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This research looks at microwave devices, specifically, patch antenna along with electromagnetic spectrum, shape, mechanism, analytical methods, simulation tools, and feeding procedures. Patch antennas are distinguished by their rectangular form, with a patch on one side and a ground plane on the other. Patch antennas work by exciting electromagnetic waves inside the patch, which are subsequently transmitted into the surrounding environment. The report also outlines numerous ways for evaluating the performance of microstrip patch antennas. The electromagnetic characteristics of the antenna are analyzed using the transmission line model, cavity model, and multiport network model (MNM). The integral equations that regulate the behavior of the antenna are solved using the method of moments (MoM) and the finite element method (FEM). The spectral domain technique (SDT) is used to analyze the antenna’s frequency response, while the finite difference time domain (FDTD) approach is used to analyze the antenna’s time-domain behavior. Overall, these methodologies give a thorough understanding of microstrip patch antenna performance and may be utilized to optimize their design. Furthermore, several patch antenna feeding methods, such as probe feed, microstrip line feeding, aperture coupling, proximity coupling, and CPW feed, are investigated. Attaching a microstrip line to the patch, which is subsequently linked to the RF source, is what microstrip line feeding entails. Aperture coupling entails making a hole in the ground plane that allows the RF source to feed the patch directly. Proximity coupling is accomplished by placing a probe near the patch, which creates an electromagnetic field on the patch. Patch antenna simulation software includes programmers such as HFSS, CST, and FEKO. These tools simulate the patch antenna’s performance, including its radiation pattern, gain, and input impedance. These simulations may be used to optimize the patch antenna design for specific applications. Moreover, recent antenna trends are presented in this article. [ABSTRACT FROM AUTHOR]

We fitted 75 pulses from 44 gamma‐ray burst (GRB) prompt emission lightcurves, including four short ones and 40 long ones. Each pulse is fitted by a fast‐rising exponential‐decay (FRED) model. The statistical properties of these pulses are analyzed and compared with previous works. We found that the FRED model is almost suitable to describe all the pulses. We reconfirmed that there is a linear correlation between the full width at half maximum FWHM$$ \mathrm{FWHM} $$ and the pulse rising time Trise$$ {T}_{\mathrm{rise}} $$, which supports the idea that the individual pulse is emitted at once within one explosion. Moreover, we found that several pulses do not obey the FWHM−Trise$$ \mathrm{FWHM}-{T}_{\mathrm{rise}} $$ correlation, this implies that the radiation process of the prompt emission especially in the multi‐pulse GRBs might involve more than one type and even possibly change with time. The innovation of this work lies in examining the statistical characteristics of lightcurves of both long and short‐duration GRBs and re‐evaluating the applicability of empirical relationships discovered by predecessors to both types of GRBs while paying special attention to the existence of outlier pulses. This work has positive implications for further exploring the diversity of GRB prompt radiation mechanisms. [ABSTRACT FROM AUTHOR]

Pulsars with the Gigahertz-Peaked Spectra (GPS) are named GPS pulsars, which means that spectra of the pulsars in the radio band turn over near 1 GHz. These pulsars are also called high-frequency inversion spectra pulsars. There are total 33 GPS pulsars discovered so far. The reason causing the turned-over spectra may be due to the free–free absorption of radio emission by the interstellar medium. We carry out the statistical research on the peak frequencies of inversion spectra, spectral indices, dispersion measure, and magnetic fields of these GPS pulsars. We find that the peak frequencies of most GPS pulsars are mainly in 0.5–1.0 GHz, the spectral indices of these GPS pulsars seems to have a bimodal distribution, which means that these GPS pulsars are possibly composed by two types of pulsars. A strong positive correlation between the periods and dispersion measure (DM) of GPS pulsars is first found. [ABSTRACT FROM AUTHOR]

