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Journal articles on the topic 'X-ray pulsars'
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1
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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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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Becker, W. "X-ray Emission Characteristics of Pulsars." Symposium - International Astronomical Union 195 (2000): 49–60. http://dx.doi.org/10.1017/s0074180900162771.
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Recent X-ray observatories such as ROSAT, ASCA, RXTE, BeppoSAX, and Chandra have achieved important progress in neutron star and pulsar astronomy. The identification of Geminga as a rotation-powered pulsar, the discovery of X-ray emission from millisecond pulsars, and the identification of cooling neutron stars are only a few of the fascinating results. In the following, I will give a brief review on the X-ray emission properties of rotation-powered pulsars and their wind nebulae.
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Wang, H. G., G. J. Qiao, and R. X. Xu. "Phase Offset of Rotation-Powered X-ray Pulsars." Symposium - International Astronomical Union 214 (2003): 224–26. http://dx.doi.org/10.1017/s0074180900194458.
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Combing the data of all the 10 rotation-powered pulsars that have measurements of relative phase of radio and X-ray pulses, we report here the behavior of radio/X-ray phase offset. We find that the radio/X-ray offset of normal pulsars does not show the trend of increase with increasing pulsar period as the radio/gamma-ray offset exhibits. The offset of millisecond pulsars is generally much less than that of the normal pulsars. Such phenomenon should also be taken into account by the high energy models for pulsars.
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Liang, Hao, Yafeng Zhan, and Chaowei Duan. "A Bayesian Classifier for X-Ray Pulsars Recognition." International Journal of Aerospace Engineering 2016 (2016): 1–10. http://dx.doi.org/10.1155/2016/1746925.
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Recognition for X-ray pulsars is important for the problem of spacecraft’s attitude determination by X-ray Pulsar Navigation (XPNAV). By using the nonhomogeneous Poisson model of the received photons and the minimum recognition error criterion, a classifier based on the Bayesian theorem is proposed. For X-ray pulsars recognition with unknown Doppler frequency and initial phase, the features of every X-ray pulsar are extracted and the unknown parameters are estimated using the Maximum Likelihood (ML) method. Besides that, a method to recognize unknown X-ray pulsars or X-ray disturbances is proposed. Simulation results certificate the validity of the proposed Bayesian classifier.
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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.
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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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Pivovaroff, M. J., V. M. Kaspi, and F. Camilo. "X-ray observations of the high magnetic field radio pulsar PSR J1814–1744." International Astronomical Union Colloquium 177 (2000): 349–50. http://dx.doi.org/10.1017/s0252921100059959.
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AbstractWe present X-ray observations of PSR J1814–1744, a 4 s radio pulsar with inferred surface dipole magnetic field strength 5.5 × 1013G recently discovered in the on-going Parkes multibeam survey. This pulsar’s spin parameters are very similar to those of anomalous X-ray pulsars (AXPs). X-ray emission is not detected from the position of the radio pulsar in observations withROSATandASCA. The derived upper flux limit implies an X-ray luminosity significantly smaller than those of all known AXPs. These results argue that magnetar mechanism invoked to explain X-ray emission from AXPs must depend on more than merely the inferred surface magnetic field strength as estimated fromPand.
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Aoki, Yu, Takahiro Enomoto, Yoichi Yatsu, Nobuyuki Kawai, Takeshi Nakamori, Jun Kataoka, and P. Saz Parkinson. "Searching for X-ray counterparts of Fermi Gamma-ray pulsars in Suzaku observations." Proceedings of the International Astronomical Union 7, S279 (April 2011): 317–18. http://dx.doi.org/10.1017/s1743921312013130.
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AbstractWe report the Suzaku follow-up observations of the Gamma-ray pulsars, 1FGL J0614,13328, J1044.55737, J1741.82101, and J1813.31246, which were discovered by the Fermi Gamma-ray observatory. Analysing Suzaku/XIS data, we detected X-ray counterparts of these pulsars in the Fermi error circle and interpreted their spectra with absorbed power-law functions. These results indicate that the origin of these X-ray sources is non-thermal emission from the pulsars or from Pulsar Wind Nebulae (PWNe) surrounding them. Moreover we found that J1741.82101 exhibits a peculiar profile: spin-down luminosity vs flux ratio between X- and gamma-rays is unusually large compared to usual radio pulsars.
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ANKAY, AŞKIN, SERKAN ŞAHIN, GÖKÇE KARANFIL, and EFE YAZGAN. "EARLY PHASES OF DIFFERENT TYPES OF ISOLATED NEUTRON STAR." International Journal of Modern Physics D 14, no. 06 (June 2005): 1075–82. http://dx.doi.org/10.1142/s0218271805006535.
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Two Galactic isolated strong X-ray pulsars seem to be in the densest environments compared to other types of Galactic pulsar. X-ray pulsar J1846-0258 can be in an early phase of anomalous X-ray pulsars and soft gamma repeaters if its average braking index is ~1.8–2.0. X-ray pulsar J1811-1925 must have a very large average braking index (~11) if this pulsar was formed by SN 386AD. This X-ray pulsar can be in an early phase of the evolution of the radio pulsars located in the region P ~ 50–150 ms and Ṗ ~ 10-14–10-16 ss -1 of the P–Ṗ diagram. X-ray/radio pulsar J0540-69 seems to be evolving in the direction to the dim isolated thermal neutron star region on the P–Ṗ diagram. Possible progenitors of different types of neutron star are also discussed.
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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.
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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.
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Becker, Werner. "X-ray emission characteristics of pulsars and their nebulae." International Astronomical Union Colloquium 177 (2000): 321–26. http://dx.doi.org/10.1017/s025292110005987x.
