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Journal articles on the topic 'PULSTAR'

Author: Grafiati

Published: 4 June 2021

Last updated: 8 February 2022

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1

Hawari, A. I., S. A. Lassell, and G. I. Gibson. "INTERNET REACTOR LABORATORY: A NUCLEAR REACTOR PHYSICS AND ENGINEERING EDUCATION MODALITY FOR THE 21st CENTURY." EPJ Web of Conferences 247 (2021): 14004. http://dx.doi.org/10.1051/epjconf/202124714004.

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The “second generation” Internet Reactor Laboratory (IRL) has been installed and is currently functional at the PULSTAR reactor of the Nuclear Reactor Program (NRP) at North Carolina State University (NCSU). The NRP has offered IRL based reactor physics experiments and training to external academic institutions and organizations since 2004. In 2016, the United States and the Republic of Vietnam entered into an Administrative Arrangement under Section 123 of the Atomic Energy Act, with a goal of enhancing nuclear training and education for Vietnamese engineering students. Funding was provided by the DOE to upgrade the PULSTAR IRL infrastructure to state-of-the-art remote data acquisition and video teleconferencing capabilities supporting content sharing across multiple remote user platforms. Subsequently, a Cisco Telepresence and LabView reactor data acquisition system were installed and commissioned at the PULSTAR facility. Using this “second generation” system, and during IRL sessions, up to 100 remote students may interact with the control room staff via the Telepresence system using their mobile device or PC, and view 130 channels of live reactor telemetry via the remote client LabView application while recording the data for subsequent review and analysis. LabView graphical user interfaces (GUI) are provided for each IRL module, and incorporate embedded supporting documents such as schematics and diagrams that aid in illustrating associated technical details and concepts. Consequently, the educational experience offered to remote students and trainees is enhanced and assured to be of the same quality as offered to onsite students/trainees at NCSU.

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2

Mishra, Kaushal K., and Ayman I. Hawari. "Phase contrast neutron imaging at the PULSTAR reactor." Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 652, no. 1 (October 2011): 615–19. http://dx.doi.org/10.1016/j.nima.2010.09.113.

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3

Xiao, Ziyu, Kaushal K. Mishra, Ayman I. Hawari, Philip R. Bingham, Hassina Z. Bilheux, and Kenneth W. Tobin. "Coded source neutron imaging at the PULSTAR reactor." Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 652, no. 1 (October 2011): 606–9. http://dx.doi.org/10.1016/j.nima.2010.10.049.

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4

Pullela, Sunita V. "Determination of the PULSTAR reactor neutron energy spectrum." Energy Conversion and Management 38, no. 10-13 (July 1997): 1015–23. http://dx.doi.org/10.1016/s0196-8904(96)00131-8.

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5

Hawari, A. I., M. Liu, and Q. Cai. "FACILITIES FOR NANO MATERIALS EXAMINATION AT THE PULSTAR REACTOR." EPJ Web of Conferences 247 (2021): 08012. http://dx.doi.org/10.1051/epjconf/202124708012.

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The PULSTAR is a 1-MWth nuclear research reactor located at North Carolina State University. It is fueled by uranium dioxide assemblies enriched to 4% or 6% in U-235 and is currently under licensing for operation at 2-MWth power. The PULSTAR is a center for irradiation testing and pre/post irradiation examination of materials. Among its unique capabilities are positron annihilation spectroscopy (PAS) and neutron powder diffraction (NPD) facilities. The PAS facility provides an intense positron beam reaching 6 × 108 e+/s, which drives two spectrometers; the e+-PAS and the Ps-PAS, used for studies of defects in thin film materials. A Na-22 bulk PAS system is also operational, which is used for studying millimeter scale materials. All spectrometers are capable of performing Doppler Broadening Spectroscopy (DBS) and Positron Annihilation Lifetime Spectroscopy (PALS). To date, the PAS systems have been used to characterize various materials (unirradiated and irradiated) that include graphite, soft matter, and metal-organic frameworks (MOF). The NPD facility uses a double focusing single crystal silicon rotating monochromator producing neutron beams with different energies. A position sensitive detection bank covers a scattering angle of 5°-125°. The facility is used in the examination of unirradiated and irradiated materials including graphitic materials, magnetic materials without rare-earth elements, and anode materials used in lithium batteries. The collected diffraction patterns can be processed to produce atomic pair distribution functions. The PAS and NPD facilities are available through user programs including the US DOE’s Nuclear Science User Facilities (NSUF) and the US NSF’s Research Triangle Nanotechnology Network (RTNN).

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6

Korobkina, E., B. W. Wehring, A. I. Hawari, A. R. Young, P. R. Huffman, R. Golub, Y. Xu, and G. Palmquist. "An ultracold neutron source at the NC State University PULSTAR reactor." Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 579, no. 1 (August 2007): 530–33. http://dx.doi.org/10.1016/j.nima.2007.04.116.

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7

Korobkina, E., G. Medlin, B. Wehring, A. I. Hawari, P. R. Huffman, A. R. Young, B. Beaumont, and G. Palmquist. "Ultracold neutron source at the PULSTAR reactor: Engineering design and cryogenic testing." Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 767 (December 2014): 169–75. http://dx.doi.org/10.1016/j.nima.2014.08.016.

