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0000-0002-7122-4963
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CSIRO Astronomy and Space Science
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Publisher: American Astronomical Society
Date: 27-02-2012
Publisher: Oxford University Press (OUP)
Date: 21-04-1998
Publisher: Oxford University Press (OUP)
Date: 15-02-2021
Abstract: We describe the ongoing Relativistic Binary programme (RelBin), a part of the MeerTime large survey project with the MeerKAT radio telescope. RelBin is primarily focused on observations of relativistic effects in binary pulsars to enable measurements of neutron star masses and tests of theories of gravity. We selected 25 pulsars as an initial high priority list of targets based on their characteristics and observational history with other telescopes. In this paper, we provide an outline of the programme, and present polarization calibrated pulse profiles for all selected pulsars as a reference catalogue along with updated dispersion measures. We report Faraday rotation measures for 24 pulsars, twelve of which have been measured for the first time. More than a third of our selected pulsars show a flat position angle swing confirming earlier observations. We demonstrate the ability of the Rotating Vector Model, fitted here to seven binary pulsars, including the Double Pulsar (PSR J0737–3039A), to obtain information about the orbital inclination angle. We present a high time resolution light curve of the eclipse of PSR J0737–3039A by the companion’s magnetosphere, a high-phase-resolution position angle swing for PSR J1141–6545, an improved detection of the Shapiro delay of PSR J1811–2405, and pulse scattering measurements for PSRs J1227–6208, J1757–1854, and J1811–1736. Finally, we demonstrate that timing observations with MeerKAT improve on existing data sets by a factor of, typically, 2–3, sometimes by an order of magnitude.
Publisher: American Astronomical Society
Date: 04-05-2012
Publisher: Oxford University Press (OUP)
Date: 07-06-2006
Publisher: American Astronomical Society
Date: 23-01-2012
Publisher: American Astronomical Society
Date: 05-06-2017
Publisher: Oxford University Press (OUP)
Date: 14-01-2020
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.
Publisher: Oxford University Press (OUP)
Date: 15-05-1995
Publisher: Oxford University Press (OUP)
Date: 11-10-2008
Publisher: Oxford University Press (OUP)
Date: 02-09-2021
Abstract: We report observed and derived timing parameters for three millisecond pulsars (MSPs) from observations collected with the Parkes 64-m telescope, Murriyang. The pulsars were found during reprocessing of archival survey data by Mickaliger et al. One of the new pulsars (PSR J1546–5925) has a spin period P = 7.8 ms and is isolated. The other two (PSR J0921–5202 with P = 9.7 ms and PSR J1146–6610 with P = 3.7 ms) are in binary systems around low-mass (${\\gt}0.2\\, {\\rm M}_{\\odot }$) companions. Their respective orbital periods are 38.2 and 62.8 d. While PSR J0921–5202 has a low orbital eccentricity e = 1.3 × 10−5, in keeping with many other Galactic MSPs, PSR J1146–6610 has a significantly larger eccentricity, e = 7.4 × 10−3. This makes it a likely member of a group of eccentric MSP–helium white dwarf binary systems in the Galactic disc whose formation is poorly understood. Two of the pulsars are co-located with previously unidentified point sources discovered with the Fermi satellite’s Large Area Telescope, but no γ-ray pulsations have been detected, likely due to their low spin-down powers. We also show that, particularly in terms of orbital ersity, the current s le of MSPs is far from complete and is subject to a number of selection biases.
Publisher: Oxford University Press (OUP)
Date: 10-2003
Publisher: American Astronomical Society
Date: 20-05-2008
DOI: 10.1086/587054
Publisher: American Astronomical Society
Date: 05-1996
DOI: 10.1086/117938
Publisher: Oxford University Press (OUP)
Date: 06-1998
Publisher: American Astronomical Society
Date: 14-03-2007
DOI: 10.1086/516630
Publisher: Oxford University Press (OUP)
Date: 07-12-2017
Publisher: American Astronomical Society
Date: 14-07-2020
Publisher: American Astronomical Society
Date: 19-12-2013
Publisher: Oxford University Press (OUP)
Date: 04-2001
Publisher: Springer Science and Business Media LLC
Date: 24-04-2017
Publisher: Springer Science and Business Media LLC
Date: 08-1999
DOI: 10.1038/23650
Publisher: Oxford University Press (OUP)
Date: 11-11-2002
Publisher: EDP Sciences
Date: 26-05-2003
Publisher: American Astronomical Society
Date: 06-1993
DOI: 10.1086/186859
Publisher: American Astronomical Society
Date: 06-1994
DOI: 10.1086/187391
Publisher: Cambridge University Press (CUP)
Date: 2010
DOI: 10.1071/AS09084
Abstract: This paper defines the mathematical convention adopted to describe an electromagnetic wave and its polarisation state, as implemented in the psrchive software and represented in the psrfits definition. Contrast is made between the convention that has been widely accepted by pulsar astronomers and the IAU/IEEE definitions of the Stokes parameters. The former is adopted as the PSR/IEEE convention, and a set of useful parameters are presented for describing the differences between the PSR/IEEE standard and the conventions (either implicit or explicit) that form part of the design of observatory instrumentation. To aid in the empirical determination of instrumental convention parameters, well-calibrated average polarisation profiles of PSR J0304+1932 and PSR J0742–2822 are presented at radio wavelengths of approximately 10, 20, and 40 cm.
Publisher: Oxford University Press (OUP)
Date: 02-09-2011
Publisher: Oxford University Press (OUP)
Date: 08-12-2014
Publisher: Oxford University Press (OUP)
Date: 31-12-2016
Publisher: Oxford University Press (OUP)
Date: 11-1991
Publisher: Oxford University Press (OUP)
Date: 12-2012
Publisher: American Astronomical Society
Date: 12-2021
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.
Publisher: Oxford University Press (OUP)
Date: 15-02-2023
Abstract: We present the largest single survey to date of average profiles of radio pulsars, observed and processed using the same telescope and data reduction software. Specifically, we present measurements for 1170 pulsars, observed by the Thousand Pulsar Array programme at the 64-dish SARAO MeerKAT radio telescope, in a frequency band from 856 to 1712 MHz. We provide rotation measures (RM), dispersion measures, flux densities, and polarization properties. The catalogue includes 254 new RMs that substantially increase the total number of known pulsar RMs. Our integration times typically span over 1000 in idual rotations per source. We show that the radio (pseudo-) luminosity has a strong, shallow dependence on the spin-down energy, proportional to $\\dot{E}^{0.15\\pm 0.04}$, that contradicts some previous proposals of population synthesis studies. In addition, we find a significant correlation between the steepness of the observed flux density spectra and $\\dot{E}$, and correlations of the fractional linear polarization with $\\dot{E}$, the spectral index, and the pulse width, which we discuss in the context of what is known about pulsar radio emission and how pulsars evolve with time. On the whole, we do not see significant correlations with the estimated surface magnetic field strength, and the correlations with $\\dot{E}$ are much stronger than those with the characteristic age. This finding lends support to the suggestion that magnetic dipole braking may not be the dominant factor for the evolution of pulsar rotation over the lifetimes of pulsars. A public data release of the high-fidelity time-averaged pulse profiles in full polarization accompanies our catalogue.
Publisher: Oxford University Press (OUP)
Date: 03-2003
Publisher: American Astronomical Society
Date: 25-01-2012
Publisher: Oxford University Press (OUP)
Date: 12-08-2017
Publisher: American Astronomical Society
Date: 05-04-2018
Publisher: Oxford University Press (OUP)
Date: 08-01-2021
Abstract: Using the state-of-the-art SKA precursor, the MeerKAT radio telescope, we explore the limits to precision pulsar timing of millisecond pulsars achievable due to pulse stochasticity (jitter). We report new jitter measurements in 15 of the 29 pulsars in our s le and find that the levels of jitter can vary dramatically between them. For some, like the 2.2 ms pulsar PSR J2241−5236, we measure an implied jitter of just ∼4 ns h−1, while others, like the 3.9 ms PSR J0636−3044, are limited to ∼100 ns h−1. While it is well known that jitter plays a central role to limiting the precision measurements of arrival times for high signal-to-noise ratio observations, its role in the measurement of dispersion measure (DM) has not been reported, particularly in broad-band observations. Using the exceptional sensitivity of MeerKAT, we explored this on the bright millisecond pulsar PSR J0437−4715 by exploring the DM of literally every pulse. We found that the derived single-pulse DMs vary by typically 0.0085 cm−3 pc from the mean, and that the best DM estimate is limited by the differential pulse jitter across the band. We postulate that all millisecond pulsars will have their own limit on DM precision which can only be overcome with longer integrations. Using high-time resolution filterbank data of 9 μs, we also present a statistical analysis of single-pulse phenomenology. Finally, we discuss optimization strategies for the MeerKAT pulsar timing program and its role in the context of the International Pulsar Timing Array.
Publisher: Oxford University Press (OUP)
Date: 07-11-2022
Abstract: We present the detection of 107 pulsars with interstellar scintillation arcs at 856–1712 MHz, observed with the MeerKAT Thousand Pulsar Array Programme. Scintillation arcs appear to be ubiquitous in clean, high S/N observations, their detection mainly limited by short observing durations and coarse frequency channel resolution. This led the survey to be sensitive to nearby, lightly scattered pulsars with high effective velocity – from a large proper motion, a screen nearby the pulsar, or a screen near the Earth. We measure the arc curvatures in all of our sources, which can be used to give an estimate of screen distances in pulsars with known proper motion, or an estimate of the proper motion. The short scintillation time-scale in J1731−4744 implies a scattering screen within 12 pc of the source, strongly suggesting the association between this pulsar and the supernova remnant RCW 114. We measure multiple parabolic arcs of five pulsars, all of which are weakly scintillating with high proper motion. Additionally, several sources show hints of inverted arclets suggesting scattering from anisotropic screens. Building on this work, further targeted MeerKAT observations of many of these pulsars will improve understanding of our local scattering environment and the origins of scintillation annual scintillation curves would lead to robust screen distance measurements, and the evolution of arclets in time and frequency can constrain models of scintillation.
