The angular momentum transfer mechanism of pulsar glitches for over four decades now stands as standalone theory with regards to glitch sizes and inter-glitch time intervals. However, recent analyses both analytic and statistical are on the verge of suppressing the theory. In this paper, we overviewed the superfluid theory to highlight the efficacy of the angular momentum process and highlighted the theoretical and observational evidences that could not be explained by processes involving transfer of angular momentum.
Several glitches have been observed in young, isolated radio pulsars, while a clear detection in accretion-powered X-ray pulsars is still lacking. We use the Pizzochero snowplow model for pulsar glitches as well as starquake models to determine for the first time the expected properties of glitches in accreting pulsars and their observability. Since some accreting pulsars show accretion-induced long-term spin-up, we also investigate the possibility that anti-glitches occur in these stars. We find that glitches caused by quakes in a slow accreting neutron star are very rare and their detection …
$\sim 6\%$ of all known pulsars have been observed to exhibit sudden spin-up events, known as glitches. For more than fifty years, these phenomena have played an important role in helping to understand pulsar (astro)physics. Based on the review of pulsar glitches search method, the progress made in observations in recent years is summarized, including the achievements obtained by Chinese telescopes. Glitching pulsars demonstrate great diversity of behaviours, which can be broadly classified into four categories: normal glitches, slow glitches, glitches with delayed spin-ups, and anti-glitches.…
Parkes pulse arrival-time data for 165 radio pulsars spanning from 1990 to 2011 have been searched for period glitches. Forty-six events out of the detected 107 glitches were found to be new contributions to the entire glitch population which currently contains approximately 400 events.
The first known pulsar glitch was discovered in the Vela pulsar at both Parkes and Goldstone in March 1969. Since then the number of known glitches has grown enormously, with more than 520 glitches now known in more than 180 pulsars. Details of glitch parameters and post-glitch recoveries are described and some implications for the physics of neutron stars are discussed.
Large pulsar frequency glitches are generally interpreted as sudden transfers of angular momentum between the neutron superfluid permeating the inner crust and the rest of the star. Despite the absence of viscous drag, the neutron superfluid is strongly coupled to the crust due to non-dissipative entrainment effects. These effects are shown to severely limit the maximum amount of angular momentum that can possibly be transferred during glitches. In particular, it is found that the glitches observed in the Vela pulsar require an additional reservoir of angular momentum.
Pulsar glitches are rapid spin-up events that occur in the rotation of neutron stars, providing a valuable probe into the physics of the interiors of these objects. Long-term monitoring of a large number of pulsars facilitates the detection of glitches and the robust measurements of their parameters. The Jodrell Bank pulsar timing programme regularly monitors more than 800 radio pulsars and has accrued, in some cases, over 50 years of timing history on individual objects. In this paper we present 106 new glitches in 70 radio pulsars as observed up to the end of 2018. For 70% of these pulsars, …
Three sudden spin-down events, termed `anti-glitches', were recently discovered in the accreting pulsar NGC 300 ULX-1 by the \textit{Neutron Star Interior Composition Explorer} (NICER) mission. Unlike previous anti-glitches detected in decelerating magnetars, these are the first anti-glitches recorded in an accelerating pulsar. One standard theory is that pulsar spin-up glitches are caused by avalanches of collectively unpinning vortices that transfer angular momentum from the superfluid interior to the crust of a neutron star. Here we test whether vortex avalanches are also consistent with th…