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8

Leach, Robert A., Patrick L. Parker, and Paul S. Veal. "PulStar differential compliance spinal instrument: a randomized interexaminer and intraexaminer reliability study." Journal of Manipulative and Physiological Therapeutics 26, no. 8 (October 2003): 493–501. http://dx.doi.org/10.1016/s0161-4754(03)00106-4.

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9

Datta, Arka, and Ayman I. Hawari. "Investigation of a model based reconstruction technique for neutron tomography at the PULSTAR reactor." Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 954 (February 2020): 161200. http://dx.doi.org/10.1016/j.nima.2018.09.035.

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10

Hathaway, A. G., M. Skalsey, W. E. Frieze, R. S. Vallery, D. W. Gidley, A. I. Hawari, and J. Xu. "Implementation of a prototype slow positron beam at the NC State University PULSTAR reactor." Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 579, no. 1 (August 2007): 538–41. http://dx.doi.org/10.1016/j.nima.2007.03.036.

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11

Hawari, Ayman I., David W. Gidley, Jeremy Moxom, Alfred G. Hathaway, and Saurabh Mukherjee. "Operation and testing of the PULSTAR reactor intense slow positron beam and PALS spectrometers." Journal of Physics: Conference Series 262 (January 1, 2011): 012024. http://dx.doi.org/10.1088/1742-6596/262/1/012024.

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12

Moxom, J., A. G. Hathaway, E. W. Bodnaruk, A. I. Hawari, and J. Xu. "Performance analysis of the intense slow-positron beam at the NC State University PULSTAR reactor." Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 579, no. 1 (August 2007): 534–37. http://dx.doi.org/10.1016/j.nima.2007.04.117.

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13

WANG, WEI. "DISTANCE INDICATORS OF GAMMA-RAY PULSARS." International Journal of Modern Physics: Conference Series 23 (January 2013): 289–94. http://dx.doi.org/10.1142/s2010194513011483.

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Distance measurements of gamma-ray pulsars are challenging questions in present pulsar studies. The Large Area Telescope (LAT) aboard the Fermi gamma-ray observatory discovered more than 100 gamma-ray pulsars including 24 new gamma-selected pulsars which nearly have no distance information. We study the relation between gamma-ray emission efficiency (η = Lγ/Ė) and pulsar parameters for young radio-selected gamma-ray pulsars with known distance information in the first gamma-ray pulsar catalog reported by Fermi/LAT. We have introduced three generation order parameters to describe gamma-ray emission properties of pulsars, and find the strong correlation of η – ζ3 a generation order parameter which reflects γ-ray photon generations in pair cascade processes induced by magnetic field absorption in pulsar magnetosphere. A good correlation of η – B LC the magnetic field at the light cylinder radius is also found. These correlations would be the distance indicators in gamma-ray pulsars to evaluate distances for gamma-selected pulsars. Distances of 25 gamma-selected pulsars are estimated, which could be tested by other distance measurement methods. Physical origin of the correlations may be also interesting for pulsar studies.

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14

Wang, Wei. "The distance indicators in gamma-ray pulsars." Proceedings of the International Astronomical Union 8, S291 (August 2012): 546–48. http://dx.doi.org/10.1017/s1743921312024829.

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AbstractDistance measurements of gamma-ray pulsars are challenging questions in present pulsar studies. The Large Area Telescope (LAT) aboard the Fermi gamma-ray observatory discovered more than 100 gamma-ray pulsars, including 34 new gamma-selected pulsars which nearly have no distance information. We study the relation between gamma-ray emission efficiency (η=Lγ/Ė) and pulsar parameters, for young radio-selected gamma-ray pulsars with known distance information. We have introduced three generation order parameters to describe gamma-ray emission properties of pulsars, and find a strong correlation between η and ζ3, the generation order parameter which reflects γ-ray photon generations in pair cascade processes induced by magnetic field absorption in pulsar magnetosphere. A good correlation between η and BLC, the magnetic field at the light cylinder radius, is also found. These correlations can serve as distance indicators in gamma-ray pulsars, to evaluate distances for gamma-selected pulsars. Distances of 35 gamma-selected pulsars are estimated, which could be tested by other distance measurement methods. The physical origin of the correlations may be also interesting for pulsar studies.

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15

McLaughlin, M. A., D. R. Lorimer, D. J. Champion, K. Xilouris, Z. Arzoumanian, D. C. Backer, J. M. Cordes, A. S. Fruchter, and A. N. Lommen. "New Pulsars from Arecibo Drift-Scan Searches." Symposium - International Astronomical Union 218 (2004): 127–28. http://dx.doi.org/10.1017/s0074180900180763.

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We report on new pulsars discovered in Arecibo drift-scan datA. Processing of 2200 deg2 of data has resulted in the detection of 41 known and 12 new pulsars. New pulsars include two millisecond pulsars, one solitary and one binary recycled pulsar, and one pulsar with very unusual pulse profile morphology and complex drifting subpulse behavior.

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16

Baykal, Altan, and Ali Alpar. "Expectancy of large pulsar glitches." International Astronomical Union Colloquium 160 (1996): 105–6. http://dx.doi.org/10.1017/s0252921100041154.

