共查询到20条相似文献，搜索用时 93 毫秒
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脉冲星的周期非常稳定.前人通过研究发现脉冲星射电辐射束半径大小应该正比于周期的-1/3或-1/2次方.通过整理收集了87颗信噪比很好的、偏振位置角明显为"S"曲线的脉冲星数据,用脉冲星辐射束几何模型计算得到了每颗脉冲星的辐射束半径及误差.发现脉冲星周期小于0.85 s时,辐射束半径正比于周期的-1/2次方.周期大于0.85 s时,辐射束半径与周期之间并没有明显的幂律关系,但这可能与选择效应有关.当假设脉冲星的磁倾角为90?时,计算得到的辐射束半径随周期分布的下边界正比于周期的-1/2次方,与前人的结论一致. 相似文献
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探讨了认为中心致密天体(CCO)起源于双星的可能性.首先, CCO与正常遗迹脉冲星有着相似的平均自旋周期,但CCO的平均表面磁场强度(B～5.4×10~(10)Gs)低于正常遗迹脉冲星(B～7.7×10~(12)Gs)～2个量级.同时,几乎所有的正常遗迹脉冲星均分布在爱丁顿吸积加速线以上,而CCO全部分布在自旋加速线以下.因此怀疑CCO可能起源于双星吸积加速过程.其次,基于中子星再加速理论,分析了CCO可能的双星演化过程:双星系统中, CCO以M～1017g·s~(-1)的吸积率,经过～106yr的时间共吸积△M～10~(-2)M⊙的物质,其自旋周期将会从P～10 s降低至P～0.1 s,表面磁场强度将会从B～10~(12)Gs降低至B～1010Gs.考虑到～106yr的演化时标远大于CCO遗迹的年龄(～0.3–7 kyr),猜想CCO可能是双星系统中第1颗恒星超新星爆发的产物,而第2颗恒星超新星爆发后双星解体,留下CCO和第2颗恒星的超新星遗迹.该模型预言在CCO附近可能存在一颗年轻的正常脉冲星(P～0.02 s, B～1012Gs),并期望未来的射电望远镜和高能探测器能够进行搜寻. 相似文献
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《天文学报》2018,(6)
PSR J1906+0746是2006年发现的一颗自旋周期为144 ms的射电脉冲星,由于探测到的是第2颗形成的非自转加速伴星,主星和伴星组成的系统极有可能成为另一对双脉冲星.从PSR J1906+0746的基本物理量出发,针对性地对比研究双中子星和脉冲双星(包括中子星-白矮星)的磁场-周期关系,大致得出他们的演化路径;其次通过双中子星的形成机制以及双星形成过程中的物质损失,假定非自转加速的伴星形成于电子俘获,得出伴星前身星的质量约为1.57 M⊙,在形成双中子星系统过程中损失了约0.23 M⊙.这可能是由于电子俘获能量较低,不能抗衡伴星的引力束缚能,最终抛出物质没有逃逸,形成了一个椭圆环,成功解释了在X射线波段观测到的围绕着PSR J1906+0746的环结构. 相似文献
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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
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反常X射线脉冲星的研究进展 总被引：1，自引：0，他引：1
反常X射线脉冲星（Anomalous X-ra Pulsars，简称AXP）是一类特殊的X射线源。与X射线脉冲星（通常处于大质量X射线双星系统中）相比，它们具有以下特征：X射线谱较软、光度低页稳定（≈10^27－10^29J.s^-1）、自转周期集中在10s左右稳定增长、迄今没有找到它们的光学、红外、射电的对应体、有一些可能戌超新星遗迹成协等。由观测到的自转周期变化可以确定它们的自转能损不足以提供有X射线辐射。解释AXP能源机制的理论模型目前主要有两大类：在吸积模型中，AXP被认为具有正常磁场强度（≈10^8T）的中子量，物质吸积提供X射线辐射原能源，并造成中子星的自转变化；另一种观点认为AXP是具有超强磁场（≈10^10-10^11T）的中子量（即磁星），其辐射能源来自它们巨大的磁或残余的热能，观测到的自转周期及其变化被归因子中子星的磁偶极辐射和物质抛射。两种模型各有优缺点，但目前看来观测事实对磁星模型较为有利。为了进一步明确AXP的性质，提供解释它们能源机制的线索，在介绍AXP的基本观测特征和理论解释的基础上，还将AXP与射电脉冲星、特强磁场射电脉冲量、射电宁静脉冲星侯选体及软γ射线复现源分别进行了比较。 相似文献
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年轻脉冲星多处于超新星遗迹(Supernova Remnant, SNR)中, 其分为转动供能脉冲星(Rotation-powered SNR-PSR)、磁星(Magnetar)和中心致密天体(Central Compact Object, CCO), 这3类年轻脉冲星有着不同的自旋周期及磁场强度分布. % 其中, 遗迹磁星(SNR-Magnetar)的平均自旋周期比转动供能遗迹脉冲星大近一个量级, 平均磁场强度高近两个量级. % 同时, 中心致密天体比转动供能遗迹脉冲星的平均磁场强度低近两个量级. % 这3类年轻脉冲星不同的物理性质, 可能源于其不同的前身星或不同的超新星爆发过程, 也可能源于其中子星诞生后的不同演化过程. % 此外, 转动供能遗迹脉冲星比年轻的转动供能非遗迹脉冲星具有更快的平均自旋周期、更大的平均磁场强度和更短的平均特征年龄. % 这暗示新诞生的中子星经时间约为$10^5$--$10^6$yr的演化过程, 其自旋速度将减小近一半, 同时其磁场强度也将衰减近一半. 相似文献
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Simon Johnston David Galloway 《Monthly notices of the Royal Astronomical Society》1999,306(4):L50-L54
Using the standard equation for the slowdown of a neutron star, we derive a formula for the braking index via integration rather than the conventional differentiation. The new formula negates the need to measure the second time derivative of the rotation frequency, ν¨ . We show that the method gives similar braking indices for PSR B1509−58 and the Crab pulsar to those already in the literature. We point out that our method is useful for obtaining the braking indices of moderate-aged pulsars without the need for long, phase-connected timing solutions. We applied the method to 20 pulsars and discuss the implications of the results. We find that virtually all the derived braking indices are dominated by the effects of (unseen) glitches, the recovery from which corrupts the value of ν˙ . However, any real, large, positive braking index has implications for magnetic field decay and offers support to recent models of pulsar evolution. 相似文献