From 2000 to 2010, monitoring of radio emission from the Crab pulsar at Xinjiang Observatory detected a total of nine glitches. The occurrence of glitches appears to be a random process as described by previous researches. A persistent change in pulse frequency and pulse frequency derivative after each glitch was found. There is no obvious correlation between glitch sizes and the time since last glitch. For these glitches $Δν_{p}$ and $Δ\dotν_{p}$ span two orders of magnitude. The pulsar suffered the largest frequency jump ever seen on MJD 53067.1. The size of the glitch is $\sim$ 6.8 $\times …
Data are gathered from the Parkes pulsar data archive of twelve young radio pulsars, with the intervals of data for each pulsar ranged between 2.8 years and 6.8 years. 31 glitches are identified by using phase connection from "pulsar timing" technology, ranging from $1.7\times10^{-9}$ to $8.5\times10^{-6}$ at the change in relative glitch sizes $Δν/ν$, where $ν=1/P$ is the pulse frequency. 8 post-glitch behaviours of 13 published glitches are updated with 4 exponential recoveries observed. Detecting 18 new glitches has great significance, but only one exponential relaxation was discovered in t…
The rotation of more than 700 pulsars has been monitored using the 76-m Lovell Telescope at Jodrell Bank. Here we report on a new search for glitches in the observations, revealing 128 new glitches in the rotation of 63 pulsars. Combining these new data with those already published we present a database containing 315 glitches in 102 pulsars. The database was used to study the glitch activity among the pulsar population, finding that it peaks for pulsars with a characteristic age tau_c ~ 10kyr and decreases for longer values of tau_c, disappearing for objects with tau_c > 20Myr. The glitch act…
The abrupt change in the pulse period of a pulsar is called a pulsar glitch. In this paper, we present eleven pulsar glitches detected using the Ooty Radio Telescope (ORT) and the upgraded Giant Metrewave Radio Telescope (uGMRT) in high cadence timing observations of 8 pulsars. The measured relative amplitude of glitches ($Δν/ν$) from our data ranges from $10^{-6}$ to $10^{-9}$. Among these glitches, three are new discoveries, being reported for the first time. We also reanalyze the largest pulsar glitch in the Crab pulsar (PSR J0534+2200) by fitting the ORT data to a new phenomenological mode…
We present evidence for three spin-down glitches (or `anti-glitches') in the ultraluminous accreting X-ray pulsar NGC 300 ULX-1 in timing observations made with the Neutron Star Interior Composition Explorer (NICER). Our timing analysis reveals three sudden spin-down events of magnitudes $Δν= -23, -30,$ and $-43 \,μ$Hz (fractional amplitudes $Δν/ν= -4.4, -5.5,$ and $-7.7 \times 10^{-4}$). We determined fully phase-coherent timing solutions through the first two glitches, giving us high confidence in their detection, while the third candidate glitch is somewhat less secure. These are larger in …
The timing properties of radio pulsars provide a unique probe of neutron star interiors. Recent observations have uncovered quasiperiodicities in the timing and pulse properties of some pulsars, a phenomenon that has often been attributed to free precession of the neutron star, with profound implications for the distribution of superfluidity and superconductivity in the star. We advance this program by developing consistency relations between free precession and pulsars glitches, and we show that there are difficulties in reconciling the two phenomena in some precession candidates. This indica…
A systematic, semi-automated search for pulsar glitches in the first UTMOST public data release is presented. The search is carried out using a hidden Markov model which incorporates both glitches and timing noise into the model of the assumed phase evolution of the pulsar. Glitches are detected through Bayesian model selection between models with and without glitches present with minimal human intervention. Nine glitches are detected among seven objects, all of which have been previously reported. No new glitches were detected. Injection studies are used to place 90\% frequentist upper limits…