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AbstractWe study the expectancy of large glitches (ΔΩ/Ω > 10−7) from a sample of 472 pulsars other than the Vela pulsar. The pulsars in this sample have exhibited 20 large glitches. In the sample the total observation span is larger than 2000 pulsar years. We assume that all pulsars experience such glitches, with rates that depend on the pulsars’ rotation rate and spin-down rate, and on the glitch model. The superfluid vortex unpinning model gives good agreement with the observed distribution of glitches and with the parameter values deduced for the Vela pulsar glitches.

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17

Manchester, R. N. "Finding Pulsars at Parkes." Publications of the Astronomical Society of Australia 18, no. 1 (2001): 1–11. http://dx.doi.org/10.1071/as01002.

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AbstractThere are many reasons why it is important to increase the number of known pulsars. Not only do pulsar searches continue to improve statistical estimates of, for example, pulsar birthrates, lifetimes and the Galactic distribution, but they continue to turn up interesting and, in some cases, unique individual pulsars. In the early days of pulsar astronomy, the Molonglo radio telescope led the world as a pulsar detection instrument. However, the Parkes radio telescope, with its frequency versatility and greater tracking ablility, combined with sensitive receivers and powerful computer detection algorithms, is now the world’s most successful telescope at finding pulsars. The Parkes multibeam survey, begun in 1997, by itself will come close to doubling the number of known pulsars. Parkes has also been very successful at finding millisecond pulsars (MSPs), especially in globular clusters. One third of the known MSPs have been found in just one cluster, 47 Tucanae.

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18

Dai, Shi, Simon Johnston, and George Hobbs. "Searching for pulsars in future radio continuum surveys." Proceedings of the International Astronomical Union 13, S337 (September 2017): 328–29. http://dx.doi.org/10.1017/s1743921317008833.

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AbstractRadio continuum surveys are equally sensitive to all pulsars, not affected by dispersion measure smearing, scattering or orbital modulation of spin periods, and therefore allow us to search for extreme pulsars, such as sub-millisecond pulsars, pulsar-black hole systems and pulsars in the Galactic Centre. As we move towards the Square Kilometre Array (SKA) era, searching for pulsars in continuum images will complement conventional pulsar searches, and make it possible to find extreme objects.

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19

Octau, Franck, Grégory Desvignes, Ismaël Cognard, David Champion, Patrick Lazarus, David Smith, and Gilles Theureau. "Search for and study of pulsars with the Nançay Radio Telescope." Proceedings of the International Astronomical Union 13, S337 (September 2017): 386–87. http://dx.doi.org/10.1017/s1743921317009516.

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AbstractSince the discovery of the first pulsar in 1967, over 2500 pulsars have been discovered. Pulsars enable a broad range of studies: from the study of the properties of the interstellar medium and of pulsar magnetospheres to tests of gravity in the strong-field regime and the characterisation of the cosmological gravitation wave background. These reasons are the main drive for searching for more pulsars. A blind pulsar survey, named SPAN512, was initiated with the Nançay Radio Telescope in 2012. Conducted at 1.4 GHz with a sampling time of 64μs and 500-kHz frequency channels, SPAN512 was designed to search for fast and distant pulsars in the Galactic plane. Here we describe the current status of the survey and present the latest discovery, PSR J2055+3829, a 2.08-ms pulsar in a black widow system.

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20

Mishra, Kaushal K., Ayman I. Hawari, and Victor H. Gillette. "Design and Performance of a Thermal Neutron Imaging Facility at the North Carolina State University PULSTAR Reactor." IEEE Transactions on Nuclear Science 53, no. 6 (December 2006): 3904–11. http://dx.doi.org/10.1109/tns.2006.884323.

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21

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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22

MANCHESTER, R. N. "PULSAR SEARCHING AND TIMING." International Journal of Modern Physics D 22, no. 01 (January 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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23

Cameron, A. D., D. J. Champion, M. Bailes, V. Balakrishnan, E. D. Barr, C. G. Bassa, S. Bates, et al. "The High Time Resolution Universe Pulsar Survey – XVI. Discovery and timing of 40 pulsars from the southern Galactic plane." Monthly Notices of the Royal Astronomical Society 493, no. 1 (January 14, 2020): 1063–87. http://dx.doi.org/10.1093/mnras/staa039.

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ABSTRACT We present the results of processing an additional 44 per cent of the High Time Resolution Universe South Low Latitude (HTRU-S LowLat) pulsar survey, the most sensitive blind pulsar survey of the southern Galactic plane to date. Our partially coherent segmented acceleration search pipeline is designed to enable the discovery of pulsars in short, highly accelerated orbits, while our 72-min integration lengths will allow us to discover pulsars at the lower end of the pulsar luminosity distribution. We report the discovery of 40 pulsars, including three millisecond pulsar-white dwarf binary systems (PSRs J1537−5312, J1547−5709, and J1618−4624), a black-widow binary system (PSR J1745−23) and a candidate black-widow binary system (PSR J1727−2951), a glitching pulsar (PSR J1706−4434), an eclipsing binary pulsar with a 1.5-yr orbital period (PSR J1653−45), and a pair of long spin-period binary pulsars which display either nulling or intermittent behaviour (PSRs J1812−15 and J1831−04). We show that the total population of 100 pulsars discovered in the HTRU-S LowLat survey to date represents both an older and lower luminosity population, and indicates that we have yet to reach the bottom of the luminosity distribution function. We present evaluations of the performance of our search technique and of the overall yield of the survey, considering the 94 per cent of the survey which we have processed to date. We show that our pulsar yield falls below earlier predictions by approximately 25 per cent (especially in the case of millisecond pulsars), and discuss explanations for this discrepancy as well as future adaptations in RFI mitigation and searching techniques which may address these shortfalls.