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AbstractRecent X-ray observatories like ROSAT, ASCA, RXTE, BeppoSAX and Chandra have achieved important progress in neutron star and pulsar astronomy. The identification of Geminga as a rotation-powered pulsar, the discovery of X-ray emission from millisecond pulsars and the identification of cooling neutron stars are only few of the fascinating results. In the following I will give a brief review on the X-ray emission properties of rotation-powered pulsars and their wind nebulae.
12
Gotthelf, E. V., G. Vasisht, B. Gaensler, and K. Torii. "Discovery of a supernova remnant with a central X-ray source: AX J184453.3-025642 in G 29.6+0.1." International Astronomical Union Colloquium 177 (2000): 707–8. http://dx.doi.org/10.1017/s0252921100061030.
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AbstractWe report preliminary results from our follow-up X-ray and radio study of AX J1845–0258, the 7-s X-ray pulsar whose characteristics are similar to those found for the anomalous X-ray pulsars (AXPs). We have located a faint X-ray source within the pulsar’s error circle implying a dramatic reduction in flux, however, the source is too faint to provide a confirmation of the expected pulsations. Centered on this X-ray source is a newly discovered supernova remnant, evident in both radio and X-ray emission. This is the third example of an AXP-like object associated with a supernova remnant.
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Brazier, K. T. S. "The X-ray synchrotron nebula around PSR 1509-58." International Astronomical Union Colloquium 160 (1996): 351–52. http://dx.doi.org/10.1017/s0252921100041853.
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PSR 1509-58 is one of the youngest and most powerful pulsars known and is visible not only in soft X-rays, but in gamma-rays. Observations of its supernova remnant (MSH 15-52) offer a rare chance to study such a young pulsar and to explore its surroundings, which in X-rays include the pulsar’s 10×6 arcmin X-ray synchrotron nebula and the peculiar, filamentary optical nebula, RCW 89, that sits on the limb of MSH 15-52 (Seward & Harnden 1982, Seward et al. 1983). This paper will concentrate on the morphology of the synchrotron nebula.
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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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Malov, I. F. "On the Mechanism of X-ray Emission from Radio Pulsars." Symposium - International Astronomical Union 218 (2004): 387–88. http://dx.doi.org/10.1017/s007418090018146x.
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The correlations between the luminosities of radio pulsars in various wavebands and the magnetic fields at the light cylinder suggest that the observed emission is generated in outer layers of the pulsar magnetospheres by the synchrotron mechanism. The formula for calculating the X-ray luminosity LX of radio pulsars is derived in the framework of the synchrotron model. It is shown that LX depends strongly on the parameter This raises the possibility of predicting the detection of X-ray emission from more than a hundred known radio pulsars.
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Gotthelf, E. V., and G. Vasisht. "A New View on Young Pulsars in Supernova Remnants: Slow, Radio-quiet & X-ray Bright." International Astronomical Union Colloquium 177 (2000): 699–702. http://dx.doi.org/10.1017/s0252921100061017.
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AbstractWe propose a simple explanation for the apparent dearth of radio pulsars associated with young supernova remnants (SNRs). Recent X-ray observations of young remnants have revealed slowly rotating (P∼ 10s) central pulsars with pulsed emission above 2 keV, lacking in detectable radio emission. Some of these objects apparently have enormous magnetic fields, evolving in a manner distinct from the Crab pulsar. We argue that these X-ray pulsars can account for a substantial fraction of the long sought after neutron stars in SNRs and that Crab-like pulsars are perhaps the rarer, but more highly visible example of these stellar embers. Magnetic field decay likely accounts for their high X-ray luminosity, which cannot be explained as rotational energy loss, as for the Crab-like pulsars. We suggest that the natal magnetic field strength of these objects control their subsequent evolution. There are currently almost a dozen slow X-ray pulsars associated with young SNRs. Remarkably, these objects, taken together, represent at least half of the confirmed pulsars in supernova remnants. This being the case, these pulsars must be the progenitors of a vast population of previously unrecognized neutron stars.
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Chen, Qiang, Yong Zhao, and Lixia Yan. "X-ray Pulsar Signal Denoising Based on Variational Mode Decomposition." Entropy 23, no. 9 (September 8, 2021): 1181. http://dx.doi.org/10.3390/e23091181.
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Pulsars, especially X-ray pulsars detectable for small-size detectors, are highly accurate natural clocks suggesting potential applications such as interplanetary navigation control. Due to various complex cosmic background noise, the original pulsar signals, namely photon sequences, observed by detectors have low signal-to-noise ratios (SNRs) that obstruct the practical uses. This paper presents the pulsar denoising strategy developed based on the variational mode decomposition (VMD) approach. It is actually the initial work of our interplanetary navigation control research. The original pulsar signals are decomposed into intrinsic mode functions (IMFs) via VMD, by which the Gaussian noise contaminating the pulsar signals can be attenuated because of the filtering effect during signal decomposition and reconstruction. Comparison experiments based on both simulation and HEASARC-archived X-ray pulsar signals are carried out to validate the effectiveness of the proposed pulsar denoising strategy.
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Yang, Bo, and Ling Ke Liu. "Deep Space Navigation Using X-Ray Pulsars." Advanced Materials Research 433-440 (January 2012): 6325–31. http://dx.doi.org/10.4028/www.scientific.net/amr.433-440.6325.
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This paper presents a novel technology for determining spacecraft position and velocity using X-ray pulsars. There are numerous potential benefits from this technology. A X-ray pulsar-based navigation (XNAV) system would be available anywhere in the Solar System that cosmic X-ray sources can be observed. The relatively low disturbance environment of deep space, as compared with low-Earth orbit, allows pulse time of arrival (TOA) to be measured precisely. Furthermore, the system require only infrequent pulsar ephemeris updates and can operate in an autonomous mode, independent of Deep Space Network (DSN). XNAV becomes increasingly attractive for deep space missions.