Timing observations from the Parkes 64-m radio telescope for 165 pulsars between 1990 and 2011 have been searched for period glitches. A total of 107 glitches were identified in 36 pulsars, where 61 have previously been reported and 46 are new discoveries. Glitch parameters were measured by fitting the timing residual data. Observed relative glitch sizes Δν_g/νrange between 10^-10 and 10^-5, where ν= 1/P is the pulse frequency. We confirm that the distribution of Δν_g/νis bimodal with peaks at approximately 10^-9 and 10^-6. Glitches are mostly observed in pulsars with characteristic ages betwe…
Pulsar glitches are sudden increase in their spin frequency, in most cases followed by the long timescale recovery process. As of this writing, about 546 glitches have been reported in 188 pulsars, the Crab pulsar is a special one with unique manifestations. This writing presents a statistic study on post-glitch observables of the Crab pulsar, especially the delayed spin-up in post-glitch phase and persistent shift in the slow-down rate of the star. By analyzing the radio data over 45 years, we find that two power law functions respectively fit the persistent shift and delayed spin-up timescal…
A microphysics-agnostic meta-model of rotational glitches in rotation-powered pulsars is developed, wherein the globally averaged internal stress accumulates as a Brownian process between glitches, and a glitch is triggered once a critical threshold is surmounted. Precise, falsifiable predictions are made regarding long-term event statistics in individual pulsars. For example, the Spearman cross-correlation coefficient between the size of a glitch and the waiting time until the next glitch should exceed 0.25 in all pulsars. Among the six pulsars with the most recorded glitches, PSR J0537$-$691…
Glitch size and waiting time probability density functions (PDFs) are estimated for the five pulsars that have glitched most using the nonparametric kernel density estimator. Two objects exhibit decreasing size and waiting time PDFs. Their activity is Poisson-like, and their size statistics are approximately scale-invariant. Three objects exhibit a statistically significant local maximum in the PDFs, including one (PSR J1341$-$6220) which was classified as Poisson-like in previous analyses. Their activity is quasiperiodic, although the dispersion in waiting times is relatively broad. The class…
Star quakes and internal phase transitions within anomalous x-ray pulsars (AXPs) and soft $γ$-ray repeaters (SGRs) can produce mini contractions and pulsar glitches. Shocks break out from their surface following such contractions produce thermal x/$γ$-ray bursts. Highly relativistic dipolar $e^+e^-$ bunches launched from the pulsar polar caps emit fast radio bursts (FRBs) of narrowly beamed coherent curvature radiation, visible if they point in the direction of Earth. Although these surface x/$γ$-ray bursts are isotropic and are many orders of magnitude more energetic than the FRBs, they are d…
We present timing solutions from the Fermi-LAT observations of gamma-ray pulsars PSR J0835$-$4510 (Vela), PSR J1023$-$5746, PSR J2111$+$4606, and PSR J2229$+$6114. Data ranges for each pulsar extend over a decade. From data analysis we have identified a total of 20 glitches, 11 of which are new discoveries. Among them, 15 glitches are large ones with $Δν/ν\gtrsim10^{-6}$. PSR J1023$-$5746 is the most active pulsar with glitch activity parameter being $A_{\rm g}=14.5\times10^{-7}$\yr~in the considered data span and should be a target for frequently glitching Vela-like pulsars in future observat…
Pulsars undergoing crustquake release strain energy, which can be absorbed in a small region inside the inner crust of the star and excite the free superfluid neutrons therein. The scattering of these neutrons with the surrounding pinned vortices may unpin a large number of vortices and effectively reduce the pinning force on vortex lines. Such unpinning by neutron scattering can produce glitches for Crab like pulsars and Vela pulsar of size in the range $\sim 10^{-8} - 10^{-7}$, and $\sim 10^{-9} - 10^{-8}$, respectively. Although we discuss here the crustquake initiated excitation, the propo…
Glitches are sudden increases in the rotation rate $ν$ of neutron stars, which are thought to be driven by the neutron superfluid inside the star. The Vela pulsar presents a comparatively high rate of glitches, with 21 events reported since observations began in 1968. These are amongst the largest known glitches (17 of them have sizes $Δν/ν\geq10^{-6}$) and exhibit very similar characteristics. This similarity, combined with the regularity with which large glitches occur, has turned Vela into an archetype of this type of glitching behaviour. The properties of its smallest glitches, on the othe…
