The vertical intensity, I(_v), and exponent of the angular distribution, n, (where I(_o) = I(_v)cos(^n) 0), of muons underground have been measured using simple telescopes comprising plastic scintillators, geiger counters and neon flash tubes at depths of 816, 1812 and 4110 m.w.e. in the Kolar Gold Fields, India. The observed values of n are 1.92 ± 0.33, 3.26 ± 0.10 and 5.33 ± 0.50 respectively, and those of I(_v) are (2.29 ± 0.09)10(^-6), (1.98 ± 0.05)10(^-7) and (4.47 ± 0.34)10(^-9) cm(^-2)sr(^-1)sec(^-1). These results have been compared with the results of other workers and the intensity-depth relation of Osborne et al (1964). The agreement is quite good at 816 and 4110 m.w.e. but the observed intensity is higher by ~30% at 1812 m.w.e. The integral sea-level muon intensities have been inferred from the range-energy relation, allowing for fluctuations in energy losses. From comparison with ɤ - ray cascade data it is shown the K/π ratio is sensibly constant at ~30% over the range of primary energy 10(^3) – 10(^6_) GeV. No significant non-Poissonian contribution to the distribution of time intervals between the arrival of successive events underground was noted indicating that the phenomenon of bursts of particles at short time intervals reported by Cowan et al (1964) has not been observed in the present experiment. The probability of electromagnetic interactions of muons in rock and lead was found to Increase (with increasing depth) demonstrating the growing Importance of energy losses by bremsstrahlung and direct pair production. Analysis of multiple penetrating particle events shows that they cfm be attributed to the production o muons (via pions) in extensive air showers, and to the nuclear interaction of muons in rock. Several neutrino induced muons and atmospheric muons have been detected in a new experiment, still in operation, at 7600 m.w.e. The vertical intensity of muons has been derived from the latter and compared with that inferred from the South African neutrino experiment at 8500 m.w.e. Finally, a best estimate of the intensity depth relation is given.

This thesis presents a study of the very high energy (VHE) gamma-ray emission from X-ray binary systems using the H.E.S.S. imaging atmospheric Cherenkov array. The historical background and basic principles of ground-based gamma-ray astronomy are briefly reviewed and an overview of the design and capabilities of the H.E.S.S. telescope system is presented. The broadband observational properties of X-ray binary systems and their relevance in a broader astrophysical context is also discussed. A review of the radiative emission mechanisms which relate to VHE gamma-ray emission in X-ray binaries is presented, with emphasis given to the leptonic emission processes of synchrotron radiation and inverse-Compton scattering. Intrinsic absorption processes which act to attenuate the emitted flux of VHE gamma-rays are also discussed. Three computer models are introduced which simulate aspects of the gamma-ray emission and absorption in X-ray binary systems. A detailed analysis of the VHE gamma-ray emission from the X-ray binary LS 5039 is presented and the relevant procedures for data selection, gamma-hadron separation and background estimation are discussed in some detail. Methods for the determination of detection significance and the calculation of gamma-ray fluxes are also reviewed and results are derived which apply specifically to LS 5039. A detailed temporal analysis of the gamma-ray signal from LS 5039 is presented, applying tests for secular, excess and periodic variability. Strong evidence is found for modulation of the observed gamma-ray flux on the orbital period of ~3.9 days. Following a brief discussion of the procedures required for spectral analysis of VHE gamma-ray data, results are presented for LS 5039 which reveal evidence for spectral variability which is correlated with the observed gamma-ray flux and therefore, the orbital phase of the binary system. The spectral and temporal characteristics of LS 5039 are then compared with the predictions of theoretical models in an attempt to explain the observed behaviour. Contemporaneous X-ray and VHE gamma-ray observations of three galactic microquasars using the Rossi X-ray Timing Explorer and H.E.S.S. are presented. Although no gamma-ray detections are reported, the observations permit the derivation of upper limits to the VHE gamma-ray flux which correspond to episodes of known X-ray behaviour. The X-ray characteristics of each target are compared with pre-existing observational data to infer the presence or otherwise of relativistic outflows at the H.E.S.S. observation epochs. The implications of the gamma-ray non-detections are then discussed in the context of these inferred system properties. The results of a survey of the VHE gamma-ray emission associated with the positions of 125 known X-ray binaries are presented. Although no conclusive detections were obtained, tentative indications were found for a population of faint, spectrally hard gamma-ray sources associated with high-mass X-ray binary systems. The inferred characteristics of the indicated population show broad agreement with the measured properties of known gamma-ray-emitting X-ray binary systems like LS 5039.

