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71.
We present an algorithm of finding numerical solutions of pulsar equation. The problem of finding the solutions was reduced
to finding expansion coefficients of the source term of the equation in a base of orthogonal functions defined on the unit
interval by minimizing a multi-variable mismatch function defined on the light cylinder. We applied the algorithm to Scharlemann
and Wagoner boundary conditions by which a smooth solution is reconstructed that by construction passes successfully the Gruzinov’s
test of the source function exponent.
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72.
研究表明 ,与磁星模型相比较 ,反常X射线脉冲星的加速模型不能说明所观测到的自转周期的分布。为了解释熟知的最慢X射线脉冲星 2S 0 114+6 5 0的性质 ,其磁场强度必须大于 10 14 Gs ,即它诞生时即为一磁体。 相似文献
73.
In a novel approach in observational high-energy gamma-ray astronomy, observations carried out by imaging atmospheric Cherenkov
telescopes provide necessary templates to pinpoint the nature of intriguing, yet unidentified EGRET gamma-ray sources. Using
GeV-photons detected by EGRET and taking advantage of high spatial resolution images from H.E.S.S. observations, we were able
to shed new light on the EGRET observed gamma-ray emission in the Kookaburra complex, whose previous coverage in the literature
is somewhat contradictory. 3EG J1420–6038 very likely accounts for two GeV gamma-ray sources (E>1 GeV), both in positional coincidence with the recently reported pulsar wind nebulae (PWN) by HESS in the Kookaburra/Rabbit
complex. PWN associations at VHE energies, supported by accumulating evidence from observations in the radio and X-ray band,
are indicative for the PSR/plerionic origin of spatially coincident, but still unidentified Galactic gamma-ray sources from
EGRET. This not only supports the already suggested connection between variable, but unidentified low-latitude gamma-ray sources
with pulsar wind nebulae (3EG J1420–6038 has been suggested as PWN candidate previously), it also documents the ability of
resolving apparently confused EGRET sources by connecting the GeV emission as measured from a large-aperture space-based gamma-ray
instrument with narrow field-of-view but superior spatial resolution observations by ground-based atmospheric Cherenkov telescopes,
a very promising identification technique for achieving convincing individual source identifications in the era of GLAST-LAT.
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74.
GianLuca Israel 《Astrophysics and Space Science》2007,308(1-4):25-31
On 27th December 2004 SGR 1806–20, one of the most active Soft γ-ray Repeaters (SGRs), displayed an extremely rare event, also known as giant flare, during which up to 1047 ergs were released in the ∼1–1000 keV range in less than 1 s. Before and after the giant flare we carried out IR observations
by using adaptive optics (NAOS-CONICA) mounted on VLT which provided images of unprecedented quality (FWHM better than 0.1″).
We discovered the likely IR counterpart to SGR 1806–20 based on positional coincidence with the VLA uncertainty region and
flux variability of a factor of about 2 correlated with that at higher energies.
Moreover, by analysing the Rossi-XTE/PCA data we have discovered rapid Quasi-Periodic Oscillations (QPOs) in the pulsating
tail of the 27th December 2004 giant flare of SGR 1806–20. QPOs at ∼92.5 Hz are detected in a 50 s interval starting 170 s
after the onset of the giant flare. These QPOs appear to be associated with increased emission by a relatively hard unpulsed
component and are seen only over phases of the 7.56 s spin period pulsations away from the main peak. QPOs at ∼18 and ∼30 Hz
are also detected ∼200–300 s after the onset of the giant flare. This is the first time that QPOs are unambiguously detected
in the flux of a Soft Gamma-ray Repeater, or any other isolated neutron star. We interpret the highest QPOs in terms of the
coupling of toroidal seismic modes with Alfvén waves propagating along magnetospheric field lines. The lowest frequency QPO
might instead provide indirect evidence on the strength of the internal magnetic field of the neutron star.
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75.
R.K. Manchanda 《Astrophysics and Space Science》2002,282(1):149-160
The spectral and temporal measurements in the hard X-ray region between 20-200 keV not only determines the extended behaviour
of thermal X-ray spectrum below 10 keV but also provide a unique insight into the non-thermal processes in relativistic astrophysical
plasma. From our present understanding of the X-ray sources, a significant fluxin the 20-200 keV band is expected from a variety
of astrophysical phenomena, however, the available spectral data on the galactic and extragalactic X-ray source is very limited.
This is mainly due to the fact that sensitivity of the detector systems used for earlier measurements was relatively poor.
