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1.
为了解释间歇脉冲星PSR B1931+24在射电噪比射电宁静状态下更大的自转减慢率和模拟蟹状星云脉冲星的自转演化,建立同时考虑了具有不同加速电势的核区和环区的环加速间隙下的星风制动模型.其中对于PSR B1931+24通过计算得到它的磁场强度和磁倾角,并且预言了其理论制动指数.对于蟹状星云脉冲星,通过计算得到它的磁场强度和磁倾角,还计算得到其制动指数随周期的演化和它在周期-周期导数图上的自转演化.相比于真空加速间隙、外加速间隙等,环加速间隙也同样能够适用于星风制动模型.  相似文献   

2.
We show that the proportionately spaced emission bands in the dynamic spectrum of the Crab pulsar fit the oscillations of the square of a Bessel function whose argument exceeds its order. This function has already been encountered in the analysis of the emission from a polarization current with a superluminal distribution pattern: a current whose distribution pattern rotates (with an angular frequency ω) and oscillates (with a frequency  Ω > ω  differing from an integral multiple of ω) at the same time. Using the results of our earlier analysis, we find that the dependence on frequency of the spacing and width of the observed emission bands can be quantitatively accounted for by an appropriate choice of the value of the single free parameter  Ω/ω  . In addition, the value of this parameter, thus implied by Hankins & Eilek's data, places the last peak in the amplitude of the oscillating Bessel function in question at a frequency  (∼Ω3/ω2)  that agrees with the position of the observed ultraviolet peak in the spectrum of the Crab pulsar. We also show how the suppression of the emission bands by the interference of the contributions from differing polarizations can account for the differences in the time and frequency signatures of the interpulse and the main pulse in the Crab pulsar. Finally, we put the emission bands in the context of the observed continuum spectrum of the Crab pulsar by fitting this broad-band spectrum (over 16 orders of magnitude of frequency) with that generated by an electric current with a superluminally rotating distribution pattern.  相似文献   

3.
Many radio pulsars exhibit glitches wherein the star's spin rate increases fractionally by ∼10−10–10−6. Glitches are ascribed to variable coupling between the neutron star crust and its superfluid interior. With the aim of distinguishing among different theoretical explanations for the glitch phenomenon, we study the response of a neutron star to two types of perturbations to the vortex array that exists in the superfluid interior: (1) thermal motion of vortices pinned to inner crust nuclei, initiated by sudden heating of the crust, (e.g., a starquake), and (2) mechanical motion of vortices (e.g., from crust cracking by superfluid stresses). Both mechanisms produce acceptable fits to glitch observations in four pulsars, with the exception of the 1989 glitch in the Crab pulsar, which is best fitted by the thermal excitation model. The two models make different predictions for the generation of internal heat and subsequent enhancement of surface emission. The mechanical glitch model predicts a negligible temperature increase. For a pure and highly conductive crust, the thermal glitch model predicts a surface temperature increase of as much as ∼2 per cent, occurring several weeks after the glitch. If the thermal conductivity of the crust is lowered by a high concentration of impurities, however, the surface temperature increases by ∼10 per cent about a decade after a thermal glitch. A thermal glitch in an impure crust is consistent with the surface emission limits following the 2000 January glitch in the Vela pulsar. Future surface emission measurements coordinated with radio observations will constrain glitch mechanisms and the conductivity of the crust.  相似文献   

4.
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   

5.
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 w5 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 w30 R L.  相似文献   

6.
Three slow glitches in the rotation rate of the pulsar B1822−09 were revealed over the 1995–2004 interval. The slow glitches observed are characterized by a gradual increase in the rotation frequency with a long time-scale of several months, accompanied by a rapid decrease in the magnitude of the frequency first derivative by ∼1–2 per cent of the initial value and subsequent exponential increase back to its initial value on the same time-scale. The cumulative fractional increase in the pulsar rotation rate for the three glitches amounts to  Δν/ν0∼ 7 × 10−8  .  相似文献   

7.
考虑到混杂星既具有奇异夸克物质核,又具有中子星固体壳层的特殊结构,运用完全自洽的二级修正方法,研究了在低温极限下(T<109K)混杂星的体粘滞耗散时标,并利用该时标计算了混杂星的临界旋转频率,发现其最小值为704.42 Hz(对应1.42 ms脉冲周期).与中子星和奇异星比较,更好地解释了观测数据.  相似文献   