In this study, kinetic interaction at the Cherenkov resonance between an electromagnetic wave pulse and a flow of electrons possessing a wide velocity spread at the scale of the characteristic range of the resonant electron wave interaction is considered. Due to the absence of a distribution function slope in the range of velocities corresponding to the electron wave's resonance, an electron's flow is a nearly stable media from the point of view of its interaction with a long enough wave pulse. In this paper, we explain our findings on the process of electron interaction with potential relief where the wave pulse is so short that the characteristic scale of the wave amplitude's inhomogeneity and the profile of the potential relief is comparable to the wavelength. We show that if an appropriate slippage between the phase and group velocities of the wave is provided, then the reflection process of particles from "fast" and "slow" close-to-resonance velocity fractions becomes non-symmetrical. This can provide a mechanism of amplification of short intensive wave pulses with electron flows with very large velocity spreads. [ABSTRACT FROM AUTHOR]

Recent theoretical considerations and observational evidence evince the spine-sheath morphology of relativistic jets emitted from active galactic nuclei (AGNs) or gamma-ray bursts (GRBs). The resulting shear boundary layers (SBLs) are likely to be an avenue for particle acceleration in relativistic jets. The effect of radiation drag on radiating particles has yet to be addressed in most studies of particle acceleration at shear boundary layers, even though radiative cooling may considerably affect particle dynamics. By using particle-in-cell simulations, we study the effects of inverse Compton cooling on particle dynamics and emerging particle spectra. [ABSTRACT FROM AUTHOR]

Fast radio bursts (FRBs) are millisecond-duration signals that are highly dispersed at distant galaxies. However, the physical origin of FRBs is still unknown. Coherent curvature emission by bunches, e.g., powered by starquakes, has already been proposed for repeating FRBs. It has the nature of understanding narrowband radiation exhibiting time-frequency drifting. Recently, a highly active FRB source, i.e., FRB 20201124A, was reported to enter a newly active episode and emit at least some highly circular-polarized bursts. In this study, we revisit the polarized FRB emission, particularly investigating the production mechanisms of a highly circular polarization (CP) by deriving the intrinsic mechanism and propagative effect. The intrinsic mechanisms of invoking charged bunches are approached with radiative coherence. Consequently, a highly CP could naturally be explained by the coherent summation of outcome waves, generated or scattered by bunches, with different phases and electric vectors. Different kinds of evolutionary trajectories are found on the Poincaré sphere for the bunch-coherent polarization, and this behavior could be tested through future observations. Cyclotron resonance can result in the absorption of R-mode photons at a low altitude region of the magnetosphere, and an FRB should then be emitted from a high-altitude region if the waves have strong linear polarization. Circularly polarized components could be produced from Faraday conversion exhibiting a λ3-oscillation, but the average CP fraction depends only on the income wave, indicating a possibility of a highly circular-polarized income wave. The analysis could be welcome if extremely high (e.g., almost 100%) CP from repeating FRBs is detected in the future. Finally, the production of a bulk of energetic bunches in the pulsar-like magnetosphere is discussed, which is relevant to the nature of the FRB central engine. [ABSTRACT FROM AUTHOR]

As a radiation source with the wide spectrum, laser-induced plasma can produce X-ray, ultraviolet, visible, infrared, terahertz, and microwave radiation. It has high practical value and can be used in astrophysics, inertial confinement fusion, biomedicine, materials science, spectral analyses, environmental engineering, information technology, ultrafast technology, lithography technology, imaging technology, radar technology, and semiconductor technology, etc. Up to now, most of the literatures about the radiation characteristics of laser-induced plasma concentrate on the interaction between lasers and matter in a certain wave band, while the mechanism of radiation production is not fully understood, and there is still a lack of comprehensive introductions of the researches on a wide spectrum. The radiation characteristics of laser-induced plasma are systematically classified from the point of view of both electromagnetic radiation spectra and radiation mechanisms in this review. The research results of relevant teams at home and abroad are summarized and analyzed, especially the physical relationship between plasma and spectral radiation is explored from different perspectives. The radiation characteristics of laser-induced plasma in various bands are introduced, and the related factors affecting the radiation are discussed. Finally, the research prospect of infrared band and terahertz band are prospected. [ABSTRACT FROM AUTHOR]