Since 1997, we have been carrying out a programme of hard X-ray observations galactic and extragalactic sources, in the 20-200
keV energy band using a highly sensitive balloon borne experiment. The X-ray telescope consists of three modules of large
area scintillation counters specially configured in the back-to-back geometry and have a combined sensitivity of ∼ 10-6 ph cm-2 s-1 keV-1 for an on-source observations of 3 hrs. A total of 30 hours of ceiling data above an altitude of 3 mbar has been collected
in 4 successful balloon flights from Hyderabad, India. Almost a dozen galactic and extragalactic X-ray sources were targeted
and tracked during these observations. A positive detection was made in each case and in some cases the observed spectra extended
right up to 150 keV. A brief account of the observed spectral and temporal features on some of the sources along with accurate
measurement of diffuse background spectrum and a weak gamma ray burst will be presented in the paper.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
76.
Yang Ting-gao Tong Ming-lei Zhao Cheng-shi Gao Yu-ping 《Chinese Astronomy and Astrophysics》2019,43(1):93-100
The X-ray timing data for the Crab pulsar obtained by the Chinese X-ray pulsar navigation test satellite are processed and analyzed. The method to build the integrated and standard X-ray pulse profiles of the Crab pulsar by using the X-ray pulsar observation data and the satellite orbit data is described. The principle and algorithm for determining the pulsar's pulse time of arrival (toa) in the frequency domain are briefly introduced. The pulsar's pulse time of arrival is calculated by using the timing data of 50 min integration for each set of observational data. By the comparison between the observed Crab pulsar's pulse time of arrival at the solar system barycenter and that predicted with the Crab pulsar ephemeris, it is found that the timing accuracy is about 14 μs after the systematic error is removed by a quadratic polynomial fitting. 相似文献
77.
We investigate the effects of inverse Compton scattering by electrons and positrons in the unshocked winds of rotationally-powered binary pulsars. This process can scatter low energy target photons to produce gamma rays with energies from MeV to TeV. The binary radio pulsars PSR B1259−63 and PSR J0045−73 are both in close eccentric orbits around bright main sequence stars which provide a huge density of low energy target photons. The inverse Compton scattering process transfers momentum from the pulsar wind to the scattered photons, and therefore provides a drag which tends to decelerate the pulsar wind. We present detailed calculations of the dynamics of a pulsar wind which is undergoing inverse Compton scattering, showing that the deceleration of the wind of PSR B1259−63 due to ‘inverse Compton drag' is small, but that this process may confine the wind of PSR J0045−73 before it attains pressure balance with the outflow of its companion star. We calculate the spectra and light curves of the resulting inverse Compton emission from PSR B1259−63 and show that if the size of the pulsar wind nebula is comparable to the binary separation, then the γ-ray emission from the unshocked wind may be detectable by atmospheric Cherenkov detectors or by the new generation of satellite-borne γ-ray detectors such as INTEGRAL and GLAST. This mechanism may therefore provide a direct probe of the freely-expanding regions of pulsar winds, previously thought to be invisible. 相似文献
78.
The power law spectra of the six known-ray pulsars are seen to cut off at energies < 1 TeV so that no steady pulsed TeV component is observed from any known-ray pulsar. In some cases we show that the cutoff is steeper than exponential, which is consistent with magnetic pair production above the polar cap region. The small upper limits on the ratio of TeV energy flux to optical - GeV energy flux is again consistent with the polar cap model, but appears to be inconsistent with inverse Compton controlled outer gaps. 相似文献
79.
X-ray pulsars, which form together with a main sequence star or a giant a close binary system, show strong variations in their pulse period. Epochs of spin-up and spin-down interchange on timescales of some tens up to some thousand days.
We study this phenomenon in the framework of the disk-fed model by Ghosh and Lamb, which we generalize by allowing for an inclination angle χ between the magnetic dipole moment μ and the rotation axis. Moreover, we take into account the relatively small magnetic field induced by currents in the magnetosphere flowing along the dipole field lines. This component, which we calculate numerically, leads to a torque perpendicular to the rotation axis and induces a precession of it. Due to this additional degree of freedom, the calculated pulse period history is much smoother than in the classical Ghosh and Lamb model. Within this extended model we compute, as an example, the pulse period history of Cen X-3 using the observed X-ray flux as a measure for the mass accretion rate. Qualitative accordance with the measured pulse period data (see e.g. Nelson et al., 1997 [ApJ, 488, L117]) is found to be good. 相似文献
80.
Tatiana V. Shabanova 《Astrophysics and Space Science》2007,308(1-4):591-593
The pulsar B1822-09 (J1825-0935) experienced a series of five unusual, slow glitches over the 1995–2004 interval. The results
of further study of this unusual glitch phenomenon are presented. It is also reported the detection a new glitch of typical
signature that occurred in the pulsar period in 2006 January.
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