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Gotthelf, E. V. "Correlation between the X-ray Spectra of Young Pulsars and their Wind Nebulae." Symposium - International Astronomical Union 214 (2003): 163–66. http://dx.doi.org/10.1017/s0074180900194331.
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A significant correlation is discovered between the X-ray spectra of young pulsars (PSRs) and that of their associated wind nebulae (PWNe). For a sample of nine bright Crab-like pulsar systems observed with the Chandra X-ray observatory, we report a linear relationship between the photon indices for the PWNe and those of the phase-averaged pulsar emission, where ΓPWN = 0.72 ± 0.13 × ΓPSR + 0.86 ± 0.20. Furthermore, we find that the spectral slopes of younger, more energetic, pulsars tend to be steeper. These results confirm a consistent pulsar emission mechanism and provide important new observational constraints on the current theory of shock acceleration models for pulsar wind emission.
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Ulmer, M. P. "Gamma-Ray Observations of Pulsars." International Astronomical Union Colloquium 142 (1994): 789–95. http://dx.doi.org/10.1017/s0252921100078106.
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AbstractWe report on Compton Gamma Ray Observatory observations of six detected pulsars: the Crab, Vela, Geminga, PSR B1509-58, PSR B1706-44, and PSR B1055-52. We combine these data with radio data and X-ray data to provide an overview of what is known about gamma-ray pulsars. We discuss light curves, spectra, and radio/gamma-ray phase offsets, and present several tentative patterns in the data. These include constant phase with γ-ray energy; a correlation between gamma-ray and X-ray luminosity; an anticorrelation between the gamma-ray luminosity and the efficiency in converting rotational energy loss into gamma-ray flux; and a correlation between the pulsar period and radio/gamma-ray phase offset. We also suggest that the emission models that have been proposed to date cannot explain the similarities of the average gamma-ray light curves observed over a wide range of energies. Further, unless a narrow beam is assumed, pulsars such as PSR B1055-52 and Geminga appear to be radiating a significant fraction of their rotational energy loss in the form of gamma rays.Subject headings: gamma rays: observations — pulsars: general — radio continuum: stars — X-rays: stars
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Klingler, Noel, Jeremy Hare, Oleg Kargaltsev, George G. Pavlov, and John Tomsick. "A NuSTAR and Chandra Investigation of the Misaligned Outflow of PSR J1101–6101 and the Lighthouse Pulsar Wind Nebula." Astrophysical Journal 950, no. 2 (June 1, 2023): 177. http://dx.doi.org/10.3847/1538-4357/accd60.
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Abstract PSR J1101–6101 is an energetic young pulsar that powers the remarkable Lighthouse pulsar wind nebula (PWN). The pulsar belongs to the rare type of radio- and gamma-ray-quiet pulsars that are bright in hard X-rays. Moreover, the Lighthouse PWN is remarkable for its misaligned outflow (which gave rise to the PWN’s nickname). Also known as “pulsar filaments,” these collimated parsec-scale X-ray structures have been recently discovered in the vicinity of a handful of fast-moving pulsars, and they appear unaffected by the ram pressure that confines pulsar tails. We report on NuSTAR observations of PSR J1101–6101 and its misaligned outflow—the first observation of such a structure above ∼10 keV. We detect the outflow up to 25 keV, spatially resolve its spectral evolution with distance from the pulsar, find unambiguous evidence of spectral cooling with distance from the pulsar, and infer physical properties of the particles and magnetic field in the outflow. We also reanalzye archival Chandra data and discuss the outflow’s small-scale structure. We detect pulsations from PSR J1101–6101 up to 20 keV, present the X-ray pulse profile, confirm its period derivative, and perform phase-resolved spectroscopy. Finally, we discuss the X-ray source 2CXO J110158.4–605649 = 2XMM J110158.5–605651 (a serendipitously observed blazar) and suggest it may be the X-ray counterpart to the GeV source 4FGL J1102.0–6054.
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Nagase, F. "Results of the Timing Analyses of X-ray Pulsars Observed by Hakucho and Tenma." Symposium - International Astronomical Union 125 (1987): 200. http://dx.doi.org/10.1017/s0074180900160735.
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A dozen of X-ray pulsars have been observed with the Japanese X-ray astronomy satellites Hakucho and Tenma between 1979 and 1984. The obsetvations revealed remarkable pulse period changes both in disk-fed and wind-fed pulsars. From the histories of the pulse period changes so far measured, we are able to classify the X-ray pulsars into three categories: (1)Pulsars which exhibit a steady spin-up with a constant rate of period change (e.g., 4U 1626-67 and GX 1+4).(2)Disk-fed pulsars in which considerable period changes are superposed on the secular trend of spin-up (e.g., Her X-1 and Cen X-3).(3)Wind-fed pulsars whose pulse periods fluctuate randomly about the average pulse period on time scales from days to years (e.g., Vela X-1 and GX 301-2).Among the dozen X-ray pulsars observed by Hakucho and Tenma, Vela X-1 was most extensively studied. Timing studies of Vela X-1 revealed an episode of secular spin-down of the pulsar between 1979 and 1982, and large rates of short-term period fluctuations superimposed on the secular trend. Recent studies of the wind-fed pulsar suggest that the angular momentum transfer expected from the wind accretion is too small to account for the observed rates. Spectroscopic studies of Vela X-1 by Tenma observations provided a variety of phenomena related to the binary system and detailed properties of matter surrounding the system, especially using an iron emission line fluoresced thereby as a probe.Formation of a disk in the wind-fed pulsar is proposed to accommodate a variety of phenomena observed from Vela X-1. A disk is expected to be formed through the interaction of the spherically accreting matter with the rotating magnetosphere, under the assumption that the closed magnetosphere extends to the corotation radius. Application of this model to Vela X-1 requires a large magnetic moment of μ ≈ 1032 gauss cm3 (1013 ≲ B ≲ 1014 gauss, depending on the stellar parameters), but once the large value is accepted, this model fits well with the large rates of period change and phenomena which would otherwise be regarded as strange. If this model works for Vela X-1, it will be also applied to some of other wind-fed pulsars.
