arXiv subjects

C. M. Espinoza

Publications and source records attributed to C. M. Espinoza.

At least 19 recordsLinked to original sources

arXiv2025

PSR J0537-6910: Exponential recoveries detected for 12 glitches

Pulsar glitches are unresolved increments of the rotation rate that sometimes trigger an enhancement of the spin-down rate. On occasions, the augmented spin-down decays gradually in an exponential manner, particularly after the largest glitch events. The young pulsar PSR J0537-6910 exhibits the highest known glitching rate, with 60 events detected in nearly 18 years of monitoring. Despite most PSR J0537-6910 glitches being large, only one exponential recovery has been reported, following its first discovered glitch. This is puzzling, as pulsars of similar characteristics typically present significant exponential recoveries. We aim to determine whether this reflects an intrinsic difference in PSR J0537-6910 or a detectability issue, for example due to its high glitch frequency. The full dataset, including recent NICER observations, was systematically searched for exponential relaxations. Each glitch was tested for evidence of a recovery over a broad range of trial timescales. Promising candidates were investigated further by comparing recovery models with and without an exponential term using Bayesian evidence. We discovered six new glitches, bringing the total to 66. Our criteria strongly indicates the presence of 11 previously undetected exponential recoveries. We presente updated glitch and timing solutions. Exponential recoveries are detected only for the largest glitches, though not all of them. The inferred timescales range from 4 to 37 d, with the decaying frequency increment generally below $1\%$ of the total. We find that $\ddotν$ can remain stable across several glitches, with persistent changes associated with only some events. In particular, it tends to be lowest after glitches with exponential recoveries, yielding inter-glitch braking indices between 6 and 9. Following glitches without recoveries, $\ddotν$ is higher, leading to braking indices between 10 and 35.

astro-ph.HE↗

arXiv2024

Glitch-induced pulse profile change of PSR J0742-2822 observed from the IAR

The radio pulsar PSR J0742-2822 is known to exhibit rapid changes between different pulse profile states that correlate with changes in its spin-down rate. However, the connection between these variations and the glitch activity of the pulsar remains unclear. We aim to study the evolution of the pulse profile and spin-down rate of PSR J0742-2822 in the period MJD 58810-60149 (November 2019 to July 2023), which includes the glitch on MJD 59839 (September 2022). In particular, we look for pulse profile or spin-down changes associated with the 2022 glitch. We observed PSR J0742-2822 with high cadence from the Argentine Institute of Radio astronomy (IAR) between November 2019 and July 2023. We used standard timing tools to characterize the times of arrival of the pulses and study the pulsar rotation, and particularly, the oscillations of $\dot ν$. We also study the evolution of the pulse profile. For both of them, we compare their behavior before and after the 2022 glitch. With respect to $\dot ν$, we found oscillations diminished in amplitude after the glitch. We found four different components contributing to the pre-glitch $\dot ν$ oscillations, and only one component after the glitch. About the emission, we found the pulse profile has two main peaks. We detected an increase in the $W_{50}$ of the total pulse profile of $\sim$12% after the glitch and we found the amplitude of the trailing peak increased with respect to the amplitude of the leading one after the glitch. We found significant changes in the pulse profile and the spin-down rate of PSR J0742-2822 after its 2022 glitch. These results suggest that there is a strong coupling between the internal superfluid of the neutron star and its magnetosphere, and that pulse profile changes may be led by this coupling instead of being led purely by magnetospheric effects.

