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1.
We discuss the implications of the recent X-ray and TeV γ-ray observations of the PSR B1259–63 system (a young rotation powered pulsar orbiting a Be star) for the theoretical models of interaction of pulsar and stellar winds. We show that previously considered models have problems to account for the observed behaviour of the system. We develop a model in which the broad band emission from the binary system is produced in result of collisions of GeV–TeV energy protons accelerated by the pulsar wind and interacting with the stellar disk. In this model the high energy γ-rays are produced in the decays of secondary neutral pions, while radio and X-ray emission are synchrotron and inverse Compton emission produced by low-energy (≤100 MeV) electrons from the decays of secondary charged π ± mesons. This model can explain not only the observed energy spectra, but also the correlations between TeV, X-ray and radio emission components.   相似文献   

2.
Radio-quiet γ-ray pulsars like Geminga may account for a number of the unidentified EGRET sources in the Galaxy. The number of Geminga-like pulsars is very sensitive to the geometry of both the γ-ray and radio beams. Recent studies of the shape and polarization of pulse profiles of young radio pulsars have provided evidence that their radio emission originates in wide cone beams at altitudes that are a significant fraction (1–10%) of their light cylinder radius. Such wide radio emission beams will be visible at a much larger range of observer angles than the narrow core components thought to originate at lower altitude. Using 3D geometrical modeling that includes relativistic effects from pulsar rotation, we study the visibility of such radio cone beams as well as that of the γ-ray beams predicted by slot gap and outer gap models. From the results of this study, one can obtain revised predictions for the fraction of Geminga-like, radio quiet pulsars present in the γ-ray pulsar population.   相似文献   

3.
The theory of pulsar radio emission has been developed in a series of our papers since 1992. It was shown that pulsar radio emission is produced in the lower part of a channel of open magnetic field lines, in a region with a height h ≈ 1.1-107 μ 30 1/3 /P4/21 cm above a magnetic cap of the neutron star (P is the pulsar’s period and μ is the star’s magnetic moment). Here, owing to vigorously occurring processes (the production of photons of curvature radiation and their annihilation into e+e- pairs), two ultrarelativistic particle fluxes are formed: an electron flux moving upward and a positron flux falling onto the star’s magnetic cap. These main fluxes are accompanied by narrow strips of positron and electron fluxes of relatively low energy, the curvature emission from which is a strong coherent radio source. The present paper is a review of earlier papers, and important additions and refinements are also made. Equations are offered for the radio luminosity of a pulsar, the solid angle of the radio beam, and the magnetic moment and moment of inertia of the pulsar’s neutron star. Translated from Astrofizika, Vol. 43, No. 1, pp. 147-169, January–March, 2000.  相似文献   

4.
We report hard X-ray emission of the non-thermal supernova remnant G337.2+0.1. The source presents centrally filled and diffuse X-ray emission. A spectral study confirms that the column density of the central part of the object is about N H∼5.9(±1.5)×1022 cm−2 and its X-ray spectrum is well represented by a single power-law with a photon index Γ=0.96±0.56. Detailed spectral analysis indicates that the outer region is highly absorbed and quite softer than the inner region. Characteristics already observed in other well-known X-ray plerions. Based on the gathered information, we confirm the SNR nature of G337.2+0.1, and suggest that the central region of the source is a pulsar wind nebula (PWN), originated by an energetic though yet undetected pulsar.  相似文献   

5.
The curvature -quanta emitted in the pulsar magnetospheres tangentially to the curved lines of force of the magnetic field are shown to be later canalized along the magnetic field—if it is strong enough,B0.1B cr =4×1012G—by gradually converting into a mutually bound electron-positron pair, i.e. a positronium atom. This happens before the photon reaches the threshold of free-pair creation. The positronium thus arising is stable against the ionizing action of the electric field near the pulsar unless it reaches a critical value about 4×107 CGSE forB1013G. This prevents the screening of the electric field up to the distances from the pulsar, where the magnetic field is already below the value of 0.1B cr and the free pair creation may become essential. This effect provides, at least within the Arons model, a higher theoretical estimate for the total luminosity of pulsars whose field at the surfaceB s exceeds 0.1B cr as compared with the conventional one.  相似文献   