Publisher: Oxford University Press (OUP)
Date: 09-06-2020
Abstract: Pulsar radio emission and its polarization are observed to evolve with frequency. This frequency dependence is key to the emission mechanism and the structure of the radio beam. With the new ultra-wideband receiver (UWL) on the Parkes radio telescope we are able, for the first time, to observe how pulsar profiles evolve over a broad continuous bandwidth of 700–4000 MHz. We describe here a technique for processing broad-band polarimetric observations to establish a meaningful alignment and visualize the data across the band. We apply this to observations of PSRs J1056–6258 and J1359–6038, chosen due to previously unresolved questions about the frequency evolution of their emission. Application of our technique reveals that it is possible to align the polarization position angle (PA) across a broad frequency range when constrained to applying only corrections for dispersion and Faraday rotation to do so. However, this does not correspond to aligned intensity profiles for these two sources. We find that it is possible to convert these misalignments into emission height range estimates that are consistent with published and simulated values, suggesting that they can be attributed to relativistic effects in the magnetosphere. We discuss this work in the context of the radio beam structure and prepare the ground for a wider study of pulsar emission using broad-band polarimetric data.
Publisher: Springer Science and Business Media LLC
Date: 10-1990
DOI: 10.1038/347650A0
Publisher: Oxford University Press (OUP)
Date: 22-08-2013
Publisher: Elsevier BV
Date: 11-2021
DOI: 10.1016/J.JPSYCHORES.2021.110600
Abstract: Urinary tract infections (UTIs) are among the most common bacterial infections in pregnant women. This is the first longitudinal study investigating the association between gestational UTIs and the risk of maternal antenatal and postnatal depressive and anxiety symptoms. Data were utilised from the Avon Longitudinal Study of Parents and Children (ALSPAC). Maternal depressive and anxiety symptoms during pregnancy and the postpartum period were assessed using the Edinburgh Postnatal Depression Scale (EPDS) and the Crown-Crisp Experiential Index (CCEI), respectively. We used logistic regression analyses to examine the associations using the recommended EPDS and CCEI cut-off scores. We also ran sensitivity analyses and repeated the analyses with the continuous scores. More than 10,000 mothers had completed exposure and outcome measures during pregnancy and the postpartum period. After adjustments were made for a wide range of confounders, our findings showed that mothers with UTI during pregnancy were 1.72 (95% CI 1.45-2.04) and 1.70 (95% CI: 1.44-1.99) times more likely to report antenatal depressive and anxiety symptoms compared with mothers without UTI, respectively. Mothers with UTI also had a 35% and a 28% higher risk of postnatal depressive symptoms at eight weeks and eight months, respectively, and the risk of postnatal anxiety was 55% higher in mothers who had UTI during pregnancy (aOR = 1.55 95% CI, 1.26-1.91). The present study found positive associations between UTI during pregnancy and antenatal and postnatal depressive and anxiety symptoms. Replication and further research determining the cause of these associations is warranted.
Publisher: Springer Science and Business Media LLC
Date: 15-10-1992
DOI: 10.1038/359615A0
Publisher: Oxford University Press (OUP)
Date: 04-03-2020
Abstract: While pulsars possess exceptional rotational stability, large-scale timing studies have revealed at least two distinct types of irregularities in their rotation: red timing noise and glitches. Using modern Bayesian techniques, we investigated the timing noise properties of 300 bright southern-sky radio pulsars that have been observed over 1.0–4.8 yr by the upgraded Molonglo Observatory Synthesis Telescope (MOST). We reanalysed the spin and spin-down changes associated with nine previously reported pulsar glitches, report the discovery of three new glitches and four unusual glitch-like events in the rotational evolution of PSR J1825−0935. We develop a refined Bayesian framework for determining how red noise strength scales with pulsar spin frequency (ν) and spin-down frequency ($\dot{\nu }$), which we apply to a s le of 280 non-recycled pulsars. With this new method and a simple power-law scaling relation, we show that red noise strength scales across the non-recycled pulsar population as $\nu ^{a} |\dot{\nu }|^{b}$, where $a = -0.84^{+0.47}_{-0.49}$ and $b = 0.97^{+0.16}_{-0.19}$. This method can be easily adapted to utilize more complex, astrophysically motivated red noise models. Lastly, we highlight our timing of the double neutron star PSR J0737−3039, and the rediscovery of a bright radio pulsar originally found during the first Molonglo pulsar surveys with an incorrectly catalogued position.
Publisher: American Astronomical Society
Date: 07-1996
DOI: 10.1086/177427
Publisher: Oxford University Press (OUP)
Date: 21-03-2011
Publisher: American Astronomical Society
Date: 29-10-2019
Publisher: Oxford University Press (OUP)
Date: 03-2016
DOI: 10.1093/MNRAS/STW186
Publisher: American Astronomical Society
Date: 11-1992
DOI: 10.1086/186630
Publisher: American Astronomical Society
Date: 07-1995
DOI: 10.1086/175919
Publisher: Oxford University Press (OUP)
Date: 14-12-2021
Abstract: Radio-loud magnetars display a wide variety of radio-pulse phenomenology seldom seen among the population of rotation-powered pulsars. Spectropolarimetry of the radio pulses from these objects has the potential to place constraints on their magnetic topology and unveil clues about the magnetar radio emission mechanism. Here, we report on eight observations of the magnetar Swift J1818.0–1607 taken with the Parkes Ultra-Wideband Low receiver covering a wide frequency range from 0.7 to 4 GHz over a period of 5 months. The magnetar exhibits significant temporal profile evolution over this period, including the emergence of a new profile component with an inverted spectrum, two distinct types of radio emission mode switching, detected during two separate observations, and the appearance and disappearance of multiple polarization modes. These various phenomena are likely a result of ongoing reconfiguration of the plasma content and electric currents within the magnetosphere. Geometric fits to the linearly polarized position angle indicate we are viewing the magnetar at an angle of ∼99○ from the spin axis, and its magnetic and rotation axes are misaligned by ∼112○. While conducting these fits, we found the position angle swing had reversed direction on MJD 59062 compared to observations taken 15 d earlier and 12 d later. We speculate this phenomena may be evidence the radio emission from this magnetar originates from magnetic field lines associated with two co-located magnetic poles that are connected by a coronal loop.
Publisher: American Astronomical Society
Date: 18-03-2010
Publisher: American Astronomical Society
Date: 1998
DOI: 10.1086/311088
Publisher: Oxford University Press (OUP)
Date: 04-1996
Publisher: Oxford University Press (OUP)
Date: 05-2002
Publisher: Oxford University Press (OUP)
Date: 02-11-2016
Publisher: Oxford University Press (OUP)
Date: 29-06-2015
Publisher: Oxford University Press (OUP)
Date: 18-11-2015
Publisher: American Astronomical Society
Date: 02-1995
DOI: 10.1086/175230
Publisher: Oxford University Press (OUP)
Date: 11-05-2005
Publisher: Oxford University Press (OUP)
Date: 08-1998
Publisher: American Astronomical Society
Date: 17-08-2011
Publisher: Oxford University Press (OUP)
Date: 23-05-2012
Publisher: Oxford University Press (OUP)
Date: 06-12-2010
Publisher: Oxford University Press (OUP)
Date: 11-12-1996
Publisher: Oxford University Press (OUP)
Date: 11-01-2023
Abstract: The radio polarization properties of the pulsar population are only superficially captured by the conventional picture of pulsar radio emission. We study the broadband polarization of 271 young radio pulsars, focusing particularly on circular polarization, using high-quality observations made with the Ultra-Wideband Low receiver on Murriyang, the Parkes radio telescope. We seek to encapsulate polarization behaviour on a population scale by defining broad categories for frequency- and phase-dependent polarization evolution, studying the co-occurrences of these categorizations and comparing them with average polarization measurements and spin-down energy ($\\dot{E}$). This work shows that deviations of the linear polarization position angle from the rotating vector model are linked to the presence of circular polarization features and to frequency evolution of the polarization. Polarization fraction, circular polarization contribution, and profile complexity all evolve with $\\dot{E}$ across the population, with the profiles of high-$\\dot{E}$ pulsars being simple and highly linearly polarized. The relationship between polarization fraction and circular contribution is also seen to evolve such that highly polarized profiles show less variation in circular contribution with frequency than less strongly polarized profiles. This evolution is seen both across the population and across frequency for in idual sources. Understanding pulsar radio polarization requires detailed study of in idual sources and collective understanding of population-level trends. For the former, we provide visualizations of their phase- and frequency-resolved polarization parameters. For the latter, we have highlighted the importance of including the impact of circular polarization and of $\\dot{E}$.
Publisher: Oxford University Press (OUP)
Date: 12-2005
Publisher: Oxford University Press (OUP)
Date: 08-2004
Publisher: Oxford University Press (OUP)
Date: 05-09-2007
Publisher: American Astronomical Society
Date: 20-05-1997
DOI: 10.1086/304041
Publisher: Oxford University Press (OUP)
Date: 08-05-2006
Publisher: American Astronomical Society
Date: 07-08-2015
Publisher: American Association for the Advancement of Science (AAAS)
Date: 05-07-2013
Abstract: It has been uncertain whether single, short, and bright bursts of radio emission that have been observed are celestial or terrestrial in origin. Thornton et al. (p. 53 see the Perspective by Cordes ) report the detection of four nonrepeating radio transient events with millisecond duration in data from the 64-meter Parkes radio telescope in Australia. The properties of these radio bursts indicate that they had their origin outside our galaxy, but it is not possible to tell what caused them. Because the intergalactic medium affects the characteristics of the bursts, it will be possible to use them to study its properties.