8.
The fast-spinning Crab pulsar (∼30 turn s−1), which powers the massive expansion and synchrotron emission of the entire Crab nebula, is surrounded by quasi-stationary features such as fibrous arc-like wisps and bright polar knots in the radial range of 2×1016≲ r ≲2×1017 cm, as revealed by high-resolution (∼0.1 arcsec) images from the Wide Field and Planetary Camera 2 (WFPC2) on board the Hubble Space Telescope ( HST ). The spin-down energy flux (∼5×1038 erg s−1) from the pulsar to the luminous outer nebula, which occupies the radial range 0.1≲ r ≲2 pc, is generally believed to be transported by a magnetized relativistic outflow of an electron–positron e± pair plasma. It is then puzzling that mysterious structures like wisps and knots, although intrinsically dynamic in synchrotron emission, remain quasi-stationary on time-scales of a few days to a week in the relativistic pulsar wind. Here we demonstrate that, as a result of slightly inhomogeneous wind streams emanating from the rotating pulsar, fast magnetohydrodynamic (MHD) shock waves are expected to appear in the pulsar wind at relevant radial distances in the forms of wisps and knots. While forward fast MHD shocks move outward with a speed close to the speed of light c , reverse fast MHD shocks may appear quasi-stationary in space under appropriate conditions. In addition, Alfvénic fluctuations in the shocked magnetized pulsar wind can effectively scatter synchrotron beams from gyrating relativistic electrons and positrons.  相似文献   

9.
Between 1997 August and October, the radio pulses from the Crab pulsar were followed by discrete moving echoes, which appear to be reflections from part of an ionized shell in the outer part of the Crab Nebula, crossing the line of sight to pulsar. Similar events have now been recognized in recordings from the past 30 yr, and it seems that the Nebula must contain a large number of ionized shell-like surfaces on a much finer scale than recognized hitherto.  相似文献   

10.
The role of binary progenitors of neutron stars (NSs) in the apparent distribution of space velocities and spin–velocity alignment observed in young pulsars is studied. We performed a Monte Carlo synthesis of pulsar populations originated from single and binary stars with different assumptions about the NS natal kick (kick–spin alignment, kick amplitude and kick reduction in electron-capture supernovae in binary progenitors with initial main-sequence masses from the range  8–11 M⊙  which experienced mass exchange due to Roche lobe overflow). The calculated spin–velocity alignment in pulsars is compared with data inferred from radio polarization measurements. The observed space velocity of pulsars is found to be mostly affected by the natal kick velocity form and its amplitude; the fraction of binaries is not important here for reasonably large kicks. The natal kick–spin alignment is found to strongly affect the spin–velocity correlation of pulsars. Comparison with the observed pulsar spin–velocity angles favours a sizeable fraction of binary progenitors and kick–spin angles  ∼5°–20°  .  相似文献   

11.
We present a precise timing analysis of the accreting millisecond pulsar XTE J1814−338 during its 2003 outburst, observed by RXTE . A full orbital solution is given for the first time; Doppler effects induced by the motion of the source in the binary system were corrected, leading to a refined estimate of the orbital period,   P orb= 15 388.7229(2)  s, and of the projected semimajor axis,   a sin  i / c = 0.390633(9)  light-second. We could then investigate the spin behaviour of the accreting compact object during the outburst. We report here a refined value of the spin frequency  (ν= 314.356 108 79(1) Hz)  and the first estimate of the spin frequency derivative of this source while accreting     . This spin-down behaviour arises when both the fundamental frequency and the second harmonic are taken into consideration. We discuss this in the context of the interaction between the disc and the quickly rotating magnetosphere, at accretion rates sufficiently low to allow a threading of the accretion disc in regions where the Keplerian velocity is slower than the magnetosphere velocity. We also present indications of a jitter of the pulse phases around the mean trend, which we argue results from movements of the accreting hotspots in response to variations of the accretion rate.  相似文献   

12.
We study the evolution of a rigidly rotating protoneutron star (PNS) with hyperons and nucleons or solely nucleons in its core due to the escape of trapped neutrinos. As the neutrinos escape, the core nucleonic neutron star (NS) expands and the stellar rotation slows. After the neutrinos escape, the range of the spin periods is narrower than the initial one, but the distribution is still nearly uniform. A PNS with hyperons, at the late stage of its evolution, keeps shrinking and spinning up until all the trapped neutrinos escape. Consequently, the distribution of the stellar initial spin periods is skewed towards shorter periods. If the hyperonic star is metastable, its rotational frequency accelerates distinguishedly before it collapses to a black hole.  相似文献   

13.
This paper provides a method for judging growth or decay of the magnetic field of pulsar by using pulse period P, or frequency ν, and its first and second derivatives $ \dot P,\ddot P $ or $ \dot v,\ddot v $ . The author uses this method to judge the growth or decay of the magnetic field of Crab pulsar. The judged result for Crab pulsar is that the magnetic field of Crab pulsar is growing now, but it is not decaying. The result corresponds with the actual case of Crab pulsar.  相似文献   

14.
Traditionally, studies aimed at inferring the distribution of birth periods of neutron stars are based on radio surveys. Here we propose an independent method to constrain the pulsar spin periods at birth based on their X-ray luminosities. In particular, the observed luminosity distribution of supernovae (SNe) poses a constraint on the initial rotational energy of the embedded pulsars, via the     correlation found for radio pulsars, and under the assumption that this relation continues to hold beyond the observed range. We have extracted X-ray luminosities (or limits) for a large sample of historical SNe observed with Chandra , XMM and Swift , which have been firmly classified as core-collapse SNe. We have then compared these observational limits with the results of Monte Carlo simulations of the pulsar X-ray luminosity distribution for a range of values of the birth parameters. We find that a pulsar population dominated by millisecond periods at birth is ruled out by the data.  相似文献   

