共查询到20条相似文献，搜索用时 15 毫秒
1.
Katherine E. McGowan W. Thomas Vestrand Jamie A. Kennea Silvia Zane Mark Cropper France A. Córdova 《Astrophysics and Space Science》2007,308(1-4):309-316
We present X-ray data of the middle-aged radio pulsar PSR B0355+54. The XMM-Newton and Chandra observations show not only
emission from the pulsar itself, but also compact diffuse emission extending ∼50″ in the opposite direction to the pulsar’s
proper motion. Our analysis also indicates the presence of fainter diffuse emission extending ∼5′ from the point source. The
morphology of the diffuse component is similar to the ram-pressure confined pulsar wind nebulae detected for other sources.
We find that the compact diffuse component is well-fitted with a power-law, with an index that is consistent with the values
found for other pulsar wind nebulae. The core emission from the pulsar can be characterized with a thermal plus power-law
fit, with the thermal emission most likely originating in a hot polar cap. 相似文献
2.
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
3.
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
4.
A. N. Timokhin 《Astrophysics and Space Science》2007,308(1-4):345-351
Pulsar “standard model”, that considers a pulsar as a rotating magnetized conducting sphere surrounded by plasma, is generalized
to the case of oscillating star. We developed an algorithm for calculation of the Goldreich-Julian charge density for this
case. We consider distortion of the accelerating zone in the polar cap of pulsar by neutron star oscillations. It is shown
that for oscillation modes with high harmonic numbers (l,m) changes in the Goldreich-Julian charge density caused by pulsations of neutron star could lead to significant altering of
an accelerating electric field in the polar cap of pulsar. In the moderately optimistic scenario, that assumes excitation
of the neutron star oscillations by glitches, it could be possible to detect altering of the pulsar radioemission due to modulation
of the accelerating field.
This work was partially supported by RFBR grant 04-02-16720, and by the grants N.Sh.-5218.2006.2 and RNP-2.1.1.5940. 相似文献
5.
In this contribution we present our preliminary investigation on pulsar sensitivity of the Large Area Telescope, the main
instrument aboard the GLAST mission. In particular we concentrated our attention to pulsars located at low galactic latitudes.
We created a set of simulated pulsars having different fluxes in an array of galactic coordinates separated by a distance
greater than the LAT Point Spread Function in order to avoid confusion between adjacent sources. Galactic gamma-ray sky background
as used during the second LAT Data Challenge (DC2) is also included. We then run an automatic routine for testing periodicity for all the pulsars considering an opportune
timing solution. In this way we can obtain a map of the sensitivity of the periodic searches for different fluxes and for
various Galactic latitudes. Some assumptions have been made by simulating the pulsar sources, but this study is a first step
toward an estimate for pulsed emission sensitivity of the GLAST LAT. The pulsed flux sensitivity profile we generate could
also be input to a population synthesis code of Galactic pulsars in order to obtain more accurate predictions of the number
of expected pulsar detections by GLAST.
On behalf of the GLAST LAT Collaboration. 相似文献
6.
由单颗脉冲星定义的脉冲星时受多种噪声源的影响,其短期和长期稳定度都不够好.为了削弱这些噪声源对单脉冲星时的影响,可以采取合适的算法对多个单脉冲星时进行综合得到综合脉冲星时,从而提高综合脉冲星时的长期稳定度.文中介绍4种综合脉冲星时算法:经典加权算法、小波分析算法、维纳滤波算法和小波域中的维纳滤波算法,将这4种算法分别应用于Arecibo天文台对两颗毫秒脉冲星PSR B1855+09和PSRB1937+21观测得到的计时残差并作出比较. 相似文献
7.
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.
相似文献
8.
9.
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.
相似文献
10.
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
11.