6.
A remarkable number of pulsar wind nebulae (PWN) are coincident with EGRET γ-ray sources. X-ray and radio imaging studies of unidentified EGRET sources have resulted in the discovery of at least six new pulsar wind nebulae (PWN). Stationary PWN (SPWN) appear to be associated with steady EGRET sources with hard spectra, typical for γ-ray pulsars. Their toroidal morphologies can help determine the geometry of the pulsar which is useful for constraining models of pulsed γ-ray emission. Rapidly moving PWN (RPWN) with more cometary morphologies seem to be associated with variable EGRET sources in regions where the ambient medium is dense compared to what is typical for the ISM.  相似文献   

7.
A theory of pulsar radio emission generation, in which the observed waves are produced directly by the maser-type plasma instabilities on the anomalous cyclotron-Cherenkov resonance and the Cherenkov-drift resonance , is capable of explaining the main observational characteristics of pulsar radio emission. The instabilities are due to the interaction of the fast particles of the primary beam and from the tail of the distribution with the normal modes of a strongly magnetized one-dimensional electron-positron plasma. The waves emitted at these resonances are vacuum-like electromagnetic waves that may leave the magnetosphere directly. The cyclotron-Cherenkov instability is responsible for core emission pattern and the Cherenkov-drift instability produces conal emission. The conditions for the development of the cyclotron-Cherenkov instability are satisfied for the both typical and millisecond pulsars provided that the streaming energy of the bulk plasma is not very high γ p = 5 ÷ 10. In a typical pulsar the cyclotron-Cherenkov and Cherenkov-drift resonances occur in the outer parts of magnetosphere at r res ≈ 109cm. This theory can account for various aspects of pulsar phenomenology including the morphology of the pulses, their polarization properties and spectral behavior. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

8.
The Cygnus region of the Milky Way is prolific in star formation and presents extended diffuse γ-ray emission with a few γ-ray point sources. Among them is 3EG J2020+4017, the brightest of the unidentified EGRET sources, positionally coincident with the supernova remnant G78.2+2.1. Even though the EGRET and multi-wavelength data have not provided a conclusive identification for this γ-ray loud, but otherwise faint object, the evidence favors a pulsar like source. The EGRET photon data lack the signal-to-noise ratio required for a period search, but will serve as a valuable timing baseline extension in the case that GLAST confirms the pulsar nature of the γ-Cygni source. Work sponsored by CONACyT grant SEP-2003-C02-42611.  相似文献   

9.
We propose a unified picture of high magnetic field radio pulsars and magnetars by arguing that they are all rotating high-field neutron stars but that their magnetic axes have different orientations with respect to their rotation axes. In strong magnetic fields where photon splitting suppresses pair creation near the surface, the high-field pulsars can have active inner accelerators while the anomalous X-ray pulsars cannot. This can account for the very different observed emission characteristics of the anomalous X-ray pulsar 1E 2259+586 and the high-field radio pulsar PSR J1814-1744. A predicted consequence of this picture is that radio pulsars having surface magnetic fields greater than about 2x1014 G should not exist.  相似文献   

10.
We make a statistical analysis of the periodsP and period-derivativesP of pulsars using a model independent theory of pulsar flow in theP-P diagram. Using the available sample ofP andP values, we estimate the current of pulsars flowing unidirectionally along theP-axis, which is related to the pulsar birthrate. Because of radio luminosity selection effects, the observed pulsar sample is biased towards lowP and highP. We allow for this by weighting each pulsar by a suitable scale factor. We obtain the number of pulsars in our galaxy to be 6.05−2.80 +3.32 × 105 and the birthrate to be 0.048−0.011 +0.014 pulsars yr−1 galaxy−1. The quoted errors refer to 95 per cent confidence limits corresponding to fluctuations arising from sampling, but make no allowance for other systematic and random errors which could be substantial. The birthrate estimated here is consistent with the supernova rate. We further conclude that a large majority of pulsars make their first appearance at periods greater than 0.5 s. This ‘injection’, which runs counter to present thinking, is probably connected with the physics of pulsar radio emission. Using a variant of our theory, where we compute the current as a function of pulsar ‘age’ (1/2P/P), we find support for the dipole braking model of pulsar evolution upto 6 × 106 yr of age. We estimate the mean pulsar braking index to be 3.7−0.8 +0.8.  相似文献   