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Gentile, P., M. McLaughlin, M. Roberts, F. Camilo, J. Hessels, M. Kerr, S. Ransom, P. Ray, and I. Stairs. "Chandra observations of black widow pulsars." Proceedings of the International Astronomical Union 8, S291 (August 2012): 389–91. http://dx.doi.org/10.1017/s1743921312024234.
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AbstractWe describe the first X-ray observations of binary millisecond pulsars PSR J0023+0923, J1810+1744, J2215+5135, and J2256−1024. All are Fermi gamma-ray sources and three are ‘black-widow’ pulsars, with companions of mass < 0.1 M⊙. Data were taken using the Chandra X-Ray Observatory and covered a full binary orbit for each pulsar. PSRs J2215+5135 and J2256−1024, show significant orbital variability and X-ray flux minima coinciding with eclipses seen at radio wavelengths. This is consistent with intrabinary shock emission characteristic of black-widow pulsars. The other two pulsars, PSRs J0023+0923 and J1810+1744, do not demonstrate significant variability, but are fainter than the other two sources. Spectral fits yield power-law indices that range from 1.4 to 2.3 and blackbody temperatures in the hundreds of eV. The spectrum for PSR J2215+5135 shows a significant hard X-ray component (41% of counts are above 2 keV), which is additional evidence for the presence of intrabinary shock emission.
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GUSEINOV, OKTAY H., AŞKIN ANKAY, SEVINÇ O. TAGIEVA, and M. ÖZGÜR TAŞKIN. "DEPENDENCE OF THE X-RAY LUMINOSITY AND PULSAR WIND NEBULA ON DIFFERENT PARAMETERS OF PULSARS AND THE EVOLUTIONARY EFFECTS." International Journal of Modern Physics D 13, no. 02 (February 2004): 197–213. http://dx.doi.org/10.1142/s0218271804004505.
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Dependences of the X-ray luminosity (Lx) of young single pulsars, due to ejection of relativistic particles, on electric field intensity, rate of rotational energy loss (Ė), magnetic field, period, and some other parameters of neutron stars are discussed. Influence of the magnetic field and effects of some other parameters of neutron stars on the Lx-Ė and the Lx-τ (characteristic time) dependences are considered. Evolutionary factors also play an important role in our considerations. Only the pulsars with L2–10 keV >1033 erg/s have pulsar wind nebula around them. The pulsars from which γ-ray radiation has been observed have low X-ray luminosity in general.
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Tauris, T. M. "On the connection between accreting X-ray and radio millisecond pulsars." Proceedings of the International Astronomical Union 8, S290 (August 2012): 141–44. http://dx.doi.org/10.1017/s1743921312019394.
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AbstractFor many years it has been recognized that the terminal stages of mass transfer in a low-mass X-ray binary (LMXB) should cause the magnetosphere of the accreting neutron star to expand, leading to a braking torque acting on the spinning pulsar. After the discovery of radio millisecond pulsars (MSPs) it was therefore somewhat a paradox (e.g. Ruderman et al. 1989) how these pulsars could retain their fast spins following the Roche-lobe decoupling phase, RLDP. Here I present a solution to this so-called “turn-off problem” which was recently found by combining binary stellar evolution models with torque computations (Tauris 2012). The solution is that during the RLDP the spin equilibrium of the pulsar is broken and therefore it remains a fast spinning object. I briefly discuss these findings in view of the two observed spin distributions in the populations of accreting X-ray millisecond pulsars (AXMSPs) and radio MSPs.
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Vahdat, A., B. Posselt, A. Santangelo, and G. G. Pavlov. "Toward an X-ray inventory of nearby neutron stars." Astronomy & Astrophysics 658 (February 2022): A95. http://dx.doi.org/10.1051/0004-6361/202141795.
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Context. The X-ray emission of neutron stars enables a probe of their temperatures, geometries and magnetospheric properties. The current number of X-ray emitting pulsars is insufficient to rule out observational biases that may arise from poorly known distance, age, or location of the neutron stars. One approach to overcome such biases is to create a distance-limited sample with sufficiently deep observations. Aims. With the aim of better sampling of the nearby (≲2 kpc) population of neutron stars, we started an XMM-Newton survey of pulsars to measure their X-ray fluxes or derive respective constraining upper limits. Methods. We investigated 14 nearby pulsars for potential X-ray counterparts using different energy bands and detectors. In addition to our new XMM-Newton data, we also considered archival data and catalogs. We discuss source properties and also check for alternative counterparts to the X-ray sources. Results. In our new XMM-Newton data, we found two pulsar counterpart candidates with significance above 4σ and one candidate with 3.5σ by combining EPIC camera detection likelihoods. We also report the detection of potential X-ray counterparts to eight radio pulsars in the 4XMM-DR10 catalog which have not been reported in the literature.
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Kaspi, V. M., and F. P. Gavriil. "(Anomalous) X-ray Pulsars." Nuclear Physics B - Proceedings Supplements 132 (June 2004): 456–65. http://dx.doi.org/10.1016/j.nuclphysbps.2004.04.080.
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Bogdanov, Slavko. "X-rays from Radio Millisecond Pulsars." Proceedings of the International Astronomical Union 13, S337 (September 2017): 116–19. http://dx.doi.org/10.1017/s1743921317011553.
