X-Ray Observations of Neutron Stars with XMM-Newton & Chandra Hui Chung Yue M¨unchen2007 X-Ray Observations of Neutron Stars with XMM-Newton & Chandra Hui Chung Yue Dissertation an der Fakult¨atf¨urPhysik der Ludwig–Maximilians–Universit¨at M¨unchen vorgelegt von Hui Chung Yue aus Hong Kong M¨unchen, den 6 November 2007 Erstgutachter: Priv. Doz. Dr. Werner Becker Zweitgutachter: Prof. Dr. Harald Lesch Tag der m¨undlichen Pr¨ufung:27 November 2007 Contents Summary xiii 1 Introduction 1 1.1 A Brief History of Neutron Stars ....................... 1 1.2 The Physics of Neutron Stars ......................... 4 1.2.1 Formation ................................ 4 1.2.2 Global structure ............................. 5 1.2.3 Composition ............................... 7 1.2.4 Thermal evolution ........................... 9 1.2.5 Pulsar magnetosphere and high energy radiation . 11 1.3 Manifestations of Isolated Neutron Stars ................... 18 1.3.1 Rotation-powered pulsars ....................... 19 1.3.2 Soft γ−ray repeaters/Anomalous X-ray pulsars . 19 1.3.3 Central compact objects in supernova remnants . 20 1.3.4 Dim thermal isolated neutron stars . 21 1.3.5 Rotating RAdio Transients (RRATs) . 21 1.4 Studying Neutron Stars with XMM-Newton & Chandra . 22 1.4.1 Chandra ................................. 22 1.4.2 XMM-Newton .............................. 23 2 X-ray observations of RX J0822-4300 and Puppis-A 25 2.1 Introduction ................................... 25 2.2 Observations ................................... 27 2.2.1 XMM-Newton Observations ...................... 27 2.2.2 Chandra Observations ......................... 28 2.3 Data Analysis .................................. 29 2.3.1 Spatial Analysis ............................. 29 2.3.2 Spectral Analysis ............................ 31 2.3.3 Timing Analysis ............................. 33 2.4 Discussion & Conclusion ............................ 35 vi CONTENTS 3 Probing the Proper Motion of the Compact Object in Puppis-A 51 3.1 Introduction ................................... 51 3.2 Observation and data analysis ......................... 52 3.3 Results and Discussion ............................. 55 4 XMM-Newton Observations of the Compact Object in RX J0852.0-4622 59 4.1 Introduction ................................... 59 4.2 Observations & Data Reduction ........................ 61 4.3 Data Analysis .................................. 62 4.3.1 Spatial Analysis ............................. 62 4.3.2 Spectral Analysis ............................ 63 4.3.3 Timing Analysis ............................. 64 4.4 Discussion .................................... 65 5 Radio and X-ray Nebulae associated with PSR J1509-5850 75 5.1 Introduction ................................... 75 5.2 Observations and data analysis ........................ 76 5.3 Discussion & Conclusion ............................ 78 6 Discovery of an X-ray Nebula associated with PSR J2124-3358 87 6.1 Introduction ................................... 87 6.2 Observations and data analysis ........................ 88 6.3 Discussion & Conclusion ............................ 90 7 X-ray emission properties of the old pulsar PSR B2224+65 97 7.1 Introduction ................................... 97 7.2 Observations and data analysis ........................ 98 7.3 Discussion & Conclusion ............................ 101 8 Chandra observation of the old pulsar PSR B1929+10 113 8.1 Introduction ................................... 113 8.2 Observations and data analysis . 114 8.2.1 Spatial analysis ............................. 115 8.2.2 Spectral analysis ............................ 116 8.3 Discussion .................................... 118 9 Searches for X-ray counterparts of millisecond pulsars in M28 127 9.1 Introduction ................................... 127 9.2 Observations and Data Analysis . 128 9.3 Discussion .................................... 130 CONTENTS vii 10 Conclusions & Discussions 135 10.1 The nature of central compact objects in supernova remnants . 135 10.2 Emission mechanism of non-recycled old pulsars . 137 10.3 High energy emission of pulsar wind nebulae . 138 10.4 Millisecond pulsars in globular clusters . 139 10.5 Future prospects ................................ 140 Bibliography 147 Acknowledgments 155 Curriculum Vitae 156 viii CONTENTS List of Figures 1.1 Illustration of the structure of the neutron star interior ........... 7 1.2 Illustration of the pulsar magnetosphere ................... 12 2.1 MOS1/2 false color X-ray image of the central region of Puppis−A. 39 2.2 RASS false color image of Puppis−A and parts of the Vela SNR . 40 2.3 XMM PN False color image of the 4.40 × 4.40 region around RX J0822-4300 41 2.4 Chandra HRC-I brightness profile for RX J0822-4300 . 42 2.5 X-ray images of Puppis−A with radio contour lines . 43 2.6 Energy spectrum of RX J0822-4300 ...................... 