Journal articles on the topic 'Pulsars'
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1
Moran, Abigail, Chiara M. F. Mingarelli, Megan Bedell, Deborah Good, and David N. Spergel. "Improving Distances to Binary Millisecond Pulsars with Gaia." Astrophysical Journal 954, no. 1 (August 25, 2023): 89. http://dx.doi.org/10.3847/1538-4357/acec75.
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Abstract Pulsar distances are notoriously difficult to measure, and play an important role in many fundamental physics experiments, such as pulsar timing arrays. Here, we perform a cross-match between International PTA pulsars (IPTA) and Gaia's Data Release 2 (DR2) and Data Release 3 (DR3). We then combine the IPTA pulsar’s parallax with its binary companion’s parallax, found in Gaia, to improve the distance measurement to the binary. We find seven cross-matched IPTA pulsars in Gaia DR2, and when using Gaia DR3 we find six IPTA pulsar cross-matches but with seven Gaia objects. Moving from Gaia DR2 to Gaia DR3, we find that the Gaia parallaxes for the successfully cross-matched pulsars improved by 53%, and pulsar distances improved by 29%. Finally, we find that binary companions with a <3.0σ detection are unreliable associations, setting a high bar for successful cross-matches.
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Nice, David J., and Stephen E. Thorsett. "Rotational and Orbital Fluctuations of Eclipsing Binary Pulsar PSR B1744-24A." International Astronomical Union Colloquium 160 (1996): 523–24. http://dx.doi.org/10.1017/s0252921100042275.
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Eclipsing binary pulsars systems highlight an important stage in the evolution of isolated millisecond pulsars. In these systems, the pulsar’s companion is losing mass due to Roche lobe overflow and/or a stellar wind induced by intercepted energy from the pulsar flux. Eventual evaporation of the companions could yield isolated millisecond puslars. PSR B1744-24A was the second eclipsing millisecond pulsar to be discovered (Lyneet al. 1990). It is in a 1.8 hr orbit with a ∼ 0.1 M⊙companion. Its eclipses show some variability, and the pulsar is undetectable at about 25% of observing epochs, presumably because it is completely enveloped by the companion’s outflow (Nice & Thorsett 1992).
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Doroshenko, Oleg V., and Sergei M. Kopeikin. "Relativistic effect of gravitational deflection of light in binary pulsars." International Astronomical Union Colloquium 160 (1996): 131. http://dx.doi.org/10.1017/s0252921100041269.
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Timing formula for data processing of observations of binary pulsars that accounts for the relativistic deflection of light in the gravitational field of the pulsar’s companion is presented, and the measurability of this effect along with its variance estimates is discussed. The deflection of the pulsar’s pulse trajectory in the gravitational field of its companion leads to variation in the pulsar’s rotational phase. This variation appears as a narrow sharp growth of the magnitude of the post-fit residuals in the vicinity of the moment of the superior conjunction of the pulsar with its companion. In contrast to the relativistic Shapiro effect, the amplitude of the effect of gravitational deflection of the pulsar radio beam has two peaks with opposite signs, which become sharper as the inclinationiof the pulsar’s orbit approaches to the right angle. The effect under consideration influences the estimation of parameters of the relativistic Shapiro effect in the binary pulsars with nearly edgewise orbits. Its inclusion in the fitting procedure provides a more careful measurement of the sine of the orbital inclinationi, as well as the masses of the pulsar and its companion. This permits an improved testing of alternative theories of gravity in the strong field regime. The effect of the gravitational deflection of light has been numerically investigated for binary pulsars with nearly edgewise orbits. It is shown that the effect is observed in general only when cosi is less than 0.003. This estimate becomes less restrictive as the pulsar’s spin axis approaches the line of sight.
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Dewey, Rachel J., and James M. Cordes. "Monte Carlo Simulations of Radio Pulsars and Their Progenitors." Symposium - International Astronomical Union 125 (1987): 408. http://dx.doi.org/10.1017/s0074180900161030.
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The formation of neutron stars in binary systems is often used to explain the nature of specific radio pulsars and characteristics of the pulsar population as a whole. We have investigated the extent to which such scenarios provide a self-consistent description of the pulsar population. Using a computer simulation, we modeled the evolution of the main sequence stellar population and compared the predicted neutron star population to the observed radio pulsar population, focusing our attention on the pulsar velocity distribution and the incidence of binary pulsars. These characteristics relate very directly to the binary nature of pulsar progenitors, and are not strongly dependent on models of pulsar magentic field and luminosity evolution.The need to reproduce both the high velocities typical of pulsars and the low incidence of binary pulsars strongly constrains the formation of pulsars in binary systems. Unless one assumes that virtually all pulsars originate in close binary systems, the observed velocity distribution cannot result from the disruption of binary systems by symmetric supernova explosions; some additional acceleration process (e.g. asymmetric supernova mass ejection or asymmetries in pulsar radiation) must act during or soon after a pulsar's formation. It is possible to reproduce the velocity distribution by assuming that all pulsars are born in binary systems with initial orbital periods less than about 30 years. However, the predicted incidence of binaries is then too large by more than an order of magnitude, unless one also assumes that the process of mass transfer from the primary to the secondary is almost always non-conservative, or that the minimum mass necessary for a stripped helium core to explode as a supernova is larger (over 4 M⊙) than currently believed. Further analyses of the radio pulsar population, the X-ray binary population and the abundances of elements ejected in supernovae should help determine which of these alternatives is most reasonble. Additional studies of the main sequence stellar population, accounting more accurately for evolutionary and observational selection effects, will reduce the uncertainties in modeling the formation of the neutron star population.It has also been suggested that the observed correlation between pulsar velocities and magnetic moments (see Cordes, these Proceedings) is induced by the differing evolutionary paths by which stars in binary systems form radio pulsars. Our simulation does not reproduce this correlation, and we do not find any paths likely to produce low velocity, low magnetic field neutron stars not in binary systems.We are submitting a full description of our model and results to The Astrophysical Journal.
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Shearer, Andrew, and Eoin O’ Connor. "Optical pulsars and polarimetry." Proceedings of the International Astronomical Union 13, S337 (September 2017): 191–94. http://dx.doi.org/10.1017/s174392131700998x.
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AbstractDespite the early optical detection of the Crab pulsar in 1969, optical pulsars have become the poor cousin of the neutron star family. Only five normal pulsars have been observed to pulse in the optical waveband. A further three magnetars/SGRs have been detected in the optical/near IR. Optical pulsars are intrinsically faint with a first order luminosity, predicted by Pacini, to be proportional to P−10, where P is the pulsar’s period. Consequently they require both large telescopes, generally over-subscribed, and long exposure times, generally difficult to get. However optical observations have the benefit that polarisation and spectral observations are possible compared to X-ray and gamma-ray observations where polarisation measurements are limited. Over the next decade the number of optical pulsars should increase as optical detectors approach 100% quantum efficiency and as we move into the era of extremely large telescopes where limiting fluxes will be 30 to 100 times fainter compared to existing optical telescopes.
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Wang, Ziteng, David L. Kaplan, Rahul Sengar, Emil Lenc, Andrew Zic, Akash Anumarlapudi, B. M. Gaensler, Natasha Hurley-Walker, Tara Murphy, and Yuanming Wang. "Discovery of a Young, Highly Scattered Pulsar PSR J1032-5804 with the Australian Square Kilometre Array Pathfinder." Astrophysical Journal 961, no. 2 (January 24, 2024): 175. http://dx.doi.org/10.3847/1538-4357/ad0fe8.