Publisher: American Astronomical Society
Date: 23-01-2019
Publisher: Oxford University Press (OUP)
Date: 12-2017
Publisher: EDP Sciences
Date: 12-2018
DOI: 10.1051/0004-6361/201732153
Abstract: Aims. We report on the measurement and investigation of pulsed high-energy γ -ray emission from the Vela pulsar, PSR B0833−45, based on observations with the largest telescope of H.E.S.S., CT5, in monoscopic mode, and on data obtained with the Fermi -LAT. Methods. Data from 40.3 h of observations carried out with the H.E.S.S. II array from 2013 to 2015 have been used. A dedicated very low-threshold event reconstruction and analysis pipeline was developed to achieve the lowest possible energy threshold. Eight years of Fermi -LAT data were analysed and also used as reference to validate the CT5 telescope response model and analysis methods. Results. A pulsed γ -ray signal at a significance level of more than 15 σ is detected from the P2 peak of the Vela pulsar light curve. Of a total of 15 835 events, more than 6000 lie at an energy below 20 GeV, implying a significant overlap between H.E.S.S. II-CT5 and the Fermi -LAT. While the investigation of the pulsar light curve with the LAT confirms characteristics previously known up to 20 GeV in the tens of GeV energy range, CT5 data show a change in the pulse morphology of P2, i.e. an extreme sharpening of its trailing edge, together with the possible onset of a new component at 3.4 σ significance level. Assuming a power-law model for the P2 spectrum, an excellent agreement is found for the photon indices (Γ ≃ 4.1) obtained with the two telescopes above 10 GeV and an upper bound of 8% is derived on the relative offset between their energy scales. Using data from both instruments, it is shown however that the spectrum of P2 in the 10–100 GeV has a pronounced curvature this is a confirmation of the sub-exponential cut-off form found at lower energies with the LAT. This is further supported by weak evidence of an emission above 100 GeV obtained with CT5. In contrast, converging indications are found from both CT5 and LAT data for the emergence of a hard component above 50 GeV in the leading wing (LW2) of P2, which possibly extends beyond 100 GeV. Conclusions. The detection demonstrates the performance and understanding of CT5 from 100 GeV down to the sub-20 GeV domain, i.e. unprecedented low energy for ground-based γ -ray astronomy. The extreme sharpening of the trailing edge of the P2 peak found in the H.E.S.S. II light curve of the Vela pulsar and the possible extension beyond 100 GeV of at least one of its features, LW2, provide further constraints to models of γ -Ray emission from pulsars.
Publisher: Oxford University Press (OUP)
Date: 29-08-2015
DOI: 10.1093/MNRAS/STV508
Publisher: Oxford University Press (OUP)
Date: 28-04-2011
Publisher: American Astronomical Society
Date: 02-01-2013
Publisher: Elsevier BV
Date: 2005
Publisher: Oxford University Press (OUP)
Date: 21-09-2021
Abstract: We report on a timing programme of 74 young pulsars that have been observed by the Parkes 64-m radio telescope over the past decade. Using modern Bayesian timing techniques, we have measured the properties of 124 glitches in 52 of these pulsars, of which 74 are new. We demonstrate that the glitch s le is complete to fractional increases in spin frequency greater than $\\Delta \\nu ^{90{{\\ \\rm per\\ cent}}}_{\\mathrm{ g}}/\\nu \\approx 8.1 \\times 10^{-9}$ . We measure values of the braking index, n, in 33 pulsars. In most of these pulsars, their rotational evolution is dominated by episodes of spin-down with n & 10, punctuated by step changes in the spin-down rate at the time of a large glitch. The step changes are such that, averaged over the glitches, the long-term n is small. We find a near one-to-one relationship between the interglitch value of n and the change in spin-down of the previous glitch ided by the interglitch time interval. We discuss the results in the context of a range of physical models.
Publisher: Oxford University Press (OUP)
Date: 11-01-1999
Publisher: Elsevier BV
Date: 12-2004
Publisher: EDP Sciences
Date: 09-2017
Publisher: EDP Sciences
Date: 29-07-2002
Publisher: American Astronomical Society
Date: 03-2023
Abstract: We report the radio and high-energy properties of a new outburst from the radio-loud magnetar 1E 1547.0−5408. Following the detection of a short burst from the source with Swift-BAT on 2022 April 7, observations by NICER detected an increased flux peaking at (6.0 ± 0.4) × 10 −11 erg s −1 cm −2 in the soft X-ray band, falling to a baseline level of 1.7 × 10 −11 erg s −1 cm −2 over a 17 day period. Joint spectroscopic measurements by NICER and NuSTAR indicated no change in the hard nonthermal tail despite the prominent increase in soft X-rays. Observations at radio wavelengths with Murriyang, the 64 m Parkes radio telescope, revealed that the persistent radio emission from the magnetar disappeared at least 22 days prior to the initial Swift-BAT detection and was redetected two weeks later. Such behavior is unprecedented in a radio-loud magnetar, and may point to an unnoticed slow rise in the high-energy activity prior to the detected short bursts. Finally, our combined radio and X-ray timing revealed the outburst coincided with a spin-up glitch, where the spin frequency and spin-down rate increased by 0.2 ± 0.1 μ Hz and (−2.4 ± 0.1) × 10 −12 s −2 , respectively. A linear increase in the spin-down rate of (−2.0 ± 0.1) × 10 −19 s −3 was also observed over 147 days of postoutburst timing. Our results suggest that the outburst may have been associated with a reconfiguration of the quasi-polar field lines, likely signaling a changing twist, accompanied by spatially broader heating of the surface and a brief quenching of the radio signal, yet without any measurable impact on the hard X-ray properties.
Publisher: Oxford University Press (OUP)
Date: 08-2003
Publisher: Oxford University Press (OUP)
Date: 29-01-2015
Publisher: Oxford University Press (OUP)
Date: 17-02-2017
DOI: 10.1093/MNRAS/STX377
Publisher: American Astronomical Society
Date: 17-12-2019
Publisher: American Astronomical Society
Date: 25-11-2015
Publisher: Oxford University Press (OUP)
Date: 03-08-2015
Publisher: American Astronomical Society
Date: 03-2001
DOI: 10.1086/319154
Publisher: American Astronomical Society
Date: 02-04-2019
Publisher: Oxford University Press (OUP)
Date: 05-07-2018
Publisher: Oxford University Press (OUP)
Date: 09-12-2014
Publisher: Oxford University Press (OUP)
Date: 09-01-2018
Publisher: Oxford University Press (OUP)
Date: 11-04-2016
Publisher: Oxford University Press (OUP)
Date: 14-09-2010
Publisher: American Astronomical Society
Date: 18-06-2020
Publisher: Springer Science and Business Media LLC
Date: 02-2016
DOI: 10.1038/NATURE17140
Abstract: In recent years, millisecond-duration radio signals originating in distant galaxies appear to have been discovered in the so-called fast radio bursts. These signals are dispersed according to a precise physical law and this dispersion is a key observable quantity, which, in tandem with a redshift measurement, can be used for fundamental physical investigations. Every fast radio burst has a dispersion measurement, but none before now have had a redshift measurement, because of the difficulty in pinpointing their celestial coordinates. Here we report the discovery of a fast radio burst and the identification of a fading radio transient lasting ~6 days after the event, which we use to identify the host galaxy we measure the galaxy's redshift to be z = 0.492 ± 0.008. The dispersion measure and redshift, in combination, provide a direct measurement of the cosmic density of ionized baryons in the intergalactic medium of ΩIGM = 4.9 ± 1.3 per cent, in agreement with the expectation from the Wilkinson Microwave Anisotropy Probe, and including all of the so-called 'missing baryons'. The ~6-day radio transient is largely consistent with the radio afterglow of a short γ-ray burst, and its existence and timescale do not support progenitor models such as giant pulses from pulsars, and supernovae. This contrasts with the interpretation of another recently discovered fast radio burst, suggesting that there are at least two classes of bursts.
Publisher: Oxford University Press (OUP)
Date: 08-2018
Publisher: Oxford University Press (OUP)
Date: 24-10-2013
Publisher: Oxford University Press (OUP)
Date: 06-12-2012
DOI: 10.1093/MNRAS/STS366
Publisher: Oxford University Press (OUP)
Date: 03-2018
DOI: 10.1093/MNRAS/STV753
Publisher: Oxford University Press (OUP)
Date: 12-04-2016
DOI: 10.1093/MNRAS/STW842
Publisher: Oxford University Press (OUP)
Date: 02-2004
Publisher: Oxford University Press (OUP)
Date: 21-02-2010
Publisher: Oxford University Press (OUP)
Date: 23-09-2016
Publisher: Oxford University Press (OUP)
Date: 11-02-2019
DOI: 10.1093/MNRAS/STZ401
Publisher: American Astronomical Society
Date: 03-1992
DOI: 10.1086/186300
Publisher: Oxford University Press (OUP)
Date: 07-06-2019
Publisher: American Association for the Advancement of Science (AAAS)
Date: 09-12-2016
Abstract: Fast radio bursts (FRBs) are powerful flashes of astronomical radio waves that last just milliseconds and whose origins are a matter of debate. Ravi et al. discovered a FRB that is exceptionally bright (see the Perspective by Kaspi). This allowed them to measure how the polarization of the signal varies with wavelength (Faraday rotation). Combining this with the time delay of the flash at different wavelengths revealed the mean magnetic field along the line of sight. Assuming that the FRB originates from a colocated galaxy, the results constrain the intergalactic magnetic field and will inform models of galaxy formation and cosmology. Science , this issue p. 1249 see also p. 1230
Publisher: Springer Berlin Heidelberg
Date: 14-12-2010
Publisher: American Astronomical Society
Date: 02-2016
Publisher: American Astronomical Society
Date: 10-12-2001
DOI: 10.1086/338359
Publisher: Oxford University Press (OUP)
Date: 02-10-2017
Publisher: American Astronomical Society
Date: 08-04-2011
Publisher: Oxford University Press (OUP)
Date: 19-06-2019
Abstract: Radio pulsars are often used as clocks in a wide variety of experiments. Imperfections in the clock, known as timing noise, have the potential to reduce the significance of, or even thwart e.g. the attempt to find a stochastic gravitational wave (GW) background. We measure the timing noise in a group of 129 mostly middle-aged pulsars (i.e. characteristic ages near 1 Myr) observed with the Parkes radio telescope on a monthly basis since 2014. We examine four different metrics for timing noise, but it remains unclear which, if any, provides the best determination. In spite of this, it is evident that these pulsars have significantly less timing noise than their younger counterparts, but significantly more than the (much older) millisecond pulsars (MSPs). As with previous authors, we find a strong correlation between timing noise and the pulsar spin-down rate, $\\dot{\\nu}$. However, for a given $\\dot{\\nu}$ there is a spread of about a factor of 30 in the strength of the timing noise likely indicating that nuclear conditions in the interior of the stars differ between objects. We briefly comment on the implications for GW detection through pulsar timing arrays as the level of timing noise in MSPs may be less than predicted.
