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Journal articles on the topic 'Pulsar classes'
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1
MANCHESTER, R. N. "PULSAR SEARCHING AND TIMING." International Journal of Modern Physics D 22, no. 01 (2013): 1341007. http://dx.doi.org/10.1142/s0218271813410071.
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More than 2000 pulsars are now known. These pulsars may be divided into a number of different classes according to their period, period derivative, binary properties, emission characteristics and so on. Some important classes have relatively few members, e.g. double-neutron-star binary systems, and so continued searches for currently unknown pulsars are important. Such searches are being undertaken at various observatories around the world. Somewhat unexpectedly, the Fermi Gamma-ray Observatory, has proved to be an efficient pulsar detector, especially for millisecond pulsars (MSPs). The great stability of pulsar periods, especially for MSPs, leads to a number of important applications of pulsar timing. The detection and study of relativistic orbit perturbations in double-neutron-star systems has proved to be a powerful tool with measurements of the original binary pulsar, PSR B1913+16, and more recently the double pulsar, PSR J0737-3039A/B, showing that Einstein's general theory of relativity accurately describes these gravitational interactions. Direct detection of gravitational waves using pulsar timing is close to being achieved with the development of pulsar timing arrays (PTAs) in Europe, North America and Australia. Combining data from these PTAs to form the International Pulsar Timing Array (IPTA) will lead to improved significance of such a detection. Ultimately, detailed study of gravitational-wave sources will be possible using future large radio telescopes such as FAST and the SKA.
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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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Biggs, James D. "An Analysis of Pulsar Nulling Statistics." International Astronomical Union Colloquium 128 (1992): 265–70. http://dx.doi.org/10.1017/s0002731600155301.
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AbstractWe have sought correlations between the fraction of null pulses with other pulsar parameters for an ensemble of 72 pulsars using survival analysis methods. The strongest correlation was found between the null fraction and pulse period. Correlations were also found between other parameters that typically have strong dependencies on pulse period, and this tends to indicate that the null fraction increases with age as was first suggested by Ritchings (1976). However, no explicit correlation was found between pulsar characteristic age and null fraction. A significant anti-correlation was found between the angle subtended by the magnetic and rotation axes and the null fraction.Many of the pulsars presented here were found to null. In particular, all pulse profile classes in the scheme devised by Rankin (1983a) have members that null. Differences in the mean age of these pulsar classes are not very pronounced, and the influence of class on pulse nulling statistics is probably less than that suggested by Rankin (1986), but cannot entirely be ruled out. Also, there is considerable variation in the fraction of null pulses from pulsars within each class, but generally class St pulsars null the least. Of special note is the fact that two pulsars PSR 0833-45 and PSR 1556-44 apparently do not null. The upper limit for PSR 0833–45 is quite low; no nulls were detected in observations of over 120,000 pulses.The similarity of the nulling parameters of pulsars observed at two frequencies near 400 MHz and 843 MHz suggests that the pulsar emission mechanism is wide band over this frequency range.
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Ronchi, M., N. Rea, V. Graber, and N. Hurley-Walker. "Long-period Pulsars as Possible Outcomes of Supernova Fallback Accretion." Astrophysical Journal 934, no. 2 (2022): 184. http://dx.doi.org/10.3847/1538-4357/ac7cec.
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Abstract For about half a century, the radio pulsar population was observed to spin in the ∼0.002–12 s range, with different pulsar classes having a spin-period evolution that differs substantially depending on their magnetic fields or past accretion history. The recent detection of several slowly rotating pulsars has reopened the long-standing question of the exact physics, and observational biases, driving the upper bound of the period range of the pulsar population. In this work, we perform a parameter study of the spin-period evolution of pulsars interacting with supernova fallback matter and specifically look at the fallback accretion disk scenario. Depending on the initial conditions at formation, this evolution can differ substantially from the typical dipolar spin-down, resulting in pulsars that show spin periods longer than their coeval peers. By using general assumptions for the pulsar spin period and magnetic field at birth, initial fallback accretion rates, and including magnetic field decay, we find that very long spin periods (≳100 s) can be reached in the presence of strong, magnetar-like magnetic fields (≳1014 G) and moderate initial fallback accretion rates (∼1022−1027 g s−1). In addition, we study the cases of two recently discovered periodic radio sources, the pulsar PSR J0901–4046 (P = 75.9 s) and the radio transient GLEAM-X J162759.5–523504.3 (P = 1091 s), in light of our model. We conclude that the supernova fallback scenario could represent a viable channel to produce a population of long-period isolated pulsars that only recent observation campaigns are starting to unveil.
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Olmi, Barbara. "Evolved Pulsar Wind Nebulae." Universe 9, no. 9 (2023): 402. http://dx.doi.org/10.3390/universe9090402.
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Based on the expected population of core collapse supernova remnants and the huge number of detected pulsars in the Galaxy, still representing only a fraction of the real population, pulsar wind nebulae are likely to constitute one of the largest classes of extended Galactic sources in many energy bands. For simple evolutionary reasons, the majority of the population is made of evolved systems, whose detection and identification are complicated by their reduced luminosity, the possible lack of X-ray emission (that fades progressively away with the age of the pulsar), and by their modified morphology with respect to young systems. Nevertheless they have gained renewed attention in recent years, following the detection of misaligned X-ray tails protruding from an increasing number of nebulae created by fast moving pulsars, and of extended TeV halos surrounding aged systems. Both these features are clear signs of an efficient escape of particles, with energy close to the maximum acceleration limit of the pulsar. Here we discuss the properties of those evolved systems and what we have understood about the process of particle escape, and the formation of observed features.
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McLaughlin, M. A., D. R. Lorimer, A. G. Lyne, et al. "Two Radio Pulsars with Magnetar Fields." Symposium - International Astronomical Union 218 (2004): 255–56. http://dx.doi.org/10.1017/s0074180900181094.
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PSRs J1847–0130 and J1718–37184 have inferred surface dipole magnetic fields greater than those of any other known pulsars and well above the “quantum critical field” above which some models predict radio emission should not occur. These fields are similar to those of the anomalous X-ray pulsars (AXPs), which growing evidence suggests are “magnetars”. The lack of AXP-like X-ray emission from these radio pulsars (and the non-detection of radio emission from the AXPs) creates new challenges for understanding pulsar emission physics and the relationship between these classes of apparently young neutron stars.
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Malov, Igor’ F., Oleg I. Malov, and Valerij M. Malofeev. "The investigations of pulsar integral radio luminosities." International Astronomical Union Colloquium 160 (1996): 59–60. http://dx.doi.org/10.1017/s025292110004104x.
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We have calculated accurate integral radio luminositiesLfor 232 pulsars (Malov et al., 1994) using new average spectra of these objects. Histogram ofL-distribution is characterized by the mean value < logL>= 28.45 and by the mean-square-root deviationS= 1.0. We have analysed also data for short-periodic pulsars (P < 0.1 s) and long-periodic ones (P > 1 s) separately.The main goal of such separation was to test the hypothesis on two types of pulsars (Malov, 1987): i) for the first group of objects radiation is emitted from the neighbourhood of the light cylinder (r=rLC=cP/2π, P is the pulsar period), ii) for the second one emission is generated at distancesr≪rLC. In the second case the main mechanism of radiation is curvature radiation. For the first group of pulsars the radiation is connected with the cyclotron mechanism. The difference between two basic mechanisms and the locations of the emission generation regions must cause some differences in the observable features for these two classes of pulsars.
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Agazie, Gabriella, Akash Anumarlapudi, Anne M. Archibald, et al. "The NANOGrav 15 yr Data Set: Detector Characterization and Noise Budget." Astrophysical Journal Letters 951, no. 1 (2023): L10. http://dx.doi.org/10.3847/2041-8213/acda88.