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Wang, Na, R. N. Manchester, Aili Yusup, Xinji Wu, Jin Zhang, and Maozheng Chen. "Scintillation Observations of Strong Northern Pulsars." International Astronomical Union Colloquium 182 (2001): 57–60. http://dx.doi.org/10.1017/s0252921100000695.

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AbstractScintillation of pulsar radio emission provides information about the interstellar medium along the path to the pulsar and the velocities of pulsars. It also affects the precision of pulse timing observations. Using a pulsar timing system developed at the Urumqi Astronomical Observatory 25 m telescope, we observed diffractive scintillation dynamic spectra for several strong northern pulsars. This paper introduces the observing system and discusses the observational results.

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25

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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26

Wielebinski, Richard. "Pulsar Studies at High Radio Frequencies." International Astronomical Union Colloquium 177 (2000): 205–10. http://dx.doi.org/10.1017/s0252921100059480.

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AbstractPulsars were discovered at 81.5 MHz and a lot of the studies of these exciting objects have been made up to the present time at radio frequencies below 1.6 GHz. The reasons for this concentration on the low radio frequency characteristics of pulsars is the fact that the spectra are very steep and that very few radio telescopes exist that are capable of efficient operations at high radio frequencies. The Effelsberg 100-m radio telescope of the Max-Planck-Institut fur Radioastronomie operates regularly up to the frequency of 50 GHz and was used to study pulsars at cm/mm-wavelengths. In the southern skies the Parkes 64-m telescope has been used to study pulsars up to 8.4 GHz. One pulsar has been detected at 87 GHz with the 30-m Pico Veleta telescope of IRAM.The studies of pulsars over the whole frequency range are of great importance because this is necessary for the elucidation of the mechanism that is responsible for the pulsar emission. The high polarization of pulsar radio emission at lower radio frequencies has supported the hypothesis of a coherent emission mechanism, which is required to generate the high luminosity. It has been known for some time that pulsars, unlike other radio sources, have a lower polarization at high radio frequencies. Recently a change of pulsar spectrum, a flattening or possibly an inversion has been observed at the highest radio frequencies. The inversion of the pulsar spectrum seems to coincide with a complete depolarization of some pulsars.Millisecond pulsars are less luminous than normal pulsars. This makes them even more difficult to detect at higher radio frequencies. Recent observations have extended the spectra of ten millisecond pulsars up to 4.85 GHz. The results imply that millisecond pulsars have properties very similar to normal (slow) pulsars, which suggests similar emission mechanisms.

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27

Guillemot, L. "Radio counterparts of gamma-ray pulsars." Proceedings of the International Astronomical Union 8, S291 (August 2012): 87–92. http://dx.doi.org/10.1017/s1743921312023241.

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AbstractObservations of pulsars with the Large Area Telescope (LAT) on the Fermi satellite have revolutionized our view of the gamma-ray pulsar population. For the first time, a large number of young gamma-ray pulsars have been discovered in blind searches of the LAT data. More generally, the LAT has discovered many new gamma-ray sources whose properties suggest that they are powered by unknown pulsars. Radio observations of gamma-ray sources have been key to the success of pulsar studies with the LAT. For example, radio observations of LAT-discovered pulsars provide constraints on the relative beaming fractions, which are crucial for pulsar population studies. Also, radio searches of LAT sources with no known counterparts have been very efficient, with the discovery of over forty millisecond pulsars. I review radio follow-up studies of LAT-discovered pulsars and unidentified sources, and discuss some of the implications of the results.

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28

McLaughlin, Maura, and James Cordes. "Gamma Ray Pulsar Luminosities." International Astronomical Union Colloquium 177 (2000): 359–62. http://dx.doi.org/10.1017/s0252921100059996.

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AbstractWe apply a likelihood analysis to pulsar detections, pulsar upper limits, and diffuse background measurements from the OSSE and EGRET instruments to constrain theγ-rays pulsar luminosity law. We find a steeper dependence on period and magnetic field at OSSE than at EGRET energies. We also find that pulsars may be an important component of the OSSE diffuse flux, but are most likely not important for EGRET. We estimate that as many as half of the unidentified EGRET sources may beγ-rays pulsars. Furthermore, we predict that GLAST will detect roughly 1000γ-rays pulsars, only 100 of which are currently known.

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29

Pan, Yuanyue, Chengmin Zhang, and Na Wang. "Minimum accretion rate for millisecond pulsar formation in binary system." Proceedings of the International Astronomical Union 8, S290 (August 2012): 291–92. http://dx.doi.org/10.1017/s1743921312020066.