We present a calculation of a three-dimensional pulsar magnetosphere model to explain high-energy emission from the Geminga pulsar with a thick outer gap. High-energy γ -rays are produced by primary accelerated particles with a power-law energy distribution through curvature radiation inside the outer gap. We also calculate the emission pattern, pulse profile and phase-resolved spectra of high-energy γ -rays of the Geminga pulsar, and find that its pulse profile is consistent with the observed one if the magnetic inclination and viewing angle are ∼50° and ∼86° respectively. We describe the relative phases among soft (thermal) X-rays, hard (non-thermal) X-rays, and γ -rays. Our results indicate that X-ray and γ -ray emission from the Geminga pulsar may be explained by the single thick outer gap model. Finally, we discuss the implications of the radio and optical emission of the Geminga pulsar. 相似文献
12.
毫秒脉冲星在时间计量中的可能应用 总被引：1，自引：0，他引：1
在分析射电脉冲星的自转和时间尺度的基本特征及其相互之间的关系的基础上，讨论了毫秒脉冲星在时间工作中的可能应用。基于毫秒脉冲星的到达时间的测量，经过必要的时空转换、改正及参数拟合，可以建立脉冲星时及综合脉冲星时。虽然脉冲星时及综合脉冲星时对原子有所依赖，但它们，特别是综合脉冲星时，可以用来将原子时的准确度从一个时段传递到另一个时段，并可用来分析原子时的长期稳定度。另外，可以利用双星脉冲星的轨道运动的相位来定义一种动力学时间尺度－－双星脉冲星时。 相似文献
13.
We explore the detailed polarization behaviour of pulsar 0823 + 26 using the technique of constructing partial ‘mode-separated’
profiles corresponding to the primary and secondary polarization modes. The characteristics of the two polarization modes
in this pulsar are particularly interesting, both because they are anything but orthogonal and because the secondary mode
exhibits a structure seen neither in the primary mode nor in the total profile. The new leading and trailing features in the
secondary mode, which appear to represent a conal component pair, are interpreted geometrically on the basis of their width
and the associated polarization-angle traverse as an outer cone.
If the secondary-mode features are, indeed, an outer cone, then questions about the significance of the pulsar’s postcursor
component become more pressing. It seems that 0823 + 26 has a very nearly equatorial geometry, in that both magnetic poles
and the sightline all fall close to the rotational equator of the star. We thus associate the postcursor component with emission
along those bundles of field lines which are also equatorial and which continue to have a tangent in the direction of our
sight line for a significant portion of the star’s rotation cycle. It seems that in all pulsars with postcursor components,
this emission follows the core component, and all may thus have equatorial emission geometries. No pulsars with precursors
in this sense — including the Crab pulsar — are known.
The distribution of power between the primary and secondary modes is very similar at both 430 and 1400 MHz. Our analysis shows
that in this pulsar considerable depolarization must be occurring on time scales that are short compared to the time resolution
of our observations, which is here some 0.5–1.0 milliseconds. One of the most interesting features of the modeseparated partial
profiles is a phase offset between the primary and secondary modes. The secondary-mode ‘main pulse’ arrives some 1.5 ± 0.1‡
before the primary-mode one at 430 MHz and some 1.3 +0.1 ‡ at 21 cm. Given that the polar cap has an angular diameter of 3.36‡,
we consider whether this is a geometric effect or an effect of differential propagation of the two modes in the inner magnetosphere
of the pulsar. 相似文献
14.
Pulsar B1929+10 is remarkable on a number of grounds. Its narrow primary components exhibit virtually complete and highly
stable linear polarisation, which can be detected over most of its rotation cycle. Various workers have been lured by the
unprecedented range over which its linear polarisation angle can be determined, and more attempts have been made to model
its emission geometry than perhaps for any other pulsar. Paradoxically, there is compelling evidence to interpret the pulsar’s
emission geometryboth in terms of an aligned configuration whereby its observed radiation comes from a single magnetic-polar emission regionand in terms of a nearly orthogonal configuration in which we receive emission from regions near each of its two poles. Pulsar
1929+10 thus provides a fascinating context in which to probe the conflict between these lines of interpretation in an effort
to deepen our understanding of pulsar radio emission.