Pulsar glitches are attributed to the sudden re-coupling of very weakly coupled large scale superfluid components in the neutron star interior. This process leads to rapid exchange of angular momentum and an increase in spin frequency. The transfer of angular momentum is regulated by a dissipative mutual friction, whose strength defines the spin-up timescale of a glitch. Hence, observations of glitch rises can be used to shed light on the dominant microphysical interactions at work in the high density interior of the star. We present a simple analytical model, complemented with more detailed n…
Pulsar-like compact stars provide us a unique laboratory to explore properties of dense matter at supra-nuclear densities. One of the models for pulsar-like stars is that they are totally composed of "strangeons", and in this paper we studied the pulsar glitches in a strangeon star model. Strangeon stars would be solidified during cooling, and the solid stars would be natural to have glitches as the result of starquakes. Based on the starquake model established before, we proposed that when the starquake occurs, the inner motion of the star which changes the moment of inertia and has impact on…
The glitch size, $ Δν/ν$, inter-glitch time interval, $ t_{i} $ and frequency of glitches in pulsars are key parameters in discussing glitch phenomena. In this paper, the glitch sizes and inter-glitch time intervals were statistically analysed in a sample of 168 pulsars with a total of 483 glitches. The glitches were broadly divided into two groups. Those with $ Δν/ν< 10^{-7} $ are regarded as small size glitches, while those with $ Δν/ν\geq 10^{-7} $ are regarded as relatively large size glitches. In the ensemble of glitches, the distribution of $ Δν/ν$ is seen to be bimodal as usual. The dis…
The bright radio pulsar B1727$-$47 with a characteristic age of 80 kyr is among the first pulsars discovered 50 yr ago. Using its regular timing observations and interferometric positions at three epochs, we measured, for the first time, the pulsar proper motion of $151 \pm 19$ mas yr$^{-1}$. At the dispersion measure distance of $\gtrsim 2.7$ kpc, this would suggest a record transverse velocity of the pulsar $\gtrsim 1900$ km s$^{-1}$. However, a backward extrapolation of the pulsar track to its birth epoch points remarkably close to the center of the evolved nearby supernova remnant RCW 114,…
Glitch (sudden spinup) is a common phenomenon in pulsar observations. However, the physical mechanism of glitch is still a matter of debate because it depends on the puzzle of pulsar's inner structure, i.e., the equation of state of dense matter. Some pulsars (e.g., Vela-like) show large glitches (Δν/ν~10^-6) but release negligible energy, whereas the large glitches of AXPs/SGRs (anomalous X-ray pulsars/soft gamma repeaters) are usually (but not always) accompanied with detectable energy releases manifesting as X-ray bursts or outbursts. We try to understand this aspect of glitches in a starqu…
Glitch (sudden spinup) is a common phenomenon in pulsar observations. However, the physical mechanism of glitch is still a matter of debate because it depends on the puzzle of pulsar's inner structure, i.e., the equation of state of dense matter. Some pulsars (e.g., Vela-like) show large glitches (Δν/ν~10^-6) but release negligible energy, whereas the large glitches of AXPs/SGRs (anomalous X-ray pulsars/soft gamma repeaters) are usually (but not always) accompanied with detectable energy releases manifesting as X-ray bursts or outbursts. We try to understand this aspect of glitches in a starqu…
TThe glitch of anomalous X-ray pulsars \& soft gamma repeaters (AXP/SGRs) usually accompanied with detectable energy releases manifesting as X-ray bursts or outbursts, while the glitch of some pulsars like Vela release negligible energy. We find that these two types of glitches can naturally correspond to two types of starquake of solid strange stars. By applying the EoS of quark cluster star and some realistic pulsar parameters, we can reproduce consistent results compared with previous constraints and observations.