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Abstract186 binary pulsars are shown in the magnetic field versus spin period (B-P) diagram, and their relations to the millisecond pulsars can be clearly seen. We declaim a minimum accretion rate for the millisecond pulsar formation both from the observation and theory. If the accretion rate is lower than the minimum accretion rate, the pulsar in binary system will not become a millisecond pulsar after the evolution.

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30

Itoh, Naoki, and Takemi Kotouda. "Velocity-Magnetic Field Correlation of Pulsars." International Astronomical Union Colloquium 160 (1996): 49–50. http://dx.doi.org/10.1017/s0252921100040999.

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Monte Carlo simulations of the evolution of pulsars are carried out in order to compare with the recent measurement of the pulsar transverse velocity by Lyne & Lorimer (1994). The new electron density distribution model of Taylor & Cordes (1993) is adopted in the simulation. Accurate pulsar orbits in the Galactic gravitational field are calculated. It is found that the constant magnetic field model of pulsars can account for the new measurement of the pulsar transverse velocity and the apparent correlation between the strength of the magnetic field and the transverse velocity of the pulsars. The present finding confirms the validity of the constant magnetic field model of pulsars and consolidates the idea that the apparent correlation between the strength of the magnetic field and the transverse velocity of the pulsars is caused by observational selection effects.

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31

Perera, B. B. P., M. E. DeCesar, P. B. Demorest, M. Kerr, L. Lentati, D. J. Nice, S. Osłowski, et al. "The International Pulsar Timing Array: second data release." Monthly Notices of the Royal Astronomical Society 490, no. 4 (October 12, 2019): 4666–87. http://dx.doi.org/10.1093/mnras/stz2857.

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ABSTRACT In this paper, we describe the International Pulsar Timing Array second data release, which includes recent pulsar timing data obtained by three regional consortia: the European Pulsar Timing Array, the North American Nanohertz Observatory for Gravitational Waves, and the Parkes Pulsar Timing Array. We analyse and where possible combine high-precision timing data for 65 millisecond pulsars which are regularly observed by these groups. A basic noise analysis, including the processes which are both correlated and uncorrelated in time, provides noise models and timing ephemerides for the pulsars. We find that the timing precisions of pulsars are generally improved compared to the previous data release, mainly due to the addition of new data in the combination. The main purpose of this work is to create the most up-to-date IPTA data release. These data are publicly available for searches for low-frequency gravitational waves and other pulsar science.

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32

Yang, Tinggao, and Guangren Ni. "Ensemble Pulsar Time Study by Pulsar Timing Observations." Symposium - International Astronomical Union 218 (2004): 439–40. http://dx.doi.org/10.1017/s0074180900181604.

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Long term timing of multiple millisecond pulsars can contribute to the study of an ensemble pulsar time scale PTens. A wavelet decomposition algorithm (WDA) was applied to define a PTens using the available millisecond pulsar timing datA. The PTens obtained from WDA is more stable than those resulting from other algorithms. The Chinese 50 m radio telescope is specially designed for PTens study and detection of gravitational wave background via millisecond pulsars timing observations. A scheme for multiple millisecond pulsar timing and ensemble pulsar time study is discussed in some detail.

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33

Galama, T. J., J. Van Paradijs, E. P. J. van den Heuvel, A. G. de Bruyn, R. M. Campbell, R. C. Vermeulen, J. F. Lestrade, F. Verbunt, and R. T. Schilizzi. "Determining Motions and Birthplaces of Pulsars through VLBI Astrometry." International Astronomical Union Colloquium 164 (1998): 391–92. http://dx.doi.org/10.1017/s025292110004608x.

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AbstractWe present first results of global VLBI astrometric pulsar parallax and proper motion measurements (phase-reference). The aim is to obtain information on pulsar motions and pulsar birthplaces. Proper motions could provide answers to questions like: How large are pulsar velocities at birth? How are these velocities produced and what is the final galactic pulsar distribution? Identification of birthplaces (with, e.g., an OB-association) provides information on the pulsar progenitor population (the fraction of pulsars born in binaries; the mass range of the progenitors etc.). We have a first epoch on three pulsars, selected on the basis of age (young < 3 Myr), flux density (relatively strong) and presence in the solar neighborhood (d < 3 kpc). Gating increases the SNR by typically a factor of 5.

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Dewey, Rachel J., and James M. Cordes. "Monte Carlo Simulations of Radio Pulsars and Their Progenitors." Symposium - International Astronomical Union 125 (1987): 408. http://dx.doi.org/10.1017/s0074180900161030.

