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Simulating Pulsar Signal Scattering in the Interstellar Medium with Two Distinct Scattering PhenomenaJussila, Adam P. 20 December 2018 (has links)
No description available.
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Nonparametric estimation of the off-pulse interval(s) of a pulsar light curve / Willem Daniël SchutteSchutte, Willem Daniël January 2014 (has links)
The main objective of this thesis is the development of a nonparametric sequential estimation
technique for the off-pulse interval(s) of a source function originating from a pulsar. It is important
to identify the off-pulse interval of each pulsar accurately, since the properties of the off-pulse
emissions are further researched by astrophysicists in an attempt to detect potential emissions
from the associated pulsar wind nebula (PWN). The identification technique currently used in the
literature is subjective in nature, since it is based on the visual inspection of the histogram estimate
of the pulsar light curve. The developed nonparametric estimation technique is not only objective
in nature, but also accurate in the estimation of the off-pulse interval of a pulsar, as evident from
the simulation study and the application of the developed technique to observed pulsar data.
The first two chapters of this thesis are devoted to a literature study that provides background
information on the pulsar environment and -ray astronomy, together with an explanation of the
on-pulse and off-pulse interval of a pulsar and the importance thereof for the present study. This
is followed by a discussion on some fundamental circular statistical ideas, as well as an overview
of kernel density estimation techniques. These two statistical topics are then united in order to
illustrate kernel density estimation techniques applied to circular data, since this concept is the
starting point of the developed nonparametric sequential estimation technique.
Once the basic theoretical background of the pulsar environment and circular kernel density
estimation has been established, the new sequential off-pulse interval estimator is formulated. The
estimation technique will be referred to as `SOPIE'. A number of tuning parameters form part
of SOPIE, and therefore the performed simulation study not only serves as an evaluation of the
performance of SOPIE, but also as a mechanism to establish which tuning parameter configurations
consistently perform better than some other configurations.
In conclusion, the optimal parameter configurations are utilised in the application of SOPIE to
pulsar data. For several pulsars, the sequential off-pulse interval estimators are compared to the
off-pulse intervals published in research papers, which were identified with the subjective \eye-ball"
technique. It is found that the sequential off-pulse interval estimators are closely related to the
off-pulse intervals identified with subjective visual inspection, with the benefit that the estimated
intervals are objectively obtained with a nonparametric estimation technique. / PhD (Statistics), North-West University, Potchefstroom Campus, 2014
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Nonparametric estimation of the off-pulse interval(s) of a pulsar light curve / Willem Daniël SchutteSchutte, Willem Daniël January 2014 (has links)
The main objective of this thesis is the development of a nonparametric sequential estimation
technique for the off-pulse interval(s) of a source function originating from a pulsar. It is important
to identify the off-pulse interval of each pulsar accurately, since the properties of the off-pulse
emissions are further researched by astrophysicists in an attempt to detect potential emissions
from the associated pulsar wind nebula (PWN). The identification technique currently used in the
literature is subjective in nature, since it is based on the visual inspection of the histogram estimate
of the pulsar light curve. The developed nonparametric estimation technique is not only objective
in nature, but also accurate in the estimation of the off-pulse interval of a pulsar, as evident from
the simulation study and the application of the developed technique to observed pulsar data.
The first two chapters of this thesis are devoted to a literature study that provides background
information on the pulsar environment and -ray astronomy, together with an explanation of the
on-pulse and off-pulse interval of a pulsar and the importance thereof for the present study. This
is followed by a discussion on some fundamental circular statistical ideas, as well as an overview
of kernel density estimation techniques. These two statistical topics are then united in order to
illustrate kernel density estimation techniques applied to circular data, since this concept is the
starting point of the developed nonparametric sequential estimation technique.