Publisher: Oxford University Press (OUP)
Date: 03-2004
Publisher: Oxford University Press (OUP)
Date: 1993
Publisher: Oxford University Press (OUP)
Date: 11-07-2008
Publisher: Elsevier BV
Date: 12-2004
Publisher: Oxford University Press (OUP)
Date: 31-07-2019
Abstract: It is now known that the emission from radio pulsars can vary over a wide range of time-scales, from fractions of seconds to decades. However, it is not yet known if long- and short-term emission variability are caused by the same physical processes. It has been observed that long-term emission variability is often correlated with rotational changes in the pulsar. We do not yet know if the same is true of short-term emission variability, as the rotational changes involved cannot be directly measured over such short time-scales. To remedy this, we propose a continuous pulsar monitoring technique that permits the statistical detection of any rotational changes in nulling and mode-changing pulsars with certain properties. Using a simulation, we explore the range of pulsar properties over which such an experiment would be possible.
Publisher: Oxford University Press (OUP)
Date: 09-2004
Publisher: Oxford University Press (OUP)
Date: 05-1995
Publisher: Oxford University Press (OUP)
Date: 11-03-1996
Publisher: Oxford University Press (OUP)
Date: 09-05-2013
DOI: 10.1093/MNRAS/STT660
Publisher: EDP Sciences
Date: 10-2014
Publisher: Oxford University Press (OUP)
Date: 08-2003
Publisher: American Astronomical Society
Date: 20-08-2001
DOI: 10.1086/323415
Publisher: Elsevier BV
Date: 2005
Publisher: Oxford University Press (OUP)
Date: 17-08-2017
Publisher: Oxford University Press (OUP)
Date: 21-06-2004
Publisher: American Astronomical Society
Date: 21-05-2003
DOI: 10.1086/376826
Publisher: Oxford University Press (OUP)
Date: 21-07-2008
Publisher: American Astronomical Society
Date: 08-11-2012
Publisher: Oxford University Press (OUP)
Date: 21-11-2019
Abstract: We establish that for PSR B0031−07 the orthogonal polarization modes switch at a single pulse level synchronously with the periodic drifting subpulses seen in total intensity. There are only four other pulsars known for which this phenomenon is observed. PSR B0031−07 is unique as it is the only source in this group which has multiple stable drift modes. For both drift modes visible at our observing frequency centered at 1369 MHz, the modulation of polarization modes is synchronous with the drifting subpulses. In one of the drift modes, a discontinuity in the modulation pattern of polarization properties occurs halfway through the pulse, coinciding with a slight change in the slope of the intensity drift band. In contrast to what has been suggested for this pulsar in the past, this, plus other differences in the polarization of the modulated emission observed for the two drift modes, suggests that a drift mode change is more than a change in the underlying carousel radius and that magnetospheric propagation effects play an important role. The ellipticity evolves asymmetrically in time during the modulation cycle, which in the framework of a carousel model implies that the polarized sub-beams are asymmetric with respect to the sense of circulation, something which is not observed for other pulsars. Birefringence in the magnetosphere, resulting in the orthogonal polarization modes to spatially separate, is not enough to explain these results. It is argued that more complex magnetospheric processes, which possibly allow conversion between orthogonal polarization modes, play a role.
Publisher: EDP Sciences
Date: 03-2001
Publisher: Oxford University Press (OUP)
Date: 21-05-2003
Publisher: Oxford University Press (OUP)
Date: 14-01-2016
Publisher: Oxford University Press (OUP)
Date: 09-08-2023
Abstract: The population of radio pulsars is observed to demonstrate certain polarization properties not explained by the conventional picture of pulsar polarization, namely frequency evolution of polarization, deviations of the linear polarization angle from a curve of geometric origins, and the presence of features in the circular polarization. We present the partial-coherence model as a way to explain the co-occurrence of these features and to provide an origin for circular polarization in radio pulsar profiles. We describe the mathematics of the model and demonstrate how it can explain these observed features, both on a population level and for the idiosyncrasies of in idual pulsars. The partial coherence model can account for complex polarization behaviour, enabling improved access to information about pulsar geometries. We discuss the scientific implications of this for our understanding of pulsar radio emission and propagation.
Publisher: Oxford University Press (OUP)
Date: 28-08-2008
Publisher: Oxford University Press (OUP)
Date: 11-2004
Publisher: Oxford University Press (OUP)
Date: 11-04-2005
Publisher: American Astronomical Society
Date: 23-12-2010
Publisher: Oxford University Press (OUP)
Date: 21-05-1999
Publisher: American Astronomical Society
Date: 10-11-2001
DOI: 10.1086/324752
Publisher: American Astronomical Society
Date: 08-01-2013
Publisher: EDP Sciences
Date: 17-07-2012
Publisher: American Association for the Advancement of Science (AAAS)
Date: 07-2005
Abstract: Stimulated emission of radiation has not been directly observed in astrophysical situations up to this time. Here we demonstrate that photons from pulsar B1641–45 stimulate pulses of excess 1720-megahertz line emission in an interstellar hydroxyl (OH) cloud. As this stimulated emission is driven by the pulsar, it varies on a few-millisecond time scale, which is orders of magnitude shorter than the quickest OH maser variations previously detected. Our 1612-megahertz spectra are inverted copies of the 1720-megahertz spectra. This “conjugate line” phenomenon enables us to constrain the properties of the interstellar OH line–producing gas. We also show that pulsar signals undergo significantly deeper OH absorption than do other background sources, which confirms earlier tentative findings that OH clouds are clumpier on small scales than are neutral hydrogen clouds.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 23-09-2011
Abstract: Timing observations of a millisecond pulsar reveal a planet that is far denser than any known planet.
Publisher: Oxford University Press (OUP)
Date: 15-12-1995
Publisher: Cambridge University Press (CUP)
Date: 2002
DOI: 10.1071/AS01062
Abstract: Using the formalism of Hamaker, Bregman & Sault (1996), I derive a method for the polarisation calibration of observations made with a single radio telescope. This method is particularly appropriate for observations of pulsars, where the sign and magnitude of the circular polarisation are useful for understanding the emission processes at work. I apply the method to observations of PSR J1359–6038 made using the multibeam receiver on the Parkes radio telescope.
Publisher: American Astronomical Society
Date: 19-11-2010
Publisher: Oxford University Press (OUP)
Date: 28-06-2012
Publisher: Oxford University Press (OUP)
Date: 21-10-2019
Abstract: In the canonical picture of pulsars, radio emission arises from a narrow cone centred on the star’s magnetic axis but many basic details remain unclear. We use high-quality polarization data taken with the Parkes radio telescope to constrain the geometry and emission heights of pulsars showing interpulse emission, and include the possibility that emission heights in the main and interpulse may be different. We show that emission heights are low in the centre of the beam, typically less than 3 per cent of the light cylinder radius. The emission beams are underfilled in longitude, with an average profile width only 60 per cent of the maximal beamwidth and there is a strong preference for the visible emission to be located on the trailing part of the beam. We show substantial evidence that the emission heights are larger at the beam edges than in the beam centre. There is some indication that a fan-like emission beam explains the data better than conal structures. Finally, there is a strong correlation between handedness of circular polarization in the main and interpulse profiles, which implies that the hand of circular polarization is determined by the hemisphere of the visible emission.
Publisher: Oxford University Press (OUP)
Date: 15-05-1994
Publisher: Oxford University Press (OUP)
Date: 21-12-2020
Abstract: The Parkes telescope has been monitoring 286 radio pulsars approximately monthly since 2007 at an observing frequency of 1.4 GHz. The wide dispersion measure (DM) range of the pulsar s le and the uniformity of the observing procedure make the data set extremely valuable for studies of flux density variability and the interstellar medium (ISM). Here, we present flux density measurements and modulation indices of these pulsars over this period. We derive the structure function from the light curves and discuss the contributions to it from measurement noise, intrinsic variability, and interstellar scintillation. Despite a large scatter, we show that the modulation index is inversely correlated with DM, and can be generally described by a power law with an index of ∼−0.7 covering DMs from ∼10 to 1000 cm−3 pc. We present refractive time-scales and/or lower limits for a group of 42 pulsars. These often have values significantly different from theoretical expectations, indicating the complex nature of the ISM along in idual lines of sight. In particular, local structures and non-Kolmogorov density fluctuations are likely playing important roles in the observed flux density variation of many of these pulsars.
