arXiv subjects

R. N. Manchester

Publications and source records attributed to R. N. Manchester.

At least 199 records · Page 11Linked to original sources

arXiv2004

PSRCHIVE and PSRFITS An Open Approach to Radio Pulsar Data Storage and Analysis

A new set of software applications and libraries for use in the archival and analysis of pulsar astronomical data is introduced. Known collectively as the PSRCHIVE scheme, the code was developed in parallel with a new data storage format called PSRFITS, which is based on the Flexible Image Transport System (FITS). Both of these projects utilise a modular, object-oriented design philosophy. PSRCHIVE is an open source development environment that incorporates an extensive range of C++ object classes and pre-built command line and graphical utilities. These deal transparently and simultaneously with multiple data storage formats, thereby enhancing data portability and facilitating the adoption of the PSRFITS file format. Here, data are stored in a series of modular header-data units that provide flexibility and scope for future expansion. As it is based on FITS, various standard libraries and applications may be used for data input/output and visualisation. Both PSRCHIVE and PSRFITS are made publicly available to the academic community in the hope that this will promote their widespread use and acceptance.

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arXiv2004

Two clocks in the PSR J0737--3039 binary system and their implications for the system's origin and evolution

As discussed elsewhere in these proceedings, the double pulsar system is a magnificent laboratory for gravitational physics and for studying pulsar magnetospheres. Here we consider the uses of having two clocks in the system in the context of its origin and evolution. We find that the ``standard'' evolutionary scenario involving spin-up of the first-born neutron star in an X-ray binary phase is consistent with the observed parameters. Equality of the spin-down ages of the two pulsars requires that the post-accretion spin period of A most likely lies in the range $16 \lapp P_{\rm 0,A} \lapp 21$ ms. The likely age of the system is 30-70 Myr.

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arXiv2004

The spatial energy spectrum of magnetic fields in our Galaxy

Interstellar magnetic fields exist over a broad range of spatial scales, extending from the large Galactic scales ($\sim 10$ kpc) down to the very small dissipative scales ($\ll 1$ pc). In this paper, we use a set of 490 pulsars distributed over roughly one third of the Galactic disk out to a radius $R \simeq 10$ kpc (assuming $R_\odot = 8.5$ kpc) and combine their observed rotation and dispersion measures with their estimated distances to derive the spatial energy spectrum of the Galactic interstellar magnetic field over the scale range $0.5 - 15$ kpc. We obtain a nearly flat spectrum, with a 1D power-law index $α=-0.37\pm0.10$ for $E_{\rm B}(k)=C k^α$ and an rms field strength of approximately $6 μ$G over the relevant scales. Our study complements the derivation of the magnetic energy spectrum over the scale range $0.03 - 100$ pc by \citet{ms96b}, showing that the magnetic spectrum becomes flatter at larger scales. This observational result is discussed in the framework of current theoretical and numerical models.

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arXiv2004

13 Years of Timing of PSR B1259-63

This paper summarizes the results of 13 years of timing observations of a unique binary pulsar, PSR B1259$-$63, which has a massive B2e star companion. The data span encompasses four complete orbits and includes the periastron passages in 1990, 1994, 1997 and 2000. Changes in dispersion measure occurring around the 1994, 1997 and 2000 periastrons are measured and accounted for in the timing analysis. There is good evidence for a small glitch in the pulsar period in 1997 August, not long after the 1997 periastron, and a significant frequency second derivative indicating timing noise. We find that spin-orbit coupling with secular changes in periastron longitude and projected semi-major axis ($x$) cannot account for the observed period variations over the whole data set. While fitting the data fairly well, changes in pulsar period parameters at each periastron seem ruled out both by X-ray observations and by the large apparent changes in pulsar frequency derivative. Essentially all of the systematic period variations are accounted for by a model consisting of the 1997 August glitch and step changes in $x$ at each periastron. These changes must be due to changes in the orbit inclination, but we can find no plausible mechanism to account for them. It is possible that timing noise may mask the actual changes in orbital parameters at each periastron, but the good fit to the data of the $x$ step-change model suggests that short-term timing noise is not significant.

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arXiv2004

X-Ray Emission from the Double Pulsar System J0737-3039

We report on a 10 ksec observation of the double pulsar system J0737-3039 obtained with the Chandra X-ray Observatory's Advanced CCD Imaging Spectrometer. We detect the system as a point source with coordinates (J2000) RA = 07:37:51.23, Decl. = -30:39:40.9, making this the first double neutron star system to be detected at X-ray energies. Only 77 source counts are detected. The data are represented satisfactorily by a power-law spectrum with photon index = 2.9 +/- 0.4. The inferred 0.2-10 keV luminosity is approximately 2e30 erg/s for a distance of 0.5 kpc. We do not detect any significant variability with orbital phase in these data, which span one full orbit. These results are consistent with the X-ray emission originating solely from the magnetosphere of the energetic A pulsar, with an efficiency for conversion of rotational energy to X-rays in this band of roughly 0.04%, although we cannot exclude other possibilities.