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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
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Raka Dona Ray Mandal Sushan Konar Mira Dey Jishnu Dey 《Monthly notices of the Royal Astronomical Society》2009,399(2):822-826
The single glitch observed in PSR B1821−24, a millisecond pulsar in M28, is unusual on two counts. First, the magnitude of this glitch is at least an order of magnitude smaller (Δν/ν∼ 10−11 ) than the smallest glitch observed to date. Secondly, all other glitching pulsars have strong magnetic fields with B ≳ 1011 G and are young, whereas PSR B1821−24 is an old recycled pulsar with a field strength of 2.25 × 109 G . We have earlier suggested that some of the recycled pulsars could actually be strange quark stars. In this work, we argue that the crustal properties of such a strange pulsar are just right to give rise to a glitch of this magnitude, explaining the scarcity of larger glitches in millisecond pulsars. 相似文献
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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
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Zhan-Kui Huang Xin-Ji Wu Department of Astronomy Peking University Beijing Chinese Academy of Sciences-Peking University Joint Beijing Astrophysics Center Beijing National Astronomical Observatories Urumqi Astronomical Observatory Chinese Academic of Science Urumqi 《中国天文和天体物理学报》2003,3(2):166-174
The initial period of a pulsar is an important factor in our understanding of the formation of neutron stars and of the nature of the equation of state of neutron star matter.Up to now this quantity can only be obtained for a few pulsars for which accurate age and braking index are known.Based on the theory of the offcenter dipole emission,in which pulsars obtain theiry high velocities depending on the initial periods,we calculate the initial period using the proper motion data,Because the orbital velocity of the progenitor and asymmetric kick in the supernova explosion may also contribute to the observed velocity of the pusar,the derived values of initial periods are lower limits.For normal pulsars,the initial periods are in the range of 0.6～2.6ms.For the millisecond pulsars,the initial periods are comparable to their current periods,and the ratio between the initial period and the current period increases with the decrease of the current period.For PSR B1937 21 with the shortest period of 1.56ms,the ratio is 0.77. 相似文献
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E. G. Tsikarishvili G. D. Chagelishvili O. V. Chedia J. G. Lominadze Z. A. Sokhadze 《Astrophysics and Space Science》1988,149(2):255-272
The mechanism of the large-scale magnetic field generation in the Crab Nebula is proposed. The basis for the considered fast mechanism is the model of the central region of Crab Nebula amorphous part having the form of slightly divergent double-layer disk consisting of the relativistic electron-positron plasma.The nebula toroidal magnetic field generation occurs in the double-layer disk in the immediate neighbourhood of the light cylinder of pulsar PSR 0531+21 due to the differential rotation by means of dynamo-mechanism. The generated field is transferred into the nebula by the pulsar wind which forms the double-layer disk.By use of the known parameters of pulsar PSR 0531+21, the considered mechanism yields the strength of magnetic fieldB=10–3 G observed in the nebula. The disk structure must be destroyed toward the edges of the nebula. 相似文献
