TABLE OF CONTENTS
Title Page                                                            i
Certification                                                                                     ii
Approval Page                                                                                       iii
Dedication                                iv
Acknowledgements                                                          v
Table of Contents                                                                            vi
List of Figures                                                                                                ix
Abstract                                                                                              x
CHAPTER ONE: GENERAL INTRODUCTION
1.0      An Overview of Rotating Neutron Stars                               1
1.1      Neutron Star Structure                                        1
  1.2      Types of Pulsars                                         2
1.2.1Â Â Â Rotation-Powered Pulsars (RPPs)Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 2
1.2.1.1 Normal Pulsars                                                                  3
1.2.1.2 Millisecond Pulsars (MSPs) Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 3
1.2.2     Accretion-Powered pulsars                                        4
1.2.3   Magnetars                                                              4
1.3      Pulsar Spin Down Model                                   5
1.4      Pulsar Properties                                            6
1.4.1   Pulsar Period                                           6                    Â
1.4.2   Gravitational Field                                                                       7
1.4.3   Spin Momentum                                                                               7
1.4.4   Spin down luminosity                                              9
1.4.5   The magnetic field                              9
1.4.6   The Induced External Electric Field                    9
1.4.7   The Braking Index                                    10
1.4.8   The Characteristic Age                                            11
1.5      Timing Irregularities in Pulsars                                          12
1.5.1   Timing Noise                                                    12
1.5.1.1 Statistical Properties of Pulsar Timing Noise                13
1.5.1.1 Activity Parameter (A)Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 14
1.5.1.2 Stability Parameter (Δ8)                                                     15
1.5.1.3 Timing Noise Statistic (s23) Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 15
1.5.1.4 Pulsar Clock Stability Statistic (sZ( ) Â Â Â Â Â Â Â Â Â Â Â Â Â Â 16
1.5.2   Glitches                                                       16
1.5.2.1 Macroglitches                                                                   17
1.5.2.2 Microglitches                                                          18
1.6      Purpose of Study                                           19
CHAPTER TWO: LITERATURE REVIEW
2.1      Glitch Activity                                                              20
2.2      Glitch Recoveries                                            21
CHAPTER THREE: PULSAR GLITCH THEORIES
3.1      The Starquake Model or the Spheriodality Mechanism           23
3.2      Differential Rotations Mechanisms        24
3.3      Glitch Mechanisms Due to the Vortices                     26
3.3.1   Crust Fracture Model                                                 27
3.3.2   Thermally Driven Glitches                                                      33
3.4      Two-Component Model                                              37
CHAPTER FOUR: DATA ANALYSIS AND RESULT
4.1      Sample Description                                                        40
4.2      Data Analysis and Results                                                41
4.2.1   Analysis of the Glitch Parameters               42
4.2.2   Descriptive Analysis of the Cumulative Glitch Parameter     45
4.2.3 Relationships Between the Cumulative Glitch Parameter  48
4.2.4 Relationships Between the Cumulative Glitch Parameters and the Pulsar Spin Down Parameters                            49
4.2.5 Distribution of the Cumulative Glitch Parameters Over the Pulsar Spin Down Parameters                    58
CHAPTER FIVE: DISCUSSION, CONCLUSION AND RECOMMENDATION
5.1      Discussion                                                           60
5.2      Conclusion                                                                             64
REFERENCES
APPENDICES
LIST OF FIGURES
Figure 1.1: Typical cross-section of a neutron star              1
Figure 1.2: The P-P ̇ diagram shown for a sample consisting of radio pulsars,’ radio quiet’ pulsars, soft-gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs)                                      8
