X-ray and Optical observations of Globular Clusters and Pulsars Hsiu-Hui Huang Munchen¨ 2010 X-ray and Optical observations of Globular Clusters and Pulsars Hsiu-Hui Huang Dissertation an der Fakultat¨ fur¨ Physik der Ludwig–Maximilians–Universitat¨ Munchen¨ vorgelegt von Hsiu-Hui Huang aus Taiwan Munchen,¨ den 22 April 2010 Erstgutachter: Prof. Dr. Werner Becker Zweitgutachter: PD Dr. Markus Kissler-Patig Tag der mundlichen¨ Prufung:¨ 10 June 2010 Contents Summary xiii 1 Introduction I – Globular Clusters 1 1.1 Properties ...................................... 2 1.2 Structural and Dynamical Properties ........................ 2 1.3 Binary Systems ................................... 8 2 Introduction II – Neutron Stars and Pulsars 19 2.1 A brief History of Neutron Stars .......................... 19 2.2 Physics and Astrophysics of Neutron Stars ..................... 20 2.2.1 Rotation-powered Pulsars: the Magnetic Braking Model . 21 2.2.2 High-energy Emission Models ....................... 22 2.2.3 Rotation-powered Millisecond Pulsars ................... 30 3 Observatories & Telescopes 33 3.1 X-ray Observatories ................................. 33 3.1.1 Chandra X-ray Observatory ........................ 33 3.1.2 XMM-Newton X-ray Observatory ..................... 37 3.2 The Hubble Space Telescope ............................ 40 4 XMM-Newton Observations of PSR B1957+20 45 4.1 Abstract ....................................... 45 4.2 Introduction ..................................... 45 4.3 Observations and Data Analysis .......................... 48 4.3.1 Spatial Analysis .............................. 48 4.3.2 Spectral Analysis .............................. 48 4.3.3 Timing Analysis .............................. 51 4.4 Summary and Discussion .............................. 53 5 X-rays from the Eclipsing Millisecond Pulsar PSR J1740–5340 in NGC 6397 57 5.1 Abstract ....................................... 57 5.2 Introduction ..................................... 57 5.3 Observations and Data Analysis .......................... 59 vi CONTENTS 5.3.1 Search for Orbital Modulation ....................... 59 5.3.2 Spectral Analysis .............................. 61 5.4 Summary and Discussion .............................. 63 6 X-ray counterparts of millisecond pulsars in Globular Clusters 67 6.1 Abstract ....................................... 67 6.2 Introduction ..................................... 68 6.3 Observation and Data Reduction .......................... 70 6.3.1 Source Detection and Identification .................... 71 6.3.2 Search for Temporal Variability ...................... 72 6.3.3 Spectral Analysis .............................. 83 6.4 Discussion ...................................... 86 7 Chandra X-ray Observatory Observations of the Globular Cluster M71 101 7.1 Abstract .......................................101 7.2 Introduction .....................................101 7.3 Observations, Data Reprocessing, and Source Detection . 103 7.4 Distributions ....................................111 7.5 Power-law Spectral Fits ...............................115 7.6 X-ray Color–Color Diagram ............................119 7.7 Searches for Counterparts ..............................119 7.7.1 2MASS, USNO, & TYCHO-2 Catalogs . 119 7.7.2 HST data ..................................121 7.7.3 Variable Sources ..............................122 7.7.4 X-ray Catalogs ...............................122 7.7.5 The Milli-second Pulsar . 122 7.8 Individual Sources .................................125 7.9 Discussion ......................................127 8 Study of HST counterparts to Chandra X-ray sources in M71 131 8.1 Abstract .......................................131 8.2 Introduction .....................................131 8.3 X-ray Observations .................................133 8.4 Optical Observations ................................134 8.4.1 Data Reduction and Photometry . 135 8.4.2 Astrometry .................................137 8.5 Source Identification and Classification . 139 8.6 Summary and Discussion ..............................145 9 Conclusion and Future Prospect 151 9.1 Eclipsing Binary Pulsars ..............................151 9.2 Millisecond Pulsars in Galactic Globular Clusters . 155 9.3 Globular Clusters ..................................157 Inhaltsverzeichnis vii 9.4 Future Prospects ...................................158 Bibliography 161 Acknowledgements 173 Curriculum Vitae 174 viii CONTENTS List of Figures 1.1 Schematic color-magnitude diagram of a typical globular cluster . 3 1.2 The evolution of a globular cluster ......................... 4 1.3 The various types of objects suggested as X-ray sources in globular clusters . 10 1.4 An artists impression of the flow of material onto a compact object. 