Publisher: American Astronomical Society
Date: 27-06-2017
Publisher: American Astronomical Society
Date: 28-03-2016
Publisher: Oxford University Press (OUP)
Date: 16-01-2021
Abstract: The major programme for observing young, non-recycled pulsars with the Parkes telescope has transitioned from a narrow-band system to an ultra-wide-band system capable of observing between 704 and 4032 MHz. We report here on the initial 2 yr of observations with this receiver. Results include dispersion measure (DM) and Faraday rotation measure (RM) variability with time, determined with higher precision than hitherto, flux density measurements and the discovery of several nulling and mode changing pulsars. PSR J1703−4851 is shown to be one of a small subclass of pulsars that has a weak and a strong mode which alternate rapidly in time. PSR J1114−6100 has the fourth highest |RM| of any known pulsar despite its location far from the Galactic Centre. PSR J1825−1446 shows variations in both DM and RM likely due to its motion behind a foreground supernova remnant.
Publisher: Oxford University Press (OUP)
Date: 06-2006
Publisher: Oxford University Press (OUP)
Date: 22-11-2010
Publisher: EDP Sciences
Date: 16-03-2006
Publisher: Oxford University Press (OUP)
Date: 30-07-2016
Publisher: Oxford University Press (OUP)
Date: 21-01-1998
Publisher: Oxford University Press (OUP)
Date: 25-09-2014
Publisher: Oxford University Press (OUP)
Date: 05-02-2020
Abstract: We report the discovery of PSR J2251−3711, a radio pulsar with a spin period of 12.1 s, the second longest currently known. Its timing parameters imply a characteristic age of 15 Myr, a surface magnetic field of 1.3 × 1013 G, and a spin-down luminosity of 2.9 × 1029 erg s−1. Its dispersion measure of 12.12(1) pc cm−3 leads to distance estimates of 0.5 and 1.3 kpc according to the NE2001 and YMW16 Galactic free electron density models, respectively. Some of its single pulses show an uninterrupted 180-deg sweep of the phase-resolved polarization position angle, with an S-shape reminiscent of the rotating vector model prediction. However, the fact that this sweep occurs at different phases from one pulse to another is remarkable and without straightforward explanation. Although PSR J2251−3711 lies in the region of the $P-\\dot{P}$ parameter space occupied by the X-ray isolated neutron stars (XINS), there is no evidence for an X-ray counterpart in our Swift XRT observation this places a 99 per cent-confidence upper bound on its unabsorbed bolometric thermal luminosity of $1.1 \\times 10^{31}~(d / 1~\\mathrm{kpc})^2~\\mathrm{erg\\, s}^{-1}$ for an assumed temperature of 85 eV, where d is the distance to the pulsar. Further observations are needed to determine whether it is a rotation-powered pulsar with a true age of at least several Myr, or a much younger object such as an XINS or a recently cooled magnetar. Extreme specimens like PSR J2251−3711 help bridge populations in the so-called neutron star zoo in an attempt to understand their origins and evolution.
Publisher: Oxford University Press (OUP)
Date: 27-07-2023
Abstract: We present a comprehensive study of the rotational and emission properties of PSR J0738−4042 using a combination of observations taken by the Deep Space Network, Hartebeesthoek, Parkes (Murriyang) and Molonglo observatories between 1972 and 2023. Our timing of the pulsar is motivated by previously reported profile/spin-down events that occurred in 2005 September and 2015 December, which result in an anomalously large braking index of n = 23 300 ± 1800. Using a Gaussian process regression framework, we develop continuous models for the evolution of the pulsar spin-down rate ($\\dot{\\nu }$) and profile shape. We find that the pulse profile variations are similar regardless of radio observing frequency and polarization. Small-scale differences can be ascribed to changes in the interstellar medium along the line of sight and frequency-dependent changes in magnetospheric radio emission height. No new correlated spin-down or profile events were identified in our extended data set. However, we found that the disappearance of a bright emission component in the leading edge of archival profiles between 1981 and 1988 was not associated with a substantial change in $\\dot{\\nu }$. This marks a notable departure from the previous profile/spin-down events in this pulsar. We discuss the challenges these observations pose for physical models and conclude that interactions between the pulsar and in-falling asteroids or a form of magnetospheric state-switching with a long periodicity are plausible explanations.
Publisher: Oxford University Press (OUP)
Date: 13-03-2023
Abstract: We present the timing of the first five millisecond pulsars discovered in the globular cluster Omega Centauri and the discovery of a pulsar with a spin period of 3.68 ms. With a timing baseline of ∼3.5 yr we are able to measure the derivative of the spin frequency ($\\dot{\\nu }$) for the first five pulsars. Upper limits on the pulsar line-of-sight acceleration are estimated and compared with predictions based on analytical models of the cluster. We find that PSRs J1326−4728B and D show large negative accelerations, which are in tension with the minimum acceleration predicted by analytical models. We searched for pulsed γ-ray signals using 14.3 yr of data from the Fermi Large Area Telescope. Although we found no evidence for γ-ray pulsations, PSRs J1326−4728A, B, C, and E are associated with X-ray sources. This suggests that the observed γ-ray emission from Omega Centauri is likely caused by the emission of the ensemble of MSPs. Finally, the linearly polarized emission from PSR J1326−4728A yields a rotation measure of −18 ± 8 rad m−2.
Publisher: Oxford University Press (OUP)
Date: 18-07-2013
Publisher: American Astronomical Society
Date: 09-01-2020
Publisher: Oxford University Press (OUP)
Date: 03-1995
Publisher: Oxford University Press (OUP)
Date: 08-12-2014
Publisher: Oxford University Press (OUP)
Date: 29-05-2021
Abstract: The Thousand-Pulsar-Array (TPA) programme currently monitors about 500 pulsars with the sensitive MeerKAT radio telescope by using subarrays to observe multiple sources simultaneously. Here we define the adopted observing strategy, which guarantees that each target is observed long enough to obtain a high-fidelity pulse profile, thereby reaching a sufficient precision of a simple pulse shape parameter. This precision is estimated from the contribution of the system noise of the telescope, and the pulse-to-pulse variability of each pulsar, which we quantify under some simplifying assumptions. We test the assumptions and choice of model parameters using data from the MeerKAT 64-dish array and the Lovell and Parkes telescopes. We demonstrate that the observing times derived from our method produce high-fidelity pulse profiles that meet the needs of the TPA in studying pulse shape variability and pulsar timing. Our method can also be used to compare strategies for observing large numbers of pulsars with telescopes capable of forming multiple subarray configurations. We find that using two 32-dish MeerKAT subarrays is the most efficient strategy for the TPA project. We also find that the ability to observe in different array configurations will become increasingly important for large observing programmes using the Square Kilometre Array telescope.
Publisher: American Astronomical Society
Date: 30-08-2010
Publisher: Oxford University Press (OUP)
Date: 05-08-2021
Abstract: A recent measurement of the proper motion of PSR J0908–4913 shows that it is a fast-moving object at a distance of some 3 kpc. Here, we present evidence that the pulsar is located at the edge of a previously unknown, filled-centre supernova remnant (SNR), G270.4–1.0. The velocity vector of the pulsar points directly away from the centre of the remnant. The putative association of the pulsar with SNR G270.4–1.0 implies the pulsar is ∼12 kyr old, significantly less than its characteristic age of 110 kyr. We show that the rotation axis of the pulsar points in the direction of the proper motion. Rotation measure and dispersion measure variations are seen over time, likely indicating the pulsar is passing behind a filament of the remnant.
Publisher: Oxford University Press (OUP)
Date: 27-06-2020
Abstract: The SUrvey for Pulsars and Extragalactic Radio Bursts ran from 2014 April to 2019 August, covering a large fraction of the Southern hemisphere at mid- to high-galactic latitudes and consisting of 9-min pointings taken with the 20-cm multibeam receiver on the Parkes Radio Telescope. Data up to 2017 September 21 have been searched using standard Fourier techniques, single-pulse searches, and Fast Folding Algorithm searches. We present 19 new discoveries, bringing the total to 27 discoveries in the programme, and we report the results of follow-up timing observations at Parkes for 26 of these pulsars, including the millisecond pulsar PSR J1421−4409 the faint, highly modulated, slow pulsar PSR J1646−1910 and the nulling pulsar PSR J1337−4441. We present new timing solutions for 23 pulsars, and we report flux densities, modulation indices, and polarization properties.
Publisher: American Astronomical Society
Date: 04-1994
DOI: 10.1086/187306
Publisher: Oxford University Press (OUP)
Date: 10-2003
Publisher: Oxford University Press (OUP)
Date: 21-05-1999
Publisher: Oxford University Press (OUP)
Date: 22-02-2023
Abstract: In spite of the rich phenomenology of the polarization properties of radio pulsars, the rotating vector model (RVM) created 50 years ago remains the best method to determine the beam geometry of a pulsar. We apply the RVM to a s le of 854 radio pulsars observed with the MeerKAT telescope in order to draw conclusions about the population of pulsars as a whole. The main results are that (i) the geometrical interpretation of the position angle (PA) traverse is valid in the majority of the population, (ii) the pulsars for which the RVM fails tend to have a high fraction of circular polarization compared to linear polarization, (iii) emission heights obtained through both geometrical and relativistic methods show that the majority of pulsars must have emission heights less than 1000 km independent of the spin period, (iv) orthogonal mode jumps are seen in the PA traverse in about one third of the population. All these results are weakly dependent on the pulsar spin-down energy.