astro-ph.HE↗

arXiv2024

Timing irregularities and glitches from the pulsar monitoring campaign at IAR

Context. Pulsars have a very stable rotation. However, sudden increases in their rotation frequency known as glitches, perturb their evolution. While large glitches are commonly detected, small glitches are harder to detect because of the lack of daily-cadence observations over long periods of time. Aims. We aim to explore the timing behaviour of young pulsars at daily timescales looking for small glitches and other irregularities. This will further our comprehension of the distribution of glitch sizes, which has also consequences for the theoretical modeling of the glitch mechanism. Methods. We observed six pulsars with up to daily cadence during 5 years with the antennas of the Argentine Institute of Radio Astronomy (IAR). We used standard pulsar timing tools to characterise the rotation of pulsars and developed an algorithm to look for small timing events in the data and calculate the changes in $ν$ and $\dotν$ at those epochs. Results. We found that the rotation of pulsars in this dataset is affected by small step changes in $ν$ and $\dotν$. We found three glitches that had not been reported before: two in PSR J1048-5832 with relative sizes $Δν/ ν= 9.1(4) \times 10^{-10}$ and $Δν/ ν= 4.5(1) \times 10^{-10}$, and one in the Vela pulsar with a size $Δν/ ν= 2.0(2) \times 10^{-10}$. We also report new decay terms on the 2021 Vela giant glitch, and on the 2022 giant glitches in PSR J0742-2822 and PSR J1740-3015 respectively. Besides, we found that the red noise contribution significantly diminished in PSR J0742-2822 after its giant glitch in 2022. Conclusions. Our results highlight the importance of high-cadence monitoring with an exhaustive analysis of the residuals to better characterize the distribution of glitch sizes and to deepen our understanding of the mechanisms behind glitches, red noise and timing irregularities.

astro-ph.HE↗

arXiv2023

A new small glitch in Vela discovered with a hidden Markov model

A striking feature of the Vela pulsar (PSR J0835$-$4510) is that it undergoes sudden increases in its spin frequency, known as glitches, with a fractional amplitude on the order of $10^{-6}$ approximately every 900 days. Glitches of smaller magnitudes are also known to occur in Vela. Their distribution in both time and amplitude is less well constrained but equally important for understanding the physical process underpinning these events. In order to better understand these small glitches in Vela, an analysis of high-cadence observations from the Mount Pleasant Observatory is presented. A hidden Markov model (HMM) is used to search for small, previously undetected glitches across 24 years of observations covering MJD 44929 to MJD 53647. One previously unknown glitch is detected around MJD 48636 (Jan 15 1992), with fractional frequency jump $Δf/f = (8.19 \pm 0.04) \times 10^{-10}$ and frequency derivative jump $Δ\dot{f}/\dot{f} = (2.98 \pm 0.01) \times 10^{-4}$. Two previously reported small glitches are also confidently re-detected, and independent estimates of their parameters are reported. Excluding these events, 90% confidence frequentist upper limits on the sizes of missed glitches are also set, with a median upper limit of $Δf^{90\%}/f = 1.35 \times 10^{-9}$. Upper limits of this kind are enabled by the semi-automated and computationally efficient nature of the HMM, and are crucial to informing studies which are sensitive to the lower end of the glitch size distribution.

astro-ph.HE↗

arXiv2021

VLA proper motion constraints on the origin, age, and potential magnetar future of PSR J1734$-$3333

The characteristic age of PSR J1734$-$3333 estimated from its current spin down rate implies that it is a young pulsar ($τ_c<10$ kyr). But the time derivative of its spin down rate differs markedly from that assumed for normal radio pulsars, meaning its actual age is uncertain. G354.8$-$0.8 is a supernova remnant (SNR) whose centre is located 21 arcmin away of the pulsar, and with a morphology that suggests an association with the pulsar. We want to assess the likelihood of the association between PSR J1734$-$3333 and G354.8$-$0.8 or other nearby supernova remnants quantitatively, with the objective of shedding light on the real age of this pulsar. Observations with the Karl G. Jansky Very Large Array were carried out in 2015 and 2019 that allow precise astrometric measurements and consequently a proper motion estimate for the pulsar. The proper motion was found to be $μ_α=10\pm10$ mas yr$^{-1}$ and $μ_δ=-29\pm11$ mas yr$^{-1}$ (error bars are $1$-$σ$). Though marginal, this detection rules out the association with G354.8$-$0.8 because it means the pulsar is not moving away from the centre of the SNR. No SNR consistent with the measured proper motion and an age $\simτ_c$ could be found. We also present the first measurement of the spectral index for this pulsar, $α=-1.1\pm0.3$, measured between $1.5$ and $3.0$ GHz. The SNR produced by the birth supernova of PSR J1734$-$3333 could have already faded to undetectable brightness, for which estimates suggest timescales of $10$-$100$ kyr. This and other considerations lead us to conclude that the pulsar is possibly older than $45$-$100$ kyr. PSR J1734$-$3333 is a pulsar with rotational properties that place it between standard radio pulsars and magnetars, and we interpret our result in the context of a possible future life as a magnetar for this pulsar.