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AbstractThe Galactic population of rotation-powered (aka radio) millisecond pulsars (MSPs) exhibits diverse X-ray properties. Energetic MSPs show pulsed non-thermal radiation from their magnetospheres. Eclipsing binary MSPs predominantly have X-ray emission from a pulsar wind driven intra-binary shock. Typical radio MSPs emit X-rays from their heated magnetic polar caps. These thermally emitting MSPs offer the opportunity to place interesting constraints on the long sought after dense matter equation of state, making them important targets of investigation of the recently deployed Neutron Star Interior Composition Explorer (NICER) X-ray mission.
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Paduano, Alessandro, Arash Bahramian, James C. A. Miller-Jones, Adela Kawka, Jay Strader, Laura Chomiuk, Craig O. Heinke, et al. "The MAVERIC Survey: Simultaneous Chandra and VLA observations of the transitional millisecond pulsar candidate NGC 6652B." Monthly Notices of the Royal Astronomical Society 506, no. 3 (July 8, 2021): 4107–20. http://dx.doi.org/10.1093/mnras/stab1928.
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ABSTRACT Transitional millisecond pulsars are millisecond pulsars that switch between a rotation-powered millisecond pulsar state and an accretion-powered X-ray binary state, and are thought to be an evolutionary stage between neutron star low-mass X-ray binaries and millisecond pulsars. So far, only three confirmed systems have been identified in addition to a handful of candidates. We present the results of a multiwavelength study of the low-mass X-ray binary NGC 6652B in the globular cluster NGC 6652, including simultaneous radio and X-ray observations taken by the Karl G. Jansky Very Large Array and the Chandra X-ray Observatory, and optical spectroscopy and photometry. This source is the second brightest X-ray source in NGC 6652 ($L_{\textrm {X}}\sim 1.8 \times 10^{34}{\, \mathrm{erg\, s}^{-1}}$) and is known to be variable. We observe several X-ray flares over the duration of our X-ray observations, in addition to persistent radio emission and occasional radio flares. Simultaneous radio and X-ray data show no clear evidence of anticorrelated variability. Optical spectra of NGC 6652B indicate variable, broad H α emission that transitions from double-peaked emission to absorption over a time-scale of hours. We consider a variety of possible explanations for the source behaviour, and conclude that based on the radio and X-ray luminosities, short time-scale variability and X-ray flaring, and optical spectra, NGC 6652B is best explained as a transitional millisecond pulsar candidate that displays prolonged X-ray flaring behaviour. However, this could only be confirmed with observations of a change to the rotation-powered millisecond pulsar state.
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Gallant, Y. A., R. Bandiera, N. Bucciantini, and E. Amato. "Constraining pulsar birth properties with supernova X-ray observations." Proceedings of the International Astronomical Union 12, S331 (February 2017): 63–68. http://dx.doi.org/10.1017/s1743921317004756.
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AbstractA large fraction of core-collapse supernovae are thought to result in the birth of a rotation-powered pulsar, which is later observable as a radio pulsar up to great ages. The birth properties of these pulsars, and in particular the distribution of their initial rotation periods, are however difficult to infer from studies of the radio pulsar population in our Galaxy. Yet the distributions of their birth properties is an important assumption for scenarios in which ultra-high-energy cosmic rays (UHECRs) originate in very young, extragalactic pulsars with short birth periods and/or high magnetic fields.Using a model of the very young pulsar wind nebula’s dynamical and spectral evolution, with pulsar wind and accelerated particle parameters assumed similar to those inferred from modeling young pulsar wind nebulae (PWNe) in our Galaxy, we show that X-ray observations of supernovae, a few years to decades after the explosion, constitute a favored window to obtain meaningful constraints on the initial spin-down luminosity of the newly-formed pulsar. We examine the expected emerging PWN spectral component, taking into account the X-ray opacity of the expanding supernova ejecta, and find that it is typically best detectable in < 10 keV X-rays some years after the explosion. We use this framework to assess available X-ray observations and flux upper limits on supernovae, building on the work of Pernaet al.(2008). We note that a resulting limit on spin-down luminosity corresponds univocally to a limit on the maximum magnetospheric acceleration potential, irrespective of the specific combination of magnetic field and rotation period that achieves it. We use available X-ray observations of supernovae to place constraints on the birth spin-down luminosity and period distribution of classical pulsars. We also examine the case of magnetars, born with much higher magnetic fields, and show that their much shorter initial spin-down time implies that any plausible signature of young magnetar wind nebulae can only be observed in harder X-ray or gamma-rays.
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Lobato, Ronaldo V., Manuel Malheiro, and Jaziel G. Coelho. "Magnetars and white dwarf pulsars." International Journal of Modern Physics D 25, no. 09 (August 2016): 1641025. http://dx.doi.org/10.1142/s021827181641025x.
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The anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs) are a class of pulsars understood as neutron stars (NSs) with super strong surface magnetic fields, namely [Formula: see text][Formula: see text]G, and for that reason are known as magnetars. However, in the last years, some SGRs/AXPs with low surface magnetic fields [Formula: see text]–[Formula: see text][Formula: see text]G have been detected, challenging the magnetar description. Moreover, some fast and very magnetic white dwarfs (WDs) have also been observed, and at least one showed X-ray energy emission as an ordinary pulsar. Following this fact, an alternative model based on WDs pulsars has been proposed to explain this special class of pulsars. In this model, AXPs and SGRs as dense and magnetized WDs can have surface magnetic field [Formula: see text]–[Formula: see text] G and rotate very fast with frequencies [Formula: see text][Formula: see text]rad/s, consistent with the observed rotation periods [Formula: see text]–12)[Formula: see text]s.
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Poutanen, Juri. "Relativistic rotating vector model for X-ray millisecond pulsars." Astronomy & Astrophysics 641 (September 2020): A166. http://dx.doi.org/10.1051/0004-6361/202038689.