We revisit the mechanism of vortex unpinning caused by the neutron-vortex scattering \cite{prad1} in the inner crust of a pulsar. The strain energy released by the crustquake is assumed to be absorbed in some part of the inner crust and causes pair-breaking quasi-neutron excitations from the existing free neutron superfluid in the bulk of the inner crust. The scattering of these quasi-neutrons with the vortex core normal neutrons unpins a large number of vortices from the thermally affected regions and results in pulsar glitches. We consider the geometry of a cylindrical shell of the affected …
Glitches are rare spin-up events that punctuate the smooth slow-down of the rotation of pulsars. For the Vela pulsar and PSR J0537-6910, the glitch sizes and the times between consecutive events have clear preferred scales, contrary to the handful of other pulsars with enough glitches for such a study. Moreover, PSR J0537-6910 is the only pulsar showing a strong positive correlation between the size of each glitch and the waiting time until the following one. We attempt to understand this behavior through a detailed study of the distributions and correlations of glitch properties for the eight…
It is an open question whether glitch activity in individual pulsars varies on decadal time-scales. The Crab pulsar has experienced 23 spin-up glitches in the last 36 years, interrupting an otherwise monotonic deceleration. A homogeneous Poisson process, i.e. a process with constant rate, is not sufficient to describe the time-ordered distribution of glitch epochs in the Crab pulsar. There are signs of clustering at the $2σ$ level when testing with Ripley's $K$ function. Two alternative, inhomogeneous models with one and two step-wise rate changes are found to have higher relative evidence (Ba…
Glitching pulsars fall broadly into two statistical classes: those with Poisson-like waiting times and power-law sizes, and those with unimodal waiting times and sizes. Previous glitch modeling based on a state-dependent Poisson process readily generates Poisson-like behaviour but struggles to produce unimodal waiting times or sizes. Here it is shown that, when some of the inputs to the model are modified, both classes of statistical behaviour can be reproduced by varying a single control parameter related to the spin-down rate. The implications for past and future glitch observations and the …
Search for gamma-ray variability around Fermi-LAT pulsar glitches
Friedrich-Alexander Universität Erlangen-Nürnberg（弗里德里希·亚历山大埃尔朗根-纽伦堡大学）；Istituto Nazionale di Fisica Nucleare, Sezione di Pisa（意大利国家核物理研究所比萨分部）；Università di Pisa, Dipartimento di Fisica E. Fermi（比萨大学E.费米物理系）；Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz（加州大学圣克鲁兹分校粒子物理研究所、物理系和天文与天体物理系）
We report on a timing programme of 74 young pulsars that have been observed by the Parkes 64-m radio telescope over the past decade. Using modern Bayesian timing techniques, we have measured the properties of 124 glitches in 52 of these pulsars, of which 74 are new. We demonstrate that the glitch sample is complete to fractional increases in spin-frequency greater than $Δν^{90\%}_{g}/ν\approx 8.1 \times 10^{-9}$. We measure values of the braking index, $n$, in 33 pulsars. In most of these pulsars, their rotational evolution is dominated by episodes of spin-down with $n > 10$, punctuated by ste…
We use data from pulsar gamma-ray glitches recorded by the Fermi Large Area Telescope as input to theoretical models of gravitational wave signals the glitches might generate. We find that the typical peak amplitude of the gravity wave signal from gamma-ray pulsar glitches lies between 10^{-23} and 10^{-35} in dimensionless units, with peak frequencies in the range of 1 to 1000 Hz, depending on the model. We estimate the signal-to-noise for all gamma-ray glitches, and discuss detectability with current gravity wave detectors. Our results indicate that the strongest predicted signals are potent…
Pulsars are spinning extremely rapidly with periods as short as about $1.4$ milliseconds and delays of a few milliseconds per year at most, thus providing the most accurate clocks in the Universe. Nevertheless, sudden spin ups have been detected in some pulsars like the emblematic Vela pulsar. These abrupt changes in the pulsar's rotation period have long been thought to be the manifestation of a neutron superfluid permeating the inner crust of neutron stars. However, the neutron superfluid has been recently found to be so strongly coupled to the crust that it does not carry enough angular mom…
A region of toroidally oriented quantized flux lines must exist in the proton superconductor in the core of the neutron star. This region will be a site of vortex pinning and creep. Entrainment of the neutron superfluid with the crustal lattice leads to a requirement of superfluid moment of inertia associated with vortex creep in excess of the available crustal moment of inertia. This will effect constraints on the equation of state. The toroidal flux region provides the moment of inertia necessary to complement the crust superfluid with postglitch relaxation behavior fitting the observations.