Publisher: Oxford University Press (OUP)
Date: 11-2006
Publisher: Oxford University Press (OUP)
Date: 21-12-2012
DOI: 10.1093/MNRAS/STS449
Publisher: American Astronomical Society
Date: 11-1993
DOI: 10.1086/173353
Publisher: Oxford University Press (OUP)
Date: 11-08-2002
Publisher: Oxford University Press (OUP)
Date: 23-12-2015
Publisher: American Astronomical Society
Date: 20-06-2017
Publisher: American Astronomical Society
Date: 02-12-2011
Publisher: Oxford University Press (OUP)
Date: 17-02-2014
DOI: 10.1093/MNRAS/STU067
Publisher: Oxford University Press (OUP)
Date: 09-2001
Publisher: American Astronomical Society
Date: 06-1994
DOI: 10.1086/174204
Publisher: American Astronomical Society
Date: 20-04-1999
DOI: 10.1086/307058
Publisher: Oxford University Press (OUP)
Date: 03-2016
DOI: 10.1093/MNRAS/STW451
Publisher: Oxford University Press (OUP)
Date: 11-07-1999
Publisher: Springer Science and Business Media LLC
Date: 02-1993
DOI: 10.1038/361613A0
Publisher: American Astronomical Society
Date: 28-04-2015
Publisher: American Astronomical Society
Date: 27-03-2019
Publisher: Oxford University Press (OUP)
Date: 15-07-1995
Publisher: American Astronomical Society
Date: 03-1995
DOI: 10.1086/187791
Publisher: American Astronomical Society
Date: 20-06-2014
Publisher: Oxford University Press (OUP)
Date: 04-04-2012
Publisher: Oxford University Press (OUP)
Date: 18-05-2017
Publisher: Oxford University Press (OUP)
Date: 06-2011
Publisher: American Astronomical Society
Date: 04-2021
Abstract: We present the discovery and timing of the young (age ∼28.6 kyr) pulsar PSR J0837–2454. Based on its high latitude ( b = 98) and dispersion measure (DM = 143 pc cm −3 ), the pulsar appears to be at a z -height of kpc above the Galactic plane, but near the edge of our Galaxy. This is many times the observed scale height of the canonical pulsar population, which suggests this pulsar may have been born far out of the plane. If accurate, the young age and high z -height imply that this is the first pulsar known to be born from a runaway O/B star. In follow-up imaging with the Australia Telescope Compact Array (ATCA), we detect the pulsar with a flux density S 1400 = 0.18 ± 0.05 mJy. We do not detect an obvious supernova remnant around the pulsar in our ATCA data, but we detect a colocated, low-surface-brightness region of ∼15 extent in archival Galactic and Extragalactic All-sky MWA Survey data. We also detect colocated H α emission from the Southern H α Sky Survey Atlas. Distance estimates based on these two detections come out to ∼0.9 kpc and ∼0.2 kpc, respectively, both of which are much smaller than the distance predicted by the NE2001 model (6.3 kpc) and YMW model ( kpc) and place the pulsar much closer to the plane of the Galaxy. If the pulsar/remnant association holds, this result also highlights the inherent difficulty in the classification of transients as “Galactic” (pulsar) or “extragalactic” (fast radio burst) toward the Galactic anticenter based solely on the modeled Galactic electron contribution to a detection.
Publisher: American Astronomical Society
Date: 10-07-1996
DOI: 10.1086/310148
Publisher: Cambridge University Press (CUP)
Date: 2017
DOI: 10.1017/PASA.2017.20
Abstract: During 2016 February, CSIRO Astronomy and Space Science and the Max-Planck-Institute for Radio Astronomy installed, commissioned, and carried out science observations with a phased array feed receiver system on the 64-m diameter Parkes radio telescope. Here, we demonstrate that the phased array feed can be used for pulsar observations and we highlight some unique capabilities. We demonstrate that the pulse profiles obtained using the phased array feed can be calibrated and that multiple pulsars can be simultaneously observed. Significantly, we find that an intrinsic polarisation leakage of −31 dB can be achieved with a phased array feed beam offset from the centre of the field of view. We discuss the possibilities for using a phased array feed for future pulsar observations and for searching for fast radio bursts with the Parkes and Effelsberg telescopes.
Publisher: Oxford University Press (OUP)
Date: 02-10-2021
Abstract: We present pulse width measurements for a s le of radio pulsars observed with the MeerKAT telescope as part of the Thousand-Pulsar-Array (TPA) programme in the MeerTime project. For a centre frequency of 1284 MHz, we obtain 762 W10 measurements across the total bandwidth of 775 MHz, where W10 is the width at the 10 per cent level of the pulse peak. We also measure about 400 W10 values in each of the four or eight frequency sub-bands. Assuming, the width is a function of the rotation period P, this relationship can be described with a power law with power law index μ = −0.29 ± 0.03. However, using orthogonal distance regression, we determine a steeper power law with μ = −0.63 ± 0.06. A density plot of the period-width data reveals such a fit to align well with the contours of highest density. Building on a previous population synthesis model, we obtain population-based estimates of the obliquity of the magnetic axis with respect to the rotation axis for our pulsars. Investigating the width changes over frequency, we unambiguously identify a group of pulsars that have width broadening at higher frequencies. The measured width changes show a monotonic behaviour with frequency for the whole TPA pulsar population, whether the pulses are becoming narrower or broader with increasing frequency. We exclude a sensitivity bias, scattering and noticeable differences in the pulse component numbers as explanations for these width changes, and attempt an explanation using a qualitative model of five contributing Gaussian pulse components with flux density spectra that depend on their rotational phase.
Publisher: Oxford University Press (OUP)
Date: 24-04-2012
Publisher: Oxford University Press (OUP)
Date: 06-12-2017
Publisher: Oxford University Press (OUP)
Date: 25-01-2013
DOI: 10.1093/MNRAS/STS657
Publisher: Oxford University Press (OUP)
Date: 07-12-2018
Publisher: Oxford University Press (OUP)
Date: 24-08-2015
Publisher: American Astronomical Society
Date: 02-09-2015
Publisher: Elsevier BV
Date: 02-2011
Publisher: Cambridge University Press (CUP)
Date: 2020
DOI: 10.1017/PASA.2020.2
Abstract: We describe an ultra-wide-bandwidth, low-frequency receiver recently installed on the Parkes radio telescope. The receiver system provides continuous frequency coverage from 704 to 4032 MHz. For much of the band ( ${\\sim}60\\%$ ), the system temperature is approximately 22 K and the receiver system remains in a linear regime even in the presence of strong mobile phone transmissions. We discuss the scientific and technical aspects of the new receiver, including its astronomical objectives, as well as the feed, receiver, digitiser, and signal processor design. We describe the pipeline routines that form the archive-ready data products and how those data files can be accessed from the archives. The system performance is quantified, including the system noise and linearity, beam shape, antenna efficiency, polarisation calibration, and timing stability.
Publisher: Oxford University Press (OUP)
Date: 02-09-2011
Publisher: American Astronomical Society
Date: 20-03-1999
DOI: 10.1086/311928
Publisher: Oxford University Press (OUP)
Date: 07-2009
Publisher: Oxford University Press (OUP)
Date: 06-2008
Publisher: Springer Science and Business Media LLC
Date: 09-1993
DOI: 10.1038/365188B0
Publisher: Oxford University Press (OUP)
Date: 18-10-2018
Publisher: Oxford University Press (OUP)
Date: 09-1994
Publisher: Oxford University Press (OUP)
Date: 15-05-1994
Publisher: Oxford University Press (OUP)
Date: 23-11-2021
Abstract: The Magellanic Clouds are the only external galaxies known to host radio pulsars. The dispersion and rotation measures of pulsars in the Clouds can aid in understanding their structure, and studies of the pulsars themselves can point to potential differences between them and their Galactic counterparts. We use the high sensitivity of the MeerKAT telescope to observe 17 pulsars in the Small and Large Magellanic Clouds in addition to five foreground (Galactic) pulsars. We provide polarisation profiles for 18 of these pulsars, improved measurements of their dispersion and rotation measures, and derive the mean parallel magnetic field along the lines of sight. The results are broadly in agreement with expectations for the structure and strength of the magnetic field in the Large and Small Magellanic Clouds. The Magellanic Cloud pulsars have profiles which are narrower than expected from the period-width relationship and we show this is due to selection effects in pulsar surveys rather than any intrinsic difference between the population of Galactic and Magellanic objects.
Publisher: American Astronomical Society
Date: 02-1994
DOI: 10.1086/187218
Publisher: Oxford University Press (OUP)
Date: 30-08-2019
Abstract: The smooth spin-down of young pulsars is perturbed by two non-deterministic phenomenon, glitches, and timing noise. Although the timing noise provides insights into nuclear and plasma physics at extreme densities, it acts as a barrier to high-precision pulsar timing experiments. An improved methodology based on the Bayesian inference is developed to simultaneously model the stochastic and deterministic parameters for a s le of 85 high-$\dot{E}$ radio pulsars observed for ∼10 yr with the 64-m Parkes radio telescope. Timing noise is known to be a red process and we develop a parametrization based on the red-noise litude (Ared) and spectral index (β). We measure the median Ared to be $-10.4^{+1.8}_{-1.7}$ yr3/2 and β to be $-5.2^{+3.0}_{-3.8}$ and show that the strength of timing noise scales proportionally to $\nu ^{1}|\dot{\nu }|^{-0.6\pm 0.1}$, where ν is the spin frequency of the pulsar and $\dot{\nu }$ is its spin-down rate. Finally, we measure significant braking indices for 19 pulsars and proper motions for 2 pulsars, and discuss the presence of periodic modulation in the arrival times of 5 pulsars.
