in these compact variable sources. In addition, this energy range, when taken together with lower energy bands, is a key piece for constructing a comprehensive picture of the processes occurring in the emitter. Until recently, the very-high-energy range was hard to probe due to the lack of sensitivity and spatial and spectral resolution of previous instrumentation. Nowadays, however, powerful gamma-ray instruments are operating and the quality of their observations is allowing one, for the first time, to start to understand the production of high-energy emission in microquasars. To date, several galactic sources showing extended radio emission — among them at least one confirmed microquasar, Cygnus X-1 — have shown a TeV signal. All of them show complex patterns of spectral and temporal behavior. In this work, we discuss the physics behind the very-high-energy emission in Cygnus X-1, and also in the other two TeV binaries with detected extended outflows, LS 5039 and LS I +61 303, pointing out relevant aspects of the complex phenomena occurring in them. We conclude that the TeV emission is likely of leptonic origin, although hadrons cannot be discarded. In addition, efficient electromagnetic cascades can hardly develop since even relatively low magnetic fields suppress them. Also, the modeling of the radiation from some of the detected sources points to them as extremely efficient accelerators and/or having the TeV emitter at a distance from the compact object of about ~ 1012 cm. Finally, we point out that the role of a massive and hot stellar companion, due to its strong photon field and wind, cannot be neglected when trying to understand the behavior of microquasars at high and very high energies. The complexity of microquasars precludes straightforward generalizations to a whole population, and are better studied presently on a source-by-source basis. The new and future gamma-ray instrumentation will imply a big step further in our understanding of the processes in microquasars and gamma-ray-emitting binaries.

scholarly journals ON THE X-RAY/TEV CONNECTION IN GALACTIC JET SOURCES

2008 ◽  
Vol 17 (10) ◽  
pp. 1883-1888
Author(s):  
V. BOSCH-RAMON ◽  
D. V. KHANGULYAN ◽  
F. A. AHARONIAN
Keyword(s):  
Gamma Rays ◽  
Gamma Ray ◽  
Orbital Motion ◽  
Pair Creation ◽  
Strong Impact ◽  
Complex Behavior ◽  
X Rays ◽  
X Ray ◽  
Nonthermal Radiation ◽  
Transient Events

There are three Galactic jet sources from which TeV emission has been detected: LS 5039, LS I +61 303 and Cygnus X-1. These three sources show power-law tails in X-rays and soft gamma-rays that could indicate a nonthermal origin of this radiation. In addition, all three sources apparently show correlated and complex behavior at X-ray and TeV energies. In some cases, this complex behavior is related to the orbital motion (e.g. LS 5039, LS I +61 303), and in some others it is related to some transient events occurring in the system (e.g. Cygnus X-1, and likely also LS I +61 303 and LS 5039). Based on modeling results or on energetic grounds, it seems difficult to explain the emission in the X-/soft gamma-ray and the TeV bands as coming from the same (i.e. one-zone) region. We also stress the importance of the pair creation phenomena in these systems, which harbor a massive and hot star, for the radio and the X-ray emission, as a secondary pair radiation component may be significant in these energy ranges. Finally, we point out that the presence of the star can indeed have a strong impact on both the nonthermal radiation production and the jet dynamics.

scholarly journals Gravitational waves from mountains in newly born millisecond magnetars

2021 ◽  
Vol 502 (4) ◽  
pp. 4680-4688
Author(s):  
Ankan Sur ◽  
Brynmor Haskell
Keyword(s):  
Gravitational Wave ◽  
Gravitational Waves ◽  
Massive Star ◽  
Gamma Ray ◽  
Dipole Radiation ◽  
X Ray ◽  
Binary Neutron Star ◽  
Spin Period ◽  
Lower Maximum ◽  
Wave Emission