 Figure 1.3:The schematic plot of timing noise phase residuals               13
Figure 1.4: Anatomy of a typical highly resolved large glitch.           17
Figure 3.1: Diagram used to illustrate crust-cracking parameters 30
Figure 3.2: Diagram showing the structure of the cylindrical regime considered in the thermal glitch mechanism                   35
Figure 3.3: A possible configuration for the two component model      37
Figure 3.4: A response of neutron star to glitch, as predicted by the two-component model                                                       39
Figures 4.2.1 Analysis of the Glitch Parameters                                            42
Figures 4.2.2.1 Descriptive Analysis of the Cumulative Glitch Parameters 45
Figures 4.2.2.2. Relationships between the Cumulative Glitch Parameters 48
Figures 4.2.2.3. Relationships between the Cumulative Glitch Parameters and the Pulsar Spin Down Parameter          Â
Figure 4.2.3 Distribution of the Cumulative Glitch parameters over the Pulsar Spin down parameters                  58                                        Â
ABSTRACT
A total of 660 discrete jumps in the rotation frequency ( ) and the spin-down rate ( ) of about 140 pulsars were studied. Out of the 660 discrete jumps, 394 were classical glitches (the so-called macroglitches) and 266 were microglitches. The objects are grouped into normal radio pulsars, anomalous x-ray pulsars and recycled millisecond pulsars. A bimodal distribution was observed in many of the pulsar glitch parameters, namely the discrete absolute fractional jumps in the rotation frequency ( ), the entire absolute discrete jumps in the spin down rate (|Δ |), cumulative of the absolute jumps in the rotation frequency ( ), cumulative of the absolute fractional jumps in rotation frequency) for macroglitches may suggest that glitch events may be triggered by dual glitch mechanism. The distribution of the entire absolute discrete fractional jumps in the rotation frequency (| |)  cumulative of the absolute jumps in the rotation frequency ( ) and the cumulative of the absolute jumps in spin down rate (∑|Δ |) of microglitches equally suggests that a glitch event is triggered by one mechanism. It was observed that some of the macroglitches have magnitudes in  (rotation frequency) which overlapped with the microglitches completely which suggest that some of the rotational jumps that was characterized as macroglitches by previous authors should have been recorded as microglitches since their glitch magnitude. The distribution of the glitches over the spin down parameters shows that pulsars with characteristic age 3  4, rotational frequency of 0.9, spin down rate) and surface magnetic field strength of 12 13 on logarithmic scales exhibit the highest frequency of macroglitches while those within the characteristic age 5  6 , rotational frequency of 0.4 , spin down rate of and surface magnetic field strength of 11 12 on logarithmic scales exhibit the highest frequency of microglitches. From the regression analysis, it was observed that there was a strong positive linear relationship between ( ) (∑|Δ |)for the macroglitches and microglitches data when analysed separately and jointly. There was no correlation between ( ) data for both samples. On the otherhand, there was a strong (correlation for the macroglitches and microglitches data when analysed separately and jointly.Â
CHAPTER ONE
GENERAL INTRODUCTION
1.0 An Overview of Rotating Neutron Stars
A neutron star is the core remnant of a supernova event, a violent explosion that marks the death of a massive (to,where is mass of the sun) star. A typical neutron star is believed to be spherical in structure with a radius of about 12 km (Kaspi et al.,1994) and a mass of about 1.2 Â to 2.1 Â (Kramer et al., 2006). Neutron stars rotate and can emit broad band beams of electromagnetic radiations that are detected as pulsars. Pulsars are rapidly rotating highly magnetized neutron stars (Lorimer & Kramer, 2005). The beams of radiation are emitted along the magnetic axis of the pulsar as it spins about the rotation axis. The emitted radiations can be observed when the beam of emission sweeps across the earth much the same way a lighthouse can be seen when it is pointed in the direction of an observer (Lorimer et al., 2005). These pulsed emissions have been detected and studied over the whole electromagnetic spectrum ranging from the high energy gamma rays to the low energy radio waves (Lyne & Graham-Smith, 1998). Pulsars are well known for their stable rotation which allows them to be used as cosmic clocks. According to the data in Australia Telescope National Facility catalogue of pulsars, over 2500 pulsars have being discovered (Manchester et al. 2005).