astro-ph.HE↗

arXiv2021

Spontaneous Magnetic Fluctuations and Collisionless Regulation of Turbulence in the Earth's Magnetotail

Among the fundamental and most challenging problems of laboratory, space, and astrophysical plasma physics is to understand the relaxation processes of nearly collisionless plasmas toward quasi-stationary states; and the resultant states of electromagnetic plasma turbulence. Recently, it has been argued that solar wind plasma $β$ and temperature anisotropy observations may be regulated by kinetic instabilities such as the ion-cyclotron, mirror, electron-cyclotron, and firehose instabilities; and that magnetic fluctuation observations are consistent with the predictions of the Fluctuation-Dissipation theorem, even far below the kinetic instability thresholds. Here, using in-situ magnetic field and plasma measurements by the THEMIS satellite mission, we show that such regulation seems to occur also in the Earth's magnetotail plasma sheet at the ion and electron scales. Regardless of the clear differences between the solar wind and the magnetotail environments, our results indicate that spontaneous fluctuations and their collisionless regulation are fundamental features of space and astrophysical plasmas, thereby suggesting the processes is universal.

physics.space-ph↗

arXiv2021

Small glitches and other rotational irregularities of the Vela pulsar

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 other hand, are not clearly established. High-cadence observations of the Vela pulsar were taken between 1981 and 2005 at the Mount Pleasant Radio Observatory. An automated systematic search was carried out that investigated whether a significant change of spin frequency $ν$ and/or the spin-down rate $\dotν$ takes place at any given time. We find two new glitches, with respective sizes $Δν/ν$ of $(5.55\pm0.03)\times10^{-9}$ and $(38\pm4)\times10^{-9}$. In addition to these two glitch events, our study reveals numerous events of all possible signatures (i.e. combinations of $Δν$ and $Δ\dotν$ signs), all of them small with $|Δν|/ν<10^{-9}$, which contribute to the Vela timing noise. The Vela pulsar presents an under-abundance of small glitches compared to many other glitching pulsars, which appears genuine and not a result of observational biases. In addition to typical glitches, the smooth spin-down of the pulsar is also affected by an almost continuous activity that can be partially characterised by small step-like changes in $ν$, $\dot{ν,}$ or both. Simulations indicate that a continuous wandering of the rotational phase, following a red spectrum, could mimic such step-like changes in the timing residuals.

astro-ph.HE↗

arXiv2019

Glitch time series and size distributions in eight prolific pulsars

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 pulsars with at least ten detected glitches. We model the distributions of glitch sizes and times between consecutive glitches for this sample and perform Monte Carlo simulations to explore two hypotheses that could explain why the correlation is so much weaker in other pulsars than in PSR J0537-6910. We confirm the above results for the Vela pulsar and PSR J0537-6910, and verify that the latter is the only pulsar with a strong correlation between glitch size and waiting time to the following glitch. For the remaining six pulsars, the waiting time distributions are best fitted by exponentials, and the size distributions either by power laws, exponentials, or log-normal functions. Some pulsars in the sample yield significant Pearson and Spearman coefficients ($r_p$ and $r_s$) for the aforementioned correlation. Moreover, for all except the Crab, both coefficients are positive. Our simulations show that the weaker correlations in pulsars other than PSR J0537$-$6910 cannot be due to missing glitches too small to be detected. We also tested the hypothesis that each pulsar may have two kinds of glitches, namely large, correlated ones and small, uncorrelated ones. We found for all pulsars that their glitches are not consistent with a pure uncorrelated population either.

