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 pulsars with mixture of glitch sizes, Lilliefore test is used to identify the distribution pattern of SSGs and LSGs in such pulsars. The result indicates that each half of the size distribution is fundamentally different from one another. LSGs are seen to be normally distributed, while the SSGs are lognormal.
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 …
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, …
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.
In this paper we present a new mechanism for rationalizing, explaining and predicting pulsar glitches. Our new mechanism is based upon the concepts of type II superconductivity and the Bradlow bound.
$\sim 6\%$ 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.…
Pulsar glitches, sudden jumps in frequency in otherwise steadily spinning down radio pulsars, offer a unique glimpse into the superfluid interior of neutron stars. The exact trigger of these events remains, however, elusive and this has hampered attempts to use glitch observations to constrain fundamental physics. In this paper we propose a new method to measure the mass of glitching pulsars, using observations of the maximum glitch recorded in a star, together with state of the art microphysical models of the pinning interaction between superfluid vortices and ions in the crust. Studying syst…
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…
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 $\times …
Parkes pulse arrival-time data for 165 radio pulsars spanning from 1990 to 2011 have been searched for period glitches. Forty-six events out of the detected 107 glitches were found to be new contributions to the entire glitch population which currently contains approximately 400 events.
The abrupt change in the pulse period of a pulsar is called a pulsar glitch. In this paper, we present eleven pulsar glitches detected using the Ooty Radio Telescope (ORT) and the upgraded Giant Metrewave Radio Telescope (uGMRT) in high cadence timing observations of 8 pulsars. The measured relative amplitude of glitches ($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…
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…
Braking index measurements offer the opportunity to explore the processes affecting the long-term spin evolution of pulsars and possible evolutionary connections between the various pulsar populations. For young pulsars the long-term trends are generally obscured by short term phenomena such as timing noise and the recoveries form large glitches. Here we present a new method to overcome the latter and report on braking index measurements for the Vela-like pulsars PSR B1800-21 and PSR B1823-13, an updated measurement for Vela and new estimates for four more glitching pulsars observed at Jodrell…
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…
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…
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…
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.
We present updated measurements of the Crab pulsar glitch of 2019 July 23 using a dataset of pulse arrival times spanning $\sim$5 months. On MJD 58687, the pulsar underwent its seventh largest glitch observed to date, characterised by an instantaneous spin-up of $\sim$1 $μ$Hz. Following the glitch the pulsar's rotation frequency relaxed exponentially towards pre-glitch values over a timescale of approximately one week, resulting in a permanent frequency increment of $\sim$0.5 $μ$Hz. Due to our semi-continuous monitoring of the Crab pulsar, we were able to partially resolve a fraction of the to…
We investigated the long-term spin properties of the anomalous X-ray pulsar (AXP) 1E 1841-045 by performing a temporal analysis of archival RXTE observations spanning about 5.2 yr from 2006 September to 2011 December. We identified two peculiar timing anomalies within ~1 yr of each other: a glitch with Delta(nu)/nu ~ 4.8 x 10^{-6} near MJD 54303; and an anti-glitch with Delta(nu)/nu ~ -5.8 x 10^{-7} near MJD 54656. The glitch that we identified, which is the fourth glitch seen in this source in the 13 yr of RXTE monitoring, is similar to the last two detected glitches. The anti-glitch from 1E …
On 2006 August 23 the Crab Pulsar underwent a glitch, that was reported by the Jodrell Bank and the Xinjiang radio observatories. Neither data are available to the public. However, the Jodrell group publishes monthly arrival times of the Crab Pulsar pulse (their actual observations are done daily), using which it is shown that about five months earlier, the Crab Pulsar most probably underwent a small glitch, which has not been reported before. Neither observatory discusses the detailed analysis of data from 2006 March to August; either they may not have detected this small glitch, or may have …
The number of sudden spin-ups in radio pulsars known as pulsar glitches has increased over the years. Though a consensus has not been reached with regards to the actual cause of the phenomenon, the electromagnetic braking torque on the crust quantified via the magnitude of pulsar spin frequency first derivative, $ \dotν $ is a key factor in mechanisms put across toward the understanding of the underlying principles involved. The glitch size has been used to establish a quantity used to constrain the mean possible change in pulsar spin frequency $ (ν) $ per year due to a glitch known as the `gl…
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…
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.