Least-squares fits to the polarisation-angle traverse fit poorly near the main pulse and interpulse and have an inflection
point far from the centre of the main pulse. This and a number of other circumstances suggest that the position-angle traverse
is an unreliable indicator of the geometry in this pulsar, possibly in part because its low level ‘pedestal’ emission makes
it impossible to properly calibrate a Polarimeter which correlates orthogonal circular polarisations.
Taking the interpulse and main-pulse comp. II widths as indicators of the magnetic latitude, it appears that pulsar 1929+10
has anα value near 90‡ and thus has a two-pole interpulse geometry. This line of interpretation leads to interesting and consistent
results regarding the geometry of the conal components. Features corresponding to both an inner and outer cone are identified.
In addition, it appears that pulsar 1929+10–and a few other stars–have what we are forced to identify as a ‘furtherin’ cone,
with a conal emission radius of about2.3‡/P
1/2
Secondarily, 1929+10’s nearly complete linear polarisation provides an ideal opportunity to study how mechanisms of depolarisation
function on a pulse-to-pulse basis. Secondary-polarisation-mode emission appears in significant proportion only in some limited
ranges of longitude, and the subsequent depolarization is studied using different mode-separation techniques. The characteristics
of the two polarisation modes are particularly interesting, both because the primary mode usually dominates the secondary
so completely and because the structure seen in the secondary mode appears to bear importantly on the question of the pulsar’s
basic emission geometry. New secondary-mode features are detected in the average profile of this pulsar which appear independent
of the main-pulse component structure and which apparently constitute displaced modal emission.
Individual pulses during which the secondary-mode dominates the primary one are found to be considerably more intense than
the others and largely depolarised. Monte-Carlo modeling of the mode mixing in this region, near the boundary of comps. II
and III, indicates that the incoherent interference of two fully and orthogonally polarised modes can adequately account for
the observed depolarisation. The amplitude distributions of the two polarisation modes are both quite steady: the primary
polarisation mode is well fitted by a χ2 distribution with about nine degrees of freedom; whereas the secondary mode requires a more intense distribution which is
constant, but sporadic. 相似文献
15.
A. A. Deshpande F. D’Alessandro P. M. McCulloch 《Journal of Astrophysics and Astronomy》1996,17(1-2):7-16
Spectral analysis of the residual pulsearrival times of pulsars is a useful tool in understanding the nature of the underlying
processes that may be responsible for the timing noise observed from pulsars. Power spectra of pulsar timing residuals may
be described by one or a combination of powerlaws. As these spectra are expected to be very steep, it is important to ensure
a high dynamic range in the estimation of the spectrum. This is difficult in practice since one is, in general, dealing with
timing measurements made at unevenly placed epochs. In this paper, we present a technique based on, ‘CLEAN’ to obtain high
dynamic range spectra from unevenly sampled data. We compare the performance of this technique with other techniques including
some that were used earlier for estimation of power spectra of pulsar timing residuals. 相似文献
16.
Nino Chkheidze 《New Astronomy》2012,17(2):227-231
A plasma emission model is presented interpreting the observational properties of RX J1856.5-3754. In particular, on the basis of the Vlasov’s kinetic equation we study the process of the quasi-linear diffusion (QLD) developed by means of the cyclotron instability. This mechanism provides simultaneous generation of optical and X-ray emission on the light cylinder scales, in one location of the pulsar magnetosphere. It is assumed that the observed X-ray spectrum of this source is generated via the synchrotron mechanism. A different approach of the synchrotron theory is considered, giving a spectral energy distribution that is in a good agreement with the observational data. 相似文献
17.
We study the concept of radius-to-frequency mapping using a geometrical method for the estimation of pulsar emission altitudes. The semi-empirical relationship proposed by Kijak &38; Gil is examined over three decades of radio frequency. It is argued that the emission region in a millisecond pulsar occupies the magnetosphere over a distance of up to about 30 per cent of the light-cylinder radius, and that in a normal pulsar occupies up to approximately 10 per cent of the light-cylinder radius. 相似文献
18.