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arXiv2004

A Double-Pulsar System - A Rare Laboratory for Relativistic Gravity and Plasma Physics

The clock-like properties of pulsars moving in the gravitational fields of their unseen neutron-star companions have allowed unique tests of general relativity and provided evidence for gravitational radiation. We report here the detection of the 2.8-sec pulsar J0737-3039B as the companion to the 23-ms pulsar J0737-3039A in a highly-relativistic double-neutron-star system, allowing unprecedented tests of fundamental gravitational physics. We observe a short eclipse of J0737-3039A by J0737-3039B and orbital modulation of the flux density and pulse shape of J0737-3039B, probably due to the influence of J0737-3039A's energy flux upon its magnetosphere. These effects will allow us to probe magneto-ionic properties of a pulsar magnetosphere.

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arXiv2003

An increased estimate of the merger rate of double neutron stars from observations of a highly relativistic system

The merger of close binary systems containing two neutron stars should produce a burst of gravitational waves, as predicted by the theory of general relativity. A reliable estimate of the double-neutron-star merger rate in the Galaxy is crucial in order to predict whether current gravity wave detectors will be successful in detecting such bursts. Present estimates of this rate are rather low, because we know of only a few double-neutron-star binaries with merger times less than the age of the Universe. Here we report the discovery of a 22-ms pulsar, PSR J0737-3039, which is a member of a highly relativistic double-neutron-star binary with an orbital period of 2.4 hours. This system will merge in about 85 Myr, a time much shorter than for any other known neutron-star binary. Together with the relatively low radio luminosity of PSR J0737-3039, this timescale implies an order-of-magnitude increase in the predicted merger rate for double-neutron-star systems in our Galaxy (and in the rest of the Universe).

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arXiv2003

Searching for sub-millisecond pulsars from highly polarized radio sources

Pulsars are among the most highly polarized sources in the universe. The NVSS has catalogued 2 million radio sources with linear polarization measurements, from which we have selected 253 sources, with polarization percentage greater than 25%, as targets for pulsar searches. We believe that such a sample is not biased by selection effects against ultra-short spin or orbit periods. Using the Parkes 64m telescope, we conducted searches with sample intervals of 0.05 ms and 0.08 ms, sensitive to submillisecond pulsars. Unfortunately we did not find any new pulsars.

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arXiv2003

Two Radio Pulsars with Magnetar Fields

PSRs J1847-0130 and J1718-37184 have inferred surface dipole magnetic fields greater than those of any other known pulsars and well above the ``quantum critical field'' above which some models predict radio emission should not occur.These fields are similar to those of the anomalous X-ray pulsars (AXPs), which growing evidence suggests are ``magnetars''. The lack of AXP-like X-ray emission from these radio pulsars (and the non-detection of radio emission from the AXPs) creates new challenges for understanding pulsar emission physics and the relationship between these classes of apparently young neutron stars.

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arXiv2003

Pulsar Birthrate from Parkes Multi-beam Survey

We report on calculations of the pulsar birthrate based on the results of the Parkes multibeam survey. From 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 birthrate as a function of the surface dipole magnetic field strengths. We show that pulsars with magnetic fields greater than 10**12.5 G account for about half of the total birthrate.

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arXiv2003

Three Binary Millisecond Pulsars in NGC 6266

We present rotational and astrometric parameters of three millisecond pulsars located near the center of the globular cluster NGC 6266 (M62) resulting from timing observations with the Parkes radio telescope. Their accelerations toward the cluster center yield values of the cluster central density and mass-to-light ratio consistent with those derived from optical data. The three pulsars are in binary systems. One (spin period P=5.24 ms) is in a 3.5-day orbit around a companion of minimum mass 0.2 Msun. The other two millisecond pulsars (P=3.59 ms and 3.81 ms) have shorter orbital periods (3.4 hr and 5.0 hr) and lighter companions (minimum mass 0.12 Msun and 0.07 Msun respectively). The pulsar in the closest system is the fifth member of an emerging class of millisecond pulsars displaying irregular radio eclipses and having a relatively massive companion. This system is a good candidate for optical identification of the companion star. The lack of known isolated pulsars in NGC 6266 is also discussed.