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Abstract We report the discovery of a young, highly scattered pulsar in a search for highly circularly polarized radio sources as part of the Australian Square Kilometre Array Pathfinder Variables and Slow Transients survey. In follow-up observations with the Parkes radio telescope, Murriyang, we identified PSR J1032−5804 and measured a period of 78.7 ms, a dispersion measure of 819 ± 4 pc cm−3, a rotation measure of −2000 ± 1 rad m−2, and a characteristic age of 34.6 kyr. We found a pulse scattering timescale at 3 GHz of ∼22 ms, implying a timescale at 1 GHz of ∼3845 ms, which is the third most scattered pulsar known and explains its nondetection in previous pulsar surveys. We discuss the identification of a possible pulsar wind nebula and supernova remnant in the pulsar’s local environment by analyzing the pulsar spectral energy distribution and the surrounding extended emission from multiwavelength images. Our result highlights the possibility of identifying extremely scattered pulsars from radio continuum images. Ongoing and future large-scale radio continuum surveys will offer us an unprecedented opportunity to find more extreme pulsars (e.g., highly scattered, highly intermittent, and highly accelerated), which will enhance our understanding of the characteristics of pulsars and the interstellar medium.
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Sett, S., R. P. Breton, C. J. Clark, M. H. Kerkwijk, and D. L. Kaplan. "A search for radio pulsars in five nearby supernova remnants." Astronomy & Astrophysics 647 (March 2021): A183. http://dx.doi.org/10.1051/0004-6361/201936108.
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Context. Most neutron stars are expected to be born in supernovae, but only about half of supernova remnants (SNRs) are associated with a compact object. In many cases, a supernova progenitor may have resulted in a black hole. However, there are several possible reasons why true pulsar-SNR associations may have been missed in previous surveys: The pulsar’s radio beam may not be oriented towards us; the pulsar may be too faint to be detectable; or there may be an offset in the pulsar position caused by a kick. Aims. Our goal is to find new pulsars in SNRs and explore their possible association with the remnant. The search and selection of the remnants presented in this paper was inspired by the non-detection of any X-ray bright compact objects in these remnants when previously studied. Methods. Five SNRs were searched for radio pulsars with the Green Bank Telescope at 820 MHz with multiple pointings to cover the full spatial extent of the remnants. A periodicity search plus an acceleration search up to 500 m s−2 and a single pulse search were performed for each pointing in order to detect potential isolated binary pulsars and single pulses, respectively. Results. No new pulsars were detected in the survey. However, we were able to re-detect a known pulsar, PSR J2047+5029, near SNR G89.0+4.7. We were unable to detect the radio-quiet gamma-ray pulsar PSR J2021+4026, but we do find a flux density limit of 0.08 mJy. Our flux density limits make our survey two to 16 times more sensitive than previous surveys, while also covering the whole spatial extent of the same remnants. Conclusions. We discuss potential explanations for the non-detection of a pulsar in the studied SNRs and conclude that sensitivity is still the most likely factor responsible for the lack of pulsars in some remnants.
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Bondonneau, Louis, Jean-Mathias Grießmeier, Gilles Theureau, and Maciej Serylak. "Low frequency pulsar observations with the international LOFAR station FR606." Proceedings of the International Astronomical Union 13, S337 (September 2017): 313–14. http://dx.doi.org/10.1017/s1743921317009656.
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AbstractThe pulsar’s signal passes through the interstellar medium (ISM) which leads to both chromatic dispersive delays and multipath pulse broadening. These effects have a strong frequency dependence (f−2 and f−4 respectively). Pulse profiles of pulsars are also frequency-dependent leading to some degeneracy with the ISM imprint. Furthermore, many pulsars show a turnover of their spectrum around ~100 MHz. For all these reasons, the frequency band below 100 MHz contains a lot of information about both the pulsar emission and the ISM. Our study is based on a LOw Frequency ARray (LOFAR) monitoring campaign using the international station FR606. Firstly, we demonstrate the importance of a monitoring campaign. Secondly, we calculate median spectra and locate the turnover frequency for 3 pulsars (B0809+74, B1133+16, B1508+55).
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WANG, WEI. "DISTANCE INDICATORS OF GAMMA-RAY PULSARS." International Journal of Modern Physics: Conference Series 23 (January 2013): 289–94. http://dx.doi.org/10.1142/s2010194513011483.
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Distance measurements of gamma-ray pulsars are challenging questions in present pulsar studies. The Large Area Telescope (LAT) aboard the Fermi gamma-ray observatory discovered more than 100 gamma-ray pulsars including 24 new gamma-selected pulsars which nearly have no distance information. We study the relation between gamma-ray emission efficiency (η = Lγ/Ė) and pulsar parameters for young radio-selected gamma-ray pulsars with known distance information in the first gamma-ray pulsar catalog reported by Fermi/LAT. We have introduced three generation order parameters to describe gamma-ray emission properties of pulsars, and find the strong correlation of η – ζ3 a generation order parameter which reflects γ-ray photon generations in pair cascade processes induced by magnetic field absorption in pulsar magnetosphere. A good correlation of η – B LC the magnetic field at the light cylinder radius is also found. These correlations would be the distance indicators in gamma-ray pulsars to evaluate distances for gamma-selected pulsars. Distances of 25 gamma-selected pulsars are estimated, which could be tested by other distance measurement methods. Physical origin of the correlations may be also interesting for pulsar studies.
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Zhang, Xinyuan, Ping Shuai, Liangwei Huang, Shaolong Chen, and Lihong Xu. "Mission Overview and Initial Observation Results of the X-Ray Pulsar Navigation-I Satellite." International Journal of Aerospace Engineering 2017 (2017): 1–7. http://dx.doi.org/10.1155/2017/8561830.
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The newly launched X-ray pulsar navigation-I (XPNAV-1) is an experimental satellite of China that is designed for X-ray pulsar observation. This paper presents the initial observation results and aims to recover the Crab pulsar’s pulse profile to verify the X-ray instrument’s capability of observing pulsars in space. With the grazing-incidence focusing type instrument working at the soft X-ray band (0.5–10 keV), up to 162 segments of observations of the Crab pulsar are fulfilled, and more than 5 million X-ray events are recorded. Arrival times of photons are corrected to the solar system barycentre, and the 33 ms pulse period is sought out for Crab. Epoch folding of all the corrected photon times generates the refined pulse profile of Crab. The characteristic two-peak profile proves that the Crab pulsar has been clearly seen, so that the conclusion is made that XPNAV-1’s goal of being capable of observing pulsars is achieved.
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Wang, Wei. "The distance indicators in gamma-ray pulsars." Proceedings of the International Astronomical Union 8, S291 (August 2012): 546–48. http://dx.doi.org/10.1017/s1743921312024829.
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AbstractDistance measurements of gamma-ray pulsars are challenging questions in present pulsar studies. The Large Area Telescope (LAT) aboard the Fermi gamma-ray observatory discovered more than 100 gamma-ray pulsars, including 34 new gamma-selected pulsars which nearly have no distance information. We study the relation between gamma-ray emission efficiency (η=Lγ/Ė) and pulsar parameters, for young radio-selected gamma-ray pulsars with known distance information. We have introduced three generation order parameters to describe gamma-ray emission properties of pulsars, and find a strong correlation between η and ζ3, the generation order parameter which reflects γ-ray photon generations in pair cascade processes induced by magnetic field absorption in pulsar magnetosphere. A good correlation between η and BLC, the magnetic field at the light cylinder radius, is also found. These correlations can serve as distance indicators in gamma-ray pulsars, to evaluate distances for gamma-selected pulsars. Distances of 35 gamma-selected pulsars are estimated, which could be tested by other distance measurement methods. The physical origin of the correlations may be also interesting for pulsar studies.
