共查询到20条相似文献，搜索用时 31 毫秒
1.
本文讨论了共轴、纯转动、force-free的脉冲星系统,在Burman理论基础上建立了一个非共转模型(其中含待定参量,共转情况是它的特例)。利用系统稳定的近似条件——系统能量最小确定特定参量,得到一个与G-J模型类似的共转模型。由于考虑了惯性效应,不存在星风,是稳定态,但没有辐射。在转轴与磁矩有小偏角时,利用非平衡系统更普遍的稳定条件——熵产生最小,确定本模型的参量,得到的辐射能量在量级上与观测值相符合。 相似文献
2.
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
3.
A. V. Gurevich Ya. N. Istomin 《Monthly notices of the Royal Astronomical Society》2007,377(4):1663-1667
The analysis of observations of pulsar B1931+24 shows that the mechanism of the spin-down of a rotating magnetized neutron star is due to the plasma generation in its magnetosphere and, consequently, the radio emission generation. The unique observation of the switch on and switch off of this pulsar allows us to distinguish between the energy loss in the absence of radio emission (the magnetodipole radiation) and the current loss due to the rotation energy expenditure to the relativistic plasma generation and acceleration in the pulsar magnetosphere. The inclination angle χ, the angle between the rotation axis and the magnetic dipole axis, can be stationary for this pulsar, χ=χst . From observations and theory it follows that χst = 59° . 相似文献
4.
R. N. Manchester 《Journal of Astrophysics and Astronomy》1995,16(2):107-117
Observations of mean or average pulse profiles and their polarization give us much information on the shape of pulsar beams.
The observed polarization variations, profile symmetry and frequency dependence of profile shape strongly suggest that the
emission beam is conical and emitted from the vicinity of a magnetic pole. Central and outer parts of the beam have somewhat
different properties, but the evidence is that they are emitted by the same basic mechanism. Recent observations suggest that
the highly polarized pulse components seen in young pulsars may be emitted at a large angle to the magnetic axis. 相似文献
5.
It is shown that knowing the energy flux density of the radio emission, the rate of increase in the period, and the distance
of a pulsar enables one to calculate all the rest of its most important characteristics (the solid angle of the radio emission
beam, the radio luminosity, the solid angle of the beam of γ rays, the energy flux density of the g-ray emission, and the
magnetic moment, moment of inertia, and mass of the neutron star). Equations from which these pulsar characteristics can be
calculated are given at the end of the paper. The results of calculations for a number of pulsars are given in Tables 2 and
3 as an illustration.
Translated from Astrofizika, Vol. 43, No. 2, pp. 277-291, April–June, 2000. 相似文献
6.
研究了高斯辐射成分在可视点所画出轨迹上的分布,这个可视点因脉冲星的转动而作非匀速度运动.通过假设辐射区域围绕磁轴均匀分布,一个高斯辐射成分便对应于可视轨迹划过的一个辐射区域.因为演示辐射区域在可视轨迹上是不均匀的分布,因此高斯成分沿轨迹也是不均匀的,而高斯成分的密度在磁轴与视线距离最近时为最大.高斯成分的分布取决于脉冲星的两个角度:旋转轴和视线之间的夹角,以及磁轴和旋转轴之间的倾角.基于此模型,一个脉冲星平均轮廓中观察到的多个高斯成分便对应于可视轨迹在特定的转动相位范围内的辐射区域.演示了脉冲星旋转的近侧和远侧的相位,分别对应的主脉冲和中间脉冲,两者高斯成分的数量和分布是不同的.而且还发现,沿可视轨迹上的辐射区域总数与围绕磁轴的辐射区域的总数是不同,并且预测的辐射区域数目会因忽略可见点的运动而明显不同.拟合表明脉冲星轮廓的高斯成分的形状和数量可能与实际构成轮廓的成分的形状和数量不同.以PSR B0826–34的辐射为例,并假设辐射来自单一磁极. 相似文献
7.
As the performance of dedicated facilities has continually improved, large numbers of pulsar candidates are being received, which makes selecting valuable pulsar signals from the candidates challenging. In this paper, we describe the design for a deep convolutional neural network(CNN) with 11 layers for classifying pulsar candidates. Compared to artificially designed features, the CNN chooses the subintegrations plot and sub-bands plot for each candidate as inputs without carrying biases. To address the imbalance problem, a data augmentation method based on synthetic minority samples is proposed according to the characteristics of pulsars. The maximum pulses of pulsar candidates were first translated to the same position, and then new samples were generated by adding up multiple subplots of pulsars. The data augmentation method is simple and effective for obtaining varied and representative samples which keep pulsar characteristics. In experiments on the HTRU 1 dataset, it is shown that this model can achieve recall of 0.962 and precision of 0.963. 相似文献
8.