The prompt emission of Gamma Ray Bursts (GRBs) is still an outstanding question in the study of these cataclysmic events. Part of what makes GRBs difficult to study is how unique each event seems to be. However, aggregating many GRB observations and analyzing the population allows us to obtain a better understanding of the emission mechanism that produces the observed prompt emission. In this review, we outline some of the most prevalent correlations that have emerged from GRB prompt emission observations and how these correlations are interpreted in relation to physical properties and prompt emission models of GRB. [ABSTRACT FROM AUTHOR]

In this study, kinetic interaction at the Cherenkov resonance between an electromagnetic wave pulse and a flow of electrons possessing a wide velocity spread at the scale of the characteristic range of the resonant electron wave interaction is considered. Due to the absence of a distribution function slope in the range of velocities corresponding to the electron wave’s resonance, an electron’s flow is a nearly stable media from the point of view of its interaction with a long enough wave pulse. In this paper, we explain our findings on the process of electron interaction with potential relief where the wave pulse is so short that the characteristic scale of the wave amplitude’s inhomogeneity and the profile of the potential relief is comparable to the wavelength. We show that if an appropriate slippage between the phase and group velocities of the wave is provided, then the reflection process of particles from “fast” and “slow” close-to-resonance velocity fractions becomes non-symmetrical. This can provide a mechanism of amplification of short intensive wave pulses with electron flows with very large velocity spreads.

We perform a comparative spectro-temporal analysis on the variability classes of GRS 1915+105 and IGR J17091-3624 to draw inferences regarding the underlying accretion flow mechanism. The ν , as well as C2 class Rossi X-ray Timing Explorer observation, have been considered for analysis. We investigate the intensity variation of the source in different energy domains that correspond to different components of the accretion flow and infer the relative dominance of these flow components during the dip/flare events. We correlate the dependence of the dynamic photon index (Θ) with intensities in different energy bands and comment on the transition of the source to hard/soft phases during soft dips/flares. We also report the presence of sharp QPOs at ∼ 7.1 Hz corresponding to both softer and harder domain in the case of ν variability class of GRS 1915+105 and discuss the possible accretion flow configuration it suggests. Sharp QPO around ∼ 20 mHz is observed in ν and C2 classes of IGR J17091-3624 in low and mid energy band (2.0–6.0 keV and 6.0–15.0 keV), but remains undetected in high energy (15.0–60.0 keV). The 2.5–25.0 keV background-subtracted spectra have also been fitted with TCAF along with a Compton reflection component. A plausible accretion flow mechanism in order to explain the observed variability has been proposed. [ABSTRACT FROM AUTHOR]

The origins of the diffuse flux of cosmogenic PeV neutrinos detected in the IceCube experiment during 2010–2017 remain unidentified. A population of extragalactic newly born fast-spinning pulsars are investigated as possible candidates for generating the PeV energy scale neutrinos. A two-step mechanism of particle acceleration is adopted for transferring energy from star rotation to high energy electrons. Electrons might be boosted up to ≈ 0.01 EeV energies and above and produce ultra-high-energy (UHE) neutrinos and gamma rays when these electrons interact with low energy positrons and soft radiations in the acceleration zone. The theoretically derived extragalactic diffuse muon neutrino flux in the energy range 1–10 PeV is found consistent with the IceCube level if only a fraction ( η k ≈ 0.31 % ) of the total bolometric luminosity of pulsars are transferred to power the PeV neutrinos. Using the above value of the cosmic ray electron loading parameter η k , the diffuse gamma ray flux from inverse Compton scattering off UHE electrons in the soft radiation field might be predicted from the model. [ABSTRACT FROM AUTHOR]

The prompt emission of Gamma Ray Bursts (GRBs) is still an outstanding question in the study of these cataclysmic events. Part of what makes GRBs difficult to study is how unique each event seems to be. However, aggregating many GRB observations and analyzing the population allows us to obtain a better understanding of the emission mechanism that produces the observed prompt emission. In this review, we outline some of the most prevalent correlations that have emerged from GRB prompt emission observations and how these correlations are interpreted in relation to physical properties and prompt emission models of GRB.