astro-ph.HE↗

arXiv2018

The glitch activity of neutron stars

We present a statistical study of the glitch population and the behaviour of the glitch activity across the known population of neutron stars. An unbiased glitch database was put together based on systematic searches of radio timing data of 898 rotation-powered pulsars obtained with the Jodrell Bank and Parkes observatories. Glitches identified in similar searches of 5 magnetars were also included. The database contains 384 glitches found in the rotation of 141 of these neutron stars. We confirm that the glitch size distribution is at least bimodal, with one sharp peak at approximately $20\, \rm{μ\,Hz}$, which we call large glitches, and a broader distribution of smaller glitches. We also explored how the glitch activity $\dotν_{\rm{g}}$, defined as the mean frequency increment per unit of time due to glitches, correlates with the spin frequency $ν$, spin-down rate $|\dotν|$, and various combinations of these, such as energy loss rate, magnetic field, and spin-down age. It is found that the activity is insensitive to the magnetic field and that it correlates strongly with the energy loss rate, though magnetars deviate from the trend defined by the rotation-powered pulsars. However, we find that a constant ratio $\dotν_{\rm{g}}/|\dotν| = 0.010 \pm 0.001$ is consistent with the behaviour of all rotation-powered pulsars and magnetars. This relation is dominated by large glitches, which occur at a rate directly proportional to $|\dotν|$. The only exception are the rotation-powered pulsars with the highest values of $|\dotν|$, such as the Crab pulsar and PSR B0540$-$69, which exhibit a much smaller glitch activity, intrinsically different from each other and from the rest of the population. The activity due to small glitches also shows an increasing trend with $|\dotν|$, but this relation is biased by selection effects.

astro-ph.HE↗

arXiv2017

The enigmatic spin evolution of PSR J0537-6910: r-modes, gravitational waves and the case for continued timing

We discuss the unique spin evolution of the young X-ray pulsar PSR J0537-6910, a system in which the regular spin down is interrupted by glitches every few months. Drawing on the complete timing data from the Rossi X-ray Timing Explorer (RXTE, from 1999-2011), we argue that a trend in the inter-glitch behaviour points to an effective braking index close to $n=7$, much larger than expected. This value is interesting because it would accord with the neutron star spinning down due to gravitational waves from an unstable r-mode. We discuss to what extent this, admittedly speculative, scenario may be consistent and if the associated gravitational-wave signal would be within reach of ground based detectors. Our estimates suggest that one may, indeed, be able to use future observations to test the idea. Further precision timing would help enhance the achievable sensitivity and we advocate a joint observing campaign between the Neutron Star Interior Composition ExploreR (NICER) and the LIGO-Virgo network.

astro-ph.HE↗

arXiv2017

Pulsar spin-down: the glitch-dominated rotation of PSR J0537-6910

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 evolution is dominated by the glitches, which occur at a rate ~3.5 per year, and the post-glitch recoveries, which prevail the entire inter-glitch intervals. This distinctive behaviour provides invaluable insights into the physics of glitches. The observations can be explained with a multi-component model which accounts for the dynamics of the neutron superfluid present in the crust and core of neutron stars. We place limits on the moment of inertia of the component responsible for the spin-up and, ignoring differential rotation, the velocity difference it can sustain with the crust. Contrary to its rapid decrease between glitches, the spin-down rate increased over the 13 years, and we find the long-term braking index $n_{\rm l}=-1.22(4)$, the only negative braking index seen in a young pulsar. We briefly discuss the plausible interpretations of this result, which is in stark contrast to the predictions of standard models of pulsar spin-down.

astro-ph.HE↗

arXiv2016

New long-term braking index measurements for glitching pulsars using a glitch-template method

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 Bank Observatory. The values of braking indices describe the long-term evolution of the pulsars across the P-P' diagram. Despite some measurements being affected by considerable uncertainties, there is evidence for a common trend involving low braking indices (n<=2) among young glitching pulsars. Such values introduce a new variant in the evolution of young pulsars and their relationship with other populations in the P-P' diagram. Low braking indices also imply that these pulsars could be a few times older than their characteristic ages. We consider PSR B1757-24 and conclude that the pulsar could be old enough to be related to the supernova remnant G5.4-1.2. Between glitches, the short-term evolution of Vela-like pulsars is characterised by large inter-glitch braking indices n_ig > 10. We interpret both short and long term trends as signatures of the large glitch activity, and speculate that they are driven by short-term post-glitch re-coupling and a cumulative long-term decoupling of superfluid to the rotation of the star.