15.
The quantum phenomenon of spectral flow which has been observed in laboratory superfluids, such as 3He-B, controls the drift velocity of proton type II superconductor vortices in the liquid core of a neutron star and so determines the rate at which magnetic flux can be expelled from the core to the crust. In the earliest and most active phases of the anomalous X-ray pulsars and soft-gamma repeaters, the rates are low and consistent with a large fraction of the active crustal flux not linking the core. If normal neutrons are present in an appreciable core matter-density interval, the spectral flow force limits flux expulsion in cases of rapid spin-down, such as in the Crab pulsar or in the propeller phase of binary systems.  相似文献   

16.
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   

17.
Pulsars have been recognized to be normal neutron stars, but sometimes have been argued to be quark stars. Submillisecond pulsars, if detected, would play an essential and important role in distinguishing quark stars from neutron stars. We focus on the formation of such submillisecond pulsars in this paper. A new approach to the formation of a submillisecond pulsar (quark star) by means of the accretion-induced collapse (AIC) of a white dwarf is investigated. Under this AIC process, we found that: (i) almost all newborn quark stars could have an initial spin period of ∼0.1 ms; (ii) nascent quark stars (even with a low mass) have a sufficiently high spin-down luminosity and satisfy the conditions for pair production and sparking process and appear as submillisecond radio pulsars; (iii) in most cases, the times of newborn quark stars in the phase with spin period <1 (or <0.5) ms are long enough for the stars to be detected.
As a comparison, an accretion spin-up process (for both neutron and quark stars) is also investigated. It is found that quark stars formed through the AIC process can have shorter periods (≤0.5 ms), whereas the periods of neutron stars formed in accretion spin-up processes must be longer than 0.5 ms. Thus, if a pulsar with a period shorter than 0.5 ms is identified in the future, it could be a quark star.  相似文献   

18.
PSR J1806−2125 is a pulsar discovered in the Parkes multibeam pulsar survey with a rotational period of 0.4 s and a characteristic age of 65 kyr. Between MJDs 51462 and 51894 this pulsar underwent an increase in rotational frequency of  Δ ν / ν ≈16×10-6  . The magnitude of this glitch is ∼2.5 times greater than any previously observed in any pulsar and 16 times greater than the mean glitch size. This Letter gives the parameters of the glitch and compares its properties with those of previously observed events. The existence of such large and rare glitches offers new hope for attempts to observe thermal X-ray emission from the internal heat released following a glitch, and suggests that pulsars which previously have not been observed to glitch may do so on long time-scales .  相似文献   

19.
Stairs, Lyne & Shemar have found that the arrival-time residuals from PSR B1828−11 vary periodically with a period ≈500 d. This behaviour can be accounted for by precession of the radio pulsar, an interpretation that is reinforced by the detection of variations in its pulse profile on the same time-scale. Here, we model the period residuals from PSR B1828−11 in terms of precession of a triaxial rigid body. We include two contributions to the residuals: (i) the geometric effect, which arises because the times at which the pulsar emission beam points towards the observer varies with precession phase; and (ii) the spin-down contribution, which arises from any dependence of the spin-down torque acting on the pulsar on the angle between its spin     and magnetic     axes. We use the data to probe numerous properties of the pulsar, most notably its shape, and the dependence of its spin-down torque on     , for which we assume the sum of a spin-aligned component (with a weight  1 − a   ) and a dipolar component perpendicular to the magnetic beam axis (weight a ), rather than the vacuum dipole torque  ( a = 1)  . We find that a variety of shapes are consistent with the residuals, with a slight statistical preference for a prolate star. Moreover, a range of torque possibilities fit the data equally well, with no strong preference for the vacuum model. In the case of a prolate star, we find evidence for an angle-dependent spin-down torque. Our results show that the combination of geometrical and spin-down effects associated with precession can account for the principal features of the timing behaviour of PSR B1828−11, without fine tuning of the parameters.  相似文献   

20.
In 1982 we discovered a pulsar with the phenomenal rotation rate of 642 Hz, 20 times faster than the spin rate of the Crab pulsar. The absence of supernova debris in the vicinity of the pulsar at any wavelength indicates an age of the neutron star greater than 105 yr. The miniscule spindown rate of 1.1 × 10-19 confirms the old age and indicates a surface magnetic field of 109 G. A second millisecond pulsar was discovered by Boriakoff, Buccheri & Fauci (1983) in a 120-day orbit. These fast pulsars may have been spun-up by mass transfer in a close binary evolutionary stage. Arrival-time observations of the 642-Hz pulsar display remarkably low residuals over the first 14 months. The stability implied by these observations, 3 × 10-14, suggests that millisecond pulsars will provide the most accurate basis for terrestrial dynamical time. If so, the pulsar data will lead to improvements in the planetary ephemeris and to new searches for light-year scale gravitational waves. Many new searches for fast pulsars are under way since previous sky surveys excluded pulsars with spins above 60 Hz.  相似文献   

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