Pulsars are magnetized neutron stars. They are not resolved by modern radio telescopes and are studied only by radiation coming from the regions of the magnetic poles. Because of the rotation, this narrow radiation is received as pulses. In a few pulsars whose magnetic axis is almost orthogonal to the rotation axis (the simplest hypothesis), pulses are observed from both poles: the (main) pulse and the interpulse. Such objects primarily include a pulsar in the Crab nebula, observed at many frequencies of the electromagnetic spectrum. In the remarkable work of Hankins and Eilek, a striking difference between the spectra of the main pulse and the interpulse in the Crab nebula in the centimeter wavelength range at microsecond resolution was found (surprising the authors: "In traditional pulsar models... the MP and IP should be the same in their observable quantities (such as spectrum, time signature, or dispersion). We were—and remain—quite surprised that this turns out not to be the case in the Crab pulsar." See T. H. Hankins and J. A. Eilek, "Radio emission signatures in the Crab pulsar," Astrophys. J., 670:693–701, 2007). In particular, a wide range of frequencies was observed in the spectra of the main pulse forming "vertical structures," while "horizontal structures" with distinguished frequencies were observed in the spectra of the interpulse at the same frequencies. Such a difference, related to different radiation mechanisms (nonrelativistic electron emission in a longitudinal accelerating field for the main pulse and relativistic positron radiation due to the curvature of magnetic field lines for the interpulse), is explained by the change from the nonrelativistic to the relativistic mechanism as the frequency increases. Therefore, the frequencies at which the mechanism changes differ for the main pulse and the interpulse. The frequency of observation in the work of Hankins and Eilek is just between these frequencies with which the difference in the microstructure is connected. [ABSTRACT FROM AUTHOR]

A two element multiband multiple-input multiple-output (MIMO) antenna system with low specific absorption rate is proposed for Ka-band space satellite, millimeter-wave (mm-wave), fifth-generation (5G), and future sixth-generation (6G) wireless communication applications. The essential characteristics of both 5G and future 6G communications can be fulfilled by the proposed MIMO antenna design. The proposed MIMO antenna system has significant advantage of covering four relevant and usable frequency bands, i.e., 16 GHz, 25.5 GHz, 28 GHz, and 32 GHz used for the above mentioned applications. The design of the presented antenna looks like a vertical Yagi-Uda antenna with L-shaped ladder. Moreover, two circular slots and a slotted vertical stub are etched in a partially shared ground. The complete electrical dimension of the presented antenna is 6.8 λ 0 × 5. 7 λ 0 × 0. 068 λ 0 , calculated at resonating frequency 25.5 GHz, where λ 0 is wavelength in free space. The geometry of the presented antenna is fabricated using Rogers RO4350TM with dielectric constant (ϵ r) of 3.48, a loss tangent of 0.0025, and the substrate thickness of 0.8 mm. The presented MIMO antenna is excited with a 3 mm wide microstrip feed line having 50 Ω characteristics matched impedance. In terms of performance, the proposed antenna has achieved a reflection coefficient < - 10 dB, and isolation < -15 dB in all the resonating bands, radiation efficiency varies 72%–84%, impedance bandwidth of 4.6 GHz, 1.5 GHz, 1.11 GHz, and 7.5 GHz, and realized gain of 10.18, 12.05, 13.07, & 5.55 dBi is also achieved at frequencies 16 GHz, 25.5 GHz, 28 GHz, and 32 GHz. The achieved values for various MIMO matrices are envelope correlation coefficient > 0.0048, diversity gain of 9.98 dB, channel capacity loss < 0.00023 bits/s/Hz, and mean effective gain < -6 dB. The simulated results obtained by ANSYS I 2022 R2 (HFSS) and the experimental results measured by vector network analyzer (VNA) show a good agreement. [ABSTRACT FROM AUTHOR]

