This work explores whether gravitational waves (GWs) from neutron star (NS) mountains can be detected with current 2nd-generation and future 3rd-generation GW detectors. In particular, we focus on a scenario where transient mountains are formed immediately after a NS glitch. In a glitch, a NS's spin frequency abruptly increases and then often exponentially recovers back to, but never quite reaches, the spin frequency prior to the glitch. If the recovery is ascribed to an additional torque due to a transient mountain, we find that GWs from that mountain are marginally-detectable with Advanced LIGO at design sensitivity and is very likely to be detectable for 3rd-generation detectors such as the Einstein Telescope. Using this model, we are able to find analytical expressions for the GW amplitude and its duration in terms of observables.
Pulsar glitches are sudden increases in the spin frequency of an otherwise steadily spinning down neutron star. These events are thought to represent a direct probe of the dynamics of the superfluid interior of the star. However glitches can differ significantly from one another, not only in size and frequency, but also in the post-glitch response of the star. Some appear as simple steps in frequency, while others also display an increase in spin-down rate after the glitch. Others still show several exponentially relaxing components in the post-glitch recovery. We show that if glitches are ind…
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…
Providing a link between magnetars and radio pulsars, high magnetic field neutron stars are ideal targets to investigate how bursting/magnetospheric activity and braking torque variations are connected to rotational glitches. The last spin-up glitch of the highly magnetised pulsar J1119$-$6127 back in 2007 was the first glitch in a rotationally powered radio pulsar to be accompanied by radiative changes. Moreover, it was followed by an uncommon glitch relaxation that resulted in a smaller spin-down rate relative to the prediction of the pre-glitch timing model. Here, we present 4 years of new …
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 2016 Vela glitch observed by the Mt Pleasant radio telescope provides the first opportunity to study pulse-to-pulse dynamics of a pulsar glitch, opening up new possibilities to study the neutron star's interior. We fit models of the star's rotation frequency to the pulsar data, and present three new results. First, we constrain the glitch rise time to less than 12.6s with 90% confidence, almost three times shorter than the previous best constraint. Second, we find definitive evidence for a rotational-frequency overshoot and fast relaxation following the glitch. Third, we find evidence for …
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.
The Crab and Vela are well-studied glitching pulsars and the data obtained sofar should enable us to test the reliability of models of their internal structures. Very recently it was proposed that glitching pulsars are embedded in bimetric spacetime: their incompressible superfluid cores (SuSu-cores) are embedded in flat spacetime, whereas the ambient compressible and dissipative media are enclosed in Schwarzschild spacetime. In this letter we apply this model to the Crab and Vela pulsars and show that a newly born pulsar initially of $1.25\text{M}_{\odot}$ and an embryonic SuSu-core of $0.029…
In this paper we consider a simple two-fluid model for pulsar glitches. We derive the basic equations that govern the spin evolution of the system from two-fluid hydrodynamics, accounting for the vortex mediated mutual friction force that determines the glitch rise. This leads to a simple "bulk" model that can be used to describe the main properties of a glitch event resulting from vortex unpinning. In order to model the long term relaxation following the glitch our model would require additional assumptions regarding the repinning of vortices, an issue that we only touch upon briefly. Instead…
Gravitational waves (GWs) can offer a novel window into the structure and dynamics of neutron stars. Here we present the first search for long-duration quasi-monochromatic GW transients triggered by pulsar glitches. We focus on two glitches observed in radio timing of the Vela pulsar (PSR J0835-4510) on 12 December 2016 and the Crab pulsar (PSR J0534+2200) on 27 March 2017, during the Advanced LIGO second observing run (O2). We assume the GW frequency lies within a narrow band around twice the spin frequency as known from radio observatons. Using the fully-coherent transient-enabled F-statisti…
Continuous gravitational waves from neutron stars could provide an invaluable resource to learn about their interior physics. A common search method involves matched filtering a modeled template against the noisy gravitational-wave data to find signals. This method suffers a mismatch (i.e., relative loss of the signal-to-noise ratio) if the signal deviates from the template. One possible instance in which this may occur is if the neutron star undergoes a glitch, a sudden rapid increase in the rotation frequency seen in the timing of many radio pulsars. In this work, we use a statistical charac…
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.
The dynamics of quantised vorticity in neutron star interiors is at the heart of most pulsar glitch models. However, the large number of vortices (up to $\approx 10^{13}$) involved in a glitch and the huge disparity in scales between the femtometer scale of vortex cores and the kilometre scale of the star makes quantum dynamical simulations of the problem computationally intractable. In this paper we take a first step towards developing a mean field prescription to include the dynamics of vortices in large scale hydrodynamical simulations of superfluid neutron stars. We consider a one dimensio…
Pulsars are spinning neutron stars which emit an electromagnetic beam. We expect pulsars to slowly decrease their rotational frequency. However, sudden increases of the rotational frequency have been observed from different pulsars. These events are called "glitches" and they are followed by a relaxation phase with timescales from days to months. Gravitational wave (GW) emission may follow these peculiar events. We give an overview of the setup for an analysis of GW data from the Advanced LIGO and Virgo third observing run (O3) arXiv:2112.10990 searching for transient GW signals lasting hours …
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, …
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 observed in many radio pulsars, may be the macroscopic manifestation of superfluid vortex avalanches on the microscopic scale. Small scale quantum mechanical simulations of vortex motion in a decelerating container have shown that such events are possible and predict power-law distributions for the size of the events, and exponential distributions for the waiting time. Despite a paucity of data, this prediction is consistent with the size and waiting time distributions of most glitching pulsars. Nevertheless a few object appear to glitch quasi-periodi…
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 $\times …
The abrupt change in the pulse period of a pulsar is called a pulsar glitch. In this paper, we present eleven pulsar glitches detected using the Ooty Radio Telescope (ORT) and the upgraded Giant Metrewave Radio Telescope (uGMRT) in high cadence timing observations of 8 pulsars. The measured relative amplitude of glitches ($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…
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…
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…
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 …
We report on the aftermath of a magnetar outburst from the young, high-magnetic-field radio pulsar PSR J1119-6127 that occurred on 2016 July 27. We present the results of a monitoring campaign using the Neil Gehrels Swift X-ray Telescope, NuSTAR, and XMM-Newton. After reaching a peak luminosity of ~300 times the quiescent luminosity, the pulsar's X-ray flux declined by factor of ~50 on a time scale of several months. The X-ray spectra are well described by a blackbody and a hard power-law tail. After an initial rapid decline during the first day of the outburst, we observe the blackbody temper…
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…
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. …
Glitches are sudden jumps in the spin frequency of pulsars believed to originate in the superfluid interior of neutron stars. Superfluid flow in a model neutron star is simulated by solving the equations of motion of a two-component superfluid consisting of a viscous proton-electron plasma and an inviscid neutron condensate in a spherical Couette geometry. We examine the response of our model neutron star to glitches induced in three different ways: by instantaneous changes of the spin frequency of the inner and outer boundaries, and by instantaneous recoupling of the fluid components in the b…
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 …