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…
Glitches are important to understand the internal structure of neutron stars. They are studied using timing observations. The best studied neutron star in this respect is the Crab Pulsar. The first glitch recorded in this pulsar occurred in 1969 Sep, at an epoch when timing observations were still in their infancy, the regularity of the observations was relatively poor, and errors on the observations were relatively high. Lyne et al. (1993) analyzed most of the available data using modern techniques, and showed that this was a typical glitch of the Crab pulsar, with typical glitch parameters. …
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$-$691…
We present timing solutions from the Fermi-LAT observations of gamma-ray pulsars PSR J0835$-$4510 (Vela), PSR J1023$-$5746, PSR J2111$+$4606, and PSR J2229$+$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…
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…
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…
The inter-glitch timing of the Vela pulsar is characterized by a constant second derivative of the rotation rate. This takes over after the post-glitch exponential relaxation, and is completed at about the time of the next glitch. The vortex creep model explains the second derivatives in terms of non-linear response to the glitch. We present inter-glitch timing fits to the present sample covering 16 large glitches, taking into account the possibility that in some glitches part of the step in spin-down rate may involve a "persistent shift", as observed in the Crab pulsar. Modifying the expressi…
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…
We report the detection of a glitch event in the pulsar J1709$-$4429 (also known as B1706$-$44) during regular monitoring observations with the Molonglo Observatory Synthesis Telescope (UTMOST). The glitch was found during timing operations, in which we regularly observe over 400 pulsars with up to daily cadence, while commensally searching for Rotating Radio Transients, pulsars, and FRBs. With a fractional size of $Δν/ν\approx 52.4 \times10^{-9}$, the glitch reported here is by far the smallest known for this pulsar, attesting to the efficacy of glitch searches with high cadence using UTMOST.
Among the five pulsars with the most recorded rotational glitches, only PSR J0534$+$2200 is found to have an autocorrelation between consecutive glitch sizes which differs significantly from zero (Spearman correlation coefficient $ρ=-0.46$, p-value $=0.046$). No statistically compelling autocorrelations between consecutive waiting times are found. The autocorrelation observations are interpreted within the framework of a predictive meta-model describing stress-release in terms of a state-dependent Poisson process. Specific combinations of size and waiting time autocorrelations are identified, …
The first pulse-to-pulse observations of a neutron star glitch in the Vela pulsar identified a null pulse hinting at the sudden disruption of the neutron star's magnetosphere. The only physical model connecting the glitch and the null pulse relies on a starquake either triggering, or being triggered by, the glitch itself. Until now, this was the only null pulse identified from over 50 years of observing the Vela pulsar. We identify five other null-like pulses, that we term quasi-nulls, before and after the glitch, separated by hundreds of seconds. We verify that such nulls are not found in dat…
We have observed a large glitch in the Crab pulsar (PSR B0531+21). The glitch occurred around MJD 58064 (2017 November 8) when the pulsar underwent an increase in the rotation rate of $Δν= 1.530 \times 10^{-5}$ Hz, corresponding to a fractional increase of $Δν/ ν= 0.516 \times 10^{-6}$ making this event the largest glitch ever observed in this source. Due to our high-cadence and long-dwell time observations of the Crab pulsar we are able to partially resolve a fraction of the total spin-up of the star. This delayed spin-up occurred over a timescale of $\sim$1.7 days and is similar to the behav…
Observations of pulsar glitches have the potential to provide constraints on the dynamics of the high density interior of neutron stars. However, to do so, realistic glitch models must be constructed and compared to the data. We take a step towards this goal by testing non-linear models for the mutual friction force, which is responsible for the exchange of angular momentum between the neutron superfluid and the observable normal component in a glitch. In particular, we consider a non-linear dependence of the drag force on the relative velocity between superfluid vortices and the normal compon…
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 …
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 …
Pulsar glitches offer an insight into the dynamics of superfluids in the high density interior of a neutron star. To model these phenomena, however, one needs to have an understanding of the dynamics of a turbulent array of superfluid vortices moving through a pinning lattice. In this paper we develop a theoretical approach to describe vortex mediated mutual friction in a pinned, turbulent and rotating superfluid. Our model is then applied to the study of the post glitch rotational evolution in the Vela pulsar and in PSR J0537-6910. We show that in both cases a turbulent model fits the evoluti…