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Abstract Pulsar timing arrays (PTAs) are galactic-scale gravitational wave (GW) detectors. Each individual arm, composed of a millisecond pulsar, a radio telescope, and a kiloparsecs-long path, differs in its properties but, in aggregate, can be used to extract low-frequency GW signals. We present a noise and sensitivity analysis to accompany the NANOGrav 15 yr data release and associated papers, along with an in-depth introduction to PTA noise models. As a first step in our analysis, we characterize each individual pulsar data set with three types of white-noise parameters and two red-noise parameters. These parameters, along with the timing model and, particularly, a piecewise-constant model for the time-variable dispersion measure, determine the sensitivity curve over the low-frequency GW band we are searching. We tabulate information for all of the pulsars in this data release and present some representative sensitivity curves. We then combine the individual pulsar sensitivities using a signal-to-noise ratio statistic to calculate the global sensitivity of the PTA to a stochastic background of GWs, obtaining a minimum noise characteristic strain of 7 × 10−15 at 5 nHz. A power-law-integrated analysis shows rough agreement with the amplitudes recovered in NANOGrav’s 15 yr GW background analysis. While our phenomenological noise model does not model all known physical effects explicitly, it provides an accurate characterization of the noise in the data while preserving sensitivity to multiple classes of GW signals.
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Safi-Harb, Samar. "Pulsar Wind Nebulae: On their growing diversity and association with highly magnetized neutron stars." Proceedings of the International Astronomical Union 8, S291 (2012): 251–56. http://dx.doi.org/10.1017/s1743921312023782.
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AbstractThe 1968 discovery of the Crab and Vela pulsars in their respective supernova remnants (SNRs) confirmed Baade and Zwicky's 1934 prediction that supernovae form neutron stars. Observations of Pulsar Wind Nebulae (PWNe), particularly with the Chandra X-ray Observatory, have in the past decade opened a new window to focus on the neutron stars' relativistic winds, study their interaction with their hosting SNRs, and find previously missed pulsars. While the Crab has been thought for decades to represent the prototype of PWNe, we now know of different classes of neutron stars and PWNe whose properties differ from the Crab. In this talk, I review the current status of neutron stars/PWNe-SNRs associations, and highlight the growing diversity of PWNe with an X-ray eye on their association with highly magnetized neutron stars. I conclude with an outlook to future high-energy studies.
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Shabanova, T. V. "Two classes of glitches in the pulsar B1822-09." Astronomy Reports 53, no. 5 (2009): 465–71. http://dx.doi.org/10.1134/s1063772909050102.
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Chowhan, Tanmay Tushar, Sushan Konar, and Sarmistha Banik. "The Magnetar Connection." Proceedings of the International Astronomical Union 16, S363 (2020): 322–23. http://dx.doi.org/10.1017/s1743921322000990.
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AbstractWe investigate the combined evolution of the dipolar surface magnetic field (Bs) and the spin-period (Ps) of known Magnetars and high magnetic field ( $${{\rm{B}}_s} \mathbin{\lower.3ex\hbox{$\buildrel>\over {\smash{\scriptstyle\sim}\vphantom{_x}}$}} {10^{13}}{\rm{G}}$$ ) radio pulsars. We study the long term behaviour of these objects assuming a simple Ohmic dissipation of the magnetic field. Identifying the regions (in the Ps-Bs plane) in which these neutron stars would likely move into, before crossing the death-line to enter the pulsar graveyard, we comment upon the possible connection between the Magnetars and other classes of neutron stars.
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ter Veen, S., P. Schellart, and H. Falcke. "FRATs: Searching for Fast Radio Transients in Real Time with LOFAR." Proceedings of the International Astronomical Union 7, S285 (2011): 411–13. http://dx.doi.org/10.1017/s1743921312001251.
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AbstractThe aim of the FRATs project is to detect single dispersed pulses from Fast Radio Transients with LOFAR in real time. The pulses can originate from pulsars, RRATS and other classes of known or unknown objects. To detect the pulses a trigger algorithm is run on an incoherent beam from the different LOFAR stations. The beam has a wide field of view and can be formed parallel to other observations. A precise localisation is achieved by storing and processing off-line the data from each dipole, giving all-sky coverage with a spatial resolution of the order of arc-seconds. The source is identified by making high-time-resolution images. The method has been tested by detecting and identifying a giant pulse from the Crab pulsar.
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Ay, Fahrettin, Gökhan İnce, Mustafa E. Kamaşak, and K. Yavuz Ekşi. "Classification of pulsars with Dirichlet process Gaussian mixture model." Monthly Notices of the Royal Astronomical Society 493, no. 1 (2020): 713–22. http://dx.doi.org/10.1093/mnras/staa154.
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ABSTRACT Young isolated neutron stars (INSs) most commonly manifest themselves as rotationally powered pulsars that involve conventional radio pulsars as well as gamma-ray pulsars and rotating radio transients. Some other young INS families manifest themselves as anomalous X-ray pulsars and soft gamma-ray repeaters that are commonly accepted as magnetars, i.e. magnetically powered neutron stars with decaying super-strong fields. Yet some other young INSs are identified as central compact objects and X-ray dim isolated neutron stars that are cooling objects powered by their thermal energy. Older pulsars, as a result of a previous long episode of accretion from a companion, manifest themselves as millisecond pulsars and more commonly appear in binary systems. We use Dirichlet process Gaussian mixture model (DPGMM), an unsupervised machine learning algorithm, for analysing the distribution of these pulsar families in the parameter space of period and period derivative. We compare the average values of the characteristic age, magnetic dipole field strength, surface temperature, and transverse velocity of all discovered clusters. We verify that DPGMM is robust and provide hints for inferring relations between different classes of pulsars. We discuss the implications of our findings for the magnetothermal spin evolution models and fallback discs.
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Jones, P. B. "The mechanism of coherent radio emission in some classes of pulsar." Monthly Notices of the Royal Astronomical Society 445, no. 1 (2014): 770–77. http://dx.doi.org/10.1093/mnras/stu1792.
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Burman, RR. "Relativistic Electron Injection into Axisymmetric Pulsar Magnetospheres." Australian Journal of Physics 39, no. 3 (1986): 421. http://dx.doi.org/10.1071/ph860421.
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A formalism introduced by Mestel, Robertson, Wang and Westfold for the description of electron outflow in axisymmetric pulsar magnetospheres, following injection with non-negligible speeds from the stellar surface, is extended here to incorporate emission with relativistic speeds. The formalism is then used to study the possible kinds of outflow. They are organized into five types, corresponding to differences in the emission speed and its variation with latitude, and into two classes according to whether or not they reach a region of rapid acceleration.
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Dyks, Jarosław, and Bronisław Rudak. "Elementary radiation patterns in pulsar profiles." Proceedings of the International Astronomical Union 8, S291 (2012): 301–6. http://dx.doi.org/10.1017/s1743921312023939.
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AbstractHighly symmetric double features observed in averaged pulsar profiles can be interpreted as the imprint of microscopic radiation beam characteristic of radiative mechanism operating in pulsar magnetosphere. The data put strong constraints on the possible radiation patterns, excluding entire classes of mechanisms, such as those based on parallel acceleration, or those that have complicated beams. Instead, several properties of double features (such as their symmetry, depth, shape, merging rate, large polarisation degree, and the association with bifurcated emission components) are consistent with the extraordinary-mode part of the curvature radiation beam. This shows that double notches are a clear signature of the curvature radiation process. We show that even with the emission process fixed, detailed modelling of double features remains a rather sophisticated and demanding task.