Once the basic theoretical background of the pulsar environment and circular kernel density
estimation has been established, the new sequential off-pulse interval estimator is formulated. The
estimation technique will be referred to as `SOPIE'. A number of tuning parameters form part
of SOPIE, and therefore the performed simulation study not only serves as an evaluation of the
performance of SOPIE, but also as a mechanism to establish which tuning parameter configurations
consistently perform better than some other configurations.
In conclusion, the optimal parameter configurations are utilised in the application of SOPIE to
pulsar data. For several pulsars, the sequential off-pulse interval estimators are compared to the
off-pulse intervals published in research papers, which were identified with the subjective \eye-ball"
technique. It is found that the sequential off-pulse interval estimators are closely related to the
off-pulse intervals identified with subjective visual inspection, with the benefit that the estimated
intervals are objectively obtained with a nonparametric estimation technique. / PhD (Statistics), North-West University, Potchefstroom Campus, 2014
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Millisecond pulsars and pulsar wind nebulae as sources of gamma rays and cosmic rays / C. VenterVenter, Christo January 2008 (has links)
Thesis (Ph.D. (Space Physics)--North-West University, Potchefstroom Campus, 2008.
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Millisecond pulsars and pulsar wind nebulae as sources of gamma rays and cosmic rays / C. VenterVenter, Christo January 2008 (has links)
Thesis (Ph.D. (Space Physics)--North-West University, Potchefstroom Campus, 2008.
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Millisecond pulsars and pulsar wind nebulae as sources of gamma rays and cosmic rays / C. VenterVenter, Christo January 2008 (has links)
Thesis (Ph.D. (Space Physics)--North-West University, Potchefstroom Campus, 2008.
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Quantum Foundations with Astronomical PhotonsLeung, Calvin 01 January 2017 (has links)
Theoretical work in quantum information has demonstrated that a classical hidden-variable model of an entangled singlet state can explain nonclassical correlations observed in tests of Bell’s inequality if while measuring the Bell correlation, the underlying probability distribution of the hidden-variable changes depending on the measurement basis. To rule out this possibility, distant quasars can be utilized as random number generators to set measurement bases in an experimental test of Bell’s inequality. Here we report on the design and characterization of a device that uses the color of incoming quasar photons to output a random bit with nanosecond latency. Through the 1-meter telescope at JPL Table Mountain Observatory, we observe and generate random bits from quasars with redshifts z = 0.1−3.9. In addition, we formulate a mathematical model that quantifies the fidelity of the bits generated.
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Determining The Asymmetry In Supernova Explosions By Studying The Radial Velocities Of Ob Runaway StarsDincel, Baha 01 July 2012 (has links) (PDF)
Understanding the asymmetry in core collapse supernova explosions is
pointed out by various astrophysicists as it is the key factor in determining
the observational properties of the pulsars. The initial kick given by the ex-
plosion to the pulsar affects its spin period and space velocity. Up to now,
although the observations do not show a direct relation between the observational features of the pulsar and its space velocity, they show a clear relation between the spin period and the magnetic field strength, hence its radiation processes. In this thesis, as the method, tracing the companions of progenitors if they were in close binaries, which becomes a runaway star after the supernova explosion was chosen. Over the candidates selected in Guseinov et al (2005), the spectral types of 11 runaway candidates from 7 supernova remnants determined through analyzing their spectroscopic observations. Radial velocity determination was applied to the discovered B6V type star GSC 03156-01430 inside the supernova remnant G78.2+2.1. Also by studying the proper motion data, we compared the motion of the runaway star and the related pulsar in order to determine the asymmetry in the supernova explosion. The neutron star PSR 2021+4026 is moving with a 2-D velocity of &sim / 580 km/s with respect to the rest frame of its birth association Cyg OB9. &sim / 550 km/s more than expected in the symmetric case. Re-constructing the pre-supernova binary shows that the asymmetry in the supernova explosion does not depend on the binarity.
