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
1.2.1 Rotation-Powered Pulsars (RPPs) 2
1.2.1.1 Normal Pulsars 3
1.2.1.2 Millisecond Pulsars (MSPs) 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
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) 14
1.5.1.2 Stability Parameter (Δ8) 15
1.5.1.3 Timing Noise Statistic (s23) 15
1.5.1.4 Pulsar Clock Stability Statistic (sZ( ) 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
Figure 4.2.3 Distribution of the Cumulative Glitch parameters over the Pulsar Spin down parameters 58
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.
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 to 2.1 (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).