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Hu, Huanchen, and Paulo C. C. Freire. "Measuring the Lense–Thirring Precession and the Neutron Star Moment of Inertia with Pulsars." Universe 10, no. 4 (2024): 160. http://dx.doi.org/10.3390/universe10040160.
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Neutron stars (NSs) are compact objects that host the densest forms of matter in the observable universe, providing unique opportunities to study the behaviour of matter at extreme densities. While precision measurements of NS masses through pulsar timing have imposed effective constraints on the equation of state (EoS) of dense matter, accurately determining the radius or moment of inertia (MoI) of an NS remains a major challenge. This article presents a detailed review on measuring the Lense–Thirring (LT) precession effect in the orbit of binary pulsars, which would give access to the MoI of NSs and offer further constraints on the EoS. We discuss the suitability of certain classes of binary pulsars for measuring the LT precession from the perspective of binary star evolution and highlight five pulsars that exhibit properties promising to realise these goals in the near future. Finally, discoveries of compact binaries with shorter orbital periods hold the potential to greatly enhance measurements of the MoI of NSs. The MoI measurements of binary pulsars are pivotal to advancing our understanding of matter at supranuclear densities, as well as improving the precision of gravity tests, such as the orbital decay due to gravitational wave emission, and of tests of alternative gravity theories.
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Sathyaprakash, R., N. Rea, F. Coti Zelati, et al. "Long-term Study of the 2020 Magnetar-like Outburst of the Young Pulsar PSR J1846-0258 in Kes 75." Astrophysical Journal 976, no. 1 (2024): 56. http://dx.doi.org/10.3847/1538-4357/ad8226.
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Abstract Magnetar-like activity has been observed in a large variety of neutron stars. PSR J1846−0258 is a young 327 ms radio-quiet pulsar with a large rotational power (∼8 × 1036 erg s−1), and resides at the center of the supernova remnant Kes 75. It is one of the rare examples of a high-magnetic-field pulsar showing characteristics both of magnetars and radio pulsars, and can thus provide important clues on the differences in the emission mechanisms between these two classes. In 2006, PSR J1846−0258 was detected to undergo an outburst for the first time, accompanied by a large flux increase, millisecond X-ray bursts, significant spectral changes, and a large timing glitch. In the period between 2020 May and June, after 14 yr of quiescent stable emission, the source underwent a second magnetar-like outburst, which was followed up with several observations by Neutron Star Interior Composition Explorer, XMM-Newton, NuSTAR, and Swift. In this work, we report on the long-term timing and X-ray spectral properties of the source following the 2020 outburst, and place upper limits on any source activity at radio wavelengths. We demonstrate that the pulsed flux increased by a factor >6 during the outburst, followed by nontrivial variability in the spin-down rate. Our timing analysis shows that the spin frequency and its derivative are clearly affected by magnetospheric activity due to the outburst. We find hints for an oscillation in the frequency derivative with a timescale of 50–60 days, recovering later on to stable quiescence.
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Luo, Shengda, Alex P. Leung, C. Y. Hui, and K. L. Li. "An investigation on the factors affecting machine learning classifications in gamma-ray astronomy." Monthly Notices of the Royal Astronomical Society 492, no. 4 (2020): 5377–90. http://dx.doi.org/10.1093/mnras/staa166.
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ABSTRACT We have investigated a number of factors that can have significant impacts on the classification performance of gamma-ray sources detected by Fermi Large Area Telescope (LAT) with machine learning techniques. We show that a framework of automatic feature selection can construct a simple model with a small set of features that yields better performance over previous results. Secondly, because of the small sample size of the training/test sets of certain classes in gamma-ray, nested re-sampling and cross-validations are suggested for quantifying the statistical fluctuations of the quoted accuracy. We have also constructed a test set by cross-matching the identified active galactic nuclei (AGNs) and the pulsars (PSRs) in the Fermi-LAT 8-yr point source catalogue (4FGL) with those unidentified sources in the previous 3rd Fermi-LAT Source Catalog (3FGL). Using this cross-matched set, we show that some features used for building classification model with the identified source can suffer from the problem of covariate shift, which can be a result of various observational effects. This can possibly hamper the actual performance when one applies such model in classifying unidentified sources. Using our framework, both AGN/PSR and young pulsar (YNG)/millisecond pulsar (MSP) classifiers are automatically updated with the new features and the enlarged training samples in 4FGL catalogue incorporated. Using a two-layer model with these updated classifiers, we have selected 20 promising MSP candidates with confidence scores $\gt 98{{\ \rm per\ cent}}$ from the unidentified sources in 4FGL catalogue that can provide inputs for a multiwavelength identification campaign.
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Abe, S., J. Abhir, A. Abhishek, et al. "Prospects for a survey of the galactic plane with the Cherenkov Telescope Array." Journal of Cosmology and Astroparticle Physics 2024, no. 10 (2024): 081. http://dx.doi.org/10.1088/1475-7516/2024/10/081.
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Abstract Approximately one hundred sources of very-high-energy (VHE) gamma rays are known in the Milky Way, detected with a combination of targeted observations and surveys. A survey of the entire Galactic Plane in the energy range from a few tens of GeV to a few hundred TeV has been proposed as a Key Science Project for the upcoming Cherenkov Telescope Array Observatory (CTAO). This article presents the status of the studies towards the Galactic Plane Survey (GPS). We build and make publicly available a sky model that combines data from recent observations of known gamma-ray emitters with state-of-the-art physically-driven models of synthetic populations of the three main classes of established Galactic VHE sources (pulsar wind nebulae, young and interacting supernova remnants, and compact binary systems), as well as of interstellar emission from cosmic-ray interactions in the Milky Way. We also perform an optimisation of the observation strategy (pointing pattern and scheduling) based on recent estimations of the instrument performance. We use the improved sky model and observation strategy to simulate GPS data corresponding to a total observation time of 1620 hours spread over ten years. Data are then analysed using the methods and software tools under development for real data. Under our model assumptions and for the realisation considered, we show that the GPS has the potential to increase the number of known Galactic VHE emitters by almost a factor of five. This corresponds to the detection of more than two hundred pulsar wind nebulae and a few tens of supernova remnants at average integral fluxes one order of magnitude lower than in the existing sample above 1 TeV, therefore opening the possibility to perform unprecedented population studies. The GPS also has the potential to provide new VHE detections of binary systems and pulsars, to confirm the existence of a hypothetical population of gamma-ray pulsars with an additional TeV emission component, and to detect bright sources capable of accelerating particles to PeV energies (PeVatrons). Furthermore, the GPS will constitute a pathfinder for deeper follow-up observations of these source classes. Finally, we show that we can extract from GPS data an estimate of the contribution to diffuse emission from unresolved sources, and that there are good prospects of detecting interstellar emission and statistically distinguishing different scenarios. Thus, a survey of the entire Galactic plane carried out from both hemispheres with CTAO will ensure a transformational advance in our knowledge of Galactic VHE source populations and interstellar emission.
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Omerbashich, M. "Jupiter's primordial beat of superoutbursting stars." Journal of Geophysics 66, no. 1 (2024): 1–14. https://doi.org/10.5281/zenodo.14599072.