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The effect of general relativistic frame dragging on millisecond pulsar visibility for the H.E.S.S. telescope / C. VenterVenter, Christo January 2004 (has links)
It has been noted by several authors that General Relativistic frame dragging in rotating
neutron stars is a first order effect which has to be included in a self-consistent model of pulsar
magnetospheric structure and associated radiation and transport processes. To this end, I
undertook the present study with the aim of investigating the effect of General Relativity
(GR) on millisecond pulsar (MSP) visibility.
I developed a numerical code for simulating a pulsar magnetosphere, incorporating the
GR-corrected expressions for the electric potential and field. I included curvature radiation
(CR) due to primary electrons accelerated above the stellar surface, as well as inverse Compton
scattering (ICS) of thermal X-ray photons by these electrons. I then applied the model to
PSR J0437-4715, a prime candidate for testing the GR-Electrodynamic theory, and examined
its visibility for the H.E.S.S. telescope. I also considered the question of whether magnetic
photon absorption would take place for this particular pulsar. In addition, I developed a
classical model for comparison with the GR results.
I found that the typical electron energies and associated CR photon energies are functions
of position above the polar cap (PC). These energies are also quite smaller in the GR case
than in the classical case due to the different functional forms of the GR and classical electric
fields. I found the CR energy cut-off to be ~ 4 GeV compared to the well-known classical
value of ~ 100 GeV. Since the H.E.S.S. energy threshold is ~ 100 GeV, it seems as though
the CR component will not be visible, contrary to wide-held opinion. However, the ICS
component seems to be well in excess of the H.E.S.S. energy threshold and is expected to be
visible. I also found that no pair production will take place for PSR J0437-4715.
Hopefully, forthcoming H.E.S.S. observations will provide validation of these results.
KEY WORDS: General relativistic frame dragging, GR electrodynamics, millisecond pulsar
visibility, non-thermal radiation processes, pair production, H.E.S.S., individual pulsars:
PSR J0437-4715. / Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2004.
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The effect of general relativistic frame dragging on millisecond pulsar visibility for the H.E.S.S. telescope / C. VenterVenter, Christo January 2004 (has links)
It has been noted by several authors that General Relativistic frame dragging in rotating
neutron stars is a first order effect which has to be included in a self-consistent model of pulsar
magnetospheric structure and associated radiation and transport processes. To this end, I
undertook the present study with the aim of investigating the effect of General Relativity
(GR) on millisecond pulsar (MSP) visibility.
I developed a numerical code for simulating a pulsar magnetosphere, incorporating the
GR-corrected expressions for the electric potential and field. I included curvature radiation
(CR) due to primary electrons accelerated above the stellar surface, as well as inverse Compton
scattering (ICS) of thermal X-ray photons by these electrons. I then applied the model to
PSR J0437-4715, a prime candidate for testing the GR-Electrodynamic theory, and examined
its visibility for the H.E.S.S. telescope. I also considered the question of whether magnetic
photon absorption would take place for this particular pulsar. In addition, I developed a
classical model for comparison with the GR results.
I found that the typical electron energies and associated CR photon energies are functions
of position above the polar cap (PC). These energies are also quite smaller in the GR case
than in the classical case due to the different functional forms of the GR and classical electric
fields. I found the CR energy cut-off to be ~ 4 GeV compared to the well-known classical
value of ~ 100 GeV. Since the H.E.S.S. energy threshold is ~ 100 GeV, it seems as though
the CR component will not be visible, contrary to wide-held opinion. However, the ICS
component seems to be well in excess of the H.E.S.S. energy threshold and is expected to be
visible. I also found that no pair production will take place for PSR J0437-4715.
Hopefully, forthcoming H.E.S.S. observations will provide validation of these results.
KEY WORDS: General relativistic frame dragging, GR electrodynamics, millisecond pulsar
visibility, non-thermal radiation processes, pair production, H.E.S.S., individual pulsars:
PSR J0437-4715. / Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2004.
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