45 2.7 Components of the model fitted to the spectral data of RX J0822−4300 . 46 2.8 Error contours for the best-fit model to the spectrum of RX J0822−4300 . 47 2.9 Energy spectrum of the rim emission underneath RX J0822−4300 . 48 2 2.10 Pulse profiles of RX J0822−4300 and the Z1 -distribution . 50 3.1 Part of the HRC-I image of Puppis−A as observed in April 2005 . 57 3.2 The best-fit positions of RX J0822−4300 in two HRC-I observations . 58 4.1 RASS image of Puppis−A and RX J0852.0-4622 . 67 4.2 MOS1/2 false color image of RX J0852.0-4622 . 69 4.3 Energy spectrum of CXOU J085201.4-461753 . 71 4.4 Error contours for the best-fitted spectral model for CXOU J085201.4-461753 72 5.1 ACIS image of the field around PSR J1509−5850 . 82 5.2 Energy spectrum of the X-ray trail of PSR J1509−5850 . 83 5.3 Radio image of the field around PSR J1509−5850 . 84 5.4 X-ray image of PSR J1509−5850 with radio contour lines . 85 6.1 MOS1/2 and ACIS images of PSR J2124−3358 . 93 6.2 Energy spectrum of the X-ray trail of PSR J2124−3358 . 94 7.1 ACIS image of the field around PSR B2224+65 . 104 7.2 Brightness profile of the extend feature associated with PSR B2224+65 . 105 7.3 Energy spectrum of PSR B2224+65 . 107 7.4 Temperature upper limits of the polar cap of PSR B2224+65 . 108 x LIST OF FIGURES 7.5 Energy spectrum of the extended feature associated with PSR B2224+65 . 109 7.6 Variation of f(rin, α) with the magnetic inclination angle . 111 8.1 ACIS images of the field around PSR B1929+10 . 120 8.2 Radial profile of PSR B1929+10 . 121 8.3 Comparison between Chandra and XMM images . 122 8.4 Energy spectra of PSR B1929+10 . 124 8.5 Error contours for the best-fit model to the spectra of PSR B1929+10 . 125 8.6 Energy spectra of the arc-like structure associated PSR B1929+10 . 126 9.1 ACIS-S3 image of the central region of M28 . 132 10.1 ROSAT PSPC image of G67.7+1.8 . 144 10.2 ACIS-I false color image of G67.7+1.8 . 145 List of Tables 2.1 Details of the XMM-Newton and Chandra observations of RXJ0822-4300 . 38 2.2 Spectral parameters of RX J0822−4300 .................... 44 2.3 Observed fluxes of RX J0822−4300 ...................... 49 3.1 X-ray properties of serendipitous sources around RX J0822−4300. 58 4.1 Details of XMM-Newton observations of CXOU J085201.4-461753 . 68 4.2 Faint X-ray sources detected serendipitously within RX J0852.0-4622. 70 4.3 Spectral parameters of CXOU J085201.4-461753 . 73 5.1 Pulsar parameters of PSR J1509−5850 .................... 81 6.1 Ephemeris of J0030+0451, J2124-3358, J1024-0719 and J0437-4715 . 92 6.2 Identifications of the stars around the X-ray trail of PSR J2124−3358. 94 6.3 Properties of rotation-powered pulsars with X-ray/Hα bow shocks. 95 7.1 Proper-motion corrected ephemeris of PSR B2224+65 . 103 7.2 Spectral parameters of PSR B2224+65 and the X-ray feature . 106 7.3 The theoretical outer-gap sizes of old pulsars . 110 8.1 Ephemerides of PSR B1929+10 . 120 8.2 Spectral parameters of PSR B1929+10 and its compact nebula . 123 8.3 Energetics of PSR B1929+10 . 123 9.1 PSR J1824−2452A positions (J2000) . 131 9.2 Properties of the millisecond pulsars in M28 . 133 10.1 Physical properties of non-recycled old pulsars . 143 xii LIST OF TABLES Summary xiii Summary Utilizing the state-of-art X-ray telescopes — XMM-Newton and Chandra, I have carried out detailed studies covering a wide range of topics on the X-ray emission from young neutron stars in supernova remnants, pulsar wind nebulae, old non-recycled pulsars as well as millisecond pulsars. I have observed two neutron star candidates located in the supernova remnants, Puppis- A and RX J0852.0-4622, with XMM-Newton and Chandra. X-ray spectroscopy suggested that the X-ray emission from these objects is of thermal origin and is emitted from high temperature hot spots on the stellar surfaces. Searching for the possible pulsations from these objects revealed an interesting periodicity candidate of ∼ 0.22 s from the compact object in Puppis-A. Utilizing the superior spatial resolution of Chandra, the point source nature of the compact object in Puppis-A was constrained to an accuracy of sub-arcseconds. No compact nebula is detected around this object. Moreover, making use of two Chandra observations with an epoch separation of somewhat more than five years, I measured the proper motion of this compact object. I found that the transverse velocity of this object is at the order of ∼ 1000 km/s to the southwest. Both the magnitude and the direction of the proper motion are in agreement with the birth place of the object in the supernova remnant being near to its optical center. This is the first case that a proper motion of a central compact object in the supernova remnant was measured directly. In searching for diffuse X-ray emission around pulsars, trail-like nebulae associated with PSRs J2124−3358 and J1509−5850 were discovered. Examining the diffuse emission suggested that the observed X-rays are non-thermal in nature.