The analysis of compact astronomical objects has generally dealt with the physical properties of the source within a two-parameter space, which is defined by the spectral characteristics and time variability. This approach often leads to the situation whereby two or more very different models can explain the observations successfully. Polarimetric observations have the diagnostic potential to discriminate between the different compact source models and can offer a unique insight into the geometrical nature of the emission zones. To date, however, no polarization observation in the gamma-ray energy domain has been successfully performed, due to the difficulties in making polarimetric measurements in this high-energy region of the spectrum. In this paper the polarized gamma-ray emission mechanisms are reviewed with the emphasis on their detectable characteristics. Potential astronomical sites in which these emission mechanisms may be at work are discussed. Observational results obtained in other wavebands and theoretical predications made for some of the most likely astronomical sources of polarization are reviewed. Compton polarimetry has long been used in the field of nuclear gamma-ray spectroscopy in the laboratory. The operational principle behind all generations of nuclear gamma-ray polarimeters has been to measure the asymmetry in the azimuthal distribution of the scattered photons. However none of the polarimeters designed for laboratory experiments will be sensitive enough to observe even the strongest astronomical source. In the past few years there have been a number of innovative developments aimed at the construction of astronomical gamma-ray polarimeters, either as dedicated experiments or in missions with polarimetric capability. The designs of all the polarimeters are based on either discrete or continuous position sensitive detector planes. In this paper the data analysis techniques associated with this type of polarimeter are discussed as well as methods of removing some of the systematic effects introduced by a non-ideal detector response function and observation conditions. Laboratory tests of these new polarimetric techniques are reviewed. They demonstrate the feasibility of building a suitably sensitive astronomical gamma-ray polarimeter. Optimization of the design of pixellated detector array based polarimeters is also addressed. The INTEGRAL mission, which is to be launched by ESA in the year 2001, is the most likely telescope to perform the first successful gamma-ray polarization observation. The polarimetric characteristics of the two main instruments on board INTEGRAL are evaluated and their sensitivities to a wide range of potentially polarized gamma-ray sources are estimated.

Compton Polarimetry in Gamma-Ray Astronomy

estimated as being 112 Wm � 2 . The basin average sensible, latent and soil heat fluxes were estimated to be 80, 32, and 0 Wm � 2 , respectively. The average evapotranspiration (ET) and evaporative fraction were 1.2 mm d � 1 and 0.28, respectively. The basin wide ET was 496 6 16.8 km 3 yr � 1 . Monte Carlo analysis have indicated 3.4% error at 95% confidence interval for a dominant land use class. Results compared well with previously conducted soil moisture, lysimeter and Bowen ratio measurements at field scale (R 2 ¼ 0.70; RMSE ¼ 0.45 mm d � 1 ; RE ¼ –11.5% for annual ET). ET results were also compared against earlier remote sensing and modeling studies for various regions and provinces in Pakistan (R 2 ¼ 0.76; RMSE ¼ 0.29 mmd � 1 ;R E¼ 6.5% for annual ET). The water balance for all irrigated areas together as one total system in Pakistan and India (26.02 million ha) show a total ET value that is congruent with the ET value from the ETLook surface energy balance computations. An unpublished validation of the same ETLook model for 23 jurisdictional areas covering the entire Australian continent showed satisfactory results given the quality of the watershed data and the diverging physiographic and climatic conditions (R 2 ¼ 0.70; RMSE ¼ 0.31 mmd � 1 ;R E¼ –2.8% for annual ET). Eight day values of latent heat fluxes in Heibei (China) showed a good resemblance (R 2 ¼ 0.92; RMSE ¼ 0.04 mm d � 1 ;R E¼ 9.5% for annual ET). It is concluded that ETLook is a novel model that can be operationalized further—especially after improving the preprocessing of spaceborne soil moisture data. This preprocessing includes (1) downscaling of topsoil moisture from 25 to 1 km pixels, and (2) translation of topsoil moisture into subsoil moisture values.

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Surface energy balance and actual evapotranspiration of the transboundary Indus Basin estimated from satellite measurements and the ETLook model

Multi-objective design of optical systems for space situational awareness

The second edition of this popular text provides undergraduates with a quantitative yet accessible introduction to the physical principles underlying the collection and analysis of observational data in contemporary optical and infrared astronomy. The text clearly links recent developments in ground- and space-based telescopes, observatory and instrument design, adaptive optics, and detector technologies to the more modest telescopes and detectors that students may use themselves. Beginning with reviews of the most relevant physical concepts and an introduction to elementary statistics, students are given the firm theoretical foundation they need. New topics, including an expanded treatment of spectroscopy, Gaia, the Large Synoptic Survey Telescope, and photometry at large redshifts bring the text up to date. Historical development of topics and quotations emphasize that astronomy is both a scientific and a human endeavour, while extensive end-of-chapter exercises facilitate the students' practical learning experience.

To Measure the Sky: An Introduction to Observational Astronomy

Despite an astonishing 100 million-fold range in adult body mass from bumblebee bat to blue whale, all mammals are formed of the same kinds of molecules, cells, tissues and organs and to the same overall body plan. A scaling approach investigates the principles of mammal design by examining the ways in which mammals of diverse size and taxonomy are quantitatively comparable. This book presents an extensive reanalysis of scaling data collected over a quarter of a century, including many rarely or never-cited sources. The result is an unparalleled contribution to understanding scaling in mammals, addressing a uniquely extensive range of mammal attributes and using substantially larger and more rigorously screened samples than in any prior works. An invaluable resource for all those interested in the 'design' of mammals, this is an ideal resource for postgraduates and researchers in a range of fields from comparative physiology to ecology.