Timing of the Crab and Vela pulsars have recently revealed very peculiar evolutions of their spin frequency during the early stage of a glitch. We show that these differences can be interpreted from the interactions between neutron superfluid vortices and proton fluxoids in the core of these neutron stars. In particular, pinning of individual vortices to fluxoids is found to have a dramatic impact on the mutual friction between the neutron superfluid and the rest of the star. The number of fluxoids attached to vortices turns out to be a key parameter governing the global dynamics of the star. …
Stress accumulation-relaxation meta-models of pulsar glitches make precise, microphysics-agnostic predictions of long-term glitch statistics, which can be falsified by existing and future timing data. Previous meta-models assume that glitches are triggered by an avalanche process, e.g. involving superfluid vortices, and that the probability density function (PDF) of the avalanche sizes is history-independent and specified exogenously. Here a recipe is proposed to generate the avalanche sizes endogenously in a history-dependent manner, by tracking the thresholds of occupied vortex pinning sites…
We present the results of our detailed timing studies of an anomalous X-ray pulsar, 1RXS J170849.0-400910, using Rossi X-ray Timing Explorer (RXTE) observations spanning over ~6 yr from 2005 until the end of RXTE mission. We constructed the long-term spin characteristics of the source and investigated time and energy dependence of pulse profile and pulsed count rates. We find that pulse profile and pulsed count rates in the 2-10 keV band do not show any significant variations in ~6 yr. 1RXS J170849.0-400910 has been the most frequently glitching anomalous X-ray pulsar: three spin-up glitches a…
Few statistically compelling correlations are found in pulsar timing data between the size of a rotational glitch and the time to the preceding glitch (backward waiting time) or the succeeding glitch (forward waiting time), except for a strong correlation between sizes and forward waiting times in PSR J0537-6910. This situation is counterintuitive, if glitches are threshold-triggered events, as in standard theories (e.g. starquakes, superfluid vortex avalanches). Here it is shown that the lack of correlation emerges naturally, when a threshold trigger is combined with secular stellar braking s…
Anomalous X-ray Pulsars (AXPs) are now established to exhibit significant X-ray variability and be prolific glitchers, with some glitches being accompanied by large radiative changes. An open issue is whether AXP glitches are generically accompanied by radiative changes, relevant for understanding magnetar physical properties. Here we report on an analysis of archival X-ray data from the AXP 1E~1841$-$045, obtained between 1993 and 2007. This AXP, located in the center of SNR Kes~73, has exhibited three glitches between 2002 and 2007, as determined by {\it RXTE} monitoring since 1999. We have …
The neutron superfluid permeating the inner crust of mature neutron stars is expected to play a key role in various astrophysical phenomena like pulsar glitches. Despite the absence of viscous drag, the neutron superfluid can still be coupled to the solid crust due to non-dissipative entrainment effects. Entrainment challenges the interpretation of pulsar glitches and suggests that a revision of the interpretation of other observed neutron-star phenomena might be necessary.
The pulsar glitches are generally assumed to be an apparent manifestation of the superfluid interior of the neutron stars. Most of them were discovered and extensively studied by continuous monitoring in the radio wavelengths. The Fermi-LAT space telescope has made a revolution uncovering a large population of gamma-ray pulsars. In this paper we suggest to employ these observations for the searches of new glitches. We develop the method capable of detecting step-like frequency change associated with glitches in a sparse gamma-ray data. It is based on the calculations of the weighted H-test sta…
Radio pulsar glitches probe far-from-equilibrium processes involving stress accumulation and relaxation in neutron star interiors. Previous studies of glitch rates have focused on individual pulsars with as many recorded glitches as possible. In this work we analyze glitch rates using all available data including objects that have glitched never or once. We assume the glitch rate follows a homogeneous Poisson process, and therefore exclude pulsars which exhibit quasiperiodic glitching behavior. Calculating relevant Bayes factors shows that a model in which the glitch rate $λ$ scales as a power…
PSR J1420-6048 is a young gamma-ray pulsar with recurrent glitches. Utilizing long-term monitoring data obtained from the Fermi Gamma-ray Space Telescope, we found that PSR J1420-6048 has shown gamma-ray flux variation and we also detected four glitches between 2008 and 2019. Two of the glitches are previously unknown, and their gamma-ray spectrum also shows variability between each glitch. Since the results might be contaminated by background sources, we discuss whether the observed changes in flux and spectra were caused by artificial misallocations of photons from a nearby pulsar wind nebul…
Recent observation of a sudden spin down, occurring on a timescale not exceeding two weeks, of the magnetar 1E2259+586 (see Archibald et al. 2013, where this event was dubbed an `anti-glitch') has not still received any interpretation in terms of the standard scenario of pulsar glitches proposed by Anderson and Itoh (1975). Motivated by this observation, here we present a toy model that allows, under certain conditions, for anti-glitches in neutron stars within the standard approach.