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The decadal global magnetoactivity evolution profile that precedes short-burst pulses in magnetar 4U 0142+61 and superhumps (superoutbursts) in dwarf novae now also emerges from mean least-squares spectra of >12 billion mission-integrated Galileo–Cassini–Juno 1996–2020 annual samplings of Jupiter ⪅8nT global magnetic field. For the first time in any planetary magnetosphere, the profile has revealed a ubiquitous primordial physical property: the presence of a high-power, pulsar-like global dynamic from temporally mapping hyperlow-frequency (<1μHz) systematic dynamics of Jovian magnetospheric signature in the solar wind (Rieger-resonance band of 385.8–64.3 nHz or ~0.3·10<sup>9</sup>–3·10<sup>9</sup> erg energetic perturbations). The signature served as a proxy of Jovian magnetoactivity expressed in mean least-squares-spectral magnitudes as a novel method for measuring relative field dynamics. The magnetoactivity impressed thus and entirely into the solar wind, and it encompassed the well-known, solar system-permeating ~154-day Rieger period and its first six harmonics. Statistical fidelity of the spectral peaks remained within a very high (Φ≫12) range of 10<sup>7</sup>–10<sup>5</sup>, reflecting the signature’s completeness and incessantness. The magnetoactivity upsurge from spectral means that maintained a stunning ~20% field variance (total annual energy budget) began reformatting the signature around 1999, gradually transforming it into the anomalous state by 2002, as supported by an increased anisotropic splitting of spectral peaks. By contrast, a comparison against 2005–2016 Cassini global samplings revealed a calm Saturnian magnetoactivity at a low ⪅1% field variance except for every ~7.1 yrs when it is ⪅5%, possibly due to orbital–tidal forcing. While this discovery of planetary pulsars as a new pulsar class calls for redefining pulsars to include failed stars, a global pulsation profile of the magnetar–novae type in a failed-star-turned-planet calls for beacon-orbiter missions to monitor Jupiter’s activity and its disruption capacity to solar system infrastructure. Shannon’s theory-based rigorous Gauss–Vaniček least-squares spectral analysis revolutionizes astrophysics by directly computing relative dynamics of global astrophysical fields and space physics by rigorously simulating completed orbits and fleet formations from a single spacecraft.
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Gallant, Yves A. "Galactic acceleration phenomena." Proceedings of the International Astronomical Union 2, no. 14 (2006): 91–92. http://dx.doi.org/10.1017/s1743921307009945.
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AbstractI review the current status of our observational knowledge of prominent classes of particle accelerators in the Galaxy, namely shell-type supernova remnants (SNRs) and pulsar wind nebulae. I highlight in particular the contribution of the recent improvement in sensitivity of very-high-energy (VHE) γ-ray observations, which are currently the most direct probe of particle acceleration in the Galaxy up to energies of several hundreds of TeV.Shell-type SNRs have long been proposed as sources of the Galactic cosmic rays. In recent years, X-ray observations have revealed very thin, non-thermal rims in many young SNRs, and I discuss the implications of these observations for magnetic field amplification and the maximum particle energy attainable by acceleration at the blast wave. I then review the current status of the evidence for accelerated nuclei in these objects, and summarise current uncertainties.The most numerous class of identified Galactic VHE gamma-ray sources is currently that of pulsar wind nebulae (PWNe). The emission from these objects is generally assumed to be predominantly leptonic, and I outline the new information provided by VHE gamma-ray observations beyond what could be inferred from observations of synchrotron emission.
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Savva, A. P., T. N. Telezhenko, and V. A. Suvorova. "Agroecological assessment of herbicides application on soybean crops in the central zone of Krasnodar Territory, Russia." South of Russia: ecology, development 18, no. 3 (2023): 170–78. http://dx.doi.org/10.18470/1992-1098-2023-3-170-178.
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Aim. Agroecological assessment of herbicides application on crops of soybean variety Arleta in the central zone of Krasnodar Territory.Materials and Methods. The experiments were carried out on the experimental field of the Federal Research Centre of Biological Plant Protection in 2022 according to the methodological recommendations for testing herbicides in agriculture. Herbicides from different chemical classes were used in the experiment. Efficiency was assessed by the difference in weed and soybean grain yield in comparison with the control. The comparative ecotoxicological load of preparations was carried out according to the ecological load and the coefficient of selectivity of action for the soil.Results. Weed species in the experiment were highly effectively suppressed by the herbicides Pulsar, BP, Pivot, VK and a mixture of Bazagran, BP + Zellek Super, and KE (88–98 %). When using Dual Gold, EC, Frontier Optima, EC and Proponit, and EC before the soybean shoots, the biological efficacy was lower. The preparations Pulsar, BP and Pivot, and VK, in comparison with other herbicides, had a lower level of environmental load and a high coefficient of selective action and meet modern safety requirements for the natural environment.Conclusions. In order to protect the environment when choosing herbicides for application on soybean crops in the central zone of Krasnodar Territory, they should be comprehensively selected taking into account the ecotoxicological load of the preparations.
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Hotan, A. W., W. van Straten, and R. N. Manchester. "psrchive and psrfits: An Open Approach to Radio Pulsar Data Storage and Analysis." Publications of the Astronomical Society of Australia 21, no. 3 (2004): 302–9. http://dx.doi.org/10.1071/as04022.
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AbstractA new set of software applications and libraries for use in the archival and analysis of pulsar astronomical data is introduced. Known collectively as the psrchive scheme, the code was developed in parallel with a new data storage format called psrfits, which is based on the Flexible Image Transport System (FITS). Both of these projects utilise a modular, object-oriented design philosophy. psrchive is an open source development environment that incorporates an extensive range of c++ object classes and pre-built command line and graphical utilities. These deal transparently and simultaneously with multiple data storage formats, thereby enhancing data portability and facilitating the adoption of the psrfits file format. Here, data are stored in a series of modular header–data units that provide flexibility and scope for future expansion. As it is based on FITS, various standard libraries and applications may be used for data input, output, and visualisation. Both psrchive and psrfits are made publicly available to the academic community in the hope that this will promote their widespread use and acceptance.
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Rodriguez, Antonio C., Kareem El-Badry, Pasi Hakala, et al. "A Link Between White Dwarf Pulsars and Polars: Multiwavelength Observations of the 9.36-minute Period Variable Gaia22ayj." Publications of the Astronomical Society of the Pacific 137, no. 2 (2025): 024202. https://doi.org/10.1088/1538-3873/adb0f1.
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Abstract White dwarfs (WDs) are the most abundant compact objects, and recent surveys have suggested that over a third of WDs in accreting binaries host a strong (B ≳ 1 MG) magnetic field. However, the origin and evolution of WD magnetism remain under debate. Two WD pulsars, AR Sco and J191213.72–441045.1 (J1912), have been found, which are non-accreting binaries hosting rapidly spinning (1.97 minutes and 5.30 minutes, respectively) magnetic WDs. The WD in AR Sco is slowing down on a P / P ̇ ≈ 5.6 × 1 0 6 yr timescale. It is believed they will eventually become polars, accreting systems in which a magnetic WD (B ≈ 10−240 MG) accretes from a Roche lobe-filling donor spinning in sync with the orbit (≳78 minutes). Here, we present multiwavelength data and analysis of Gaia22ayj, which outbursted in 2022 March. We find that Gaia22ayj is a magnetic accreting WD that is rapidly spinning down ( P / P ̇ = 6 . 1 − 0.2 + 0.3 × 1 0 6 yr) like WD pulsars, but shows clear evidence of accretion, like polars. Strong linear polarization (40%) is detected in Gaia22ayj; such high levels have only been seen in the WD pulsar AR Sco and demonstrate the WD is magnetic. High speed photometry reveals a 9.36 minutes period accompanying a high amplitude (∼2 mag) modulation. We associate this with a WD spin or spin–orbit beat period, not an orbital period as was previously suggested. Fast (60 s) optical spectroscopy reveals a broad “hump,” reminiscent of cyclotron emission in polars, between 4000 and 8000 Å. We find an X-ray luminosity of L X = 2 . 7 − 0.8 + 6.2 × 1 0 32 ergs − 1 in the 0.3–8 keV energy range, while two very large array radio campaigns resulted in a non-detection with a F r < 15.8 μJy 3σ upper limit. The shared properties of both WD pulsars and polars suggest that Gaia22ayj is a missing link between the two classes of magnetic WD binaries.