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Haliki, Emir. "Broadcast network model of pulsars as beacons of extraterrestrial civilizations." International Journal of Astrobiology 18, no. 05 (December 11, 2018): 455–62. http://dx.doi.org/10.1017/s1473550418000459.
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AbstractAccording to the Kardashev scale, likely extraterrestrial civilizations above Type-I might use natural energy sources of the Universe, which is also true for transmitting their signals out to distances. A variety of studies have shown that radio pulsars are most likely candidates for this. First, the current study examined how the radio beams of pulsars scan across their environment. Later when the radio beams of pulsars have been modulated, a network model has been proposed on how many habitable planets possible to be home for other assumed advanced civilizations could be reached. It has been found that size of each pulsar's broadcast network depends on the inclination angle. If a civilization controls multiple pulsars, it could comb a considerable fraction of their own celestial sphere and pulsars share their signals in a decentralized fashion as in the mail servers. Moreover, it is briefly cited how beam-modulating mechanisms can be built and searched around pulsars.Highlights • It has been shown how pulsars would behave like beacons only when they have been used by modulating their radio signals.• It has also been indicated how each pulsar could constitute an increasingly growing broadcast network by sweeping geometries and in what way it would emerge as number of controlled pulsars increases.• It has been interpreted how a modulation mechanism could be established and searched under basic physical principles.
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Jones, Megan L., David L. Kaplan, Maura A. McLaughlin, and Duncan R. Lorimer. "Constraints on Undetected Long-period Binaries in the Known Pulsar Population." Astrophysical Journal 951, no. 1 (June 29, 2023): 20. http://dx.doi.org/10.3847/1538-4357/acd248.
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Abstract Although neutron star–black hole binaries have been identified through mergers detected in gravitational waves, a pulsar–black hole binary has yet to be detected. While short-period binaries are detectable due to a clear signal in the pulsar’s timing residuals, effects from a long-period binary could be masked by other timing effects, allowing them to go undetected. In particular, a long-period binary measured over a small subset of its orbital period could manifest via time derivatives of the spin frequency incompatible with isolated pulsar properties. We assess the possibility of pulsars having unknown companions in long-period binaries and put constraints on the range of binary properties that may remain undetected in current data, but that may be detectable with further observations. We find that for 35% of canonical pulsars with published higher-order derivatives, the precision of measurements is not enough to confidently reject binarity (period ≳2 kyr), and that a black hole binary companion could not be ruled out for a sample of pulsars without published constraints if the period is >1 kyr. While we find no convincing cases in the literature, we put more stringent limits on orbital period and longitude of periastron for the few pulsars with published higher-order frequency derivatives (n ≥ 3). We discuss the detectability of candidates and find that a sample pulsar in a 100 yr orbit could be detectable within 5–10 yr.
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Xie, J. T., J. B. Wang, N. Wang, R. Manchester, and G. Hobbs. "Modeling the Radial Distribution of Pulsars in the Galaxy." Astrophysical Journal Letters 963, no. 2 (March 1, 2024): L39. http://dx.doi.org/10.3847/2041-8213/ad2850.
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Abstract The Parkes 20 cm multibeam pulsar surveys have discovered nearly half of the known pulsars and revealed many distant pulsars with high dispersion measures. Using a sample of 1301 pulsars from these surveys, we have explored the spatial distribution and birth rate of normal pulsars. The pulsar distances used to calculate the pulsar surface density are estimated from the YMW16 electron-density model. When estimating the impact of the Galactic background radiation on our survey, we projected pulsars in the galaxy onto the Galactic plane, assuming that the flux density distribution of pulsars is uniform in all directions, and utilized the most up-to-date background temperature map. We also used an up-to-date version of the ATNF Pulsar Catalogue to model the distribution of pulsar flux densities at 1400 MHz. We derive an improved radial distribution for the pulsar surface density projected onto the Galactic plane, which has a maximum value at ∼4 kpc from the Galactic center. We also derive the local surface density and birth rate of pulsars, obtaining 47 ± 5 kpc−2 and ∼4.7 ± 0.5 kpc−2 Myr−1, respectively. For the total number of potentially detectable pulsars in the galaxy, we obtain (1.1 ± 0.2) × 104 and (1.1 ± 0.2)×105 before and after applying the Tauris & Manchester beaming correction model. The radial distribution function is used to estimate the proportion of pulsars in each spiral arm and the Galactic center.
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Dai, Shi, Simon Johnston, and George Hobbs. "Searching for pulsars in future radio continuum surveys." Proceedings of the International Astronomical Union 13, S337 (September 2017): 328–29. http://dx.doi.org/10.1017/s1743921317008833.
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AbstractRadio continuum surveys are equally sensitive to all pulsars, not affected by dispersion measure smearing, scattering or orbital modulation of spin periods, and therefore allow us to search for extreme pulsars, such as sub-millisecond pulsars, pulsar-black hole systems and pulsars in the Galactic Centre. As we move towards the Square Kilometre Array (SKA) era, searching for pulsars in continuum images will complement conventional pulsar searches, and make it possible to find extreme objects.
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McLaughlin, M. A., D. R. Lorimer, D. J. Champion, K. Xilouris, Z. Arzoumanian, D. C. Backer, J. M. Cordes, A. S. Fruchter, and A. N. Lommen. "New Pulsars from Arecibo Drift-Scan Searches." Symposium - International Astronomical Union 218 (2004): 127–28. http://dx.doi.org/10.1017/s0074180900180763.
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We report on new pulsars discovered in Arecibo drift-scan datA. Processing of 2200 deg2 of data has resulted in the detection of 41 known and 12 new pulsars. New pulsars include two millisecond pulsars, one solitary and one binary recycled pulsar, and one pulsar with very unusual pulse profile morphology and complex drifting subpulse behavior.
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Losovsky, Boris Ya. "The specifics of pulsar radio emission." Open Astronomy 31, no. 1 (January 1, 2022): 189–97. http://dx.doi.org/10.1515/astro-2022-0025.
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Abstract A characteristic property of pulsars is pulsed periodic radio emission, which has a high stability of periods. Despite the high stability of the emission periods of pulsars, monitoring the time of arrival of pulses (timing) shows the presence of different types of irregularities: variations of residual deviations, changes in the shape of the pulse, switching on and off of radio emission, and rotation discontinuities. Numerous observations of the radio emission of pulsars indicate that they are caused mainly by processes occurring in the pulsar’s magnetosphere. The special interest causes the observations of a pulsar in the Crab Nebula, performed, in particular, at Jodrell Bank and Pushchino Radio Astronomy Observatory of Lebedev Physical Institute. The connection between the scattering of radio pulses and the measure of the pulsar dispersion, which was established earlier in Pushchino together with Jodrell Bank, has been confirmed. The observed variations in the scattering of radio pulses and their partial correlation with the dispersion measure are explained by the eclipse of the pulsar by plasma clouds with electron density fluctuations significantly exceeding the corresponding fluctuations in the interstellar medium. The question of a possible connection between glitches, dispersion measure variations, radio pulses scattering, and gamma-ray flares is discussed.
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Lazarov, Andon D. "ISAR Imaging of a Rotating Asteroid Irradiated by Pulsar’s Electromagnetic Emission." Cybernetics and Information Technologies 19, no. 2 (June 1, 2019): 38–50. http://dx.doi.org/10.2478/cait-2019-0014.