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The formation of neutron stars in binary systems is often used to explain the nature of specific radio pulsars and characteristics of the pulsar population as a whole. We have investigated the extent to which such scenarios provide a self-consistent description of the pulsar population. Using a computer simulation, we modeled the evolution of the main sequence stellar population and compared the predicted neutron star population to the observed radio pulsar population, focusing our attention on the pulsar velocity distribution and the incidence of binary pulsars. These characteristics relate very directly to the binary nature of pulsar progenitors, and are not strongly dependent on models of pulsar magentic field and luminosity evolution.The need to reproduce both the high velocities typical of pulsars and the low incidence of binary pulsars strongly constrains the formation of pulsars in binary systems. Unless one assumes that virtually all pulsars originate in close binary systems, the observed velocity distribution cannot result from the disruption of binary systems by symmetric supernova explosions; some additional acceleration process (e.g. asymmetric supernova mass ejection or asymmetries in pulsar radiation) must act during or soon after a pulsar's formation. It is possible to reproduce the velocity distribution by assuming that all pulsars are born in binary systems with initial orbital periods less than about 30 years. However, the predicted incidence of binaries is then too large by more than an order of magnitude, unless one also assumes that the process of mass transfer from the primary to the secondary is almost always non-conservative, or that the minimum mass necessary for a stripped helium core to explode as a supernova is larger (over 4 M⊙) than currently believed. Further analyses of the radio pulsar population, the X-ray binary population and the abundances of elements ejected in supernovae should help determine which of these alternatives is most reasonble. Additional studies of the main sequence stellar population, accounting more accurately for evolutionary and observational selection effects, will reduce the uncertainties in modeling the formation of the neutron star population.It has also been suggested that the observed correlation between pulsar velocities and magnetic moments (see Cordes, these Proceedings) is induced by the differing evolutionary paths by which stars in binary systems form radio pulsars. Our simulation does not reproduce this correlation, and we do not find any paths likely to produce low velocity, low magnetic field neutron stars not in binary systems.We are submitting a full description of our model and results to The Astrophysical Journal.

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Sekido, M., M. Imae, Y. Hanado, Y. Takahashi, Y. Koyama, Y. P. Ilyasov, A. E. Rodin, A. E. Avramenko, V. V. Oreshko, and B. A. Poperechenko. "Pulsar VLBI Experiment with Kashima(Japan)-Kalyazin(Russia) Baseline." International Astronomical Union Colloquium 160 (1996): 117–18. http://dx.doi.org/10.1017/s0252921100041208.

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Interferometric measurement of a pulsar is one of the most effective techniques to measure accurate source position. Precise measurement of pulsar position will give us the information of proper motion and parallax. Interferometric measurements on pulsars have been carried out, but the number of the pulsars whose position were measured is still smaller than the total number of pulsars. Because newly discovered pulsars are rapidly increasing due to recent intensive systematic surveys. We have started measuring their position by using VLBI between Kashima and Kalyazin. This report shows the results of the first experiment.

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Manchester, R. N., A. G. Lyne, F. Camilo, V. M. Kaspi, I. H. Stairs, F. Crawford, D. J. Morris, J. F. Bell, and N. D’Amico. "Timing the Parkes Multibeam Pulsars." International Astronomical Union Colloquium 177 (2000): 49–54. http://dx.doi.org/10.1017/s0252921100058991.

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AbstractMeasurement of accurate positions, pulse periods and period derivatives is an essential follow-up to any pulsar survey. The procedures being used to obtain timing parameters for the pulsars discovered in the Parkes multibeam pulsar survey are described. Completed solutions have been obtained so far for about 80 pulsars. They show that the survey is preferentially finding pulsars with higher than average surface dipole magnetic fields. Eight pulsars have been shown to be members of binary systems and some of the more interesting results relating to these are presented.

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Wang, Na, Jin Zhang, and Xin-Ji Wu. "Pulsar Observations in China – Status and Results." Symposium - International Astronomical Union 214 (2003): 159–62. http://dx.doi.org/10.1017/s007418090019432x.

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We present the status and results of pulsar observations in China. Pulsar observations at Urumqi Observatory over more than two years have resulted in updated rotation parameters for 74 pulsars. Comparison with earlier observations shows that long-term period and period-derivative fluctuations are probably dominated by unseen glitches. We also monitored the variation of pulsar scintillation dynamic spectra for a few strong pulsars. The data show major variations in the scintillation parameters. A new system at a lower frequency is planned to allow investigation of the frequency dependence of pulsar properties. A 50-m telescope for millisecond pulsar timing is also being planned at the National Astronomical Observatories, Beijing, and should be constructed within three years.

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Levin, L., W. Armour, C. Baffa, E. Barr, S. Cooper, R. Eatough, A. Ensor, et al. "Pulsar Searches with the SKA." Proceedings of the International Astronomical Union 13, S337 (September 2017): 171–74. http://dx.doi.org/10.1017/s1743921317009528.

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AbstractThe Square Kilometre Array will be an amazing instrument for pulsar astronomy. While the full SKA will be sensitive enough to detect all pulsars in the Galaxy visible from Earth, already with SKA1, pulsar searches will discover enough pulsars to increase the currently known population by a factor of four, no doubt including a range of amazing unknown sources. Real time processing is needed to deal with the 60 PB of pulsar search data collected per day, using a signal processing pipeline required to perform more than 10 POps. Here we present the suggested design of the pulsar search engine for the SKA and discuss challenges and solutions to the pulsar search venture.

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Liu, Kuo. "Update on the European Pulsar Timing Array." Proceedings of the International Astronomical Union 8, S291 (August 2012): 180. http://dx.doi.org/10.1017/s1743921312023575.