Even though the radial velocity technique has detected almost all of the 269 extrasolar planets discovered to date, this method does not directly observe the light from the planet. The ability to directly detect this light would allow spectra of extrasolar planets to be obtained, providing information about their information and evolution through the investigation of their composition and structure. To date, none of the extrasolar planets found using the radial velocity technique have been directly imaged, as these faint companions are too close to their bright parent stars. White dwarfs are intrinsically faint objects and can be upto 10,000 times less luminous than their main sequence progenitors, substantially increasing the probability of directly imaging an extrasolar planet in orbit around them. The Degenerate Objects around Degenerate Objects (DODO) survey aims to obtain a direct image of an extrasolar planet in a wide orbit around a white dwarf. By acquiring J band images of 26 equatorial and northern hemisphere white dwarfs a year or two apart, common proper motion companions to the white dwarfs can be identified. The discovery of such a system could supply new information on the frequency and mass distribution of extrasolar planets around intermediate mass main sequence starts and confirm whether these companions can survive the final stages of stellar evolution. In addition, the direct detection of an extrasolar planet in orbit around a white dwarf would allow the spectroscopic investigation of planets much older than any previously found. Using the 24 white dwarfs in the DODO survey within 20pc, the frequency of substellar companions with effective temperatures > 500K and projected physical separations from the white dwarf between 60-200AU is estimated to be <5%. For the same range of projected physical separations, the frequency of substellar companions with masses >10Mjup is estimated to be<9%.

Analogue studies importantly underpin planetary missions and can provide essential continuity between payload development and actual mission operations. This thesis focuses on three topics related to analogue studies, namely planetary analogue materials, analogue experiments and the application of scientific autonomy for robotic missions. The common theme of the work relates to field geology on Mars and the search for life (astrobiology). Examples of astrobiology-related missions to Mars are described to illustrate what has been undertaken so far and what strategies are planned for the future, including where and how one might look for signs of past and present life. A range of in situ techniques essential for planetary field geology are reviewed including imaging (multi-scale), analytical measurements (spectroscopy) and geotechnics (physical interaction with surface materials). A comprehensive specimen archive and associated experiment database called GSPARC (Geological Specimen Archive) is described. Samples from the archive were used in the experimental part of this thesis. Two mission-like studies were undertaken based on the ability of a combination of imaging and spectroscopic techniques (X-ray, Mössbauer and Raman) to unambiguously identify morphological biosignatures and to assess the biogenic potential of sedimentary structures in ancient rocks. The techniques employed confirmed their effectiveness for in situ astrobiology when used collectively. Empowering planetary robots with scientific autonomy has the potential to increase science return and extend ground coverage. To address these desires, a novel approach to autonomous science operations is defined and the results from robotic trials using an early implementation of the concept showed that basic geological parameters can be recognised, appropriately scored and used to influence operations. The need for further work within each of the topics is argued and recommendations are made to ensure the continuation of an integrated programme of analogue studies. Spin-off potential to other areas of science is highlighted.

Normal galaxies are galaxies whose emission is not dominated by active galactic nuclei (AGN). Current X-ray observatories allow X-ray studies of normal galaxies beyond the local group (≥ 1 Mpc). This thesis presents a study of normal galaxy samples drawn from serendipitous sources detected by the XMM-Newton Observatory up to a few hundred Mpc. The work begins with a pilot study in which a sample of 72 normal galaxy candidates is selected from the XMM-Newton/2dF Wide Angle Serendipitous Survey using X-ray-to-optical flux ratios, X-ray luminosities and the 2dF optical spectra. This sample is classified, based on optical emission lines, into five subsamples: AGN, star-forming (SF) galaxies, composite galaxies, unclassified narrow-emission-line galaxies (NELGs) and absorption-line galaxies (ALGs). The X-ray properties of these subsamples, shown by X-ray spectra and hardness ratios, are broadly consistent with the optical classifications. The Second XMM-Newton Serendipitous Catalogue (2XMM) is then used to cross-correlate with Sloan Digital Sky Survey (SDSS) and yields a sample 463 normal galaxy candidates (the XS sample) using the same selection criteria as in the pilot study. Using the continuum-subtracted optical emission line measurements from the Max-Planck-Institute for Astrophysics/Johns Hopkins University catalogues (the MPA/JHU catalogues), a complete subset of the XS sample is separated into five subsamples: AGN, SF galaxies, composite galaxies, unclassified NELGs and ALGs. The X-ray properties, on the basis of the X-ray spectra and hardness ratios, are largely consistent with expectations from their optical classifications. Additional parameters from the MPA/JHU catalogues, such as star-formation rates (SFRs) and stellar masses, are used for further investigation of the nature and properties of individual subsamples. The effectiveness of the normal galaxy selection criteria is investigated to show how efficient the X-ray-to-optical flux ratios are on separating AGN from truly normal galaxies.