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Abstract The aim of the present study is imaging of moving objects, asteroids illuminated by continuous coherent wideband pulsar’s signals. As pulsars are located on more than thousands of light years from Earth, objects crossing pulsars’ emission beams are considered as second sources of electromagnetic waves, carrying object’s shape and velocity information that can be extracted by application pulsar emission-based inverse aperture synthesis. Inverse Synthetic Aperture Radar (ISAR) scenario, geometry and kinematics are analytically described. Models of pulsar signals and ISAR signals secondary emitted by asteroids are developed. White Gaussian noise of high level is added to the deterministic reemitted signal in order to approach the real signal scenario. Two-Dimensional (2D) Fourier transform for image extraction is applied. Special iterative noise removing procedure is suggested for asteroid’s image enhancement. To verify mathematical model and imaging algorithms numerical experiments are carried out.
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Wielebinski, Richard. "Pulsar Studies at High Radio Frequencies." International Astronomical Union Colloquium 177 (2000): 205–10. http://dx.doi.org/10.1017/s0252921100059480.
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AbstractPulsars were discovered at 81.5 MHz and a lot of the studies of these exciting objects have been made up to the present time at radio frequencies below 1.6 GHz. The reasons for this concentration on the low radio frequency characteristics of pulsars is the fact that the spectra are very steep and that very few radio telescopes exist that are capable of efficient operations at high radio frequencies. The Effelsberg 100-m radio telescope of the Max-Planck-Institut fur Radioastronomie operates regularly up to the frequency of 50 GHz and was used to study pulsars at cm/mm-wavelengths. In the southern skies the Parkes 64-m telescope has been used to study pulsars up to 8.4 GHz. One pulsar has been detected at 87 GHz with the 30-m Pico Veleta telescope of IRAM.The studies of pulsars over the whole frequency range are of great importance because this is necessary for the elucidation of the mechanism that is responsible for the pulsar emission. The high polarization of pulsar radio emission at lower radio frequencies has supported the hypothesis of a coherent emission mechanism, which is required to generate the high luminosity. It has been known for some time that pulsars, unlike other radio sources, have a lower polarization at high radio frequencies. Recently a change of pulsar spectrum, a flattening or possibly an inversion has been observed at the highest radio frequencies. The inversion of the pulsar spectrum seems to coincide with a complete depolarization of some pulsars.Millisecond pulsars are less luminous than normal pulsars. This makes them even more difficult to detect at higher radio frequencies. Recent observations have extended the spectra of ten millisecond pulsars up to 4.85 GHz. The results imply that millisecond pulsars have properties very similar to normal (slow) pulsars, which suggests similar emission mechanisms.
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Baykal, Altan, and Ali Alpar. "Expectancy of large pulsar glitches." International Astronomical Union Colloquium 160 (1996): 105–6. http://dx.doi.org/10.1017/s0252921100041154.
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AbstractWe study the expectancy of large glitches (ΔΩ/Ω > 10−7) from a sample of 472 pulsars other than the Vela pulsar. The pulsars in this sample have exhibited 20 large glitches. In the sample the total observation span is larger than 2000 pulsar years. We assume that all pulsars experience such glitches, with rates that depend on the pulsars’ rotation rate and spin-down rate, and on the glitch model. The superfluid vortex unpinning model gives good agreement with the observed distribution of glitches and with the parameter values deduced for the Vela pulsar glitches.
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Guillemot, L. "Radio counterparts of gamma-ray pulsars." Proceedings of the International Astronomical Union 8, S291 (August 2012): 87–92. http://dx.doi.org/10.1017/s1743921312023241.
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AbstractObservations of pulsars with the Large Area Telescope (LAT) on the Fermi satellite have revolutionized our view of the gamma-ray pulsar population. For the first time, a large number of young gamma-ray pulsars have been discovered in blind searches of the LAT data. More generally, the LAT has discovered many new gamma-ray sources whose properties suggest that they are powered by unknown pulsars. Radio observations of gamma-ray sources have been key to the success of pulsar studies with the LAT. For example, radio observations of LAT-discovered pulsars provide constraints on the relative beaming fractions, which are crucial for pulsar population studies. Also, radio searches of LAT sources with no known counterparts have been very efficient, with the discovery of over forty millisecond pulsars. I review radio follow-up studies of LAT-discovered pulsars and unidentified sources, and discuss some of the implications of the results.
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Manchester, R. N. "Finding Pulsars at Parkes." Publications of the Astronomical Society of Australia 18, no. 1 (2001): 1–11. http://dx.doi.org/10.1071/as01002.
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AbstractThere are many reasons why it is important to increase the number of known pulsars. Not only do pulsar searches continue to improve statistical estimates of, for example, pulsar birthrates, lifetimes and the Galactic distribution, but they continue to turn up interesting and, in some cases, unique individual pulsars. In the early days of pulsar astronomy, the Molonglo radio telescope led the world as a pulsar detection instrument. However, the Parkes radio telescope, with its frequency versatility and greater tracking ablility, combined with sensitive receivers and powerful computer detection algorithms, is now the world’s most successful telescope at finding pulsars. The Parkes multibeam survey, begun in 1997, by itself will come close to doubling the number of known pulsars. Parkes has also been very successful at finding millisecond pulsars (MSPs), especially in globular clusters. One third of the known MSPs have been found in just one cluster, 47 Tucanae.
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Parent, E., H. Sewalls, P. C. C. Freire, T. Matheny, A. G. Lyne, B. B. P. Perera, F. Cardoso, et al. "Study of 72 Pulsars Discovered in the PALFA Survey: Timing Analysis, Glitch Activity, Emission Variability, and a Pulsar in an Eccentric Binary." Astrophysical Journal 924, no. 2 (January 1, 2022): 135. http://dx.doi.org/10.3847/1538-4357/ac375d.
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Abstract We present new discoveries and results from long-term timing of 72 pulsars discovered in the Pulsar Arecibo L-band Feed Array (PALFA) survey, including precise determination of astrometric and spin parameters, and flux density and scatter broadening measurements at 1.4 GHz. Notable discoveries include two young pulsars (characteristic ages ∼30 kyr) with no apparent supernova remnant associations, three mode-changing, 12 nulling and two intermittent pulsars. We detected eight glitches in five pulsars. Among them is PSR J1939+2609, an apparently old pulsar (characteristic age ∼1 Gy), and PSR J1954+2529, which likely belongs to a newly emerging class of binary pulsars. The latter is the only pulsar among the 72 that is clearly not isolated: a nonrecycled neutron star with a 931 ms spin period in an eccentric (e = 0.114) wide (P b = 82.7 days) orbit with a companion of undetermined nature having a minimum mass of ∼0.6 M ⊙. Since operations at Arecibo ceased in 2020 August, we give a final tally of PALFA sky coverage, and compare its 207 pulsar discoveries to the known population. On average, they are 50% more distant than other Galactic plane radio pulsars; PALFA millisecond pulsars (MSPs) have twice the dispersion measure per unit spin period than the known population of MSP in the plane. The four intermittent pulsars discovered by PALFA more than double the population of such objects, which should help to improve our understanding of pulsar magnetosphere physics. The statistics for these, rotating radio transients, and nulling pulsars suggest that there are many more of these objects in the Galaxy than was previously thought.
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McCulloch, P. M. "Closing Comments: Observations." International Astronomical Union Colloquium 128 (1992): 410–11. http://dx.doi.org/10.1017/s0002731600155659.
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During the course of this colloquium many papers have been presented on observational aspects of pulsar astronomy. In the following discussion I have not attempted to be comprehensive but have selected a number of areas of interest to me.The basic pulsar properties appear to be consistent over the full range of pulsar periods from 1 ms to 4s, implying that the emission mechanism is the same for all pulsars. There was a general consensus among the observers that the radio emission occurs low down in the pulsar's magnetosphere above the magnetic polar region.