Publisher: American Astronomical Society
Date: 07-04-2009
Publisher: American Astronomical Society
Date: 10-08-2011
Publisher: Oxford University Press (OUP)
Date: 04-1992
Publisher: Oxford University Press (OUP)
Date: 09-04-2020
Abstract: In Paper I of this series, we detected a significant value of the braking index (n) for 19 young, high-$\\dot{E}$ radio pulsars using ∼10 yr of timing observations from the 64-m Parkes radio telescope. Here, we investigate this result in more detail using a Bayesian pulsar timing framework to model timing noise and to perform selection to distinguish between models containing exponential glitch recovery and braking index signatures. We show that consistent values of n are maintained with the addition of substantial archival data, even in the presence of glitches. We provide strong arguments that our measurements are unlikely due to exponential recovery signals from unseen glitches even though glitches play a key role in the evolution of a pulsar’s spin frequency. We conclude that, at least over decadal time-scales, the value of n can be significantly larger than the canonical 3 and discuss the implications for the evolution of pulsars.
Publisher: American Astronomical Society
Date: 29-07-2013
Publisher: Oxford University Press (OUP)
Date: 07-1995
Publisher: Oxford University Press (OUP)
Date: 08-2013
Publisher: Oxford University Press (OUP)
Date: 21-02-2020
Abstract: We report here on initial results from the Thousand-Pulsar-Array (TPA) programme, part of the Large Survey Project ‘MeerTime’ on the MeerKAT telescope. The interferometer is used in the tied-array mode in the band from 856 to 1712 MHz, and the wide band coupled with the large collecting area and low receiver temperature make it an excellent telescope for the study of radio pulsars. The TPA is a 5 year project, which aims at to observing (a) more than 1000 pulsars to obtain high-fidelity pulse profiles, (b) some 500 of these pulsars over multiple epochs, and (c) long sequences of single-pulse trains from several hundred pulsars. The scientific outcomes from the programme will include the determination of pulsar geometries, the location of the radio emission within the pulsar magnetosphere, the connection between the magnetosphere and the crust and core of the star, tighter constraints on the nature of the radio emission itself, as well as interstellar medium studies. First, results presented here include updated dispersion measures, 26 pulsars with Faraday rotation measures derived for the first time, and a description of interesting emission phenomena observed thus far.
Publisher: Oxford University Press (OUP)
Date: 08-02-2013
DOI: 10.1093/MNRAS/STT047
Publisher: American Astronomical Society
Date: 07-1995
DOI: 10.1086/175866
Publisher: Oxford University Press (OUP)
Date: 22-09-2015
Publisher: American Astronomical Society
Date: 11-1994
DOI: 10.1086/174895
Publisher: Oxford University Press (OUP)
Date: 11-04-1996
Publisher: Oxford University Press (OUP)
Date: 21-05-2013
DOI: 10.1093/MNRAS/STT721
Publisher: American Association for the Advancement of Science (AAAS)
Date: 22-01-2016
Abstract: Radio emissions from distant quasars are occasionally modified for a few weeks by foreground interstellar plasma, in an extreme scattering event (ESE). Understanding this process has been difficult, because existing techniques do not allow events to be identified fast enough for follow-up before they finish. Bannister et al. developed a radio survey technique that allows ESEs to be identified in real time. After finding their first live ESE, they followed it up with additional radio and optical telescopes. The results constrain the size and density of the plasma and rule out one popular model of ESEs. Science , this issue p. 354
Publisher: Oxford University Press (OUP)
Date: 29-05-2021
Abstract: PSR J0540−6919 is the second-most energetic radio pulsar known and resides in the Large Magellanic Cloud. Like the Crab pulsar, it is observed to emit giant radio pulses (GPs). We used the newly commissioned PTUSE instrument on the MeerKAT radio telescope to search for GPs across three observations. In a total integration time of 5.7 h, we detected 865 pulses above our 7σ threshold. With full polarization information for a subset of the data, we estimated the Faraday rotation measure, $\\rm {RM}=-245.8 \\pm 1.0$ rad m−2 towards the pulsar. The brightest of these pulses is ∼60 per cent linearly polarized but the pulse-to-pulse variability in the polarization fraction is significant. We find that the cumulative GP flux distribution follows a power-law distribution with index −2.75 ± 0.02. Although the detected GPs make up only ∼10 per cent of the mean flux, their average pulse shape is indistinguishable from the integrated pulse profile, and we postulate that, unlike in the Crab pulsar, there are no additional regular emission components. The pulses are scattered at L-band frequencies with the brightest pulse exhibiting a scattering time-scale of τ = 0.92 ± 0.02 ms at 1.2 GHz. We find several of the giants display very narrow-band flux knots similar to those seen in many Fast Radio Bursts, which we assert cannot be due to scintillation or plasma lensing. The GP time-of-arrival distribution is found to be Poissonian on all but the shortest time-scales where we find four GPs in six rotations, which if GPs are statistically independent is expected to occur in only 1 of 7000 observations equivalent to our data.
Publisher: Cambridge University Press (CUP)
Date: 2004
DOI: 10.1071/AS03053
Abstract: We have carried out a study of the neutral hydrogen in the direction of the X-ray source 1E 161348–5055, a compact central object (CCO) located in the interior of the supernova remnant (SNR) RCW 103. The H i 21 cm line observations were carried out using the Australia Telescope Compact Array, complemented with single dish data from the Parkes radio telescope to recover information at all spatial scales. We derive a distance to RCW 103 of 3.1 kpc, in agreement with previous distance measurements. We have also detected a small hole in the H i emission which is positionally and kinematically coincident with the location of the CCO which confirms the association between the SNR and the CCO. This is the third case of a depression in H i emission seemingly associated with CCOs in SNRs. The characteristic parameters of the holes such as their size, eccentricity and evacuated mass are similar in all three cases. We estimate the absorbing H I column density towards 1E 161348–5055 to be ∼6 × 10 21 cm –2 , a value compatible with a blackbody solution for the CCO X-ray emission. However, the implied temperature and luminosity are very high compared to most neutron stars. Moreover, the strong long-term variability in X-rays favours the hypothesis that 1E 161348–5055 is an accreting binary source rather than an isolated, cooling neutron star. An analysis of the continuum image obtained at 1.4 GHz from these observations shows no trace of a pulsar wind nebula around 1E 161348–5055, in spite of it being a young object.
Publisher: Springer Science and Business Media LLC
Date: 06-1990
DOI: 10.1038/345598A0
Publisher: Oxford University Press (OUP)
Date: 15-09-1991
Publisher: American Astronomical Society
Date: 22-05-2017
Publisher: Oxford University Press (OUP)
Date: 30-01-2014
DOI: 10.1093/MNRAS/STU021
Publisher: Oxford University Press (OUP)
Date: 11-10-2000
Publisher: American Astronomical Society
Date: 29-04-2011
Publisher: Oxford University Press (OUP)
Date: 27-10-2018
Publisher: Oxford University Press (OUP)
Date: 11-01-2006
Publisher: Oxford University Press (OUP)
Date: 20-07-2020
Abstract: The population of young, non-recycled pulsars with spin-down energies $\\dot{E} \\gt 10^{35}$ erg s−1 is s led predominantly at γ-ray and radio wavelengths. A total of 137 such pulsars are known, with partial overlap between the sources detectable in radio and γ-rays. We use a very small set of assumptions in an attempt to test whether the observed pulsar s le can be explained by a single underlying population of neutron stars. For radio emission we assume a canonical conal beam with a fixed emission height of 300 km across all spin periods and a luminosity law which depends on $\\dot{E}^{0.25}$. For γ-ray emission we assume the outer-gap model and a luminosity law which depends on $\\dot{E}^{0.5}$. We synthesize a population of fast-spinning pulsars with a birth rate of one per 100 yr. We find that this simple model can reproduce most characteristics of the observed population with two caveats. The first is a deficit of γ-ray pulsars at the highest $\\dot{E}$ which we surmise to be an observational selection effect due to the difficulties of finding γ-ray pulsars in the presence of glitches without prior knowledge from radio frequencies. The second is a deficit of radio pulsars with interpulse emission, which may be related to radio emission physics. We discuss the implications of these findings.
Publisher: Oxford University Press (OUP)
Date: 21-05-2009
Publisher: Oxford University Press (OUP)
Date: 16-04-2021
Abstract: We have measured the scattering time-scale, τ, and the scattering spectral index, α, for 84 single-component pulsars. Observations were carried out with the MeerKAT telescope as part of the Thousand-Pulsar-Array programme in the MeerTime project at frequencies between 0.895 and 1.670 GHz. Our results give a distribution of values for α (defined in terms of τ and frequency ν as τ ∝ ν−α) for which, upon fitting a Gaussian, we obtain a mean and standard deviation of 〈α〉 = 4.0 ± 0.6. This is due to our identification of possible causes of inaccurate measurement of τ, which, if not filtered out of modelling results, tend to lead to underestimation of α. The pulsars in our s le have large dispersion measures and are therefore likely to be distant. We find that a model using an isotropic scatter broadening function is consistent with the data, likely due to the averaging effect of multiple scattering screens along the line of sight. Our s le of scattering parameters provides a strong data set upon which we can build to test more complex and time-dependent scattering phenomena, such as extreme scattering events.
Publisher: Oxford University Press (OUP)
Date: 26-03-2021
Abstract: We present high signal-to-noise ratio, full polarization pulse profiles for 40 bright, ‘slowly’ rotating (non-recycled) pulsars using the new ultrawideband low-frequency (UWL 704–4032 MHz) receiver on the Parkes radio telescope. We obtain updated and accurate interstellar medium parameters towards these pulsars (dispersion measures and Faraday rotation measures), and reveal Faraday dispersion towards PSR J1721–3532 caused by interstellar scattering. We find general trends in the pulse profiles including decreasing fractional linear polarization and increasing degree of circular polarization with increasing frequency, consistent with previous studies, while also revealing new features and frequency evolution. This demonstrates results that can be obtained using UWL monitoring observations of slow pulsars, which are valuable for improving our understanding of pulsar emission and the intervening interstellar medium. The calibrated data products are publicly available.