astro-ph.HE↗

arXiv2014

The unusual glitch recoveries of the high magnetic field pulsar J1119$-$6127

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 radio timing observations and analyse the total of 16 years of timing data for this source. The new data uncover an ongoing evolution of the spin-down rate, thereby allowing us to exclude permanent changes in the external or internal torque as a stand-alone cause of the peculiar features of the glitch recovery. Furthermore, no additional variations of the radio pulse profile are detected, strengthening the association of the previously observed transient emission features with the glitching activity. A self-consistent measurement of the braking index yields a value $n\simeq2.7$, indicating a trajectory in the $P-\dot{P}$ plane inclined towards the magnetars. Such a potential evolutionary link might be strengthened by a, possibly permanent, reduction of $\sim15\%$ in $n$ at the epoch of the 2007 glitch.

astro-ph.HE↗

arXiv2014

Six Faint Gamma-ray Pulsars Seen with the Fermi Large Area Telescope -- Towards a Sample Blending into the Background

Context: GeV gamma-ray pulsations from over 140 pulsars have been characterized using the Fermi Large Area Telescope, enabling improved understanding of the emission regions within the neutron star magnetospheres, and the contributions of pulsars to high energy electrons and diffuse gamma rays in the Milky Way. The first gamma-ray pulsars to be detected were the most intense and/or those with narrow pulses. Aims: As the Fermi mission progresses, progressively fainter objects can be studied. In addition to more distant pulsars (thus probing a larger volume of the Galaxy), or ones in high background regions (thus improving the sampling uniformity across the Galactic plane), we detect pulsars with broader pulses or lower luminosity. Adding pulsars to our catalog with inclination angles that are rare in the observed sample, and/or with lower spindown power, will reduce the bias in the currently known gamma-ray pulsar population. Methods: We use rotation ephemerides derived from radio observations to phase-fold gamma rays recorded by the Fermi Large Area Telescope, to then determine the pulse profile properties. Spectral analysis provides the luminosities and, when the signal-to-noise ratio allows, the cutoff energies. We constrain the pulsar distances by different means in order to minimize the luminosity uncertainties. Results: We present six new gamma-ray pulsars with an eclectic mix of properties. Three are young, and three are recycled. They include the farthest, the lowest power, two of the highest duty-cycle pulsars seen, and only the fourth young gamma-ray pulsar with a radio interpulse. We discuss the biases existing in the current gamma-ray pulsar catalog, and steps to be taken to mitigate the bias.

astro-ph.HE↗

arXiv2014

Neutron star glitches have a substantial minimum size

Glitches are sudden spin-up events that punctuate the steady spin down of pulsars and are thought to be due to the presence of a superfluid component within neutron stars. The precise glitch mechanism and its trigger, however, remain unknown. The size of glitches is a key diagnostic for models of the underlying physics. While the largest glitches have long been taken into account by theoretical models, it has always been assumed that the minimum size lay below the detectability limit of the measurements. In this paper we define general glitch detectability limits and use them on 29 years of daily observations of the Crab pulsar, carried out at Jodrell Bank Observatory. We find that all glitches lie well above the detectability limits and by using an automated method to search for small events we are able to uncover the full glitch size distribution, with no biases. Contrary to the prediction of most models, the distribution presents a rapid decrease of the number of glitches below ~0.05 $μ$Hz. This substantial minimum size indicates that a glitch must involve the motion of at least several billion superfluid vortices and provides an extra observable which can greatly help the identification of the trigger mechanism. Our study also shows that glitches are clearly separated from all the other rotation irregularities. This supports the idea that the origin of glitches is different to that of timing noise, which comprises the unmodelled random fluctuations in the rotation rates of pulsars.

astro-ph.HE↗

arXiv2013

Broadband Pulsations from PSR B1821-24: Implications for Emission Models and the Pulsar Population of M28