We discuss the minimum glitch size of Crab observed by Espinoza et al. (2014). Modelling the crustquake as a trigger mechanism we estimate the size of the broken plate. The plate size obtained, D $\sim 100 m$ is comparable to plate size estimates for PSR J1119--6127. The plate size naturally leads to an estimate of the number of unpinned vortices involved in the glitch, $N \sim 10^{13} $. This number is of the same order in all Crab and Vela pulsar glitches. The mimimum glitch relates the constancy of all these numbers among different pulsars to the basic plate size involved in crust breaking.…
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 …
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…
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…
Glitch is supposed to be a useful probe into pulsar's interior, but the underlying physics remains puzzling. The glitch activity may reflect a lower limit of the crustal moment of inertia in conventional neutron star models. Nevertheless, its statistical feature could also be reproduced in the strangeon star model, which is focused here. We formulate the glitch activity of normal radio pulsars under the framework of starquake of solid strangeon star model, the shear modulus of strangeon matter is constrained to be $μ\simeq 3\times10^{34}~\rm erg/cm^{3}$, consistent with previous work. Neverthe…
Since its discovery as a pulsar in 2000, the central compact object (CCO) 1E 1207.4-5209 in the supernova remnant PKS 1209-51/52 had been a stable 0.424 s rotator with an extremely small spin-down rate and weak (Bs ~ 9E10 G) surface dipole magnetic field. In 2016 we observed a glitch from 1E 1207.4-5209 of at least Delta f/f = (2.8+/-0.4)E-9, which is typical in size for the general pulsar population. However, glitch activity is closely correlated with spin-down rate fdot, and pulsars with fdot as small as that of 1E 1207.4-5209 are never seen to glitch. Unlike in glitches of ordinary pulsars,…
During the spin-up phase of a large pulsar glitch - a sudden decrease of the rotational period of a neutron star - the angular velocity of the star may overshoot, namely reach values greater than that observed for the new post-glitch equilibrium. These transient phenomena are expected on the basis of theoretical models for pulsar internal dynamics and their observation has the potential to provide an important diagnostic for glitch modelling. We present a simple criterion to assess the presence of an overshoot, based on the minimal analytical model that is able to reproduce an overshooting spi…
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…
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$-$6220) which was classified as Poisson-like in previous analyses. Their activity is quasiperiodic, although the dispersion in waiting times is relatively broad. The class…
Pulsar-like compact stars provide us a unique laboratory to explore properties of dense matter at supra-nuclear densities. One of the models for pulsar-like stars is that they are totally composed of "strangeons", and in this paper we studied the pulsar glitches in a strangeon star model. Strangeon stars would be solidified during cooling, and the solid stars would be natural to have glitches as the result of starquakes. Based on the starquake model established before, we proposed that when the starquake occurs, the inner motion of the star which changes the moment of inertia and has impact on…
Anomalous X-ray Pulsars (AXPs) are now established to exhibit significant X-ray variability and be prolific glitchers, with some glitches being accompanied by large radiative changes. An open issue is whether AXP glitches are generically accompanied by radiative changes, relevant for understanding magnetar physical properties. Here we report on an analysis of archival X-ray data from the AXP 1E~1841$-$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 …
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…
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 …
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…
We present a timing and glitch analysis of the young X-ray pulsar PSR J0537$-$6910, located within the Large Magellanic Cloud, using 13 years of data from the now decommissioned Rossi X-ray Timing Explorer. Rotating with a spin period of 16 ms, PSR J0537$-$6910 is the fastest spinning and most energetic young pulsar known. It also displays the highest glitch activity of any known pulsar. We have found 42 glitches over the data span, corresponding to a glitch rate of 3.2 yr$^{-1}$, with an overall glitch activity rate of $8.8\times 10^{-7}\,$yr$^{-1}$. The high glitch frequency has allowed us t…
Context: The Crab pulsar underwent its largest timing glitch on 2017 Nov 8. The event was discovered at radio wavelengths, and was followed at soft X-ray energies by observatories, such as XPNAV and NICER. aims: This work aims to compare the glitch behavior at the two wavelengths mentioned above. Preliminary work in this regard has been done by the X-ray satellite XPNAV. NICER with its far superior sensitivity is expected to reveal much more detailed behavior. methods: NICER has accumulated more than $301$ kilo seconds of data on the Crab pulsar, equivalent to more than $3.3$ billion soft X-ra…
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.