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The X-ray radiation produced on the surface of accreting magnetised neutron stars is expected to be strongly polarised. A swing of the polarisation vector with the pulsar phase gives a direct measure of the source inclination and magnetic obliquity. In the case of rapidly rotating millisecond pulsars, the relativistic motion of the emission region causes additional rotation of the polarisation plane. Here, we develop a relativistic rotating vector model, where we derive analytical expression for the polarisation angle as a function of the pulsar phase accounting for relativistic aberration and gravitational light bending in the Schwarzschild metric. We show that in the case of fast pulsars the rotation of the polarisation plane can reach tens of degrees, strongly influencing the observed shape of the polarisation angle’s phase dependence. The rotation angle grows nearly linearly with the spin rate but it is less sensitive to the neutron star radius. Overall, this angle is large even for large spots. Our results have implications with regard to the modelling of X-ray polarisation from accreting millisecond pulsars that are to be observed with the upcoming Imaging X-ray Polarimeter Explorer and the enhanced X-ray Timing and Polarimetry mission. The X-ray polarisation may improve constraints on the neutron star mass and radius coming from the pulse profile modelling.
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Liu, Li, Wei Zheng, and Guojian Tang. "Autonomous Positioning of Satellite Constellations via X-ray Pulsar Measurements." Journal of Navigation 66, no. 5 (June 21, 2013): 671–82. http://dx.doi.org/10.1017/s0373463313000325.
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A novel autonomous positioning approach based on X-ray pulsars is proposed in this paper. First, the principles of the pulsar–based measurement model and the inter-satellite range model in the autonomous positioning of satellite constellations are presented. The observability of the pulsar-based measurement model is then shown. Second, the autonomous positioning algorithms, including measurement models and orbital dynamics models, are formulated using an unscented Kalman filter to estimate the position vectors of satellites. Finally, the feasibility of the proposed measurement scheme compared with an inter-satellite range scheme is illustrated by numerical simulation. The results show that the proposed approach can keep the satellite state convergent, and achieve position accuracies of 2 m. The proposed scheme provides a promising approach for autonomous absolute positioning of constellation systems by using X-ray pulsars.
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COELHO, J. G., and M. MALHEIRO. "SIMILARITIES OF SGRs WITH LOW MAGNETIC FIELD AND WHITE DWARF PULSARS." International Journal of Modern Physics: Conference Series 18 (January 2012): 96–100. http://dx.doi.org/10.1142/s2010194512008276.
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Some of the most interesting types of astrophysical objects that have been intensively studied in the recent years are the Anomalous X-ray Pulsars (AXPs) and Soft Gamma-ray Repeaters (SGRs) seen usually as neutron stars pulsars with super strong magnetic fields. However, in the last two years two SGRs with low magnetic fields have been detected. Moreover, fast and very magnetic white dwarf pulsars have also been observed in the last years. Based on these new pulsar discoveries, white dwarf pulsars have been proposed as an alternative explanation to the observational features of SGRs and AXPs. Here we present several properties of these SGRs/AXPs as WD pulsar, in particular the surface magnetic field and the magnetic dipole momentum.
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Forsblom, Sofia V., Juri Poutanen, Sergey S. Tsygankov, Matteo Bachetti, Alessandro Di Marco, Victor Doroshenko, Jeremy Heyl, et al. "IXPE Observations of the Quintessential Wind-accreting X-Ray Pulsar Vela X-1." Astrophysical Journal Letters 947, no. 2 (April 1, 2023): L20. http://dx.doi.org/10.3847/2041-8213/acc391.
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Abstract The radiation from accreting X-ray pulsars was expected to be highly polarized, with some estimates for the polarization degree of up to 80%. However, phase-resolved and energy-resolved polarimetry of X-ray pulsars is required in order to test different models and to shed light on the emission processes and the geometry of the emission region. Here we present the first results of the observations of the accreting X-ray pulsar Vela X-1 performed with the Imaging X-ray Polarimetry Explorer. Vela X-1 is considered to be the archetypal example of a wind-accreting, high-mass X-ray binary system, consisting of a highly magnetized neutron star accreting matter from its supergiant stellar companion. The spectropolarimetric analysis of the phase-averaged data for Vela X-1 reveals a polarization degree (PD) of 2.3% ± 0.4% at the polarization angle (PA) of −47.°3 ± 5.°4. A low PD is consistent with the results obtained for other X-ray pulsars and is likely related to the inverse temperature structure of the neutron star atmosphere. The energy-resolved analysis shows the PD above 5 keV reaching 6%–10% and a ∼90° difference in the PA compared to the data in the 2–3 keV range. The phase-resolved spectropolarimetric analysis finds a PD in the range 0%–9% with the PA varying between −80° and 40°.
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Dodson, Richard, Dion Lewis, David Legge, Peter McCulloch, John Reynolds, David McConnell, and Avinash Deshpande. "The Vela Pulsar, the Key?" Symposium - International Astronomical Union 218 (2004): 193–94. http://dx.doi.org/10.1017/s0074180900180945.
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Of all pulsars known, Vela has been one of the most productive in terms in understanding pulsars and their characteristics. We present the latest results derived from Australian telescopes. These include a more accurate pulsar distance, a more precise pulsar local space velocity, a new model of spin-up at a glitch, and the association of a radio nebula with the X-ray pulsar wind nebula.
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McLaughlin, M. A., D. R. Lorimer, A. G. Lyne, M. Kramer, A. J. Faulkner, V. M. Kaspi, I. H. Stairs, 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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Meliani, M. T. "A Catalogue of X-ray Sources in the Sky Region between δ = −73° and δ = +27°." Publications of the Astronomical Society of Australia 16, no. 2 (1999): 175–205. http://dx.doi.org/10.1071/as99175.