We report a 5.4σ detection of pulsed gamma rays from PSR B1821-24 in the globular cluster M28 using ~44 months of Fermi Large Area Telescope (LAT) data that have been reprocessed with improved instrument calibration constants. We constructed a phase-coherent ephemeris, with post-fit residual RMS of 3 μs, using radio data spanning ~23.2 years, enabling measurements of the multi-wavelength light curve properties of PSR B1821-24 at the milliperiod level. We fold RXTE observations of PSR B1821-24 from 1996 to 2007 and discuss implications on the emission zones. The gamma-ray light curve consists of two peaks, separated by 0.41$\pm$0.02 in phase, with the first gamma-ray peak lagging the first radio peak by 0.05$\pm$0.02 in phase, consistent with the phase of giant radio pulses. We observe significant emission in the off-peak interval of PSR B1821-24 with a best-fit LAT position inconsistent with the core of M28. We do not detect significant gamma-ray pulsations at the spin or orbital periods from any other known pulsar in M28, and we place limits on the number of energetic pulsars in the cluster. The derived gamma-ray efficiency, ~2%, is typical of other gamma-ray pulsars with comparable spin-down power, suggesting that the measured spin-down rate ($2.2\times10^{36}$ erg s$^{-1}$) is not appreciably distorted by acceleration in the cluster potential. This confirms PSR B1821-24 as the second very energetic millisecond pulsar in a globular cluster and raises the question of whether these represent a separate class of objects that only form in regions of very high stellar density

astro-ph.HE↗

arXiv2013

Six millisecond pulsars detected by the Fermi Large Area Telescope and the radio/gamma-ray connection of millisecond pulsars

We report on the discovery of gamma-ray pulsations from five millisecond pulsars (MSPs) using the Fermi Large Area Telescope (LAT) and timing ephemerides provided by various radio observatories. We also present confirmation of the gamma-ray pulsations from a sixth source, PSR J2051-0827. Five of these six MSPs are in binary systems: PSRs J1713+0747, J1741+1351, J1600-3053 and the two black widow binary pulsars PSRs J0610-2100 and 2051-0827. The only isolated MSP is the nearby PSR J1024-0719, which is also known to emit X-rays. We present X-ray observations in the direction of PSRs J1600-3053 and J2051-0827. While the latter is firmly detected, we an only give upper limits for the X-ray flux of the former. There are no dedicated X-ray observations available for the other 3 objects. The MSPs mentioned above, together with most of the MSPs detected by Fermi, are used to put together a sample of 30 gamma-ray MSPs which is used to study the morphology and phase connection of radio and gamma-ray pulse profiles. We show that MSPs with pulsed gamma-ray emission which is phase aligned with the radio emission present the steepest radio spectra and the largest magnetic fields at the light cylinder among all MSPs. As well, we also observe a trend towards very low, or undetectable, radio linear polarisation levels. These properties could be attributed to caustic radio emission produced at a range of different altitudes in the magnetosphere. We note that most of these characteristics are also observed in the Crab pulsar, the only other radio pulsar known to exhibit phase-aligned radio and gamma-ray emission.

astro-ph.HE↗

arXiv2012

X-ray Observations of High-B Radio Pulsars

The study of high-magnetic-field pulsars is important for examining the relationships between radio pulsars, magnetars, and X-ray-isolated neutron stars (XINSs). Here we report on X-ray observations of three such high-magnetic-field radio pulsars. We first present the results of a deep XMM-Newton observation of PSR J1734-3333, taken to follow up on its initial detection in 2009. The pulsar's spectrum is well fit by a blackbody with a temperature of 300 +/- 60 eV, with bolometric luminosity L_bb = 2.0(+2.2 -0.7)e+32 erg/s = 0.0036E_dot for a distance of 6.1 kpc. We detect no X-ray pulsations from the source, setting a 1 sigma upper limit on the pulsed fraction of 60% in the 0.5-3 keV band. We compare PSR J1734-3333 to other rotation-powered pulsars of similar age and find that it is significantly hotter, supporting the hypothesis that the magnetic field affects the observed thermal properties of pulsars. We also report on XMM-Newton and Chandra observations of PSRs B1845-19 and J1001-5939. We do not detect either pulsar, setting 3 sigma upper limits on their blackbody temperatures of 48 and 56 eV, respectively. Despite the similarities in rotational properties, these sources are significantly cooler than all but one of the XINSs, which we attribute to the two groups having been born with different magnetic fields and hence evolving differently.

astro-ph.HE↗