This article investigates a six-port multiple-input multiple-output antenna which operates in mid-bands with a resonating frequency at 4.8 GHz. The overall dimensions of proposed antenna are 0.60 λ 0 × 1. 32 λ 0 × 0. 024 λ 0 , where λ 0 is free space wavelength corresponding to resonating frequency of 4.8 GHz. The proposed geometry consists of six-port electromagnetic wave components along with a plane rectangular patch, slotted partial ring ground, circular cutting ground plane, and inset feeding. For enhancing isolation, I-shaped stubs and slotted ring ground are responsible. Inset feeding, circular cutting ground plane, and partial ground plane are used for enhancing reflection coefficient. The overall −10 dB impedance bandwidth of proposed antenna is ranging from 3.92 GHz to 5.2 GHz. The achieved isolation between all the ports of proposed work is ¿15 dB. The peak values of gain and radiation efficiency provided by this prototype are 6.45 dB & and 86% respectively. The achieved diversity parameters such as envelope correlation coefficients are ¡0.002, diversity gain is 9.98, channel capacity loss is ¡0.014 bits/sec/Hz, and branch power ratio is ¡−1 dB. The proposed antenna can be considered as a suitable candidate for wireless local area network, n77 bands, 5G wireless communications applications, and C-band operations. [ABSTRACT FROM AUTHOR]

The pulsar radio emission originates from regions below 10% of the light cylinder radius. This requires a mechanism where coherent emission is excited in relativistic pair plasma with frequency $$\nu _{\mathrm{cr}}$$ which is below the plasma frequency $$\nu _{\circ }$$ i.e. $$\nu _{\mathrm{cr}} < \nu _{\circ }$$ . A possible model for the emission mechanism is charged bunches (charged solitons) moving relativistically along the curved open dipolar magnetic field lines capable of exciting coherent curvature radio emission. In this article, we review the results from high quality observations in conjunction with theoretical models to unravel the nature of coherent curvature radio emission in pulsars. [ABSTRACT FROM AUTHOR]

High-speed connectors contribute to system-level electromagnetic interference (EMI). Radiation from antenna-mode current and transmission-line (TL)-mode current is briefly reviewed with a backplane connector and an optical cage connector. The radiation from the high-speed connector with TL-mode current is analyzed in detail. The possible radiation mechanisms are analyzed respectively through Green's function method, steepest descent method, and electromagnetic compatibility studio method of moment. Design guidelines of high-speed connectors for EMI mitigation are proposed based on the analysis of radiation physics. [ABSTRACT FROM AUTHOR]

The existence of cosmic accelerators able to emit charged particles up to ZeV energies has been confirmed by the observations made in the last years by experiments such as Auger and Telescope Array. The interaction of such energetic cosmic-rays with gas or low energy photons, surrounding the astrophysical sources or present in the intergalactic medium, guarantee an ultra-high-energy neutrino related emission. When these energetic neutrinos interact in a medium produce a thermo-acoustic process where the energy of generated particle cascades can be conveyed in a pressure pulse propagating into the same medium. The kilometric attenuation length as well as the well-defined shape of the expected pulse suggest a large-area-undersea-array of acoustic sensors as an ideal observatory. For this scope, we propose to exploit the existing and no more operative offshore (oil rigs) powered platforms in the Adriatic sea as the main infrastructure to build an acoustic submarine array of dedicated hydrophones covering a surface area up to 10000 km2 and a volume up to 500 km 3. In this work we describe the advantages of this detector concept using a ray tracing technique as well as the scientific goals linked to the challenging purpose of observing for the first time ultra-high-energy cosmic neutrinos. This observatory will be complementary to the dedicated radio array detectors with the advantages of avoiding any possible thermo-acoustic noise from the atmospheric muons. [ABSTRACT FROM AUTHOR]