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AbstractThis Catalogue lists coordinates, X-ray fluxes in different energy ranges, magnitudes and colour indices, optical counterparts, orbital periods of binaries, pulsar periods and other characteristics of 226 X-ray sources (HMXBs, LMXBs, pulsars and galaxies) between δ = −73° and δ = +27°.
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Melikidze, George I., and Janusz Gil. "Surface magnetic fields in pulsars." Proceedings of the International Astronomical Union 4, S259 (November 2008): 131–32. http://dx.doi.org/10.1017/s1743921309030324.
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AbstractObservations of hot-spot thermal X-ray emission from radio pulsars implicate that surface magnetic field (SMF) at the polar cap is much stronger than the conventional dipolar component estimated from the pulsar spin-down. This strongly suggests that SMF is dominated by the crust anchored small scale magnetic field. We present the observed values of black body temperature and bolometric luminosity of X-ray emission from hot polar caps of a number of pulsars. In all cases the inferred value of SMF is close to 1014 G.
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Gotthelf, E. V. "A Spin-down Power Threshold for Pulsar Wind Nebula Generation?" Symposium - International Astronomical Union 218 (2004): 225–28. http://dx.doi.org/10.1017/s0074180900181045.
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A systematic X-ray survey of the most energetic rotation-powered pulsars known, based on spin-down energy loss rate, shows that all energetic pulsars with Ė > Ėc ≍ 4 × 1036 ergs s−1 are X-ray-bright, manifest a distinct pulsar wind nebula (PWN), and are associated with a supernova event, with over half residing in shell-like supernova remnants. Below Ėc, the 2–10 keV flux ratio FPWN/FPSR decreases by an order-of-magnitude. This threshold is consistent with the lower limit on the spectral slope γmin ≍ 0.6 observed for rotation-powered pulsars (Gotthelf 2003). The apparent lack of bright PWNe below Ėc suggests a change in the particle injection spectrum and serves as a constraint on emission models for rotation-powered pulsars. Neither a young age nor a high density environment is found to be a sufficient condition for generating a PWN, as often suggested, instead Ė is likely the key parameter in determining the evolution of a rotation-powered pulsar.
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Bao, Yiwei, Yang Chen, and Siming Liu. "Is PSR J0855−4644 responsible for the 1.4 TeV electron spectral bump hinted by DAMPE?" Monthly Notices of the Royal Astronomical Society 500, no. 4 (October 27, 2020): 4573–77. http://dx.doi.org/10.1093/mnras/staa3311.
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ABSTRACT DAMPE observation on the cosmic ray electron spectrum hints a narrow excess at ∼1.4 TeV. Although the excess can be ascribed to dark matter particles, pulsars and pulsar wind nebulae are believed to be more natural astrophysical origins: electrons injected from nearby pulsars at their early ages can form a bump-like feature in the spectrum due to radiative energy losses. In this paper, with a survey of nearby pulsars, we filter out four pulsars that may have notable contributions to ∼1.4 TeV cosmic ray electrons. Among them, PSR J0855−4644 has a spin-down luminosity more than 50 times higher than others and presumably dominates the electron fluxes from them. X-ray observations on the inner compact part (which may represent a tunnel for the transport of electrons from the pulsar) of PWN G267.0−01.0 are then used to constrain the spectral index of high-energy electrons injected by the pulsar. We show that high-energy electrons released by PSR J0855−4644 could indeed reproduce the 1.4 TeV spectral feature hinted by the DAMPE with reasonable parameters.
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Romani, Roger W. "High Energy Pulsars: Pulses and Populations." International Astronomical Union Colloquium 160 (1996): 331–38. http://dx.doi.org/10.1017/s0252921100041828.
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AbstractRecent X-ray and γ-ray observations have detected a number of isolated spin-powered pulsars. Studies of the pulse profiles of these objects are providing a useful guide to the site of the high energy emission. The γ-ray pulses, which are closely tied to the primary population of radiating particles, seem to be an especially useful discriminant between pulsar models. With an understanding of how the pulsar luminosity and beaming factors evolve with spin parameters, pulsar population syntheses can also be used to check the predictions of high energy emission models. In turn, comparison with γ-ray sky surveys constrains the properties of the young pulsar population.
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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 (January 17, 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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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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Thompson, D. J. "X-Ray and Gamma-Ray Observations of Isolated Neutron Stars." Symposium - International Astronomical Union 188 (1998): 113–16. http://dx.doi.org/10.1017/s0074180900114561.
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Pulsars provide useful diagnostics of isolated neutron stars, because the timing information allows many physical parameters to be derived. This brief review describes some of the X-ray and gamma-ray properties of pulsars.
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Vidal, Clément. "Pulsar positioning system: a quest for evidence of extraterrestrial engineering." International Journal of Astrobiology 18, no. 3 (November 23, 2017): 213–34. http://dx.doi.org/10.1017/s147355041700043x.
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AbstractPulsars have at least two impressive applications. First, they can be used as highly accurate clocks, comparable in stability to atomic clocks; secondly, a small subset of pulsars, millisecond X-ray pulsars, provide all the necessary ingredients for a passive galactic positioning system. This is known in astronautics as X-ray pulsar-based navigation (XNAV). XNAV is comparable to GPS, except that it operates on a galactic scale. I propose a SETI-XNAV research program to test the hypothesis that this pulsar positioning system might be an instance of galactic-scale engineering by extraterrestrial beings. The paper starts by exposing the basics of pulsar navigation, continues with a critique of the rejection of the extraterrestrial hypothesis when pulsars were first discovered. The core section of the paper proposes lines of inquiry for SETI-XNAV, related to the pulsar distribution and power in the galaxy; their population; their evolution; possible pulse synchronizations; pulsar usability when navigating near the speed of light; decoding galactic coordinates; directed panspermia; and information content in pulses. Even if pulsars are natural, they are likely to be used as standards by ETIs in the galaxy. I discuss possible objections and potential benefits for humanity, whether the research program succeeds or not.