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AbstractThe European Pulsar Timing Array (EPTA) is one the of three global Pulsar Timing Array communities, aiming to use the clock nature of pulsars to detect gravitational wave. In this talk, I will provide an introduction to the current status of EPTA pulsar observations and present an overview of the recent results. I will also give an update on the progress of the Large European Array for Pulsar (LEAP) project, which attempts to coherently combine the data from the five biggest single site radio telescopes in Europe and make an equivalently 200-metre diameter dish. The LEAP project is an ideal effort in performing high precision pulsar timing and studying characteristics of single pulses from millisecond 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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Straal, S. M., L. Connor, and J. van Leeuwen. "A dispersion excess from pulsar wind nebulae and supernova remnants: Implications for pulsars and FRBs." Astronomy & Astrophysics 634 (February 2020): A105. http://dx.doi.org/10.1051/0004-6361/201833376.

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Young pulsars and the pulsar wind nebulae (PWNe) or supernova remnants (SNRs) that surround them are some of the most dynamic and high-powered environments in our Universe. With the rise of more sensitive observations, the number of pulsar-SNR and PWN associations (hereafter, SNR/PWN) has increased, yet we do not understand to which extent this environment influences the pulsars’ impulsive radio signals. We studied the dispersive contribution of SNRs and PWNe on Galactic pulsars, and considered their relevance to fast radio bursts (FRBs) such as FRB 121102. We investigated the dispersion measure (DM) contribution of SNRs and PWNe by comparing the measured DMs of Galactic pulsars in a SNR/PWN to the DM expected only from the intervening interstellar electrons, using the NE2001 model. We find that a two-σ DM contribution of SNRs and PWNe to the pulsar signal exists, amounting to 21.1 ± 10.6 pc cm−3. The control sample of pulsars unassociated with a SNR/PWN shows no excess. We model the SNR and PWN electron densities for each young pulsar in our sample and show that these indeed predict an excess of this magnitude. By extrapolating to the kind of fast-spinning, high magnetic field, young pulsars that may power FRBs, we show their SNR and PWN are capable of significantly contributing to the observed DM.

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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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Vranesevic, N. "The Pulsar Birth Rate from the Parkes Multibeam Survey." Symposium - International Astronomical Union 218 (2004): 121–22. http://dx.doi.org/10.1017/s007418090018074x.

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We report on calculations of the pulsar birth rate based on the results of the Parkes multibeam survey. Prom the observed sample of more than 800 pulsars, we compute the pulsar current, accounting as accurately as possible for all known selection effects. The main goal of this work is to understand the pulsar birth rate as a function of the surface dipole magnetic field strength. We show that pulsars with magnetic fields greater than 1012.5 G account for about half of the total birth rate.

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Kaspi, V. M. "High-Precision Timing of Millisecond Pulsars and Precision Astrometry." Symposium - International Astronomical Union 166 (1995): 163–71. http://dx.doi.org/10.1017/s0074180900228027.

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We present the technique of long-term, high-precision timing of millisecond pulsars as applied to precision astrometry. We provide a tutorial on pulsars and pulsar timing, as well as up-to-date results of long-term timing observations of two millisecond pulsars, PSRs B1855+09 and B1937+21. We consider the feasibility of tying the extragalactic and optical reference frames to that defined by solar system objects, and we conclude that precision astrometry from millisecond pulsar timing has a bright future.

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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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Parent, E., V. M. Kaspi, S. M. Ransom, C. Patel, and M. Krasteva. "The implementation of a Fast-Folding Algorithm in the PALFA survey." Proceedings of the International Astronomical Union 13, S337 (September 2017): 388–89. http://dx.doi.org/10.1017/s1743921317008638.

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AbstractThe PALFA survey, the most sensitive blind search for radio pulsars, has now discovered 180 pulsars in the Galactic Plane, the vast of which have periods shorter than 2 seconds. One reason that pulsar surveys may miss long-period radio pulsars is the strong effect of red noise at low modulation frequencies. It is possible to address this reduction in sensitivity by using a Fast-Folding Algorithm (FFA). We have adapted this algorithm for radio pulsar searching and applied it to PALFA observations. A sensitivity analysis of the algorithm has been conducted using synthetic pulsar signals injected in real observational data and this study shows that the FFA improves the PALFA survey sensitivity, as reported in Lazarus et al.(2015), by at least a factor of two at periods of ~6 sec, implying that the PALFA survey should discover more long-period radio pulsars in the future.

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Fuentes, J. R., C. M. Espinoza, and A. Reisenegger. "Glitch time series and size distributions in eight prolific pulsars." Astronomy & Astrophysics 630 (October 2019): A115. http://dx.doi.org/10.1051/0004-6361/201935939.