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Taylor, J. H. "Binary Pulsars: Observations and Implications." Symposium - International Astronomical Union 125 (1987): 383–92. http://dx.doi.org/10.1017/s0074180900161005.
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The Galaxy contains a large number of neutron stars in gravitation-ally bound binary systems. Among the most fruitful of these to study have been the binary radio pulsars, of which seven are now known. Unlike the “accretion-powered” neutron stars located in mass-exchanging X-ray binary systems, the “rotation-powered” binary radio pulsars are found in dynamically simple, clean systems in which both stellar components have already completed their nuclear evolution, thereby shedding their atmospheres and most of their mass. In such circumstances the orbital parameters of the system and the rotational parameters of the pulsar can be determined with high precision from analysis of pulse timing data. These measurements constrain the component masses and yield an estimate of the pulsar's magnetic dipole moment, which turns out to be an essential parameter in understanding the evolution of the systems. In this paper I review the known facts concerning binary pulsars, and then briefly discuss some implications for our understanding of the place of neutron stars in stellar evolution.
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Itoh, Naoki, and Takemi Kotouda. "Velocity-Magnetic Field Correlation of Pulsars." International Astronomical Union Colloquium 160 (1996): 49–50. http://dx.doi.org/10.1017/s0252921100040999.
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Monte Carlo simulations of the evolution of pulsars are carried out in order to compare with the recent measurement of the pulsar transverse velocity by Lyne & Lorimer (1994). The new electron density distribution model of Taylor & Cordes (1993) is adopted in the simulation. Accurate pulsar orbits in the Galactic gravitational field are calculated. It is found that the constant magnetic field model of pulsars can account for the new measurement of the pulsar transverse velocity and the apparent correlation between the strength of the magnetic field and the transverse velocity of the pulsars. The present finding confirms the validity of the constant magnetic field model of pulsars and consolidates the idea that the apparent correlation between the strength of the magnetic field and the transverse velocity of the pulsars is caused by observational selection effects.
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Zhang, Jianwei, Chengmin Zhang, Di Li, Wuming Yang, Xianghan Cui, ChangQing Ye, Dehua Wang, Yiyan Yang, Shaolan Bi, and Xianfei Zhang. "Revisiting the Magnetic Field Distribution of Normal Pulsars: Implications for the Multiple Origins for Neutron Stars." Publications of the Astronomical Society of the Pacific 134, no. 1041 (November 1, 2022): 114201. http://dx.doi.org/10.1088/1538-3873/ac9ad8.
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Abstract In this study, we revisit the magnetic field (B-field) distribution of normal pulsars, motivated by the fact that the number of known pulsars has exceeded 3300. Here, we divided the normal pulsar samples into three subgroups by constant lines of characteristic age τ ch, i.e., young, middle-aged, and old pulsars. We note that τ ch is not used as the time indicator in this study; instead, it just served as cutting lines to divide the pulsar samples. Then, we applied several statistical tests, i.e., the Anderson–Darling, Shapiro–Wilk, Kolmogorov–Smirnov, and Mann–Whitney–Wilcoxon tests, to the selected normal pulsar samples (N = 1970) and to a data set of 32 neutron stars (NSs) in high-mass X-ray binaries (HMXBs) for comparison purposes. We obtained that (i) the conclusion on the characteristic B field (B ch) log-normal distribution for the normal pulsars by the previous studies is no longer appropriate, while only young pulsars (N = 24, τ ch < 15 kyr) follow a log-normal distribution, indicating that only the B ch of young pulsars is close to real B fields. (ii) In the directly measured B-field range of NS-HMXBs (∼1012–1013 G), the B ch of young pulsars (N = 15) and the real B fields of NS-HMXBs (N = 32) are inferred to be log-normal, and they are further verified to come from the same distribution, implying that there is no significant decay for real B fields, at least within the timescale of ∼10 Myr for normal pulsars. (iii) Statistically, young pulsars (N = 24) are inferred to be self-contained, suggesting that the initial spin period of pulsars is less than 515 ms. (iv) The B ch distributions of three normal pulsar subsamples are different, hinting at the existence of multiple origins for NSs.
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Octau, Franck, Grégory Desvignes, Ismaël Cognard, David Champion, Patrick Lazarus, David Smith, and Gilles Theureau. "Search for and study of pulsars with the Nançay Radio Telescope." Proceedings of the International Astronomical Union 13, S337 (September 2017): 386–87. http://dx.doi.org/10.1017/s1743921317009516.
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AbstractSince the discovery of the first pulsar in 1967, over 2500 pulsars have been discovered. Pulsars enable a broad range of studies: from the study of the properties of the interstellar medium and of pulsar magnetospheres to tests of gravity in the strong-field regime and the characterisation of the cosmological gravitation wave background. These reasons are the main drive for searching for more pulsars. A blind pulsar survey, named SPAN512, was initiated with the Nançay Radio Telescope in 2012. Conducted at 1.4 GHz with a sampling time of 64μs and 500-kHz frequency channels, SPAN512 was designed to search for fast and distant pulsars in the Galactic plane. Here we describe the current status of the survey and present the latest discovery, PSR J2055+3829, a 2.08-ms pulsar in a black widow system.
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Sekido, M., M. Imae, Y. Hanado, Y. Takahashi, Y. Koyama, Y. P. Ilyasov, A. E. Rodin, A. E. Avramenko, V. V. Oreshko, and B. A. Poperechenko. "Pulsar VLBI Experiment with Kashima(Japan)-Kalyazin(Russia) Baseline." International Astronomical Union Colloquium 160 (1996): 117–18. http://dx.doi.org/10.1017/s0252921100041208.
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Interferometric measurement of a pulsar is one of the most effective techniques to measure accurate source position. Precise measurement of pulsar position will give us the information of proper motion and parallax. Interferometric measurements on pulsars have been carried out, but the number of the pulsars whose position were measured is still smaller than the total number of pulsars. Because newly discovered pulsars are rapidly increasing due to recent intensive systematic surveys. We have started measuring their position by using VLBI between Kashima and Kalyazin. This report shows the results of the first experiment.
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Manchester, R. N., A. G. Lyne, F. Camilo, V. M. Kaspi, I. H. Stairs, F. Crawford, D. J. Morris, J. F. Bell, and N. D’Amico. "Timing the Parkes Multibeam Pulsars." International Astronomical Union Colloquium 177 (2000): 49–54. http://dx.doi.org/10.1017/s0252921100058991.
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AbstractMeasurement of accurate positions, pulse periods and period derivatives is an essential follow-up to any pulsar survey. The procedures being used to obtain timing parameters for the pulsars discovered in the Parkes multibeam pulsar survey are described. Completed solutions have been obtained so far for about 80 pulsars. They show that the survey is preferentially finding pulsars with higher than average surface dipole magnetic fields. Eight pulsars have been shown to be members of binary systems and some of the more interesting results relating to these are presented.
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Edwards, Russell T. "Discovery of Eight Recycled Pulsars – The Swinburne Intermediate Latitude Pulsar Survey." International Astronomical Union Colloquium 177 (2000): 33–34. http://dx.doi.org/10.1017/s0252921100058929.
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AbstractWe have conducted a pulsar survey of intermediate Galactic latitudes (5° < |b| < 15°) at 20 cm. The survey has been highly successful, discovering 58 new pulsars, eight of which are recycled, in only ∼14 days of integration time. One pulsar has a very narrow (2° FWHM) average profile for the pulsar’s period (278 ms). The six new recycled binary systems provide valuable information on the formation of white dwarf pulsar binaries. Two systems have massive white dwarf companions (> 0.57 M⊙and > 1.2 M⊙), while another has a low mass (∼ 0.2 M⊙) companion in a 23.3-d orbit, residing the well-known orbital period “gap”.