11.
We present the results of numerical simulations of stationary, spherically outflowing, e ± pair winds, with total luminosities in the range 1034–1042 ergs s?1. In the concrete example described here, the wind injection source is a hot, bare, strange star, predicted to be a powerful source of e ± pairs created by the Coulomb barrier at the quark surface. We find that photons dominate in the emerging emission, and the emerging photon spectrum is rather hard and differs substantially from the thermal spectrum expected from a neutron star with the same luminosity. This might help distinguish the putative bare strange stars from neutron stars.  相似文献   

12.
We investigate the production of gamma-rays in the inverse Compton (IC) scattering process by leptons accelerated inside relativistic blobs in jets of active galactic nuclei. Leptons are injected homogeneously inside the spherical blob and initiate IC e ± pair cascade in the synchrotron radiation (produced by the same population of leptons, SSC model), provided that the optical depth for gamma-rays is larger than unity. It is shown that for likely parameters internal absorption of gamma-rays has to be important. We suggest that new type of blazars might be discovered by the future simultaneous X-ray and γ-ray observations, showing peak emissions in the hard X-rays, and in the GeV γ-rays. Moreover, the considered scenario might be also responsible for the orphan X-ray flares recently reported from BL Lac type active galaxies.   相似文献   

13.
E × B-drifting jets have been generally ignored for the past 25 years even though they may well describe all the astrophysical jet sources, both on galactic and stellar scales. Here we present closed-form solutions for their joint field-and-particle distribution, argue that the observed jets are near equipartition, with extremely relativistic, monoenergetic e±-pairs of bulk Lorentz factor γ ≲ 104, and are first-order stable. We describe plausible mechanisms for the jets’ (i) formation, (ii) propagation, and (iii) termination. Wherever a beam meets with resistance, its frozen-in Poynting flux transforms the delta-shaped energy distribution of the pairs into an almost white power law,E 2 N E ∼E −∫ with ∫ ≳ 0, via single-step falls through the huge convected potential.  相似文献   

14.
The Ooty data on VHE (> 600 GeV) γ-rays from the Crab pulsar have been used to look at possible emission on three different timescales,viz. years, minutes and hours. When averaged over three years of observation, there is no significant time-averaged emission. But interesting aspects are revealed when the data are subdivided into miniruns of one-minute duration. Minutes with moderate γ-ray activity were isolated with a κ2 analysis. The summed phasogram of such minutes shows two strong peaks coinciding with the radio main pulse and the interpulse respectively. The probability that these are due to chance is small. The phasogram has a bimodal distribution which indicates some emission from the middle region between the two phases. In general, there is no significant emission on the timescale of a few hours. However, the main pulse, as well as the bimodal distribution, were seen also in the total data of two nights of simultaneous observation at two sites during 1984–1985.  相似文献   

15.
From 2000 to 2010, monitoring of radio emission from the Crab pulsar at Xinjiang Observatory detected a total of nine glitches. The occurrence of glitches appears to be a random process as described by previous researches. A persistent change in pulse frequency and pulse frequency derivative after each glitch was found. There is no obvious correlation between glitch sizes and the time since last glitch. For these glitches Δν p and D[(n)\dot]p\Delta\dot{\nu}_{p} span two orders of magnitude. The pulsar suffered the largest frequency jump ever seen on MJD 53067.1. The size of the glitch is ∼6.8×10−6 Hz, ∼3.5 times that of the glitch occurred in 1989 glitch, with a very large permanent changes in frequency and pulse frequency derivative and followed by a decay with time constant ∼21 days. The braking index presents significant changes. We attribute this variation to a varying particle wind strength which may be caused by glitch activities. We discuss the properties of detected glitches in Crab pulsar and compare them with glitches in the Vela pulsar.  相似文献   

16.
Using a well-known method for calculating the propagation of waves in an inhomogeneous medium, we have managed to reduce the problem of wave propagation in pulsar magnetospheres to a system of two ordinary differential equations that allow the polarization characteristics of the radio emission to be quantitatively described for any magnetic field structure and an arbitrary density profile of the outflowing plasma. We confirm that for ordinary pulsars (period P ∼ 1 s, magnetic field B 0 ∼ 1012 G, particle production multiplicity parameter λ ∼ 104), the polarization is formed inside the light cylinder at a distance of the order of a thousand neutron star radii. For reasonable magnetic field strengths and plasma densities on the emission propagation path, the degree of circular polarization is found to be ∼5–20%, in good agreement with observations.  相似文献   