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Mahapatra, Premachand, Chiranjeeb Singha, Ayush Hazarika, and Prasanta Kumar Das. "Implications of Fermionic Dark Matter Interactions on Anisotropic Neutron Stars." Astrophysical Journal 985, no. 1 (2025): 74. https://doi.org/10.3847/1538-4357/adc918.
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Abstract The presence of dark matter (DM) within a neutron star (NS) can substantially influence the macroscopic properties. It is commonly assumed that the pressure inside an NS is isotropic, but in reality, pressure is locally anisotropic. This study explores the properties of anisotropic NS with a subfraction of DM (isotropic) trapped inside. Implementing a two-fluid formalism with three distinct classes of equation of state: AP3 (a realistic nucleon–nucleon interaction model), BSk22 (modeling atomic nuclei and neutron matter), and MPA1 (considering relativistic effects in nuclear interactions). The properties of NS, such as mass (M), radius (R), and dimensionless tidal deformability (Λ), for various DM-anisotropic configurations, have been rigorously tested against observational constraints. These constraints include data from the binary NS merger GW170817, NICER X-ray measurements, and pulsar mass–radius observations. We observe that with increasing DM subfraction, higher anisotropies could also satisfy the observational constraints for Yukawa coupling strength g = 10−5, which satisfies the DM self-interaction cross-section (σ) i.e 0.1–10 cm−2 g−1. Furthermore, increasing the coupling (g) between DM and its mediator leads to the formation of a core–halo structure, with a DM halo surrounding the baryonic matter. Specifically, for coupling values of g = 10−4, 10−3.7, and 10−3.5, we observe that the maximum radius (R max) decreases with increasing anisotropy, which contrasts with the behavior at g = 10−5 and in scenarios with no DM. Our analysis indicates that binary pulsar systems could potentially constrain the extent of admixed anisotropic NS or, more optimistically, provide evidence for the existence of DM-admixed anisotropic NS.
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Burrows, Adam, Tianshu Wang, David Vartanyan, and Matthew S. B. Coleman. "A Theory for Neutron Star and Black Hole Kicks and Induced Spins." Astrophysical Journal 963, no. 1 (2024): 63. http://dx.doi.org/10.3847/1538-4357/ad2353.
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Abstract Using 20 long-term 3D core-collapse supernova simulations, we find that lower compactness progenitors that explode quasi-spherically due to the short delay to explosion experience smaller neutron star recoil kicks in the ∼100−200 km s−1 range, while higher compactness progenitors that explode later and more aspherically leave neutron stars with kicks in the ∼300−1000 km s−1 range. In addition, we find that these two classes are correlated with the gravitational mass of the neutron star. This correlation suggests that the survival of binary neutron star systems may in part be due to their lower kick speeds. We also find a correlation between the kick and both the mass dipole of the ejecta and the explosion energy. Furthermore, one channel of black hole birth leaves masses of ∼10 M ⊙, is not accompanied by a neutrino-driven explosion, and experiences small kicks. A second channel is through a vigorous explosion that leaves behind a black hole with a mass of ∼3.0 M ⊙ kicked to high speeds. We find that the induced spins of nascent neutron stars range from seconds to ∼10 ms, but do not yet see a significant spin/kick correlation for pulsars. We suggest that if an initial spin biases the explosion direction, a spin/kick correlation would be a common byproduct of the neutrino mechanism of core-collapse supernovae. Finally, the induced spin in explosive black hole formation is likely large and in the collapsar range. This new 3D model suite provides a greatly expanded perspective and appears to explain some observed pulsar properties by default.
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Cordes, James M. "The Dynamic Radio Sky." Proceedings of the International Astronomical Union 7, S285 (2011): 49–54. http://dx.doi.org/10.1017/s1743921312000208.
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AbstractThe radio band is known to be rich in variable and transient sources, but exploration of it has only begun only in the last few years. Relevant time scales are as small as a fraction of a nanosecond (giant pulses from the Crab pulsar). Short transients (less than one second, say) have signal structure in the time-frequency plane at the very least because of interstellar plasma propagation effects (dispersion and scattering), and in some cases due to emission structure. Optimal detection requires handling a range of signal types in the time-frequency plane. Short bursts by necessity have very large effective radiation brightness temperatures associated with coherent emission processes. This paper surveys relevant source classes and summarizes propagation effects that must be considered to optimize detection in large-scale surveys. Scattering horizons for the interstellar and intergalactic media are defined, and the role of the radio band in panchromatic and multimessenger studies is discussed.
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Dong, Dillon Z., and Gregg Hallinan. "A Flat-spectrum Radio Transient at 122 Mpc Consistent with an Emerging Pulsar Wind Nebula." Astrophysical Journal 948, no. 2 (2023): 119. http://dx.doi.org/10.3847/1538-4357/acc06c.
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Abstract We report the discovery and follow-up observations of VT 1137–0337, an unusual radio transient found in our systematic search for extragalactic explosions in the Very Large Array Sky Survey. It is located in the brightest region of a dwarf starburst galaxy at a luminosity distance of 121.6 Mpc. Its 3 GHz luminosity is comparable to luminous radio supernovae associated with dense circumstellar interaction and relativistic outflows. However, its broadband radio spectrum—proportional to ν −0.35 over a range of ≳10× in frequency and fading at a rate of 5% yr–1—cannot be directly explained by the shock of a stellar explosion. Jets launched by various classes of accreting black holes also struggle to account for VT 1137–0337's combination of observational properties. Instead, we propose that VT 1137–0337 is a decades-old pulsar wind nebula that has recently emerged from within the free–free opacity of its surrounding supernova ejecta. If the nebula is powered by spin-down, the central neutron star should have a surface dipole field of ∼1013–1014 G and a present-day spin period of ∼10–100 ms. Alternatively, the nebula may be powered by the release of magnetic energy from a magnetar. Magnetar nebulae have been proposed to explain the persistent radio sources associated with the repeating fast radio bursts FRB 121102 and FRB 190520B. These FRB persistent sources have not previously been observed as transients but do bear a striking resemblance to VT 1137–0337 in their radio luminosity, spectral index, and host galaxy properties.
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Conceição, Silas Teodoro da. "A importância da ecologia segundo a perspectiva da Igreja Evangélica Assembleia de Deus do Ministério de Madureira." Caminhos de Diálogo 12, no. 20 (2024): 95–109. http://dx.doi.org/10.7213/cda12n20p95109.
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A necessidade de cuidar e proteger a natureza deve pulsar no coração de cada ser humano. Notam-se que as recomendações relacionadas ao zelo para com o meio ambiente parecem ser veiculadas com frequência pelas mídias sociais e meios de comunicação. Entretanto, o que lamentavelmente tem acontecido é que a grande maioria das pessoas permanece insensível. Este trabalho procura responder ao seguinte problema de pesquisa: como a Igreja Evangélica Assembleia de Deus do Ministério de Madureira, Rio de Janeiro (IEAD Madureira), atua em projetos e ações ecológicas no Brasil e em Burkina Faso? Foram pesquisadas questões relacionadas à proteção ao meio ambiente e à natureza, respectivamente. Outrossim, visando levantar informações acerca da importância da ecologia, segundo a perspectiva da IEAD Madureira, foi confeccionada uma pesquisa bibliográfica. A ecologia representa o estudo do ecossistema, que por sua vez, ao funcionar em perfeito estado, pode proporcionar benefícios essenciais para a saúde dos seres vivos de todo o planeta. Isso posto, verificam-se que as diversas classes sociais e as mais variadas denominações religiosas devem engajar-se no propósito de defender o ecossistema. A partir dessa iniciativa, os benefícios podem alcançar todos os seres vivos.