The Design of Mammals: A Scaling Approach

Stars, nebulae, and the interstellar medium

Preface Atomic Processes INTRODUCTION TO SPECTROSCOPY Historical background Types of spectroscopy THE PHYSICS OF ATOMS AND MOLECULES Sommerfeld's refinements Space quantization Atomic structure Other viewpoints Quantum/wave mechanics ATOMIC ENERGY LEVELS Multiple electron atoms ^IL-S coupling Space quantization Term formation Closed shells and subshells Notation Hyperfine structure TRANSITIONS Basics Selection rules Transition probabilities Absorption and emission coefficients Ionization and recombination X-ray spectra SPECTRA OF MOLECULES Introduction Rotational transitions Vibrational transitions Electronic transitions RADIATION IN THE PRESENCE OF FIELDS Zeeman effect Stark effect Free-free radiation Synchrotron and gyrosynchrotron radiation Cerenkov radiation The Faraday effect SPECTROSCOPY OF SOLID MATERIALS ASTRONOMICAL SPECTROSCOPIC TECHNIQUES OPTICAL SPECTROSCOPES Introduction Diffraction gratings Grating problems Diffraction grating spectroscopes Prisms Prism spectroscopes Fourier transform spectroscope (Michelson interferometer) Fabry-P^D'erot etalons SPECIALIZED OPTICAL SPECTROSCOPIC TECHNIQUES FOR ASTRONOMY Introduction Detectors Guiding Widening Image dissectors Dekkers Long slit spectroscopy Comparison spectra Flexure Temperature Exposures EXAMPLES OF OPTICAL SPECTROSCOPES Introduction A small basic spectroscope A conventional Cassegrain spectroscope Transmission grating spectroscopes Coud^D'e spectroscopes A GRISM-based spectroscope Multi-object spectroscopes An echelle grating spectroscope Infrared spectroscopes Spacecraft-borne spectroscopes Fabry-P^D'erot spectroscopes Fourier transform spectroscopes Objective prism spectroscopes The future Spectroscopy of astronomical sources SPECTRAL CLASSIFICATION Spectral class The non-core classes The luminosity class RADIAL VELOCITIES Introduction Traditional approach to radial velocity determination Objective prism spectra Machine-readable spectra Griffin's method Line identification SPECTROPHOTOMETRY Introduction Spectral calibration Photometric calibration Line strengths Line broadening Pressure broadening Doppler broadening Magnetic fields Other effects STARS Introduction Distance Temperature Element abundances Variable stars The Sun PLANETS AND OTHER MINOR BODIES OF THE SOLAR SYSTEM Introduction Planetary atmospheres and comets Planetary surfaces Rotation NEBULAE AND THE INTERSTELLAR MEDIUM Nebulae The interstellar medium EXTRA-GALACTIC OBJECTS Introduction Distances Spectra Ages Sizes Background radiation APPENDICES Conversion formulae Term formation of equivalent electrons Bibliography Constants Index

Optical astronomical spectroscopy

Fundamentals: Mass. Composition of 'solar' type stars and white dwarfs. Physical background: Physics of gases. Particle physics. Radiation laws. Energy transport. Potential energy. Bulk properties of stars: Mass limits. Energy sources. Energy transfer. Luminosity. Sizes and densities. Physical background: Spectroscopy. Radiative transfer. Effective surface gravity. Atomic and ionic populations. Stars - Observations and observed types and properties: Photometry. Spectroscopy. Surface temperature. HR diagram . Variable stars. Abundances. Rotation. Magnetic fields. Black holes. The Sun: Basic data. Limb darkening. Solar surface features. Solar neutrinos. Solar corona. Stellar winds: Solar wind. Stellar winds. Physical background: Masers. Synchrotron radiation. H II regions and related objects: H II regions - theory, physical properties, formation and evolution. H II regions as distance yardsticks. Planetary nebulae. Supernova remnants. The interstellar medium: Basic properties. Dust grains. Interstellar gas. Cosmic rays. Stellar formation and evolution: Star formation. Post-main sequence evolution. Appendices.

Stars, Nebulae and the Interstellar Medium: Observational Physics and Astrophysics

Extended atmospheres and the origin of emission lines. Wolf-Rayet stars. Planetary nebulae. Cataclysmic variables. Be stars. Other emission line systems. References. Index. copy_featured F

Early emission line stars

Preface to the First Edition.- Preface to the Second Edition.- Preface to the Third Edition.- Part I: Telescopes.- Chapter 1: Types of Telescopes.- Chapter 2: Telescope Optics.- Chapter 3: Modern Small Telescope Design.- Part II: Positions and Motions.- Chapter 4: Positions in the Sky.- Chapter 5: Movements of Objects in the Sky.- Chapter 6: Telescope Mountings.- Part III: Observing.- Chapter 7: Electromagnetic Radiation.- Chapter 8: Visual Observing.- Chapter 9: Detectors and Imaging.- Chapter 10: Data Processing.- Chapter 11: Photometry.- Chapter 12: Spectroscopy.- Appendix A: For Further Reading.- Appendix B: Constellations.- Appendix C: Answers to Exercises.- Appendix D: SI and Other Units.- Appendix E: The Greek Alphabet.- Index.

C. R. Kitchin

Papers

Stars, nebulae, and the interstellar medium

Optical astronomical spectroscopy

Stars, Nebulae and the Interstellar Medium: Observational Physics and Astrophysics

Early emission line stars

Telescopes and techniques