Maxim Lyutikov 《Astrophysics and Space Science》2001,278(1-2):81-84
Diffractive and refractive magnetospheric scintillations may allow direct probing of the plasma inside the pulsar light cylinder.
The unusual electrodynamics of the strongly magnetized electron-positron plasma allows separation of the magnetospheric and
interstellar scattering. The most distinctive feature of the magnetospheric scintillations is their independence of frequency.
Diffractive scattering due to small scale inhomogeneities produces a scattering angle that may be as large as 0.1radians,
and a typical decorrelation time of 10-8 seconds. Refractive scattering due to large scale inhomogeneities is also possible, with atypical angle of 10-3 radians and a correlation time of the order of10-4 seconds. Some of the magnetospheric propagation effects may have already been observed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
Anthony Minter 《Astrophysics and Space Science》2001,278(1-2):159-162
Space Very Long Baseline Interferometry observations of PSR 0329+54 which, by luck, occurred during an interstellar fringing
event, are presented. Separate images of the pulsar were not detected. However, the pulsar was observed to be extended. The
size of PSR 0329+54 during this event is1.88 × 1.67 mas with a position angle of 30° East of North. This could be due to two separate images of the pulsar separated byΔ θ ≲ 0.5 mas or angular broadening. The
observed image size is larger than the expected angular broadening size of < 0.1 mas from the observations of Britton, Gwinn
and Ojeda (1998).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
随着500 m口径球面射电望远镜(Five-hundred-meter Aperture Spherical radio Telescope, FAST)等大型射电望远镜的建设和使用,脉冲星巡天数据进入PB时代.为解决如此大量高速采样的标量数据挖掘问题,促进新天文现象的发现,提出一种基于无监督聚类的脉冲星候选体筛选方案.该方案采用基于密度层次、划分方法的混合聚类算法,结合MapReduce/Spark并行计算模型和基于滑动窗口的分组策略,进而提高大量候选体信号筛选的效率.通过在脉冲星数据集HTRU2 (High Time Resolution Universe)上的对比实验,结果表明该算法能取得较高的精确度和召回率,分别是0.946和0.905,并且当并行节点足够时,该算法的时间复杂度相比串行执行明显下降.可见,该方法为脉冲星观测大数据的分析挖掘提供一种可行思路. 相似文献
11.
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
12.
13.
S. A. Petrova 《Monthly notices of the Royal Astronomical Society》2006,368(4):1764-1772
Pulsar radio emission is modelled as a sum of two completely polarized non-orthogonal modes with the randomly varying Stokes parameters and intensity ratio. The modes are the result of polarization evolution of the original natural waves in the hot, magnetized, weakly inhomogeneous plasma of the pulsar magnetosphere. In the course of the wavemode coupling, the linearly polarized natural waves acquire purely orthogonal elliptical polarizations. Further on, as the waves pass through the cyclotron resonance, they become non-orthogonal. The pulse-to-pulse fluctuations of the final polarization characteristics and the intensity ratio of the modes are attributed to the temporal fluctuations in the plasma flow.
The model suggested allows one to reproduce the basic features of the one-dimensional distributions of the individual-pulse polarization characteristics. Besides that, the propagation origin of the pulsar polarization implies a certain correlation between the mode ellipticity and position angle. On a qualitative level, for different sets of parameters, the expected correlations appear compatible with the observed ones. Further theoretical studies are necessary to establish the quantitative correspondence of the model to the observational results and to develop a technique of diagnostics of the pulsar plasma on this basis. 相似文献
The model suggested allows one to reproduce the basic features of the one-dimensional distributions of the individual-pulse polarization characteristics. Besides that, the propagation origin of the pulsar polarization implies a certain correlation between the mode ellipticity and position angle. On a qualitative level, for different sets of parameters, the expected correlations appear compatible with the observed ones. Further theoretical studies are necessary to establish the quantitative correspondence of the model to the observational results and to develop a technique of diagnostics of the pulsar plasma on this basis. 相似文献
14.