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Deil, Christoph. "The H.E.S.S. view of the Milky Way in TeV light." Proceedings of the International Astronomical Union 7, S284 (2011): 365–70. http://dx.doi.org/10.1017/s174392131200943x.
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AbstractSince 2003 the H.E.S.S. collaboration has been operating an array of four imaging Cherenkov telescopes in the Khomas Highlands of Namibia. H.E.S.S. can detect gamma rays in the energy range 100 GeV to 100 TeV, has a large field of view (5 degree), good angular resolution (0.1 degree), energy resolution (15%) and sensitivity (a 1% Crab flux point source is detected at 5 sigma significance in 25 h). About half of the available observing time has been spent on the Milky Way, either in scan mode or on individual sources, resulting in the detection of more than 60 Galactic TeV sources. In this talk the two most numerous source classes will be discussed, pulsar wind nebulae and supernova remnants. For the identification and understanding of the TeV emission seen by H.E.S.S. additional measurements of non-thermal emission, mainly in the radio, X-ray and lower-energy gamma-ray bands, are critical. Since August 2008 the Fermi Large Area Telescope has been scanning the whole sky in the energy range from 20 MeV to more than 300 GeV and has detected about 200 Galactic sources as well as diffuse emission from the Milky Way. This talk will give an overview of Galactic H.E.S.S. observations in the multi-wavelength context, with a focus on Fermi.
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Zhao, Yue, Craig O. Heinke, Haldan N. Cohn, et al. "A deep Chandra survey for faint X-ray sources in the Galactic globular cluster M30, and searches for optical and radio counterparts." Monthly Notices of the Royal Astronomical Society 499, no. 3 (2020): 3338–55. http://dx.doi.org/10.1093/mnras/staa2927.
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ABSTRACT We present a deep (∼330 ks) Chandra survey of the Galactic globular cluster M30 (NGC 7099). Combining the new Cycle 18 with the previous Cycle 3 observations we report a total of 10 new X-ray point sources within the 1${_{.}^{\prime}}$03 half-light radius, compiling an extended X-ray catalogue of a total of 23 sources. We incorporate imaging observations by the Hubble Space Telescope and the Karl G. Jansky Very Large Array from the MAVERIC survey to search for optical and radio counterparts to the new and old sources. Two X-ray sources are found to have a radio counterpart, including the known millisecond pulsar PSR J2140−2310A, the radio position of which also matches a previously reported faint optical counterpart which is slightly redder than the main sequence. We found optical counterparts to 18 of the 23 X-ray sources, identifying two new cataclysmic variables (CVs), five new CV candidates, two new candidates of RS CVn type of active binary (AB), and two new candidates of BY Dra type of AB. The remaining unclassified X-ray sources are likely background active galactic nuclei (AGNs), as their number is consistent with the expected number of AGN at our X-ray sensitivity. Finally, our analysis of radial profiles of different source classes suggests that bright CVs are more centrally distributed than faint CVs in M30, consistent with other core-collapsed globular clusters.
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Campana, Sergio, Luigi Stella, Sandro Mereghetti, and Domitilla de Martino. "A universal relation for the propeller mechanisms in magnetic rotating stars at different scales." Astronomy & Astrophysics 610 (February 2018): A46. http://dx.doi.org/10.1051/0004-6361/201730769.
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Accretion of matter onto a magnetic, rotating object can be strongly affected by the interaction with its magnetic field. This occurs in a variety of astrophysical settings involving young stellar objects, white dwarfs, and neutron stars. As matter is endowed with angular momentum, its inflow toward the star is often mediated by an accretion disc. The pressure of matter and that originating from the stellar magnetic field balance at the magnetospheric radius: at smaller distances the motion of matter is dominated by the magnetic field, and funnelling towards the magnetic poles ensues. However, if the star, and thus its magnetosphere, is fast spinning, most of the inflowing matter will be halted at the magnetospheric radius by centrifugal forces, resulting in a characteristic reduction of the accretion luminosity. The onset of this mechanism, called the propeller, has been widely adopted to interpret a distinctive knee in the decaying phase of the light curve of several transiently accreting X-ray pulsar systems. By comparing the observed luminosity at the knee for different classes of objects with the value predicted by accretion theory on the basis of the independently measured magnetic field, spin period, mass, and radius of the star, we disclose here a general relation for the onset of the propeller which spans about eight orders of magnitude in spin period and ten in magnetic moment. The parameter-dependence and normalisation constant that we determine are in agreement with basic accretion theory.
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Cordes, James. "Neutron Star Populations at the Millenium." International Astronomical Union Colloquium 177 (2000): 573–78. http://dx.doi.org/10.1017/s0252921100060656.
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AbstractIdentified neutron star (NS) classes evidently are determined by several intertwined features: kinematics of NS at their formation (spin and translational); magnetic field strength; and binary membership. I discuss the well-known classes of isolated and accreting NS while keeping in mind recent discoveries of magnetars, anomalous X-ray pulsars, and long-period radio pulsars. I summarize the results of several likelihood analyses on radio pulsars, which yield information on the velocity distribution, luminosity function, and birth rate of high-field radio pulsars. I review the evidence for the occurrence of momentum kicks at the time of NS birth. Discerning the relationship of the classic radio pulsars to the more exotic classes probably requires careful comparison of magnetic fields, kinematics and birthrates, a program for the next millenium. Exciting discoveries of classic pulsars will also be made: sub-millisecond pulsars, massive binaries in fast orbits and truly hyper-velocity pulsars that shed light on core-collapse processes in supernovae.
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Yorka, S. B. "Planets, Pulsars, And Poetry." International Astronomical Union Colloquium 105 (1990): 57–61. http://dx.doi.org/10.1017/s0252921100086401.
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For many of us in the United States, the majority of our students are in descriptive astronomy classes. And since these classes typically satisfy general education or core curriculum requirements that must be completed by all students, the students can range from those genuinely interested in astronomy to those who are taking the class because “it sounded less boring” than other options available. Whichever end of that spectrum the students occupy, many of them approach astronomy with quite a bit of anxiety because it is a science class. In student lore, a science class is a class that is by definition more difficult — perhaps verging on the impossible — than other classes, one that discusses totally foreign things in an arcane language and, above all, is a class that has no connection with anything else in the curriculum, except maybe another science class.
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Hui, Chung Yue, and Kwan Lok Li. "High Energy Radiation from Spider Pulsars." Galaxies 7, no. 4 (2019): 93. http://dx.doi.org/10.3390/galaxies7040093.
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The population of millisecond pulsars (MSPs) has been expanded considerably in the last decade. Not only is their number increasing, but also various classes of them have been revealed. Among different classes of MSPs, the behaviours of black widows and redbacks are particularly interesting. These systems consist of an MSP and a low-mass companion star in compact binaries with an orbital period of less than a day. In this article, we give an overview of the high energy nature of these two classes of MSPs. Updated catalogues of black widows and redbacks are presented and their X-ray/ γ -ray properties are reviewed. Besides the overview, using the most updated eight-year Fermi Large Area Telescope point source catalog, we have compared the γ -ray properties of these two MSP classes. The results suggest that the X-rays and γ -rays observed from these MSPs originate from different mechanisms. Lastly, we will also mention the future prospects of studying these spider pulsars with the novel methodologies as well as upcoming observing facilities.
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Kramer, Michael. "Pulsars & Magnetars." Proceedings of the International Astronomical Union 4, S259 (2008): 485–92. http://dx.doi.org/10.1017/s1743921309031159.