The aim of this article is to draw attention to the importance of the electric current loss in the energy output of radio
pulsars. We remind that even the losses attributed to the magneto-dipole radiation of a pulsar in vacuum can be written as
a result of an Ampere force action of the electric currents flowing over the neutron star surface (see the books of Michel
(Theory of Neutron Star Magnetosphere. University of Chicago Press (1991)) and of Beskin, Gurevich and Istomin (Physics of the Pulsar Magnetosphere. Cambridge Univ. Press (1993)). It is this force that is responsible for the transfer of angular momentum of a neutron star
to an outgoing magneto-dipole wave. If a pulsar is surrounded by plasma, and there is no longitudinal current in its magnetosphere,
there is no energy loss. It is the longitudinal current closing within the pulsar polar cap that exerts the retardation torque
acting on the neutron star. This torque can be determined if the structure of longitudinal current is known. Here we remind
of the solution by Beskin, Gurevich and Istomin (ed. cit.) and discuss the validity of such an assumption. The behavior of
the recently observed “part-time job” pulsar B1931+24 can be naturally explained within the model of current loss while the
magneto-dipole model faces difficulties.
This work was partially supported by the Russian Foundation for Basic Research (Grant no. 05-02-17700) and Dynasty fund. Elena
Nokhrina thanks the Conference Organizing Committee for the PPARC/Padova University Grant, and the RFFR for the travel grant
(no. 06-02-26645). 相似文献
19.
W. Bednarek 《Monthly notices of the Royal Astronomical Society》2003,345(3):847-853
We argue that γ-ray sources observed in the direction of the Cygnus OB2 association in the GeV and TeV energy range are due to a pulsar that was created by a supernova a few tens of thousands of years ago. The GeV emission is produced by a middle-aged pulsar, a factor of 2 older than the Vela pulsar. The TeV emission is produced by high-energy hadrons and/or leptons accelerated in pulsar wind nebulae. We suggest, moreover, that the excess of cosmic rays at ∼1018 eV observed from the direction of the Cygnus region can also be related to the appearance of this very energetic pulsar in the Cyg OB2 association. Some of the relativistic hadrons, captured in strong magnetic fields of a high-density region of Cyg OB2, produce neutrons and γ-rays in collisions with matter. These neutrons can arrive from Cyg OB2, creating an excess of cosmic rays. 相似文献
20.
S. V. Bogovalov F. A. Aharonian 《Monthly notices of the Royal Astronomical Society》2000,313(3):504-514
We show that the relativistic wind of the Crab pulsar, which is commonly thought to be invisible in the region upstream of the termination shock at r r S ∼0.1 pc, in fact could be directly observed through its inverse Compton (IC) γ -ray emission. This radiation is caused by illumination of the wind by low-frequency photons emitted by the pulsar, and consists of two, pulsed and unpulsed , components associated with the non-thermal (pulsed) and thermal (unpulsed) low-energy radiation of the pulsar, respectively. These two components of γ -radiation have distinct spectral characteristics, which depend essentially on the site of formation of the kinetic-energy-dominated wind, as well as on the Lorentz factor and the geometry of propagation of the wind. Thus, the search for such specific radiation components in the spectrum of the Crab Nebula can provide unique information about the unshocked pulsar wind that is not accessible at other wavelengths. In particular, we show that the comparison of the calculated flux of the unpulsed IC emission with the measured γ -ray flux of the Crab Nebula excludes the possibility of formation of a kinetic-energy-dominated wind within 5 light-cylinder radii of the pulsar, R w 5 R L . The analysis of the pulsed IC emission, calculated under reasonable assumptions concerning the production site and angular distribution of the optical pulsed radiation, yields even tighter restrictions, namely R w 30 R L . 相似文献