《Chinese Astronomy and Astrophysics》2023,47(2):335-352
Thanks to the excellent performance of FAST (Five-hundred-meter Aperture Spherical radio Telescope), the number of pulsars has increased rapidly. It is very important to analyze the physical parameters of known pulsars. The overall properties of pulsars are studied by analyzing the related physical parameters such as spatial position, period, surface magnetic flux density and so on. A large number of pulsars were detected by FAST near the galactic disk, which reflect the superiority of its detection ability. The diagram of the relationship between the period and the time derivative of period of pulsars has been updated. At present, 57 pulsars have crossed the classical “death line”, and five were discovered by FAST. Finally, the physical parameters of the binary pulsar systems are statistically analyzed, the binary pulsar systems are evolving towards the direction of low eccentricity and the decrease mass of the companion star. Moreover, 9 are located above the “spin-up line”. FAST is making China into the golden age of pulsar discovery, which will further promote the rapid development of pulsar physics. 相似文献
15.
M. O. Oestreicher & Th. Schmidt-Kaler 《Monthly notices of the Royal Astronomical Society》1998,299(3):625-636
We have analysed polarization data for a large number of isolated pulsars to investigate the evolution of pulsar radio beams. Assuming that a circular beam is directed along the axis of a dipolar magnetic field, we demonstrate that the distribution of magnetic inclination angles for the parent population of all pulsars is not flat but highly concentrated towards small inclination angles and that, consequently, the average beaming fraction is only ∼ 10 per cent. Furthermore, we find that there is a tendency for the beam axis to align with the rotational axis on a time-scale of ∼ 107 yr. This has interesting consequences for statistical studies of the pulsar population. Finally, the luminosity of pulsars is shown to be independent of the impact parameter, which indicates that pulsar beams are sharp-edged and have a relatively flat integrated intensity distribution. 相似文献
16.
Interaction of an ejecting pulsar in a binary with a matter surrounding it is considered. Around the pulsar a cavern is formed, and its shape calculated. Non-stationary regime of floating caverns filled with binary radioemission is discussed. This regime can lead to a special radio-burster. It is noticed that in binaries with rather large separation between components a pulsed radioemission from a pulsar can be observable. In this case, the pulsar will be a fine probe for exploration of physical characteristics of a stellar wind from a normal expansion. 相似文献
17.
The pulsar time defined by a single pulsar is affected by many kinds of noise sources. Its short-term and long-term degrees of stability are both not good enough. In order to weaken the influence of these noise sources on the single pulsar time, an appropriate algorithm can be adopted to make a synthesis of many single pulsar times, then the ensemble pulsar time is obtained, thereby increasing the long-term degree of stability of the ensemble pulsar time. In this article four kinds of algorithms of the ensemble pulsar time are introduced, i.e., the classical weighting algorithm, wavelet analysis algorithm, Wiener filtering algorithm and Wiener filtering algorithm in wavelet domain. These four algorithms are respectively applied to the timing residuals obtained from the observation of two millisecond pulsars, PSR B1855+09 and PSR B1937+21 made at the Arecibo Astronomical Observatory, and comparisons are carried out. 相似文献
18.
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
19.
The applications of pulsar timing to several important aspects are introduced and a skeletal definition of the pulsar time scale is given. By taking advantage of the observational timing data of millisecond pulsars obtained at the Parkes Astronomical Observatory, Australia, the ensemble pulsar time based on 4 millisecond pulsars is built up, the comparison of its stability σz, with that of the atomic time is made, and finally a few of important factors which affect the ensemble pulsar time, as well as their influences on the pulsar timing accuracy and application are analyzed. 相似文献
20.
S. M. Ord B. A. Jacoby A. W. Hotan M. Bailes 《Monthly notices of the Royal Astronomical Society》2006,371(1):337-342
We present the results of a high-precision timing campaign directed at the binary millisecond pulsar J1600−3053. Submicrosecond pulsar timing has long been the domain of bright, low dispersion measure millisecond pulsars or large diameter telescopes. This experiment, conducted using the Parkes radio telescope in New South Wales, Australia, and utilizing the latest baseband recording hardware, has allowed this pulsar, although distant and faint, to present residuals to a model of its spin behaviour of 650 ns over a period of more than 2 yr. We have also constrained the orbital inclination via Shapiro delay to be between 59° and 70° to 95 per cent confidence and obtained a scintillation velocity measurement indicating a transverse velocity less than 84 km s−1 . This pulsar is demonstrating remarkable stability comparable to, and in most cases improving upon, the very best long-term pulsar timing experiments. If this stability is maintained, the current limits on the energy density of the stochastic gravitational wave background will be reached in four more years. 相似文献