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AbstractThe largest magnetic field encountered in the observable Universe can be found in neutron stars, in particular in radio pulsars and magnetars. While recent discoveries have slowly started to blur the distinction between these two classes of highly magnetized neutron stars, it is possible that both types of sources are linked via an evolutionary sequence. Indications for this to be the case are obtained from observations of the spin-evolution of pulsars. It is found that most young pulsars are heading across the top of the main distribution of radio pulsars in the P–Ṗ-diagram, suggesting that at least a sub-class of young pulsars may evolve into objects with magnetar-like magnetic field strengths. Part of this evolutionary sequence could be represented by RRATs which appear to share at least in parts properties with both pulsars and magnetars.
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Pfeifer, Luzia Iara, Patrícia Gonçalves Rombe, and Jair Licio Ferreira Santos. "A influência socieconômica e cultural no brincar de pré-escolares." Paidéia (Ribeirão Preto) 19, no. 43 (2009): 249–55. http://dx.doi.org/10.1590/s0103-863x2009000200013.
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Considerando que o contexto econômico influencia o brincar de crianças, este trabalho teve por objetivo analisar as diferenças entre os brinquedos utilizados por crianças de duas diferentes classes socioeconômicas. Os dados foram coletados junto a 50 mães de crianças com idade entre três e seis anos, metade pertencentes à classe econômica A2 (Grupo 2), e a outra metade pertencente à classe econômica D (Grupo 1), segundo o Critério Brasil. Os resultados apontam para a existência de diferenças significativas quanto ao uso do computador (p=0,000), jogos de tabuleiro (p=0,023), jogos de armar (p=0,042) e jogo de botão (p=0,012), mais presentes no Grupo 2, e quanto ao uso de brinquedos de corda (p=0,005), brinquedos de sucata (p=0,000) e pular corda (p=0,021), mais presentes no Grupo 1. Os resultados sugerem certa influência socioeconômica no brincar de crianças pré-escolares.
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Bhat, A., and D. Malyshev. "Machine learning methods for constructing probabilistic Fermi-LAT catalogs." Astronomy & Astrophysics 660 (April 2022): A87. http://dx.doi.org/10.1051/0004-6361/202140766.
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Context. Classification of sources is one of the most important tasks in astronomy. Sources detected in one wavelength band, for example using gamma rays, may have several possible associations in other wavebands, or there may be no plausible association candidates. Aims. In this work we aim to determine the probabilistic classification of unassociated sources in the third Fermi Large Area Telescope (LAT) point source catalog (3FGL) and the fourth Fermi LAT data release 2 point source catalog (4FGL-DR2) using two classes – pulsars and active galactic nuclei (AGNs) – or three classes – pulsars, AGNs, and “OTHER” sources. Methods. We use several machine learning (ML) methods to determine a probabilistic classification of Fermi-LAT sources. We evaluate the dependence of results on the meta-parameters of the ML methods, such as the maximal depth of the trees in tree-based classification methods and the number of neurons in neural networks. Results. We determine a probabilistic classification of both associated and unassociated sources in the 3FGL and 4FGL-DR2 catalogs. We cross-check the accuracy by comparing the predicted classes of unassociated sources in 3FGL with their associations in 4FGL-DR2 for cases where such associations exist. We find that in the two-class case it is important to correct for the presence of OTHER sources among the unassociated ones in order to realistically estimate the number of pulsars and AGNs. We find that the three-class classification, despite different types of sources in the OTHER class, has a similar performance as the two-class classification in terms of reliability diagrams and, at the same time, it does not require adjustment due to presence of the OTHER sources among the unassociated sources. We show an example of the use of the probabilistic catalogs for population studies, which include associated and unassociated sources.
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Costa, Beatriz Rebêlo, Wynie Monique Pontes Nicácio, Cilmara Perrotti Santos, Anna Carolina de Campos Magano, and Samara Verçosa Lessa. "Reabsorção cervical externa: relato de caso." Brazilian Journal of Health Review 5, no. 4 (2022): 13693–708. http://dx.doi.org/10.34119/bjhrv5n4-142.
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A reabsorção cervical externa é considerada uma patologia inflamatória rara e de origem desconhecida caracterizada pela invasão da região cervical por tecido de granulação que progressivamente reabsorve tecido dentário até atingir o tecido pulpar. O presente estudo visou relatar um caso clinico do elemento dentário 23 acometido por reabsorção cervical externa, sua conduta terapêutica e a proservação no período de 4 meses de acordo com a aprovação das normas da Plataforma Brasil - CAAE nº. 14056919.5.0000.0039. O elemento 23 foi diagnosticado como reabsorção cervical externa classe 1 através de uma tomada radiográfica periapical, a opção terapêutica foi a cirurgia para a remoção do tecido de granulação invaginado no defeito radicular associada ao tratamento restaurador. Por se tratar de uma classe 1 de Heithersay (1999), não houve comprometimento pulpar. Para proteger indiretamente o complexo pulpar foi utilizado MTA HP repair (ANGELUS®) e como material restaurador, foi utilizado cimento de ionômero de vidro, sendo realizado acompanhamento clínico e radiográfico durante quatro meses. A reabsorção cervical externa representa um desafio clínico para a endodontia. O acompanhamento de pacientes que apresentam fatores predisponentes e o diagnóstico precoce são de grande importância para o sucesso do tratamento e manutenção do elemento dentário na boca e em função.
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Tauris, Thomas M. "Aspects of Mass Transfer in X-ray Binaries." International Astronomical Union Colloquium 160 (1996): 535–36. http://dx.doi.org/10.1017/s0252921100042317.
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The final stage of mass transfer in a compact binary system is very important for calculating the orbital parameters of the resulting system. We demonstrate how simple ‘bifurcation mechanisms‘ may lead to the existence of three classes of binary millisecond pulsars and a possible gap in the orbital period distribution. Recent discoveries indicate that such a gap could exist (see Fig. 2).Furthermore, we demonstrate that the expected theoretical correlation (e.g. Joss et al. 1987, Rappaport et al. 1995) between orbital periods and white dwarf companion masses does not seem to fit observations of wide-orbit lowmass binary pulsars (LMBPs). It is interesting to notice that the five LMBPs with Porb&gt; 100dall have companion masses which are lighter (at the ∼80 % confidence level on average) than expected from the theoretical core-mass period relation.
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Borghese, Alice. "Exploring the neutron star zoo: An observational review." Proceedings of the International Astronomical Union 16, S363 (2020): 51–60. http://dx.doi.org/10.1017/s1743921322000357.
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AbstractNeutron stars have shown diverse characteristics, leading us to classify them into different classes. In this proceeding, I review the observational properties of isolated neutron stars: from magnetars, the strongest magnets we know of, to central compact objects, the so-called anti-magnetars, stopping by the rotation-powered pulsars and X-ray dim isolated neutron stars. Finally, I highlight a few sources that have exhibited features straddling those of different groups, blurring the apparent diversity of the neutron star zoo.
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Martos, Josué, Michelle Furich, and Rafael Lund. "Associação de amálgama e resina composta em restauração direta de Classe II: longevidade e combinação estética?" Journal of Clinical Dentistry and Research 21, no. 3 (2024): 84–97. https://doi.org/10.14436/2447-911x.21.3.084-097.art.
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Objetivo: O objetivo deste relato de caso foi descrever o acompanhamento de 8 anos de uma paciente com 24 anos de idade, que procurou atendimento odontológico devido à sensibilidade no primeiro molar inferior direito. Relato de caso: Inicialmente, um exame clínico revelou um leve escurecimento na face mesial do dente #46 e o teste de sensibilidade pulpar revelou normalidade. A paciente apresentava uma lesão cariosa na face mesial do primeiro molar inferior, confirmada pelos exames clínico e radiográfico. Uma técnica para restaurar dentes posteriores com resina composta combinada com...