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J.O.Urama 《Monthly notices of the Royal Astronomical Society》2002,330(1):58-62
Large glitches were recently observed in the spin rates of two pulsars, B1046−58 and B1737−30. The glitches were characterized by fractional increases in rotation rate of 0.77 and 1.44×10−6 respectively. PSR B1737−30 is the most frequently glitching pulsar and this is the largest glitch so far observed from it. Most of the jump in the spin-down rate accompanying these glitches decayed away on short time-scales of a few days. For PSR B1737−30, there appears to be a cumulative shift in spin-down rate resulting from its frequent glitches. This probably accounts for its braking index of −4±2 suggested by the available data, while a value of 2.1±0.2 is obtained for B1046−58. 相似文献
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W. Z. Zou N. Wang R. N. Manchester J. O. Urama G. Hobbs Z. Y. Liu J. P. Yuan 《Monthly notices of the Royal Astronomical Society》2008,384(3):1063-1068
Six glitches have been recently observed in the rotational frequency of the young pulsar PSR B1737−30 (J1740−3015) using the 25-m Nanshan telescope of Urumqi Observatory. With a total of 20 glitches in 20 yr, it is one of the most frequently glitching pulsars of the ∼1750 known pulsars. Glitch amplitudes are very variable with fractional increases in rotation rate ranging from 10−9 to 10−6 . Interglitch intervals are also very variable, but no relationship is observed between interval and the size of the preceding glitch. There is a persistent increase in , opposite in sign to that expected from slowdown with a positive braking index, which may result from changes in the effective magnetic dipole moment of the star during the glitch. 相似文献
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Ren-Xin Xu Department of Astronomy School of Physics Peking University Beijing 《中国天文和天体物理学报》2006,6(5)
Efforts are made to understand the timing behaviors (e.g., the jumps in the projected pulsar semimajor axis at the periastron passages) observed in the 13-year monitoring of PSR B1259-63. Planet-like objects are suggested to orbit around the Be star, which may gravitationally perturb the (probably low mass) pulsar when it passes through periastron. An accretion disk should exist outside the pulsar's light cylinder, which creates a spindown torque on the pulsar due to the propeller effect. The observed negative braking index and the discrepant timing residuals close to periastron could be related to the existence of a disk with a varying accretion rate. A speculation is presented that the accretion rate may increase on a long timescale in order to explain the negative braking index. 相似文献
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Giant pulses (GPs) have been detected from the pulsar PSR B0656 + 14. A pulse that is more intense than the average pulse by a factor of 120 is encountered approximately once in 3000 observed periods of the pulsar. The peak flux density of the strongest pulse, 120 Jy, is a factor of 630 higher than that of the average pulse. The GP energy exceeds the energy of the average pulse by up to a factor of 110, which is comparable to that for other known pulsars with GPs, including the Crab pulsar and the millisecond pulsar PSR B1937+21. The giant pulses are a factor of ～6 narrower than the average pulse and are clustered at the head of the average pulse. PSR B0656+14 along with PSR B0031-07, PSR B1112+50, and PSR J1752+2359 belong to a distinctive group of pulsars in which GPs have been detected without any extremely strong magnetic field on the light cylinder. 相似文献