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Hare, Jeremy, Igor Volkov, George G. Pavlov, Oleg Kargaltsev, and Simon Johnston. "Precise Timing and Phase-resolved Spectroscopy of the Young Pulsar J1617–5055 with NuSTAR." Astrophysical Journal 923, no. 2 (December 1, 2021): 249. http://dx.doi.org/10.3847/1538-4357/ac30e2.
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Abstract We report on a Nuclear Spectroscopic Telescope Array (NuSTAR) observation of the young, energetic pulsar PSR J1617–5055. Parkes Observatory 3 GHz radio observations of the pulsar (taken about 7 yr before the NuSTAR observations) are also reported here. NuSTAR detected pulsations at a frequency of f ≈ 14.4 Hz (P ≈ 69.44 ms) and, in addition, the observation was long enough to measure the source’s frequency derivative, f ̇ ≈ − 2.8 × 10 − 11 Hz s−1. We find that the pulsar shows one peak per period at both hard X-ray and radio wavelengths, but that the hard X-ray pulse is broader (having a duty cycle of ∼0.7), than the radio pulse (having a duty cycle of ∼0.08). Additionally, the radio pulse is strongly linearly polarized. J1617's phase-integrated hard X-ray spectrum is well fit by an absorbed power-law model, with a photon index Γ = 1.59 ± 0.02. The hard X-ray pulsations are well described by three Fourier harmonics, and have a pulsed fraction that increases with energy. We also fit the phase-resolved NuSTAR spectra with an absorbed power-law model in five phase bins and find that the photon index varies with phase from Γ = 1.52 ± 0.03 at phases around the flux maximum to Γ = 1.79 ± 0.06 around the flux minimum. Last, we compare our results with other pulsars whose magnetospheric emission is detected at hard X-ray energies and find that, similar to previous studies, J1617's hard X-ray properties are more similar to the MeV pulsars than the GeV pulsars.
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Ray, Paul S., Zaven Arzoumanian, and Keith C. Gendreau. "Searching for X-ray Pulsations from Neutron Stars Using NICER." Proceedings of the International Astronomical Union 13, S337 (September 2017): 187–90. http://dx.doi.org/10.1017/s1743921317008237.
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AbstractThe Neutron Star Interior Composition Explorer (NICER) presents an exciting new capability for exploring the modulation properties of X-ray emitting neutron stars, including large area, low background, extremely precise absolute event time stamps, superb low-energy response and flexible scheduling. The Pulsation Searches and Multiwavelength Coordination working group has designed a 2.5 Ms observing program to search for emission and characterize the modulation properties of about 30 known or suspected neutron star sources across a number of source categories. A key early goal will be to search for pulsations from millisecond pulsars that might exhibit thermal pulsations from the surface suitable for pulse profile modeling to constrain the neutron star equation of state. In addition, we will search for pulsations from transitional millisecond pulsars, isolated neutron stars, low-mass X-ray binaries (LMXBs), accretion-powered millisecond pulsars, central compact objects and other sources. We present our science plan and initial results from the first months of the NICER mission, including the discovery of pulsations from the millisecond pulsar J1231–1411.
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Webb, N. A., D. Leahy, S. Guillot, N. Baillot d’Etivaux, D. Barret, L. Guillemot, J. Margueron, and M. C. Miller. "Thermal X-ray emission identified from the millisecond pulsar PSR J1909–3744." Astronomy & Astrophysics 627 (July 2019): A141. http://dx.doi.org/10.1051/0004-6361/201732040.
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Context. Pulsating thermal X-ray emission from millisecond pulsars can be used to obtain constraints on the neutron star equation of state, but to date only five such sources have been identified. Of these five millisecond pulsars, only two have well-constrained neutron star masses, which improve the determination of the radius via modelling of the X-ray waveform. Aims. We aim to find other millisecond pulsars that already have well-constrained mass and distance measurements that show pulsed thermal X-ray emission in order to obtain tight constraints on the neutron star equation of state. Methods. The millisecond pulsar PSR J1909–3744 has an accurately determined mass, M = 1.54 ± 0.03 M⊙ (1σ error) and distance, D = 1.07 ± 0.04 kpc. We analysed XMM-Newton data of this 2.95 ms pulsar to identify the nature of the X-ray emission. Results. We show that the X-ray emission from PSR J1909–3744 appears to be dominated by thermal emission from the polar cap. Only a single component model is required to fit the data. The black-body temperature of this emission is $ {kT}=0.26^{0.03}_{0.02} $ keV and we find a 0.2–10 keV un-absorbed flux of 1.1 × 10−14 erg cm−2 s−1 or an un-absorbed luminosity of 1.5 × 1030 erg s−1. Conclusion. Thanks to the previously determined mass and distance constraints of the neutron star PSR J1909–3744, and its predominantly thermal emission, deep observations of this object with future X-ray facilities should provide useful constraints on the neutron star equation of state.
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Allen, Michelle C., D. B. Melrose, and A. J. Parle. "QED and X-Ray Pulsars." Publications of the Astronomical Society of Australia 6, no. 2 (1985): 211–14. http://dx.doi.org/10.1017/s1323358000018129.
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AbstractTechniques in QED (quantum electrodynamics) have been developed previously (see for example Melrose and Parle 1983) allowing one to treat electron-photon and photon-photon interactions exactly in the magnetized vacuum and allowing one to include the effects of a medium. These techniques are extended to include particle-particle interactions. Exact cross-sections for electron-electron collisions are derived and compared with known expressions. Such calculations have application in studies of the formation and transfer of radiation in the atmospheres surrounding neutron stars.