ABSTRACT In this paper, we study the spin-evolution and gravitational-wave luminosity of a newly born millisecond magnetar, formed either after the collapse of a massive star or after the merger of two neutron stars. In both cases, we consider the effect of fallback accretion; and consider the evolution of the system due to the different torques acting on the star, namely the spin-up torque due to accretion and spin-down torques due to magnetic dipole radiation, neutrino emission, and gravitational-wave emission linked to the formation of a ‘mountain’ on the accretion poles. Initially, the spin period is mostly affected by the dipole radiation, but at later times, accretion spin the star up rapidly. We find that a magnetar formed after the collapse of a massive star can accrete up to 1 M⊙, and survive on the order of 50 s before collapsing to a black hole. The gravitational-wave strain, for an object located at 1 Mpc, is hc ∼ 10−23 at kHz frequencies, making this a potential target for next-generation ground-based detectors. A magnetar formed after a binary neutron star merger, on the other hand, accretes at the most 0.2 M⊙ and emits gravitational waves with a lower maximum strain of the order of hc ∼ 10−24, but also survives for much longer times, and may possibly be associated with the X-ray plateau observed in the light curve of a number of short gamma-ray burst.

scholarly journals SEARCH FOR NEUTRINO EMISSION FROM GAMMA-RAY SOURCES WITH THE ANTARES TELESCOPE

2012 ◽  
Vol 08 ◽  
pp. 307-310
Author(s):  
C. BIGONGIARI
Keyword(s):  
Gamma Ray ◽  
Neutrino Flux ◽  
Three Dimensional ◽  
Effective Area ◽  
High Energy ◽  
Neutrino Telescope ◽  
Neutrino Detector ◽  
Upper Limits ◽  
Cosmic Neutrino ◽  
Promising Source

ANTARES is the first undersea neutrino detector ever built and presently the neutrino telescope with the largest effective area operating in the Northern Hemisphere. A three-dimensional array of photomultiplier tubes detects the Cherenkov light induced by the muons produced in the interaction of high energy neutrinos with the matter surrounding the detector. The detection of astronomical neutrino sources is one of the main goals of ANTARES. The search for point-like neutrino sources with the ANTARES telescope is described and the preliminary results obtained with data collected from 2007 to 2010 are shown. No cosmic neutrino source has been observed and neutrino flux upper limits have been calculated for the most promising source candidates.

scholarly journals Three-dimensional tidal flow in a fjord-like basin with converging width: An analytical model

2017 ◽  
Vol 122 (9) ◽  
pp. 7558-7576 ◽  
Author(s):  
Lauren Ross ◽  
Huib de Swart ◽  
Erik Ensing ◽  
Arnoldo Valle-Levinson
Keyword(s):  
Analytical Model ◽  
Tidal Flow ◽  
Three Dimensional

Time-varying mesh stiffness calculation for gear pairs with misalignment errors in multiple degrees of freedom based on an analytical method

2021 ◽  
pp. 095440622110392
Author(s):  
Qi Wen ◽  
Qi Chen ◽  
Qungui Du ◽  
Yong Yang
Keyword(s):  
Analytical Model ◽  
Contact Line ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Single Pair ◽  
Time Varying ◽  
Mesh Stiffness ◽  
Position Change ◽  
Multiple Degrees Of Freedom ◽  
Effective Contact

Misalignment errors (MEs) in multiple degrees of freedom (multi-DOFs) at the mesh position will lead to a change in the time-varying mesh stiffness (TVMS) and then affect the dynamic behaviour of gear pairs. Therefore, a new, more rapid, three-dimensional analytical model for TVMS calculation for gear pairs with three rotational and three translational MEs is established in this paper, and a new solution method based on potential energy theory is presented. In addition, the correctness of the new model is verified by the finite element method (FEM). Moreover, the effective contact line, uneven distribution of mesh force on the contact line, and mesh position change are taken into account. Finally, the TVMS under different ME conditions is calculated with the new analytical model. The results showed that the different MEs have dissimilar effects on the TVMS, and the relationship between the ME and TVMS is nonlinear. In addition, the region of single-pair and double-pair teeth in contact would also change with ME.

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