Observations of pulsar glitches may provide insights on the internal physics of neutron stars and recent studies show how it is in principle possible to constrain pulsar masses with timing observations. The reliability of these estimates depend on the current uncertainties about the structure of neutron stars and on our ability to model the dynamics of the superfluid neutrons in the internal layers. We assume a simplified model for the rotational dynamics of a neutron star and estimate an upper bound to the mass of 25 pulsars from their largest glitch and average activity: the aim is to unders…
Giant pulsar frequency glitches as detected in the emblematic Vela pulsar have long been thought to be the manifestation of a neutron superfluid permeating the inner crust of a neutron star. However, this superfluid has been recently found to be entrained by the crust, and as a consequence it does not carry enough angular momentum to explain giant glitches. The extent to which pulsar-timing observations can be reconciled with the standard vortex-mediated glitch theory is studied considering the current uncertainties on dense-matter properties. To this end, the crustal moment of inertia of glit…
Pulsar glitches are thought to be probes of the superfluid interior of neutron stars. These sudden jumps in frequency observed in many pulsars are generally assumed to be the macroscopic manifestation of superfluid vortex motion on a microscopic scale. Resolving and modelling such phenomena on the scale of a neutron star is, however, a challenging problem which still remains open, fifty years after the discovery of pulsars. In this article I will review recent theoretical progress, both on the microscopic level and on the macroscopic level, and discuss which constraints on the models can be pr…
The young, fast-spinning, X-ray pulsar J0537-6910 displays an extreme glitch activity, with large spin-ups interrupting its decelerating rotation every ~100 days. We present nearly 13 years of timing data from this pulsar, obtained with the {\it Rossi X-ray Timing Explorer}. We discovered 22 new glitches and performed a consistent analysis of all 45 glitches detected in the complete data span. Our results corroborate the previously reported strong correlation between glitch spin-up size and the time to the next glitch, a relation that has not been observed so far in any other pulsar. The spin …
The 30-Hz rotation rate of the Crab pulsar has been monitored at Jodrell Bank Observatory since 1984 and by other observatories before then. Since 1968, the rotation rate has decreased by about $0.5$\,Hz, interrupted only by sporadic and small spin up events (glitches). 24 of these events have been observed, including a significant concentration of 15 occurring over an interval of 11 years following MJD 50000. The monotonic decrease of the slowdown rate is partially reversed at glitches. This reversal comprises a step and an asymptotic exponential with a 320-day time constant, as determined in…
Pulsar glitches are sudden spin-ups in pulsar spin frequency ($ν$). The glitch size, $Δν/ν$, is a key parameter in any mechanism puts across towards the understanding of the events.However, the distribution of the glitch sizes has persistently been bimodal.This bimodal nature could be intrinsic or otherwise. In this paper, the glitch size distribution is bisected at $Δν/ν= 10^{-7}$ with $Δν/ν< 10^{-7}$ being regarded as small size glitches (SSG), while those of $Δν/ν> 10^{-7}$ are taken as large size glitches (LSG).The magnitude of SSGis scaled to that of LSG and tested for similarity.In pulsa…