I present work on the accretion onto stellar mass black holes in several scenarios. Due to dynamical friction stellar mass black holes are expected to form high density cusps in the inner parsec of our Galaxy. These compact remnants may be accreting cold dense gas present there, and give rise to potentially observable X-ray emission. I build a simple but detailed time-dependent model of such emission. Future observations of the distribution and orbits of the gas in the inner parsec of Sgr A* will put tighter constraints on the cusp of compact remnants. GRS 1915+105 is an LMXB, whose large orbital period implies a very large accretion disc and explains the extraordinary duration of its current outburst. I present smoothed particle hydrodynamic simulations of the accretion disc. The models includes the thermo-viscous instability, irradiation from the central object and wind loss. I find that the outburst of GRS 1915+105 should last a minimum of 20 years and up to ∼ 100 years if the irradiation is playing a significant role in this system. The predicted recurrence times are of the order of 10^4 years, making the duty cycle of GRS 1915+105 to be a few 0.1%. I present a simple analytical method to describe the observable behaviour of long period black hole LMXBs, similar to GRS 1915+105. Constructing two simple models for the surface density in the disc, outburst and quiescence times are calculated as a function of orbital period. LMXBs are an important constituent of the X-ray light function (XLF) of giant elliptical galaxies. I find that the duty cycle can vary considerably with orbital period, with implications for modelling the XLF.

I present three studies of magnetospheric tail dynamics associated with bursty bulk flows (BBFs) and substorms, concentrating on observations of the current systems of the BBFs and the dynamics of magnetotail current sheet waves. From a case study, I show that the observed magnetospheric current system of a BBF consisting of two flow bursts matched the current system predicted by Sergeev et al. (1996), and that the currents were consistent with previous studies. I also show that the particle signatures of the BBF were similar to the particle signatures in the PSBL prior to the BBF observations, demonstrating that the BBF was produced by the reconnection of lobe magnetic field-lines. From a survey of 628 BBF events, I show that BBF occurrence is highest during the recovery phase of substorms and lowest during non-substorm times and substorm growth phases. Using a subset of 211 BBF encounters that were sufficiently far from the magnetotail current sheet to determine the field-aligned currents, I show that the current magnitude is larger during the expansion and recovery phases of substorms than during the growth phase. Furthermore, the current magnitude is larger in the pre-midnight sector on large scale sizes. Utilising data from ground- and space-based observatories, I investigate an interval of current sheet wave activity following a solar wind pressure pulse and two substorms. By comparing the propagation of aurora and tail dipolarization signatures and the neutral sheet waves, I conclude that the propagation of these features is controlled by the same mechanism. I test two models of neutral sheet wave propagation and find that the model of Erkaev et al. (2008) gives a good fit to the data.

