INSTITUT DE F´ISICA UNIVERSITAT AUTONOMA` D’ALTES ENERGIES DE BARCELONA Observation of the Crab pulsar wind nebula and microquasar candidates with MAGIC Ph.D. Dissertation Universitat Autonoma de Barcelona speciality: Astrophysics Roberta Zanin IFAE Edifici Cn, UAB 08193 Bellaterra (Barcelona), Spain [email protected] supervised by: Juan Cortina Blanco IFAE Edifici Cn, UAB 08193 Bellaterra (Barcelona), Spain [email protected] Enrique Fern´andezS´anchez IFAE IFAE & UAB Edifici Cn, UAB 08193 Bellaterra (Barcelona), Spain [email protected] To Florian Goebel irreplaceable friend and dearest collegue Vorrei sapere a che cosa eservito vivere, amare e soffrire spendere tutti i tuoi giorni passati se presto hai dovuto partire, se presto hai dovuto partire voglio peroricordarti com'eri pensare che ancora vivi voglio pensare che ancora mi ascolti e che come allora sorridi, e che come allora sorridi Contents Acronyms V Unit definition XI Introduction 1 1 The non-thermal universe 3 1.1 Cosmic rays . 4 1.1.1 Galactic cosmic rays . 5 1.1.2 Extra-galactic cosmic rays . 7 1.2 -ray astrophysics . 7 1.3 Neutrino astrophysics . 12 1.4 Astrophysical sources . 12 PART I. THE MAGIC DETECTOR and DATA ANALYSIS 17 2 The MAGIC Telescopes 19 2.1 Introduction . 19 2.2 Telescope subsystems . 21 2.2.1 Frame and drive system . 23 2.2.2 Starguider system . 25 2.2.3 Reflector . 26 2.2.4 Camera . 31 2.2.5 Calibration system . 34 2.2.6 Readout and data acquisition systems . 34 2.2.7 Trigger . 38 2.2.8 Sumtrigger . 39 2.2.9 Pyrometer . 39 2.2.10 GRB monitoring alert system . 39 2.2.11 Clocks . 40 2.2.12 Weather station . 40 2.3 Operation of the telescopes . 40 2.3.1 Scheduling of sources . 40 2.3.2 Regular and ToO observations . 41 2.3.3 Source pointing modes . 41 2.3.4 Calibration and data runs . 42 2.4 Central control . 42 I II CONTENTS 2.4.1 Communication with telescope subsystems . 43 2.4.2 Program structure . 43 2.4.3 Status of the subsystems: graphical user interface . 45 2.4.4 Central control functions . 50 2.4.5 Error/event logging . 55 2.5 Online analysis . 56 3 The MAGIC standard analysis chain 59 3.1 Monte Carlo simulations . 61 3.2 Conversion into ROOT format and merging of control data stream . 62 3.3 Signal reconstruction and calibration . 62 3.4 Image cleaning . 63 3.4.1 Standard timing image cleaning . 63 3.4.2 Sum image cleaning . 66 3.5 Parameter reconstruction . 67 3.5.1 Stereo parameter reconstruction . 69 3.6 Data quality checks . 71 3.7 /hadron separation . 72 3.8 Determination of the arrival direction: the Disp method . 74 3.9 Signal detection . 77 3.9.1 Sensitivity . 79 3.9.2 Cut optimization . 79 3.10 Sky maps . 79 3.10.1 Angular resolution . 80 3.11 Energy estimation . 81 3.11.1 Energy resolution . 81 3.12 Spectrum calculation . 82 3.13 Spectral unfolding . 84 3.14 Light curves . 85 3.15 Upper limits . 86 3.16 Systematic uncertainties . 87 PART II. CRAB NEBULA 91 4 Introduction to Pulsar Wind Nebulae 93 4.1 Pulsars . 94 4.1.1 Neutron stars . 95 4.1.2 Neutron star magnetosphere . 96 4.1.3 -ray emission from pulsars . 99 4.2 Supernova Remnants . 100 4.3 Pulsar wind nebulae . 101 4.3.1 Inner structure . 102 4.3.2 Evolution of pulsar wind nebulae . 102 4.3.3 Pulsar wind nebula spectra . 104 4.4 The Crab Nebula . 107 4.4.1 The Crab Pulsar . 107 4.4.2 The Crab Pulsar Wind Nebula . 108 CONTENTS III 4.4.3 The broad-band spectrum of the Crab Nebula . 111 4.4.4 The Crab Nebula at very high energies . 112 4.4.5 Theoretical models for the IC emission from Crab Nebula . 114 4.4.6 The Crab Nebula variability . 115 5 Spectrum and ux variability of the Crab Nebula 119 5.1 Data sample . 120 5.2 Description of the analysis . 123 5.2.1 Sum versus standard image cleaning . 124 5.2.2 Energy resolution and bias . 126 5.2.3 Signal clipping . 129 5.3 Differential energy spectrum . 131 5.3.1 Unfolded spectrum . 132 5.3.2 Systematic uncertainties . 137 5.4 Estimation of the Inverse Compton peak . 143 5.5 Theoretical picture . 145 5.6 Flux variability . 146 PART III. MICROQUASARS 151 6 Introduction to microquasars 153 6.1 Binary systems . 153 6.1.1 Microquasars . 154 6.2 The main components of microquasars . 157 6.2.1 The compact object . 157 6.2.2 Companion star . 158 6.2.3 Accretion disk . 159 6.2.4 The corona . 160 6.2.5 Jets . 160 6.3 Disk-jet connection . 161 6.4 Black hole X-ray binaries . 162 6.5 Neutron star X-ray binaries . 165 6.6 VHE emission from microquasars . 166 6.6.1 Leptonic models . 167 6.6.2 Hadronic models . 167 6.6.3 Microquasar in -rays: observations . 168 7 Cygnus X-3 169 7.1 MAGIC observations . 172 7.1.1 Data analysis . 175 7.2 Results . 176 7.2.1 Results during high-energy -ray emission . 179 7.2.2 Results during the soft state . ..