Publisher: American Astronomical Society
Date: 06-1995
DOI: 10.1086/187908
Publisher: Oxford University Press (OUP)
Date: 24-03-2022
Abstract: The observable population of double neutron star (DNS) systems in the Milky Way allow us to understand the nature of supernovae and binary stellar evolution. Until now, all DNS systems in wide orbits (Porb & 1 d) have been found to have orbital eccentricities, e & 0.1. In this paper, we report the discovery of pulsar PSR J1325−6253: a DNS system in a 1.81-d orbit with a surprisingly low eccentricity of just e = 0.064. Through, 1.4 yr of dedicated timing with the Parkes radio telescope we have been able to measure its rate of advance of periastron, $\\dot{\\omega }=0{_{.}^{\\circ}}138\\pm 0{_{.}^{\\circ}}002\\, \\mathrm{yr}^{-1}$. If this induced $\\dot{\\omega }$ is solely due to general relativity then the total mass of the system is, Msys = 2.57 ± 0.06 M⊙. Assuming an edge-on orbit the minimum companion mass is constrained to be Mc, min & 0.98 M⊙ which implies the pulsar mass is Mp, max & 1.59 M⊙. Its location in the P–$\\dot{P}$ diagram suggests that, like other DNS systems, PSR J1325−6253 is a recycled pulsar and if its mass is similar to the known ex les (& .3 M⊙), then the companion neutron star is probably less than ∼1.25 M⊙ and the system is inclined at about 50°–60°. The low eccentricity along with the wide orbit of the system strongly favours a formation scenario involving an ultra-stripped supernova explosion.
Publisher: American Astronomical Society
Date: 07-1996
DOI: 10.1086/177473
Publisher: Oxford University Press (OUP)
Date: 06-12-2019
Publisher: Oxford University Press (OUP)
Date: 03-05-2018
Publisher: Oxford University Press (OUP)
Date: 21-05-2007
Publisher: Oxford University Press (OUP)
Date: 24-10-2014
Publisher: American Astronomical Society
Date: 03-1994
DOI: 10.1086/187231
Publisher: Oxford University Press (OUP)
Date: 15-02-2023
Abstract: We report on the subpulse modulation properties of 1198 pulsars using the Thousand-Pulsar-Array programme on MeerKAT. About 35 per cent of the analysed pulsars exhibit drifting subpulses that are more pronounced towards the death line, consistent with previous studies. We estimate that this common phenomenon is detectable in 60 per cent of the overall pulsar population if high-quality data were available for all. This large study reveals the evolution of drifting subpulses across the pulsar population in unprecedented detail. In particular, we find that the modulation period P3 follows a V-shaped evolution with respect to the characteristic age τc, such that the smallest P3 values, corresponding to the Nyquist period P3 ≃ 2, are found at τc ≃ 107.5 yr. The V-shaped evolution can be interpreted and reproduced if young pulsars possess aliased fast intrinsic P3, which monotonically increase, ultimately achieving a slow unaliased P3. Enhancement of irregularities in intrinsic subpulse modulation by aliasing in small-τc pulsars would explain their observed less well defined P3’s and weaker spectral features. Modelling these results as rotating subbeams, their circulation must slow down as the pulsar evolves. This is the opposite to that expected if circulation is driven by $\\boldsymbol{E}\\times \\boldsymbol{B}$ drift. This can be resolved if the observed P3 periodicity is due to a beat between an $\\boldsymbol{E}\\times \\boldsymbol{B}$ system and the pulsar period. As a by-product, we identified the correct periods and spin-down rates for 12 pulsars, for which harmonically related values were reported in the literature.
Publisher: Oxford University Press (OUP)
Date: 08-2019
Abstract: The frequency widening of pulsar profiles is commonly attributed to lower frequencies being produced at greater heights above the surface of the pulsar so-called radius-to-frequency mapping (RFM). The observer’s view of pulsar emission is a 1D cut through a 3D magnetosphere: we can only see that emission which points along our line of sight. However, by comparing the frequency evolution of many single pulses positioned at different phases, we can build up an understanding of the shape of the active emission region. We use single pulses observed with the Giant Metrewave Radio Telescope to investigate the emission region of PSR J1136+1551 and test RFM. Assuming that emission is produced tangential to the magnetic field lines and that each emission frequency corresponds to a single height, we simulate the single pulse profile evolution resulting from the canonical conal beam model and a fan beam model. Comparing the results of these simulations with the observations, we conclude that the emission region of PSR J1136+1551 is better described by the fan beam model. The ersity of profile widening behaviour observed for the single pulses can be explained by orthogonally polarized modes propagating along differing frequency-dependent paths in the magnetosphere.
Publisher: Oxford University Press (OUP)
Date: 19-06-2015
Publisher: EDP Sciences
Date: 08-2003
Publisher: Oxford University Press (OUP)
Date: 11-04-2006
Publisher: Oxford University Press (OUP)
Date: 21-07-2008
Publisher: Oxford University Press (OUP)
Date: 09-12-2014
Publisher: Public Library of Science (PLoS)
Date: 25-11-2019
Publisher: American Astronomical Society
Date: 05-04-2017
Publisher: Cambridge University Press (CUP)
Date: 2010
DOI: 10.1071/AS09054
Abstract: We report here on two years of timing of 168 pulsars using the Parkes radio telescope. The vast majority of these pulsars have spin-down luminosities in excess of 10 34 erg s −1 and are prime target candidates to be detected in gamma-rays by the Fermi Gamma-Ray Space Telescope. We provide the ephemerides for the ten pulsars being timed at Parkes which have been detected by Fermi in its first year of operation. These ephemerides, in conjunction with the publicly available photonlist, can be used to generate gamma-ray profiles from the Fermi archive. We will make the ephemerides of any pulsars of interest available to the community upon request. In addition to the timing ephemerides, we present the parameters for 14 glitches which have occurred in 13 pulsars, seven of which have no previously known glitch history.The Parkes timing programme, in conjunction with Fermi observations, is expected to continue for at least the next four years.
Publisher: Oxford University Press (OUP)
Date: 11-12-2008
Publisher: Oxford University Press (OUP)
Date: 23-09-1999
Publisher: Oxford University Press (OUP)
Date: 29-05-2021
Abstract: We present observations of 35 high spin-down energy radio pulsars using the MeerKAT telescope. Polarization profiles and associated parameters are also presented. We derive the geometry for a selection of pulsars which show interpulse emission. We point out that, in several cases, these radio pulsars should also be seen in γ-rays but that improved radio timing is required to aid the high-energy detection. We discuss the relationship between the width of the radio profile and its high-energy detectability. Finally, we reflect on the correlation between the spin-down energy and the radio polarization fraction and the implications this may have for γ-ray emission.
Publisher: Oxford University Press (OUP)
Date: 03-11-2011
Publisher: American Astronomical Society
Date: 1993
DOI: 10.1086/186714
Publisher: Oxford University Press (OUP)
Date: 03-2005
Publisher: American Astronomical Society
Date: 04-03-2010
Publisher: American Astronomical Society
Date: 04-2021
Abstract: Optical depth variations in the Galactic neutral interstellar medium (ISM) with spatial scales from hundreds to thousands of astronomical units have been observed through H i absorption against pulsars and continuum sources, while extremely small structures with spatial scales of tens of astronomical units remain largely unexplored. The nature and formation of such tiny-scale atomic structures (TSAS) need to be better understood. We report a tentative detection of TSAS with a signal-to-noise ratio of 3.2 toward PSR B1557−50 in the second epoch of two Parkes sessions just 0.36 yr apart, which are the closest-spaced spectral observations toward this pulsar. One absorption component showing marginal variations has been identified. Based on the pulsar’s proper motion of 14 mas yr −1 and the component’s kinematic distance of 3.3 kpc, the corresponding characteristic spatial scale is 17 au, which is among the smallest sizes of known TSAS. Assuming a similar line-of-sight (LOS) depth, the tentative TSAS cloud detected here is overdense and overpressured relative to the cold neutral medium (CNM), and can radiatively cool fast enough to be in thermal equilibrium with the ambient environment. We find that turbulence is not sufficient to confine the overpressured TSAS. We explore the LOS elongation that would be required for the tentative TSAS to be at the canonical CNM pressure, and find that it is ∼5000—much larger than filaments observed in the ISM. We see some evidence of line width and temperature variations in the CNM components observed at the two epochs, as predicted by models of TSAS-like cloud formation colliding warm neutral medium flows.
Publisher: American Astronomical Society
Date: 08-1993
DOI: 10.1086/186951
Publisher: EDP Sciences
Date: 02-11-2006
Publisher: American Astronomical Society
Date: 03-1995
DOI: 10.1086/175397
Publisher: American Astronomical Society
Date: 23-10-2023
Publisher: Oxford University Press (OUP)
Date: 28-08-2013
Publisher: American Astronomical Society
Date: 14-04-2011
Publisher: Oxford University Press (OUP)
Date: 25-08-2015
Publisher: Oxford University Press (OUP)
Date: 21-04-2003
Publisher: American Astronomical Society
Date: 07-10-2009
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 05-2002
End Date: 05-2007
Amount: $1,208,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 01-2007
End Date: 05-2010
Amount: $270,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 10-2020
End Date: 12-2023
Amount: $1,150,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2004
End Date: 12-2009
Amount: $1,185,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 2009
End Date: 12-2010
Amount: $322,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 06-2016
End Date: 03-2017
Amount: $1,000,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 05-2011
End Date: 03-2018
Amount: $20,600,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 05-2004
End Date: 12-2004
Amount: $10,000.00
Funder: Australian Research Council
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