Variability classes in the enigmatic black hole candidate GRS 1915+105 are known to be correlated with the variation of the Comptonizing Efficiency (CE) which is defined to be the ratio between the number of power-law (hard) photons and seed (soft) photons injected into the Compton cloud. Similarities of light curves of several variability classes of GRS 1915+105 and IGR 17091-3624, some of which are already reported in the literature, motivated us to compute CE for IGR 17091-3624 as well. We find that they are similar to what were reported earlier for GRS 1915+105, even though masses of these objects could be different. The reason is that the both the sizes of the sources of the seed photons and of the Comptonizing corona scale in the same way as the mass of the black hole. This indicates that characterization of variability classes based on CE is likely to be black hole mass independent, in general. [ABSTRACT FROM AUTHOR]

Cage connectors for optical subassembly I/O modules have been identified as one of the main coupling paths in an optical link at the front-end of switches and routers. In the study presented herein, the simulation model used to study electromagnetic interference coupling physics and mitigation of the optical cage connector was corroborated by comparing the measured and simulated results for the total radiated power (TRP). Currents on the adjacent ground references to the differential signal conductors caused half-wave resonant peaks in the TRP response in the frequency range of 4–18 GHz. At frequencies from 18 to 28 GHz, both full-wave simulation and analytical formulas indicate that the radiation results primarily from the currents on the signal traces. The radiation from the optical cage connector was suppressed with absorbing materials, and the coupling path was verified, together with the optical cage and module enclosure. [ABSTRACT FROM AUTHOR]

This paper examines the transmission line structure of a planar Archimedean spiral antenna. A novel analysis is performed by unwinding the spiral into an equivalent straight transmission line to understand its impedance properties and the radiating mechanism. A relation between the input impedance of the spiral antenna and the characteristic impedance of our proposed model is established. The analytical solution completes the lossy transmission line modelling for the input impedance of the spiral antenna. The value of the stable input resistance in the spiral’s radiation region is found not due to the radiation resistance of the loop antenna, but it is dominated by the propagation characteristics of the slot-line mode, that is the travelling wave on the spiral. The accuracy of this proposed model is verified by full-wave simulations, the Babinet’s principle, and measurements. Examination of the radiation mechanism and discussion on the effects of other parameters such as feeding design are also provided. [ABSTRACT FROM AUTHOR]

Abstract: The Galactic microquasar GRS 1915+105 exhibits at least seventeen types of variability classes. Intra and inter class transitions are reported to be observed within seconds to hours. Since the observation was not continuous, these classes appeared to be exhibited in a random order. Our goal is to predict a sequence of these classes. In this paper, we compute the ratio of the photon counts obtained from the power-law component and the blackbody component of each class and call this ratio as the ‘Comptonizing efficiency’ (CE) of that class. We sequence the classes in the ascending order of CE and find that this sequence matches with a few class transitions observed by RXTE satellite and IXAE instruments on board IRS-P3. A change in CE corresponds to a change in the optical depth of the Compton cloud. Our result implies that the optical depth of the Compton cloud gradually rises as the variability class becomes harder. [Copyright &y& Elsevier]

We present a comprehensive statistical analysis of Swift X-ray light curves of gamma-ray bursts (GRBs) collecting data from more than 650 GRBs discovered by Swift and other facilities. The unprecedented sample size allows us to constrain the rest-frame X-ray properties of GRBs from a statistical perspective, with particular reference to intrinsic time-scales and the energetics of the different light-curve phases in a common rest-frame 0.3-30 keV energy band. Temporal variability episodes are also studied and their properties constrained. Two fundamental questions drive this effort: (i) Does the X-ray emission retain any kind of 'memory' of the prompt Ɣ-ray phase? (ii) Where is the dividing line between long and short GRB X-ray properties? We show that short GRBs decay faster, are less luminous and less energetic than long GRBs in the X-rays, but are interestingly characterized by similar intrinsic absorption. We furthermore reveal the existence of a number of statistically significant relations that link the X-ray to prompt Ɣ-ray parameters in long GRBs; short GRBs are outliers of the majority of these two-parameter relations. However and more importantly, we report on the existence of a universal three-parameter scaling that links the X-ray and the Ɣ-ray energy to the prompt spectral peak energy of both long and short GRBs: EX,iso Ey,iso1.00±0.06 ∞ /Epk0.60±0.10. [ABSTRACT FROM AUTHOR]