17.
Having analyzed high-resolution observations of extragalactic compact radio sources with modern systems of radio telescopes, we obtained an estimate of the upper limit for the photon electric charge, eγ ? 3×10?33 of the elementary charge (assuming the photon charge to be energy independent). This is three orders of magnitude better than the limit obtained from radio pulsar timing. We also set a limit on the charge of a gamma-ray (energy ～0.1 MeV) photon. In the future, the estimate based on extragalactic sources can be improved significantly.  相似文献   

18.
The influence of the Landau-Pomeranchuk effect on the development of a shower generated by ultrarelativistic particles bombarding the surface of a pulsar is discussed. Because of this effect, the path length of the shower increases while low-energy photon generation is strongly suppressed. In view of this, the mechanism of pair production suggested by Cheng, Ruderman, and Jones for the pulsar magnetosphere, may be essential only for pulsars whose magnetic field intensity at the surface lies in a relatively narrow range of aroundB 1012 G.  相似文献   

19.
Several BL Lac objects are confirmed sources of variable and strongly Doppler-boosted TeV emission produced in the nuclear portions of their relativistic jets. It is more than probable that also many of the Fanaroff–Riley type I (FR I) radio galaxies, believed to be the parent population of BL Lacs, are TeV sources, for which Doppler-hidden nuclear γ-ray radiation may be only too weak to be directly observed. Here we show, however, that about 1 per cent of the total time-averaged TeV radiation produced by the active nuclei of low-power FR I radio sources is inevitably absorbed and re-processed by photon–photon annihilation on the starlight photon field, and the following emission of the created and quickly isotropized electron–positron pairs. In the case of the radio galaxy Centaurus A, we found that the discussed mechanism can give a distinctive observable feature in the form of an isotropic γ-ray halo. It results from the electron–positron pairs injected to the interstellar medium of the inner parts of the elliptical host by the absorption process, and upscattering starlight radiation via the inverse-Compton process mainly to the GeV–TeV photon energy range. Such a galactic γ-ray halo is expected to possess a characteristic spectrum peaking at ∼0.1 TeV photon energies, and the photon flux strong enough to be detected by modern Cherenkov Telescopes and, in the future, by GLAST. These findings should apply as well to the other nearby FR I sources.  相似文献   

20.
LS 5039 is the only X-ray binary persistently detected at TeV energies by the Cherenkov HESS telescope. It is moreover a γ-ray emitter in the GeV and possibly MeV energy ranges. To understand important aspects of jet physics, like the magnetic field content or particle acceleration, and emission processes, such as synchrotron and inverse Compton (IC), a complete modeling of the multiwavelength data is necessary. LS 5039 has been detected along almost all the electromagnetic spectrum thanks to several radio, infrared, optical and soft X-ray detections. However, hard X-ray detections above 20 keV have been so far elusive and/or doubtful, partly due to source confusion for the poor spatial resolution of hard X-ray instruments. We report here on deep (∼300 ks) serendipitous INTEGRAL hard X-ray observations of LS 5039, coupled with simultaneous VLA radio observations. We obtain a 20–40 keV flux of 1.1±0.3 mCrab (5.9 (±1.6) ×10−12 erg cm−2 s−1), a 40–100 keV upper limit of 1.5 mCrab (9.5×10−12 erg cm−2 s−1), and typical radio flux densities of ∼25 mJy at 5 GHz. These hard X-ray fluxes are significantly lower than previous estimates obtained with BATSE in the same energy range but, in the lower interval, agree with extrapolation of previous RXTE measurements. The INTEGRAL observations also hint to a break in the spectral behavior at hard X-rays. A more sensitive characterization of the hard X-ray spectrum of LS 5039 from 20 to 100 keV could therefore constrain key aspects of the jet physics, like the relativistic particle spectrum and the magnetic field strength. Future multiwavelength observations would allow to establish whether such hard X-ray synchrotron emission is produced by the same population of relativistic electrons as those presumably producing TeV emission through IC.  相似文献   

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