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Balakrishnan, Vishnu, David Champion, Ewan Barr, Michael Kramer, V. Venkatraman Krishnan, Ralph P. Eatough, Rahul Sengar, and Matthew Bailes. "Coherent search for binary pulsars across all Five Keplerian parameters in radio observations using the template-bank algorithm." Monthly Notices of the Royal Astronomical Society 511, no. 1 (December 24, 2021): 1265–84. http://dx.doi.org/10.1093/mnras/stab3746.
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ABSTRACT Relativistic binary pulsars orbiting white dwarfs and neutron stars have already provided excellent tests of gravity. However, despite observational efforts, a pulsar orbiting a black hole has remained elusive. One possible explanation is the extreme Doppler smearing caused by the pulsar’s orbital motion which changes its apparent spin frequency during an observation. The classical solution to this problem has been to assume a constant acceleration/jerk for the entire observation. However, this assumption breaks down when the observation samples a large fraction of the orbit. This limits the length of search observations, and hence their sensitivity. This provides a strong motivation to develop techniques that can find compact binaries in longer observations. Here, we present a GPU-based radio pulsar search pipeline that can perform a coherent search for binary pulsars by directly searching over three or five Keplerian parameters using the template-bank algorithm. We compare the sensitivity obtained from our pipeline with acceleration and jerk search pipelines for simulated pulsar-stellar-mass black hole binaries and observations of PSR J0737−3039A. We also discuss the computational feasibility of our pipeline for untargeted pulsar surveys and targeted searches. Our benchmarks indicate that circular orbit searches for P-BH binaries with spin-period $P{_\mathrm{{spin}}} \ge {20}\, \mathrm{m\, s}$ covering the 3–10 Tobs regime are feasible for the High Time Resolution Universe pulsar survey. Additionally, an elliptical orbit search in Globular clusters for $P{_\mathrm{{spin}}} \ge {20}\, \mathrm{m\, s}$ pulsars orbiting intermediate-mass black holes in the 5–10 Tobs regime is feasible for observations shorter than 2 h with an eccentricity limit of 0.1.
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Liu, Huaichan. "Theory and prospects of the pulsar study." Theoretical and Natural Science 9, no. 1 (November 13, 2023): 291–95. http://dx.doi.org/10.54254/2753-8818/9/20240787.
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After the pulsar was discovered by Hewish, the relevant research has become one of the hottest research fields. Astronomers have noticed that pulsars are of great academic significance in the field of basic scientific research. Due to the large mass and small radius of pulsars, their surface gravitational field is very strong. The existence of general relativity effects cannot be ignored, making pulsars a natural laboratory for the study of strong gravitational fields. the strong magnetic field provides an identical place for the study of radio radiation process, magnetospheric particle acceleration mechanism and high energy radiation. Pulsar as the product of supernova burst after the collapse of massive stars, it is very important for the study of supernova burst theory and understand the formation mechanism of pulsars. In terms of application research, due to the high stability of its rotation period, it has significant applicating prospect in measuring time standard and X-ray pulsar navigation system. The Pulsar has made great remarkable achievements in the past 50 years since its discovery. In short, the discovery and research significance of pulsars are highly anticipated.
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Titus, N., S. Toonen, V. A. McBride, B. W. Stappers, D. A. H. Buckley, and L. Levin. "The radio pulsar population of the Small Magellanic Cloud." Monthly Notices of the Royal Astronomical Society 494, no. 1 (March 9, 2020): 500–510. http://dx.doi.org/10.1093/mnras/staa662.
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ABSTRACT We model the present-day, observable, normal radio pulsar population of the Small Magellanic Cloud (SMC). The pulsars are generated with SeBa, a binary population synthesis code that evolves binaries and the constituent stellar objects up to remnant formation and beyond. We define radio pulsars by selecting neutron stars (NSs) that satisfy a selection of criteria defined by Galactic pulsars, and apply the detection thresholds of previous and future SMC pulsar surveys. The number of synthesized and recovered pulsars is exceptionally sensitive to the assumed star formation history and applied radio luminosity model, but is not affected extensively by the assumed common-envelope model, metallicity, and NS kick velocity distribution. We estimate that the SMC formed (1.6 ± 0.3) ×104 normal pulsars during the last 100 Myr. We study which pulsars could have been observed by the Parkes multibeam survey of the SMC, by applying the survey’s specific selection effects, and recover 4.0 ± 0.8 synthetic pulsars. This is in agreement with their five observed pulsars. We also apply a proposed MeerKAT configuration for the upcoming SMC survey, and predict that the MeerKAT survey will detect 17.2 ± 2.5 pulsars.
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Kawai, Nobuyuki, and Keisuke Tamura. "Recent X-ray Observations of Pulsar Nebulae." International Astronomical Union Colloquium 160 (1996): 367–74. http://dx.doi.org/10.1017/s0252921100041920.
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AbstractResults from the X-ray observations of pulsars with ASCA are presented. The surroundings of pulsars are investigated in detail taking advantage of ASCA’s unique capabilities; high spectral resolution and a high throughput over a wide energy range from 0.4 keV to 10 keV. The spectral characteristics of the nebulae of PSR B1509—58 and the Vela pulsar are spectroscopically investigated. A jet-like feature is found from PSR B1509—58. We detected diffuse emission sources in the vicinity of many pulsars. The high probability of finding such diffuse sources for many pulsars suggests that they exist universally for all the active pulsars, and that they are powered by the pulsars. SNR Kes 32 was imaged in X-ray for the first time. Its X-ray properties can be used to examine its association with the nearby pulsar PSR B1610—50.
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Lyne, A. G. "From Crab Pulsar to Magnetar?" Symposium - International Astronomical Union 218 (2004): 257–60. http://dx.doi.org/10.1017/s0074180900181100.
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We review the evolution of the Crab pulsar's rotational history during the past 35 years. Representing 3.7% of the pulsar's age, it is possible to estimate the likely development of the magnetic field and characteristic age much better than previously. The increasing magnetic field of this pulsar and of other young pulsars, most dramatically the Vela pulsar, raises the interesting possibility that these objects might evolve into magnetars. We discuss the observational case for such a proposal, but note that the origin of these field enhancements may be associated with glitch activity. However, it is understood no better than the origin of the magnetar fields, but may be one and the same.
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Kawai, N., Keisuke Tamura, and S. Shibata. "New Detection of X-Ray Pulsar Nebulae by ASCA." Symposium - International Astronomical Union 188 (1998): 265–66. http://dx.doi.org/10.1017/s0074180900115062.
Full textAbstract:
X-ray images of rotation-powered pulsars were examined using ASCA Gas Imaging Spectrometer (GIS). The data sets are taken from those available in the ASCA public archive in the performance verification (PV) phase and the guest-observing (GO) phase 1. We detected diffuse X-ray sources in the vicinity of nine pulsars including five new detections. There are large variety in their morphology and spatial size. The high probability of finding such diffuse sources around pulsars suggests that they exist universally for all the active pulsars, and that they are powered by the pulsars. We propose that the pulsar-powered nebula is a good probe to measure the otherwise invisible energy flux dissipating from a pulsar into the surrounding space.