12 1.5 Diagram of a Polar ................................. 14 1.6 Diagram of an Intermediate Polar .......................... 15 2.1 Diagram of the magnetic dipole model of a pulsar . 25 2.2 The P − P˙ diagram ................................. 31 3.1 Illustration of the Chandra X-ray Observatory ................... 34 3.2 Chandra’s X-ray mirror assembly .......................... 35 3.3 Sketch of the XMM-Newton payload ........................ 38 3.4 The Hubble Space Telescope and its instruments . 40 4.1 A composite X-ray and optical image of the black widow pulsar . 47 4.2 XMM-Newton MOS1/2 image of the PSR B1957+20 . 49 4.3 Energy spectrum of PSR B1957+20 ........................ 50 4.4 X-ray orbital light curve of PSR B1957+20 .................... 52 4.5 The EPIC-PN count rate of PSR B1957+20 vs. the orbital phase . 54 5.1 Orbital phase coverages of Chandra observations targeted on PSR J1740–5340. 60 5.2 X-ray orbital light curve of PSR J1740–5340 ................... 62 5.3 The cumulative distribution function from the observed data of PSR J1740–5340 64 5.4 ACIS-S3 count rates of PSR J1740–5340 vs. observation dates . 64 6.1 A histogram of radio and X-ray detected MSPs in globular clusters . 69 6.2 Chandra ACIS-S view on the globular clusters Terzan 5 and 47 Tucanae . 73 6.3 Chandra images of M28 and M15 ......................... 74 6.4 Chandra ACIS-S view on the globular clusters NGC 6440 and M62 . 75 6.5 Chandra ACIS-S view on the globular clusters NGC 6752 . 76 6.6 Chandra ACIS-S view on the globular clusters M3 and M5 . 77 6.7 Chandra images of M13 and NGC 6441 ...................... 78 6.8 Chandra ACIS-S view on the globular clusters M30 and NGC 6544 . 79 x LIST OF FIGURES 6.9 Chandra ACIS-S view on the globular clusters M4 and M71 . 80 6.10 Chandra ACIS-S view on the globular clusters NGC 6397 . 81 6.11 Orbital light curves of the pulsars M28G and M28H . 82 6.12 Energy spectrum of the millisecond pulsar PSR J1824–2452A in M28 . 85 6.13 Confidence contours showing the blackbody normalization versus temperature . 87 6.14 The LX − E˙ relations for the GC and field MSPs . 90 6.15 Cumulative luminosity functions for the GC and field MSPs . 91 7.1 ACIS-S S3 0.3–8.0 keV image of the globular cluster M71 for rM71 ≤ 2rh. 104 0 7.2 Number of sources, N(≤ rM71), inside radius rM71 ( ) vs. rM71. 113 7.3 The M71 log N–log Cx distribution for sources with rM71 ≤ 2rh. 116 7.4 Color-color diagram for sources with rM71 ≤ 2rh. 120 7.5 The 0.3–8.0 keV light curve for PSR J1953+1846A . 124 7.6 Light curves for the 14 Chandra X-ray sources . 126 7.7 Number of background-subtracted sources vs. L0:5−2:5keV for 4 GCs . 129 8.1 Chandra ACIS-S3 image of the globular cluster M71 . 136 8.2 Color magnitude diagrams of M71 . 138 8.3 HST/ACS V606 finding charts (I) . 140 8.4 HST/ACS V606 finding charts (II) . 142 8.5 X-ray luminosity Lx as a function of absolute magnitude Mv . 146 8.6 Number of X-ray sources N vs. the normalized collision number Γ . 149 List of Tables 3.1 Chandra characteristics ............................... 36 3.2 XMM-Newton characteristics ............................ 38 3.3 Basic imaging parameters of NICMOS instrument on board HST . 41 4.1 Photon arrival times and its corresponding orbital phase of PSR B1957+20 . 53 5.1 List of Chandra observations of PSR J1740–5340 in NGC 6397 . 59 5.2 Significance for intra-orbital flux modulation ................... 61 5.3 Spectral fits to the PSR J1740 − 5340 binary system . 65 6.1 Chandra observations of globular clusters ..................... 92 6.1 Continued ...................................... 93 6.2 Characteristics of the X-ray counterparts of 31 GC pulsars . 94 6.3 Properties of globular clusters which are known to host pulsars . 95 6.4 Properties of X-ray detected GC pulsars ...................... 96 6.5 Counting rate upper limits for X-ray emission from GC pulsars . 97 6.6 Properties of X-ray non-detected GC pulsars .................... 98 6.7 Spectral parameters and X-ray luminosities of GC pulsars . 99 6.7 Continued ......................................100 7.1 CXO X-ray sources detected with rM71 ≤ 2rh. 106 7.1 Continued ......................................107 7.2 CXO X-ray sources detected with 2rh ≤ rM71. 108 7.2 Continued ......................................109 7.2 Continued ......................................110 7.3 Best-fit King model parameters. 112 0 7.4 Predicted No. of S3 sources inside radius rM71 ( ). 114 7.5 Power-law spectral fits for selected X-ray sources. 117 7.6 X-ray sources within 3000of a CXO source. 123 7.7 MEKAL and MEKAL+MEKAL spectral fits. 127 7.8 Background-subtracted source numbers for selected globular clusters. 128 8.1 Spectral fits of the X-ray source . 134 8.2 HST Optical Counterparts to Chandra X-ray Sources in M71 . 141 xii LIST OF