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Finke, Thorben, Michael Krämer, and Silvia Manconi. "Classification of Fermi-LAT sources with deep learning using energy and time spectra." Monthly Notices of the Royal Astronomical Society 507, no. 3 (2021): 4061–73. http://dx.doi.org/10.1093/mnras/stab2389.
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ABSTRACT Despite the growing number of gamma-ray sources detected by the Fermi-Large Area Telescope (LAT), about one-third of the sources in each survey remains of uncertain type. We present a new deep neural network approach for the classification of unidentified or unassociated gamma-ray sources in the last release of the Fermi-LAT catalogue (4FGL-DR2) obtained with 10 yr of data. In contrast to previous work, our method directly uses the measurements of the photon energy spectrum and time series as input for the classification, instead of specific, human-crafted features. Dense neural networks, and for the first time in the context of gamma-ray source classification recurrent neural networks, are studied in depth. We focus on the separation between extragalactic sources, i.e. active galactic nuclei, and Galactic pulsars, and on the further classification of pulsars into young and millisecond pulsars. Our neural network architectures provide powerful classifiers, with a performance that is comparable to previous analyses based on human-crafted features. Our benchmark neural network predicts that of the sources of uncertain type in the 4FGL-DR2 catalogue, 1050 are active galactic nuclei and 78 are Galactic pulsars, with both classes following the expected sky distribution and the clustering in the variability–curvature plane. We investigate the problem of sample selection bias by testing our architectures against a cross-match test data set using an older catalogue, and propose a feature selection algorithm using autoencoders. Our list of high-confidence candidate sources labelled by the neural networks provides a set of targets for further multiwavelength observations addressed to identify their nature. The deep neural network architectures we develop can be easily extended to include specific features, as well as multiwavelength data on the source photon energy and time spectra coming from different instruments.
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Dall'Osso, Simone. "The decaying magnetic field of magnetars: evidence and inference." Proceedings of the International Astronomical Union 8, S291 (2012): 115. http://dx.doi.org/10.1017/s1743921312023319.
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AbstractMagnetic field decay in neutron stars has been a long debated subject, since the early realization that radio pulsars were likely spinning neutron stars endowed with a 1E12 G magnetic dipole. This problem has however eluded all attempts of solution so far, mostly due to the scarcity of observational indications. Here I discuss the observational evidence for decay of the dipole magnetic field in magnetar candidates (Soft Gamma Repeaters and Anomalous X-ray Pulsars) and present a quantitative study of its main properties. I show that the decaying dipole does not have enough energy to power the persistent X-ray emission of magnetars. The latter must thus directly reveal the decay of an additional, stronger field component, presumably hidden in the interior of these neutron stars. Using existing models it is possible to characterize the salient properties of this internal field component and their implications for magnetar astrophysics. Finally, I sketch preliminary considerations on evolutionary links between magnetars and other classes of neutron stars with strong dipole field that do not show magnetar-like activity.
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Prokhorov, D. A., A. Moraghan, and J. Vink. "Search for gamma rays from SNe with a variable-size sliding-time-window analysis of the Fermi-LAT data." Monthly Notices of the Royal Astronomical Society 505, no. 1 (2021): 1413–21. http://dx.doi.org/10.1093/mnras/stab1313.
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ABSTRACT We present a systematic search for γ-ray emission from supernovae (SNe) in the Fermi Large Area Telescope (LAT) Pass 8 data. The sample of targets consists of 55,880 candidates from the Open Supernova Catalogue. We searched for γ rays from SNe by means of a variable-size sliding-time-window analysis. Our results confirm the presence of transient γ-ray emission from the sources of non-AGN classes, including transitional pulsars, solar flares, γ-ray bursts, novae, and the Crab Nebula, which are projected near some of these SN’s positions, and also strengthen support to the variable signal in the direction of SN iPTF14hls. The analysis is successful in finding both short (e.g. solar flares) and long (e.g. transitional pulsars) high flux states. Our search reveals two new γ-ray transient signals occurred in 2019 in the directions of optical transients that are SN candidates, AT2019bvr and AT2018iwp, with their flux increases within 6 months after the dates of SN’s discoveries. These signals are bright and their variability is at a higher statistical level than that of iPTF14hls. An exploration of archival multiwavelength observations towards their positions is necessary to establish their association with SNe or other classes of sources. Our analysis, in addition, shows a bright transient γ-ray signal at low Galactic latitudes in the direction of PSR J0205+6449. In addition, we report the results of an all-sky search for γ-ray transient sources. This provided two additional candidates to gamma-ray transient sources.
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Kaspi, Victoria M. "The Neutron Star Zoo." Proceedings of the International Astronomical Union 13, S337 (2017): 3–8. http://dx.doi.org/10.1017/s1743921317010390.
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AbstractSince their discovery 50 years ago, neutron stars have continually astonished. From the first-discovered radio pulsars to the powerful “magnetars” that emit sudden bursts of X-rays and γ-rays, from the so-called Isolated Neutron Stars to Central Compact Objects, observational manifestations of neutron stars are surprisingly varied, with most properties totally unpredicted. The challenge is to cement an overarching physical theory of neutron stars and their birth properties that can explain this great diversity. Here I briefly survey the disparate neutron star classes, describe their properties, highlight recent results, and describe efforts at “grand unification” of this wealth of observational phenomena.
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Thompson, Christopher. "Magnetars." International Astronomical Union Colloquium 177 (2000): 669–80. http://dx.doi.org/10.1017/s0252921100060966.
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AbstractI summarize recent observational and theoretical advances in the understanding of the Soft Gamma Repeaters and the Anomalous X-ray Pulsars. Several direct physical arguments point to very strong magnetic fields (B&gt; 10BQED= 4.4 × 1014 G) in SGR outbursts. The connection between these two classes of neutron stars is examined. Their persistent X-ray emission and spindown behavior are interpreted in the magnetar model, where a decaying magnetic field dominates all other sources of energy for radiative and particle emission. The response of a magnetic field to the violent motions in a supernova core is also examined, with a focus on mechanisms that may impart unusually large kicks.
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Wijers, Ralph A. M. J. "Diagnosing Structure and Evolution of Clusters with Neutron Star Binaries." Symposium - International Astronomical Union 174 (1996): 203–12. http://dx.doi.org/10.1017/s0074180900001546.
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A key problem in using binaries as a tool for diagnosing cluster evolution is that the tool itself is not very well understood. The theory of binary evolution, despite real successes that can be exploited, has serious problems in many areas relevant to cluster evolution. At least as important but often neglected are connective problems, which arise when theoretical model binaries need to be related to observed classes of object, which often requires poorly understood parts of their physics which can be quite irrelevant to their bulk properties. I shall discuss these issues in general briefly, and then illustrate them with the specific example of X-ray binaries and millisecond pulsars.
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Malaver, Manuel, and Rajan Iyer. "Some new relativistic charged models with anisotropic pressure." Physics & Astronomy International Journal 7, no. 4 (2023): 240–49. http://dx.doi.org/10.15406/paij.2023.07.00315.
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In this paper, we found new classes of solutions to the Einstein-Maxwell field equations with matter anisotropic distribution incorporating a particular form of electric field intensity within the framework of general relativity. We use a metric potential or ansatz that depends on an adjustable parametern in order to get the new solutions. We generated new models of compact stars with n=1 and n=2. Graphical analysis allows us to conclude that the new models satisfy all the physical characteristics for astrophysical objects and can be very useful in the study and description of compact structures. We obtained models consistent with the pulsars PSR J1311-3430 and PSR J0952–0607.