The environs of supermassive black holes are among the universe's most extreme phenomena. Understanding the physical processes occurring in the vicinity of black holes may provide the key to answer a number of fundamental astrophysical questions including the detectability of strong gravity effects, the formation and propagation of relativistic jets, the origin of the highest energy gamma-rays and cosmic rays, and the nature and evolution of the central engine in active galactic nuclei (AGN). As a step towards this direction, this paper reviews some of the progress achieved in the field based on observations in the very high energy domain. It particularly focuses on nonthermal particle acceleration and emission processes that may occur in the rotating magnetospheres originating from accreting, supermassive black hole systems. Topics covered include direct electric field acceleration in the black hole's magnetosphere, ultra-high energy cosmic ray production, Blandford-Znajek mechanism, centrifugal acceleration and magnetic reconnection, along with the relevant efficiency constraints imposed by interactions with matter, radiation and fields. By way of application, a detailed discussion of well-known sources (Sgr A*; Cen A; M87; NGC1399) is presented. [ABSTRACT FROM AUTHOR]

Abstract: Open questions in GRB physics are summarized as of 2011, including classification, progenitor, central engine, ejecta composition, energy dissipation and particle acceleration mechanism, radiation mechanism, long term engine activity, external shock afterglow physics, origin of high energy emission, and cosmological setting. Prospects of addressing some of these problems with the upcoming Chinese–French GRB mission, SVOM, are outlined. [Copyright &y& Elsevier]

Results of the second stage of the RAMBAS (RAdiation Mechanism of Biomolecular ASymmetry) experiment on investigation of the radiation mechanism of the influence on chiral molecules are presented. Optical activity of samples of racemic mixtures of amino acids with heavy metals was compared prior to and after irradiation by electron flux from a radioactive source. It is found that the irradiation results in asymmetric degradation of both complexes and amino acids and in production of chiral asymmetry of the samples under study. These results confirm the conclusions inferred from the first stage of the RAMBAS experiment and could be important for the solution of the origin-of-life and biological homochirality problems. [ABSTRACT FROM AUTHOR]

The evidence is reviewed that the primary form of energy that escapes to infinity from gamma-ray bursts (GRBs) is gamma-rays, and/or Poynting flux, and that the kinetic energy in ultrarelativistic baryons is a secondary component resulting from acceleration of baryons by radiation pressure near or beyond the photosphere. This could account for several observed characteristics of observed GRB spectra and light curves, such as the typical peak photon energy, the correlation of this peak with apparent GRB energy, and the profiles and spectral lagging of GRB subpulses. [ABSTRACT FROM AUTHOR]

The first results of the RAdiation Mechanism of Biomolecular ASymmetry (RAMBAS) experiment on investigation of the radiation mechanism of the influence on chiral molecules, as a factor leading to origination of chiral asymmetry are presented. It was found that irradiation of simple achiral materials by a flux of electrons from radioactive source initiated the synthesis of amino acids, and it resulted in asymmetric degradation and chiral asymmetry in a racemic mixture of amino acids. The results obtained can be important for the solution of the origin-of-life and biological homochirality problems. [ABSTRACT FROM AUTHOR]