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Desvignes, Gregory, Michael Kramer, Kejia Lee, Joeri van Leeuwen, Ingrid Stairs, Axel Jessner, Ismaël Cognard, Laura Kasian, Andrew Lyne, and Ben W. Stappers. "Radio emission from a pulsar’s magnetic pole revealed by general relativity." Science 365, no. 6457 (September 5, 2019): 1013–17. http://dx.doi.org/10.1126/science.aav7272.
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Binary pulsars are affected by general relativity (GR), causing the spin axis of each pulsar to precess. We present polarimetric radio observations of the pulsar PSR J1906+0746 that demonstrate the validity of the geometrical model of pulsar polarization. We reconstruct the (sky-projected) polarization emission map over the pulsar’s magnetic pole and predict the disappearance of the detectable emission by 2028. Two tests of GR are performed using this system, including the spin precession for strongly self-gravitating bodies. We constrain the relativistic treatment of the pulsar polarization model and measure the pulsar beaming fraction, with implications for the population of neutron stars and the expected rate of neutron star mergers.
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Lynch, Ryan S. "The Green Bank North Celestial Cap Pulsar Survey: Status and Future." Proceedings of the International Astronomical Union 13, S337 (September 2017): 13–16. http://dx.doi.org/10.1017/s174392131700953x.
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AbstractThe ongoing Green Bank North Celestial Cap pulsar survey is using the Green Bank Telescope to search for pulsars and transients over 85% of the celestial sphere. The survey has resulted in over 150 new pulsars, among which are high-precision millisecond pulsars, several binary pulsars, including at least one relativistic double neutron star system, nulling pulsars, and several nearby millisecond pulsars. We find no fast radio bursts in the survey to date. We present these results and discuss the future prospects for the survey.
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Yuan, Mao, Weiwei Zhu, Michael Kramer, Bo Peng, Jiguang Lu, Renxin Xu, Lijing Shao, et al. "High-altitude Magnetospheric Emissions from Two Pulsars." Astrophysical Journal 949, no. 2 (June 1, 2023): 115. http://dx.doi.org/10.3847/1538-4357/accb9a.
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Abstract We discover three new weak pulse components in two known pulsars, one in PSR J0304+1932 and two in PSR J1518+4904. These components are emitted about halfway between the main emission beam and the interpulse beam (beam from the opposite pole). They are separated from their main pulse peak by 99° ± 3° for J0304+1932 and 123.°6 ± 0.°7 (leading) and 93° ± 0.°4 (trailing) for J1518+4904. Their peak-intensity ratios to main pulses are ∼ 0.06% for J0304+1932 and ∼0.17% and ∼0.83% for J1518+4904. We also analyzed the flux fluctuations and profile variations of the emissions for the two pulsars. The results show correlations between the weak pulses and their main pulses, indicating that these emissions come from the same pole. We estimated the emission altitude of these weak pulses and derived a height of about half of the pulsar’s light-cylinder radius. These pulse components are a unique sample of high-altitude emissions from pulsars, and challenge the current pulsar emission models.
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Cameron, A. D., D. J. Champion, M. Bailes, V. Balakrishnan, E. D. Barr, C. G. Bassa, S. Bates, et al. "The High Time Resolution Universe Pulsar Survey – XVI. Discovery and timing of 40 pulsars from the southern Galactic plane." Monthly Notices of the Royal Astronomical Society 493, no. 1 (January 14, 2020): 1063–87. http://dx.doi.org/10.1093/mnras/staa039.
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ABSTRACT We present the results of processing an additional 44 per cent of the High Time Resolution Universe South Low Latitude (HTRU-S LowLat) pulsar survey, the most sensitive blind pulsar survey of the southern Galactic plane to date. Our partially coherent segmented acceleration search pipeline is designed to enable the discovery of pulsars in short, highly accelerated orbits, while our 72-min integration lengths will allow us to discover pulsars at the lower end of the pulsar luminosity distribution. We report the discovery of 40 pulsars, including three millisecond pulsar-white dwarf binary systems (PSRs J1537−5312, J1547−5709, and J1618−4624), a black-widow binary system (PSR J1745−23) and a candidate black-widow binary system (PSR J1727−2951), a glitching pulsar (PSR J1706−4434), an eclipsing binary pulsar with a 1.5-yr orbital period (PSR J1653−45), and a pair of long spin-period binary pulsars which display either nulling or intermittent behaviour (PSRs J1812−15 and J1831−04). We show that the total population of 100 pulsars discovered in the HTRU-S LowLat survey to date represents both an older and lower luminosity population, and indicates that we have yet to reach the bottom of the luminosity distribution function. We present evaluations of the performance of our search technique and of the overall yield of the survey, considering the 94 per cent of the survey which we have processed to date. We show that our pulsar yield falls below earlier predictions by approximately 25 per cent (especially in the case of millisecond pulsars), and discuss explanations for this discrepancy as well as future adaptations in RFI mitigation and searching techniques which may address these shortfalls.
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Yin, Qian, Yefan Li, Jiajie Li, Xin Zheng, and Ping Guo. "Pulsar-candidate Selection Using a Generative Adversarial Network and ResNeXt." Astrophysical Journal Supplement Series 264, no. 1 (December 13, 2022): 2. http://dx.doi.org/10.3847/1538-4365/ac9e54.
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Abstract Pulsar research has been a hot topic in the area of astronomy since they were first discovered. Pulsar discovery is fundamental for pulsar research. While pulsars are now visible across the electromagnetic spectrum, pulsar searches with modern radio telescopes are most promising. As the performance of astronomical instruments improves, the number of pulsar candidates detected by modern radio telescopes grows at an exponential rate. The application of artificial intelligence to the field of pulsar-candidate identification can automatically and efficiently address the identification problem with enormous amounts of data. However, there are still significant challenges in enhancing the accuracy of deep-learning-based pulsar-candidate identification. These problems result primarily from the fact that real pulsar data is scarce: the number of candidates that can be successfully identified as real pulsars (positive samples) is much smaller than those candidates that turn out to not be pulsars but instead radio-frequency interference or noise (negative samples). This makes it difficult to train a machine-learning model that can accurately select those candidates that are real pulsars. Therefore a novel pulsar-candidate identification framework is proposed that combines a deep convolutional generative adversarial neural network (DCGAN) and a deep aggregation residual network (ResNeXt). To overcome sample imbalance, the DCGAN is utilized to generate images that approximate real pulsars, while observed and generated candidates are employed together to train the pulsar-candidate identification model ResNeXt. Experiments on the HTRU Medlat data set back up the framework’s performance. The precision, recall, and F1-score of the framework are 100%.
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Malov, IF. "Two Types of Pulsar." Australian Journal of Physics 40, no. 6 (1987): 731. http://dx.doi.org/10.1071/ph870731.
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Some arguments for the subdivision of pulsars into two classes are considered: (i) short-period pulsars described by Smith's (1973) model and (ii) long-period pulsars for which the hollow-cone model is valid. The data for PSR 1937 + 21 (P = 1�56 ms) are in good agreement with this conception, this pulsar being a typical representative of the first group of pulsars.
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Yin, Dejiang, Li-yun Zhang, Lei Qian, Ralph P. Eatough, Baoda Li, Duncan R. Lorimer, Yinfeng Dai, et al. "FAST Discovery of Eight Isolated Millisecond Pulsars in NGC 6517." Astrophysical Journal Letters 969, no. 1 (June 24, 2024): L7. http://dx.doi.org/10.3847/2041-8213/ad534e.