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arXiv2003

PSR J1847-0130: A Radio Pulsar with Magnetar Spin Characteristics

We report the discovery of PSR J1847-0130, a radio pulsar with a 6.7-s spin period, in the Parkes multibeam survey of the Galactic plane. The slowdown rate for the pulsar, 1.3x10^{-12} s/s, is high and implies a surface dipole magnetic field strength of 9.4x10^{13} G. This inferred dipolar magnetic field strength is the highest by far among all known radio pulsars and over twice the ``quantum critical field'' above which some models predict radio emission should not occur. The inferred dipolar magnetic field strength and period of this pulsar are in the same range as those of the anomalous X-ray pulsars, which have been identified as being "magnetars" whose luminous X-ray emission is powered by their large magnetic fields. We have examined archival ASCA data and place an upper limit on the X-ray luminosity of J1847-0130 which is lower than the luminosities of all but one AXP. The properties of this pulsar prove that inferred dipolar magnetic field strength and period cannot alone be responsible for the unusual high-energy properties of the magnetars and creates new challenges for understanding the possible relationship between these two manifestations of young neutron stars.

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arXiv2003

The Parkes multibeam pulsar survey: III. Young pulsars & the discovery and timing of 200 pulsars

The Parkes multibeam pulsar survey has unlocked vast areas of the Galactic plane which were previously invisible to earlier low-frequency and less-sensitive surveys. The survey has discovered more than 600 new pulsars so far, including many that are young and exotic. In this paper we report the discovery of 200 pulsars for which we present positional and spin-down parameters, dispersion measures, flux densities and pulse profiles. A large number of these new pulsars are young and energetic, and we review possible associations of $γ$-ray sources with the sample of about 1300 pulsars for which timing solutions are known. Based on a statistical analysis, we estimate that about $19\pm6$ associations are genuine. The survey has also discovered 12 pulsars with spin properties similar to those of the Vela pulsar, nearly doubling the known population of such neutron stars. Studying the properties of all known `Vela-like' pulsars, we find their radio luminosities to be similar to normal pulsars, implying that they are very inefficient radio sources. Finally, we review the use of the newly discovered pulsars as Galactic probes and discuss the implications of the new NE2001 Galactic electron density model for the determination of pulsar distances and luminosities.

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arXiv2003

A Search for Pulsars in Quiescent Soft X-Ray Transients. I

We have carried out a deep search at 1.4 GHz for radio pulsed emission from six soft X-ray transient sources observed during their X-ray quiescent phase. The commonly accepted model for the formation of the millisecond radio pulsars predicts the presence of a rapidly rotating, weakly magnetized neutron star in the core of these systems. The sudden drop in accretion rate associated with the end of an X-ray outburst causes the Alfvèn surface to move outside the light cylinder, allowing the pulsar emission process to operate. No pulsed signal was detected from the sources in our sample. We discuss several mechanisms that could hamper the detection and suggest that free-free absorption from material ejected from the system by the pulsar radiation pressure could explain our null result.

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arXiv2003

Yet MORE PM Survey Discoveries....?

The Parkes Multibeam (PM) survey has found nearly 50% of the >1400 known pulsars and detected 20% of the pulsars in binary systems (75% within the survey area), few of these are millisecond pulsars with orbits of less than one day. It is known that the normal search techniques used in the PM Survey have selected against finding binary pulsars, due to the long integration times used. The relative performance of the search techniques used and the improvements made prior to the complete reprocessing of the data currently being undertaken are discussed. The processing is being done on COBRA - the new supercomputer at Jodrell Bank. The results of the reprocessing, as well as adding more solitary pulsars, will give more confidence on the population and types of binaries in the Galactic plane. However, it can be shown that for millisecond pulsars in binary orbits of between 20min and a few hours, the search techniques are still relatively insensitive.

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arXiv2002

The large-scale Galactic magnetic field structure and pulsar rotation measures

Pulsars provide unique probes for the {\it large-scale} interstellar magnetic field in the Galactic disk. The Parkes multibeam pulsar survey has discovered many distant pulsars which enables us for the first time to explore the magnetic field in most of the nearby half of the Galactic disk. The fields are found to be {\it coherent in direction} over a linear scale of $\sim 10$ kpc between the Carina-Sagittarius and Crux-Scutum arms from $l\sim45\degr$ to $l\sim305\degr$. The coherent spiral structures and field direction reversals, including the newly determined counterclockwise field near the Norma arm, are consistent with bi-symmetric spiral model for the disk field. However, the antisymmetric rotation measure sky from the Galactic halo and the dipole field in the Galactic center suggest that the A0 dynamo is operating there.

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arXiv2002

The Massive Binary Pulsar J1740-3052

The young pulsar J1740-3052 is in an 8-month orbit with a companion of at least 11 solar masses. We present multifrequency GBT and Parkes timing observations, and discuss implications for the nature of the companion.

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arXiv2002

Millisecond Radio Pulsars in 47 Tucanae

We review the properties of the 22 millisecond radio pulsars currently known in the globular cluster 47 Tucanae, and their implications for the mass and gas content of the cluster. Further details can be found in the publications from this project to date (Camilo et al. 2000; Freire 2000; Freire et al. 2001a,b; Freire et al. 2003). Throughout the review, we look ahead to the future results anticipated from this fascinating cluster.

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