CVs are interacting binaries accreting through Roche lobe overflow. The main motivation of this thesis is to enhance our understanding of accretion disc physics, and in particular, the mechanism producing X-rays in these and in other accreting objects. This thesis comprises four case studies. Two of the studies have focused on individual CVs; a serendipitously discovered polar candidate 2XMM J131223.4 + 173659 (J1312) and a WZ Sge-type dwarf nova (DN), GW Lib, which went into an outburst in 2007. The X-ray analysis of J1312 showed that a soft component, assumed to be a typical spectral characteristic of polars, was not observed in these data. The most likely explanation is that this component probably has too low a temperature to be seen in X-rays. The multiwavelength study of the 2007 outburst of GW Lib represents a unique opportunity for understanding the disc physics of this rare type of outbursting system. A major finding of this study is that the X-rays are not suppressed during the outburst. This is in contrast to the outburst behaviour of WZ Sge, the defining member of this class. The remainder of this thesis focused on larger source samples. First, I have derived the most accurate 2–10 keV X-ray luminosity function (XLF) of DNe to date with parallax-based distance measurements. The other study consists of a survey of serendipitous X-ray point sources in the direction of the Galactic Plane. The conclusion is that a significant fraction of the source sample could be associated with CVs based on the X-ray spectral characteristics of these sources.

This thesis describes experimental and theoretical work and technology development directed towards the next generation of X-ray astronomical instrumentation. A great heritage exists of instruments which are sensitive to X-rays which operate on board space based observatories. The next generation of such telescopes will take advantage of the rapid technology advancement of the last four decades of more accurately observe the universe and give greater insight into the objects within it, how they formed and how they will evolve. Chapters 2 and 3 describe the investigation of extremely high speed microchannel plate detectors capable of counting individual photons with a timing accuracy of a few tens of picoseconds (1 ps = 10-12s)at extremely high spatial resolution. Although many early X-ray astronomical instruments were based on MCP detectors, it is only recent manufacturing improvements which have enabled the production of such small pore diameters, enabling the unparalleled temporal and spatial resolution. Prospects for future application exist in fields as diverse as X-ray and ultraviolet astronomy and the life sciences. Chapters 4 and 5 report the testing of Microchannel plates as low mass X-ray optics where the development of square pore geometrics has made true imaging MCP telescopes possible. Two flight programs are identified as areas where such optics will provide tangible benefits: These are BepiColombo, a European mission to the planet Mercury which will contain the first ever imaging X-raytelescope on a planetary science mission and Lobster-ISS, a wide field of view telescope for X-ray astronomy which will provide coverage of, almost, the whole sky every 90 minute orbit. Testing reported herein finds that the manufacturing techniques are maturing to a point where they can exceed the <5 arcmin resolution required for these missions. Chapters 6 and 7 comprise a description of a completely novel X-ray polarimeter. For the past three decades, little or now progress has been made in the field of X-ray astrophysical polarimetry owing to the lack of suitable instrumentation, this is despite intense scientific interest in such measurements. A simple optical design for a polarimeter is made possible using highly ordered materials which exhibit dichroism at fixed, narrow energy bands, for the first time allowing simultaneous measurement of ALL astronomically pertinent observables. The areas of science influenced by these three areas of instrument development are shown to be very broad, including; astrophysics and cosmology, planetary science, life sciences, nano-science and even fundamental chemistry.

In this thesis, I study a sample of 11 nearby “normal” spiral galaxies and one starburst galaxy with the Chandra X-ray Observatory and supporting ground-based telescopes, with particular emphasis on the characterisation of the discrete X-ray point source population. Emission from discrete point sources dominates the X-ray flux from spiral galaxies. This survey spans the Hubble sequence for spirals and, hence, a range in star formation, allowing insights into the X-ray source population of many diverse systems. The inclusion of M82, the prototypical starburst galaxy in the nearby universe, allows for comparison with a system at the extreme of star formation. Presented here is a detailed catalogue of the source population of these galaxies. For each source, I have derived fluxes, luminosities, X-ray colours, and variability properties. I have also searched for optical and radio counterparts. For the most luminous sources, detailed spectral and temporal analyses have been performed. For galaxies as a whole, I have examined X-ray point source luminosity functions and how these relate to star formation of those galaxies. I have also devised a strategy for initial classification of X-ray sources based upon their position within a colour-colour diagram. The luminosity function analysis has then been performed on each class of sources, showing 1) that the method of classification appears to be robust to the first order, and 2) that the old and young (i.e. low-mass X-ray binary and high-mass X-ray binary) populations can be segregated, providing insight into the star formation history of each individual galaxy. I have also studied the environments in which the sources fall within their host galaxies and what this can tell us about the nature of the sources. I have included a discussion of the enigmatic ultraluminous X-ray sources (ULXs), which may be candidates for intermediate mass (100-10,000 Mסּ) black holes.