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Abstract We present the discovery of eight isolated millisecond pulsars in globular cluster (GC) NGC 6517 using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The spin periods of those pulsars (namely PSR J1801–0857K to R, or NGC 6517K to R) are all shorter than 10 ms. With these discoveries, NGC 6517 is currently the GC with the most known pulsars in the FAST sky. The largest difference in dispersion measure of the pulsars in NGC 6517 is 11.2 cm−3 pc, the second among all GCs. The fraction of isolated pulsars in this GC (16 of 17, 94%) is consistent with previous studies indicating an overabundance of isolated pulsars in the densest GCs, especially in those undergoing cluster core collapse. Considering the FAST GC pulsar discoveries, we modeled the GC pulsar population using the empirical Bayesian method described by Turk and Lorimer with the recent counts. Using this approach, we find that the expected number of potential pulsars in GCs seems to be correlated with the central escape velocity; hence, the GCs Liller 1, NGC 6441, M54 (NGC 6715), and ω-Cen (NGC 5139) are expected to host the largest numbers of pulsars.
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Straal, S. M., L. Connor, and J. van Leeuwen. "A dispersion excess from pulsar wind nebulae and supernova remnants: Implications for pulsars and FRBs." Astronomy & Astrophysics 634 (February 2020): A105. http://dx.doi.org/10.1051/0004-6361/201833376.
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Young pulsars and the pulsar wind nebulae (PWNe) or supernova remnants (SNRs) that surround them are some of the most dynamic and high-powered environments in our Universe. With the rise of more sensitive observations, the number of pulsar-SNR and PWN associations (hereafter, SNR/PWN) has increased, yet we do not understand to which extent this environment influences the pulsars’ impulsive radio signals. We studied the dispersive contribution of SNRs and PWNe on Galactic pulsars, and considered their relevance to fast radio bursts (FRBs) such as FRB 121102. We investigated the dispersion measure (DM) contribution of SNRs and PWNe by comparing the measured DMs of Galactic pulsars in a SNR/PWN to the DM expected only from the intervening interstellar electrons, using the NE2001 model. We find that a two-σ DM contribution of SNRs and PWNe to the pulsar signal exists, amounting to 21.1 ± 10.6 pc cm−3. The control sample of pulsars unassociated with a SNR/PWN shows no excess. We model the SNR and PWN electron densities for each young pulsar in our sample and show that these indeed predict an excess of this magnitude. By extrapolating to the kind of fast-spinning, high magnetic field, young pulsars that may power FRBs, we show their SNR and PWN are capable of significantly contributing to the observed DM.
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McLaughlin, Maura, and James Cordes. "Gamma Ray Pulsar Luminosities." International Astronomical Union Colloquium 177 (2000): 359–62. http://dx.doi.org/10.1017/s0252921100059996.
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AbstractWe apply a likelihood analysis to pulsar detections, pulsar upper limits, and diffuse background measurements from the OSSE and EGRET instruments to constrain theγ-rays pulsar luminosity law. We find a steeper dependence on period and magnetic field at OSSE than at EGRET energies. We also find that pulsars may be an important component of the OSSE diffuse flux, but are most likely not important for EGRET. We estimate that as many as half of the unidentified EGRET sources may beγ-rays pulsars. Furthermore, we predict that GLAST will detect roughly 1000γ-rays pulsars, only 100 of which are currently known.
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Basu, A., B. Shaw, D. Antonopoulou, M. J. Keith, A. G. Lyne, M. B. Mickaliger, B. W. Stappers, P. Weltevrede, and C. A. Jordan. "The Jodrell bank glitch catalogue: 106 new rotational glitches in 70 pulsars." Monthly Notices of the Royal Astronomical Society 510, no. 3 (November 25, 2021): 4049–62. http://dx.doi.org/10.1093/mnras/stab3336.
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ABSTRACT 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 yr 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 per cent of these pulsars, the event we report is its only known glitch. For each new glitch, we provide measurements of its epoch, amplitude, and any detected changes to the spin-down rate of the star. Combining these new glitches with those listed in the Jodrell Bank glitch catalogue, we analyse a total sample of 543 glitches in 178 pulsars. We model the distribution of glitch amplitudes and spin-down rate changes using a mixture of two Gaussian components. We corroborate the known dependence of glitch rate and activity on pulsar spin-down rates and characteristic ages, and show that younger pulsars tend to exhibit larger glitches. Pulsars with spin-down rates between 10−14 and 10−10.5 Hz s−1 show a mean reversal of 1.8 per cent of their spin-down as a consequence of glitches. Our results are qualitatively consistent with the superfluid vortex unpinning models of pulsar glitches.
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Lynch, Ryan S. "The hunt for new pulsars with the Green Bank Telescope." Proceedings of the International Astronomical Union 8, S291 (August 2012): 41–46. http://dx.doi.org/10.1017/s1743921312023113.
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AbstractThe Green Bank Telescope (GBT) is the largest fully steerable radio telescope in the world and is one of our greatest tools for discovering and studying radio pulsars. Over the last decade, the GBT has successfully found over 100 new pulsars through large-area surveys. Here I discuss the two most recent—the GBT 350 MHz Drift-scan survey and the Green Bank North Celestial Cap survey. The primary science goal of both surveys is to find interesting individual pulsars, including young pulsars, rotating radio transients, exotic binary systems, and especially bright millisecond pulsars (MSPs) suitable for inclusion in Pulsar Timing Arrays, which are trying to directly detect gravitational waves. These two surveys have combined to discover 85 pulsars to date, among which are 14 MSPs and many unique and fascinating systems. I present highlights from these surveys and discuss future plans. I also discuss recent results from targeted GBT pulsar searches of globular clusters and Fermi sources.
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Gajjar, Vishal, Bhal Chandra Joshi, and Michael Kramer. "A survey of nulling pulsars using the Giant Meterwave Radio Telescope." Proceedings of the International Astronomical Union 8, S291 (August 2012): 385. http://dx.doi.org/10.1017/s1743921312024210.
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AbstractSeveral pulsars show sudden cessation of pulsed emission, which is known as pulsar nulling. In this paper, the nulling behaviour of 15 pulsars is presented. The nulling fraction of these pulsars, along with the degree of reduction in the pulse energy during the null phase are reported for these pulsars. A unique nulling behaviour is re- ported for PSR J1738-2330, which also showed quasi-periodic bursts. The distributions of lengths of the null and burst phases as well as the typical nulling time scales are estimated for eight strong pulsars. A comparison of the nulling time scales of four pulsars with similar nulling fraction suggests that the fraction of null pulses probably does not quantify the nulling behaviour of a pulsar in full detail. Analysis of these distributions also indicate that while the null and the burst pulses occur in groups, the transition from the null to burst phase and vice verse can be modeled by a Poisson point process.
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Pivovaroff, M. J., V. M. Kaspi, and E. V. Gotthelf. "ASCA observations of Galactic rotation-powered pulsars." International Astronomical Union Colloquium 177 (2000): 351–52. http://dx.doi.org/10.1017/s0252921100059960.
Full textAbstract:
AbstractWe have examined several archivalASCAobservations of Galactic radio pulsars, including PSRs B1046–58 and B1610–50. X-ray emission is detected from PSR B1046–58 with a significance of ∼5σ. We find no evidence for pulsations. We argue that the emission is from a spatially unresolved synchrotron nebula powered by the pulsar. The location of the X-ray counterpart within the 95% position error ellipse of the gamma-ray source 3EG J1048–5840 strengthens the claim of Kaspi et al. (2000) that PSR B1046–58 emitϒ-rays. X-ray emission from PSR B1610–50 is not detected. We use the X-ray luminosity upper limit to constrain the pulsar’s velocity ≲ 200km s−1, arguing against an association with the nearby supernova remnant Kes 32. Our results for these radio pulsars contradict previous reports of detections of large (tens of arc minutes) associated synchrotron nebulae.