Abstract: We present a modified outer gap model to study the phase-resolved spectra of the Crab pulsar. A theoretical double peak profile of the light curve containing the whole phase is shown to be consistent with the observed light curve of the Crab pulsar by shifting the inner boundary of the outer gap inwardly to ∼10 stellar radii above the neutron star surface. In this model, the radial distances of the photons corresponding to different phases can be determined in the numerical calculation. Also the local electrodynamics, such as the accelerating electric field, the curvature radius of the magnetic field line and the soft photon energy, are sensitive to the radial distances to the neutron star. Using a synchrotron self-Compton mechanism, the phase-resolved spectra with the energy range from 100eV to 3GeV of the Crab pulsar can also be explained. [Copyright &y& Elsevier]

We numerically examine centrifugally supported shock waves in 2D rotating accretion flows around a stellar mass and a supermassive black holes over a wide range of input accretion rates of . The resultant 2D shocks are unstable with time and the luminosities show quasi-periodic oscillations (QPOs) with modulations of a factor of 2–3 and with periods of a tenth of a second to several hours, depending on the black hole masses. The shock oscillation model may explain the intermediate frequency QPOs with 1–10 Hz observed in the stellar mass black hole candidates and also suggest the existence of QPOs with the period of hours in active galactic nuclei. When the accretion rate is low, the luminosity increases in proportion to the accretion rate. However, when greatly exceeds the Eddington critical rate , the luminosity is insensitive to the accretion rate and is kept constantly around . On the other hand, the mass-outflow rate increases in proportion to and it amounts to about a few per cent of the input mass-flow rate. [ABSTRACT FROM AUTHOR]

Abstract: It has been recently observed by XMM-Newton that besides the emission line of iron Kα at 6.4 keV there also exists in the Seyfert 1 galaxy NGC 3783 the very intense emission line of iron Kβ at 7.0 keV. Moreover, the ratio of equivalent widths (EWs) of these two lines can hardly be interpreted with the traditional mechanism of “photoelectric absorption — fluorescence emission”. By using the mechanism of Cerenkov line-like radiation proposed by YOU Jun-hian et al., the ratio of EWKα /EWKβ may be reasonably interpreted by means of a detailed model theoretical computation. As shown by the results, the iron K lines in active galactic nuclei (AGNs) are formed not only by the fluorescence mechanism, but also by the Cerenkov line-like radiation. Both coexist in AGNs, with the latter playing the dominant role. [Copyright &y& Elsevier]

We study the Doppler factors for a group blazars at soft X-ray band. In our estimates, we have made the assumptions that (i) blazars can be divided into high-energy-peaked (HEP) objects whose synchrotron peak frequencies νp > 1014.7Hz, and the low-energy-peaked (LEP) objects whose synchrotron peak frequencies νp≤1014.7Hz, and (ii) the intrinsic radiation from a blazar in the energy range from radio to soft X-ray bands is the synchrotron radiation for HEP objects and the soft X-ray emission comes from inverse Compton scattering for LEP objects. Under the above assumptions, we estimate Doppler factors at optical (δO) and X-rays (δx) for 54 blazars by using the known radio Doppler factors and the observed flux densities in radio, optical and X-ray bands, and Doppler factors $(\delta_x^{\rm syn})$ at X-ray band in which X-rays are assumed to be produced only by the synchrotron radiation. We get $\delta_x^{\rm syn}>\delta_x$ . The Doppler factors are different in various wavebands, and on average, the Doppler factor decreases with frequency from radio to X-ray bands. [ABSTRACT FROM AUTHOR]

Abstract: The nature of the internal thermal X-ray emission seen in “thermal composite” supernova remnants is still uncertain. Chandra observation of the 3C391 shows a southeast–northwest elongated morphology and unveils a highly clumpy structure of the remnant. Detailed spatially resolved spectral analysis for the small-scale features reveals normal metal abundance and uniform temperature for the interior gas. The properties of the hot gas comparatively favor the cloudlet evaporation model as a main mechanism for the “thermal composite” X-ray appearance, though radiative rim and thermal conduction may also be effective. A faint protrusion is found in Si and S lines out of the southwest radio border. [Copyright &y& Elsevier]