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Context. Glitches are rare spin-up events that punctuate the smooth slow-down of the rotation of pulsars. For the Vela pulsar and PSR J0537−6910, their large glitch sizes and the times between consecutive events have clear preferred scales (Gaussian distributions), contrary to the handful of other pulsars with enough glitches for such a study. Moreover, PSR J0537−6910 is the only pulsar that shows a strong positive correlation between the size of each glitch and the waiting time until the following one. Aims. We attempt to understand this behaviour through a detailed study of the distributions and correlations of glitch properties for the eight pulsars with at least ten detected glitches. Methods. We modelled the distributions of glitch sizes and of the times between consecutive glitches for the eight pulsars with at least ten detected events. We also looked for possible correlations between these parameters and used Monte Carlo simulations to explore two hypotheses that could explain why the correlation so clearly seen in PSR J0537−6910 is absent in other pulsars. Results. We confirm the above results for Vela and PSR J0537−6910, and verify that the latter is the only pulsar with a strong correlation between glitch size and waiting time to the following glitch. For the remaining six pulsars, the waiting time distributions are best fitted by exponentials, and the size distributions are best fitted by either power laws, exponentials, or log-normal functions. Some pulsars in the sample yield significant Pearson and Spearman coefficients (rp and rs) for the aforementioned correlation, confirming previous results. Moreover, for all except the Crab pulsar, both coefficients are positive. For each coefficient taken separately, the probability of this happening is 1/16. Our simulations show that the weaker correlations in pulsars other than PSR J0537−6910 cannot be due to missing glitches that are too small to be detected. We also tested the hypothesis that each pulsar may have two kinds of glitches, namely large, correlated ones and small, uncorrelated ones. The best results are obtained for the Vela pulsar, which exhibits a correlation with rp = 0.68 (p-value = 0.003) if its two smallest glitches are removed. The other pulsars are harder to accommodate under this hypothesis, but their glitches are not consistent with a pure uncorrelated population either. We also find that all pulsars in our sample, except the Crab pulsar, are consistent with the previously found constant ratio between glitch activity and spin-down rate, ν̇g/|ν̇| = 0.010±0.001, even though some of them have not shown any large glitches. Conclusions. To explain these results, we speculate except in the case of the Crab pulsar, that all glitches draw their angular momentum from a common reservoir (presumably a neutron superfluid component containing ≈1% of the star’s moment of inertia). However, two different trigger mechanisms could be active, a more deterministic one for larger glitches and a more random one for smaller ones.

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Yusifov, I. M. "On the Shape of the Pulsar Emission Diagram." International Astronomical Union Colloquium 128 (1992): 147–49. http://dx.doi.org/10.1017/s0002731600154964.

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AbstractOn the basis of pulse profiles in a limited interval of wavelength for ~260 pulsars, the dependence of the shape and width of the pulsar radiation pattern on pulsar period is investigated. The relative pulse duration is compared with the ratio of numbers of single and multicomponent pulsars. It is shown that the simple circular hollow cone model does not agree with observational data. Preliminary estimates show that the young pulsars (with short periods) have an elliptical pattern which at long periods becomes circular.

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Reardon, D. J., R. M. Shannon, A. D. Cameron, B. Goncharov, G. B. Hobbs, H. Middleton, M. Shamohammadi, et al. "The Parkes pulsar timing array second data release: timing analysis." Monthly Notices of the Royal Astronomical Society 507, no. 2 (August 11, 2021): 2137–53. http://dx.doi.org/10.1093/mnras/stab1990.

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ABSTRACT The main goal of pulsar timing array experiments is to detect correlated signals such as nanohertz-frequency gravitational waves. Pulsar timing data collected in dense monitoring campaigns can also be used to study the stars themselves, their binary companions, and the intervening ionized interstellar medium. Timing observations are extraordinarily sensitive to changes in path-length between the pulsar and the Earth, enabling precise measurements of the pulsar positions, distances and velocities, and the shapes of their orbits. Here we present a timing analysis of 25 pulsars observed as part of the Parkes Pulsar Timing Array (PPTA) project over time spans of up to 24 yr. The data are from the second data release of the PPTA, which we have extended by including legacy data. We make the first detection of Shapiro delay in four Southern pulsars (PSRs J1017−7156, J1125−6014, J1545−4550, and J1732−5049), and of parallax in six pulsars. The prominent Shapiro delay of PSR J1125−6014 implies a neutron star mass of Mp = 1.5 ± 0.2 M⊙ (68 per cent credibility interval). Measurements of both Shapiro delay and relativistic periastron advance in PSR J1600−3053 yield a large but uncertain pulsar mass of $M_p = 2.06^{+0.44}_{-0.41}$ M⊙ (68 per cent credibility interval). We measure the distance to PSR J1909−3744 to a precision of 10 lyr, indicating that for gravitational wave periods over a decade, the pulsar provides a coherent baseline for pulsar timing array experiments.

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Gupta, Y., P. Gothoskar, and N. D. Ramesh Bhat. "First Results from Simultaneous Dual Frequency Observations of Pulsars." Symposium - International Astronomical Union 199 (2002): 369–72. http://dx.doi.org/10.1017/s0074180900169347.

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One of the unique capabilities of the GMRT is the facility for simultaneous multi-frequency observations of pulsars. We have initiated such observations with the aims of (i) studying frequency dependence of pulsar emission, (ii) accurate estimates of pulsar dispersion measure and its variations and (iii) multi-frequency interstellar scintillation studies. Here we present some results from the ongoing dual frequency observations of pulsars.

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