Population Statistics of Normal, Radio and Gamma-ray Pulsars from the Galactic Disk
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We present results of a pulsar population synthesis of normal pulsars in the Galactic plane. Over the past several years, a program has been developed to simulate pulsar birth, evolution, and emission using Monte Carlo techniques. We model the spatial distribution of pulsars by assuming they are born with a random kick velocity and then evolved within the Galactic potential. We assume that pulsars are standard candles and invoke a new relationship between core and cone emission suggested by recent studies, which we also apply to millisecond pulsars. From our studies of radio pulsars that have clearly identifiable core and cone components, in which we fit the polarization sweep as well as the pulse profiles to constrain the viewing geometry, we develop a model describing the ratio of radio core‐to‐cone peak fluxes. In this model, short period pulsars are more cone‐dominated than in our previous studies. We use both a low and high altitude slot gap model for describing the gamma‐ray emission. We also include gamma‐ray emission from an outer‐gap model to compare the statistics of radio‐loud and radio‐quiet gamma‐ray pulsars on the same footing as pulsars from our slot gap, polar cap model. We present results of our recent study and the implications for observing these pulsars with GLAST and AGILE.Keywords:
Galactic plane
X-ray pulsar
The main objectives of modeling the Galactic pulsar population are (i) to understand underlying properties of various pulsar subclasses, and (ii) to probe physical conditions relevant to the formation and evolution of these objects. A theoretical approach is useful to explore various stellar populations, but introduces large systematic uncertainties in results. An empirical approach is known to be more reliable, but is limited only to known populations. Traditionally, the pulsar population studies focused on isolated, slowly rotating 'normal' pulsars that are the majority of the known pulsars. With improved pulsar search techniques and more sensitive instruments, the known pulsar sample has been greatly expanding, both in quality and quantity, over the past 40 years. The increased number of pulsar sample allows more rigorous statistical analysis on the normal population. Moreover, there are many new populations to be studied, such as relativistic pulsar binaries, millisecond pulsars, or pulsars in globular clusters.
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The double pulsar system PSR J0737-3039 offers an unprecedented opportunity for studying General Relativity and neutron-star magnetospheres. This system has a favourable orbital inclination such that the millisecond pulsar, A, is eclipsed when its slower companion, passes in front. High time resolution light curves of the eclipses reveal periodic modulations of the radio flux corresponding to the fundamental and the first harmonic of pulsar spin frequency. Eclipse modelling is highly sensitive to the geometrical configuration of the system and thus provides a unique probe for parameters like the inclination angle of pulsar B spin axis as well as their time evolution due to relativistic effects. We report on detailed fitting of the pulsar A eclipse light curves to a model that includes, for pulsar B, a simple dipolar magnetic field. We find that the eclipses can be reproduced very well, and we obtain precise measurements of pulsar B's orientation in space. We report on a search for secular changes caused by geodetic precession of pulsar B's spin axis.
Pulsar planet
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Eclipse
Precession
Ephemeris
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A 3.5 millisecond (ms) pulsar in a binary system was recently discovered in the error box of the unidentified EGRET source GRO J0752 + 17. We extend various gamma-ray pulsar models to the ms regime and discuss their predictions for the detectability of the 3.5 ms pulsar as well as for other known ms pulsars. We use the derived luminosities from these models to predict the magnetic field of the 3.5 ms pulsar. We conclude that if the 3.5 ms pulsar is indeed the source of the gamma-ray emission, its emission will either be unpulsed or this ms pulsar cannot have been recycled according to current recycling models
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Binary radio pulsar system J0737-3039 provides an exceptional opportunity to study innermost structure of pulsar magnetospheres due to very tight orbit, favorable directions of pulsars' rotation and magnetic axes and extremely fortuitous orientation of the orbit. In this system the millisecond pulsar A is eclipsed once per orbit. During eclipse a clear modulation at the 2.77 s period of pulsar B is seen, pointing unambiguously to magnetospheric origin of eclipses. A simple geometric model, based on the idea that the radio pulses are attenuated by synchrotron absorption on the closed magnetic field lines of pulsar B, can successfully reproduces the eclipse light curves down to intricate details. This detailed agreement confirms the dipolar structure of the neutron star's magnetic field. The model gives clear predictions for temporal evolution of eclipse profile due to geodetic precession of pulsar B. In addition, pulsar B shows orbital modulations of intensity, being especially bright at two short orbital phases. We showed that these modulations are due to distortion of pulsar B magnetosphere by pulsar A wind which produces orbital phase-dependent changes of the direction along which radio waves are emitted. Thus, pulsar B is intrinsically bright at all times but its radiation beam misses the Earth at most orbital phases.
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A fully coherent acceleration search algorithm has been applied to the Parkes multibeam pulsar survey of the Galactic plane to search for previously undiscovered relativistic binary pulsars. The search has resulted in the discovery of 16 pulsars including a binary millisecond pulsar and an intermittent pulsar. Despite a number of promising candidates there have been no new discoveries of relativistic binary pulsars. Here, we detail the acceleration search performed in our analysis and present coherent timing solutions for each of the pulsars discovered. In light of the lack of discoveries of relativistic binary pulsars, we also discuss the technique of acceleration searching and its effectiveness in finding these systems.
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Binary radio pulsar system J0737-3039 provides an exceptional opportunity to study innermost structure of pulsar magnetospheres due to very tight orbit, favorable directions of pulsars' rotation and magnetic axes and extremely fortuitous orientation of the orbit. In this system the millisecond pulsar A is eclipsed once per orbit. During eclipse a clear modulation at the 2.77 s period of pulsar B is seen, pointing unambiguously to magnetospheric origin of eclipses. A simple geometric model, based on the idea that the radio pulses are attenuated by synchrotron absorption on the closed magnetic field lines of pulsar B, can successfully reproduces the eclipse light curves down to intricate details. This detailed agreement confirms the dipolar structure of the neutron star's magnetic field.
The model gives clear predictions for temporal evolution of eclipse profile due to geodetic precession of pulsar B.
In addition, pulsar B shows orbital modulations of intensity, being especially bright at two short orbital phases. We showed that these modulations are due to distortion of pulsar B magnetosphere by pulsar A wind which produces orbital phase-dependent changes of the direction along which radio waves are emitted. Thus, pulsar B is intrinsically bright at all times but its radiation beam misses the Earth at most orbital phases.
Pulsar planet
X-ray pulsar
Eclipse
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X-ray pulsar
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We report on new pulsars discovered in Arecibo drift-scan data. Processing of 2200 square degrees of data has resulted in the detection of 41 known and 12 new pulsars. New pulsars include two millisecond pulsars, one solitary and one binary recycled pulsar, and one pulsar with very unusual pulse profile morphology and complex drifting subpulse behavior.
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We report on new pulsars discovered in Arecibo drift-scan datA. Processing of 2200 deg 2 of data has resulted in the detection of 41 known and 12 new pulsars. New pulsars include two millisecond pulsars, one solitary and one binary recycled pulsar, and one pulsar with very unusual pulse profile morphology and complex drifting subpulse behavior.
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