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Synchrotron radiation

About: Synchrotron radiation is a research topic. Over the lifetime, 14639 publications have been published within this topic receiving 244775 citations. The topic is also known as: magnetobremsstrahlung radiation & Synchrotron Radiation.


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Journal ArticleDOI
TL;DR: In this paper, a set of restrictions upon the magnetic field and visible angular size of a canonical nonthermal source (one whose emission is incoherent electron synchrotron) has been obtained.
Abstract: A set of restrictions upon the magnetic field and visible angular size of a canonical nonthermal source (one whose emission is incoherent electron synchrotron) has been obtained in another paper. The degree of electron anisotropy and magnetic field disordering were left as free parameters. In the present paper these restrictions are applied to the variable compact radio sources 3C 84, 3C 120, 3C 273, 3C 279, 3C 454.3, CTA 102, 3C 446, PKS 2134 + 004, VRO 42.22.01, and OJ 287. The theoretically derived angular sizes for these sources are in reasonable agreement with published VLBI sizes, provided that the characteristic pitch angles are not extremely small. The magnetic field strengths determined from the degree of circular polarization are generally compatible with field strengths derived from the self-absorption and synchrotron self-Compton conditions, again provided that the pitch angles are not too small. It is argued that the self-absorption optical depth cannot be much less than unity near the low-frequency turnovers; otherwise, serious discrepancies with observation result.

79 citations

Journal ArticleDOI
TL;DR: In this article, the authors obtained measurements and upper limits on the emission of Cyg X-1 in the photon energy range of 003-300 GeV based on observations by Fermi.
Abstract: We have obtained measurements and upper limits on the emission of Cyg X-1 in the photon energy range of 003--300 GeV based on observations by Fermi We present the results separately for the hard and soft spectral states, as well for all of the analysed data In the hard state, we detect a weak steady emission in the 01--10 GeV range with a power-law photon index of Gamma=26+-02 at a 4 sigma statistical significance This measurement, even if considered to be an upper limit, strongly constrains Compton emission of the steady radio jet, present in that state The number of relativistic electrons in the jet has to be low enough for the spectral components due to Compton upscattering of the stellar blackbody and synchrotron radiation to be within the observed fluxes If optically-thin synchrotron emission of the jet is to account for the MeV tail, as implied by the recently-claimed strong polarization in that energy range, the magnetic field in the jet has to be much above equipartition The GeV-range measurements also strongly constrain models of hot accretion flows, most likely present in the hard state, in which gamma-rays are produced from decay of neutral pions produced in collisions of energetic ions in an inner part of the flow In the soft state, the obtained upper limits constrain electron acceleration in a non-thermal corona, most likely present around a blackbody accretion disc The coronal emission above 30 MeV has to be rather weak, which is most readily explained by absorption of gamma-rays in pair-producing photon-photon collisions Then, the size of the bulk of the corona is less than a few tens of the gravitational radii

79 citations

Journal ArticleDOI
TL;DR: In this paper, a tunable source of coherent narrowband terahertz radiation is realized by using a laser to modulate the emission characteristics of a relativistic electron beam.
Abstract: A tunable source of coherent narrowband terahertz radiation is realized by using a laser to modulate the emission characteristics of a relativistic electron beam. In the quest for sources of optical radiation in the terahertz domain, promising candidates are nonlinear optical processes occurring when an intense laser beam interacts with a material medium1,2,3,4,5. Besides conventional media (such as crystals), relativistic electrons also show striking nonlinear collective behaviours, which can lead to powerful laser-induced coherent emission6,7, revealing huge potentials of these devices as terahertz sources8. However, up to now only broadband emissions were reported, and experimental control of their radiation properties, such as their spectra9,10, remained an important challenge. Here, we demonstrate the possibility of mastering the coherent emission experimentally by producing tunable narrowband terahertz radiation. The interaction is made to occur between an electron beam and laser pulses possessing a longitudinal quasi-sinusoidal modulation, and the narrowband emission occurs in a region of quasi-uniform magnetic field. The process therefore strongly differs from classical synchrotron radiation experiments, where narrowband emission occurs inside a periodic magnetic field.

79 citations

Journal ArticleDOI
TL;DR: The phase behavior of thesn-1,3-dipalmitoyl-2-oleoylglycerol (PPP-POP) binary mixture system was studied by powder X-ray diffraction with synchrotron radiation and by differential scanning calorimetry as discussed by the authors.
Abstract: The phase behavior of thesn-1,3-dipalmitoyl-2-oleoylglycerol (PPP-POP) binary mixture system was studied by powder X-ray diffraction with synchrotron radiation and by differential scanning calorimetry. The results showed that the immiscible phases were observed in metastable and in the most stable forms. In particular, synchrotron X-ray diffraction enabled us to reveal the monotectic nature of α as a kinetic phase behavior. The equilibrium phase diagram of the PPP-POP mixture is divided into two regions. In POP concentration ratios below 40%, solid-state transformation from α to β was observed, indicating that the α-β transition of PPP was promoted in the presence of POP. By contrast, the polymorphic transition proceeds from α to β through the occurrence of the intermediate β′ form at POP concentration ratios above 50%.

78 citations

Journal ArticleDOI
TL;DR: In this article, the authors used a modified outer gap model to study the multi-frequency phase-resolved spectra of the Crab pulsar and found that the emission from the north pole mainly contributes to Leading Wing 1 and the remaining phases are mainly dominated by the south pole.
Abstract: We use a modified outer gap model to study the multi-frequency phase-resolved spectra of the Crab pulsar. The emissions from both poles contribute to the light curve and the phase-resolved spectra. Using the synchrotron self-Compton mechanism and by considering the incomplete conversion of curvature photons into secondary pairs, the observed phase-averaged spectrum from 100 eV - 10 GeV can be explained very well. The predicted phase-resolved spectra can match the observed data reasonably well, too. We find that the emission from the north pole mainly contributes to Leading Wing 1. The emissions in the remaining phases are mainly dominated by the south pole. The widening of the azimuthal extension of the outer gap explains Trailing Wing 2. The complicated phase-resolved spectra for the phases between the two peaks, namely Trailing Wing 1, Bridge and Leading Wing 2, strongly suggest that there are at least two well-separated emission regions with multiple emission mechanisms, i.e. synchrotron radiation, inverse Compton scattering and curvature radiation. Our best fit results indicate that there may exist some asymmetry between the south and the north poles. Our model predictions can be examined by GLAST.

78 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023266
2022661
2021203
2020258
2019288
2018260