The purpose of this book is to discuss certain aspects of the theory of the formation and analysis of the line spectrum of a hot gas. The underlying motivation for most of the studies discussed here lies in a desire to develop a physically sound procedure for interpreting the line spectrum of a stellar atmosphere ; correspondingly, the major emphasis is given to problems encountered in astrophysics.

Spectral line formation theory is at the heart of astrophysical diagnostic. Our knowledge of abundances, in both stellar and interstellar contexts, comes almost enti rely from line analysis, as does a major fraction of our ability to model stellar atmospheres. As new facets of the universe become observable so the techniques of high reso lution spectroscopy are brought to bear, with great reward. Improved instruments, such as echelle spectrographs, employ ing detectors of high quantum efficiency, have revolutioned our ability to observe high quality line profiles, although until now this ability has been confined to the brightest stars. Fabry-Perot interferometers and their modern deriva tives are bringing new ranges of resolving power to studies of atomic and ionic interstellar lines, and of course radio techniques imply exceedingly high resolution for the cool interstellar medium of molecules and radicals. Telescopes in space are extending the spectral range of these types of observations. Already the Copernicus and IUE high resolution spectrographs have given us a tantalizing glimmer of what it will be like to obtain ultraviolet spectra with resolution and signal to noise ratio approaching those obtainable on the ground. Fairly soon Space Telescope will be producing high resolution spectroscopic data of unparal leled quali ty and distance range. As often happens in astro physics the challenge is now coming from the observers to the theorists to provide interpretational tools which are adequate to the state of the data.

This accessible guide presents the astrophysical concepts behind astronomical spectroscopy, covering both theoretical and practical elements. Suitable for anyone with only a little background knowledge and access to amateur-level equipment, it will help you understand and practise the scientifically important and growing field of amateur astronomy.

The scientific research based on spectropolarimetric techniques is undergoing a phase of rapid growth. Instruments of unprecedented sensitivity are nowadays available, particularly for solar observations. To fully exploit the rich diagnostic content of such observations, it is necessary to understand the physical mechanisms involved in the generation and transfer of polarized radiation in astrophysical (or laboratory) plasmas. After an introductory part based on classical physics, this book tackles the subject by a rigorous quantum-mechanical approach. The transfer equations for polarized radiation and the statistical equilibrium equations for the atomic density matrix are derived directly from the principles of Quantum Electrodynamics. The two sets of equations are then used to present a number of applications, mainly concerning the diagnostics of solar magnetic fields. This book is primarily addressed to scientists working in the field of spectropolarimetry. It may also serve as a textbook for a course at the graduate or advanced undergraduate level.

Emission line stars are attractive to many people because of their spectacular phenomena and their amazing varieties and variability. This book offers general information on emission line stars, starting from a brief introduction to stellar astrophysics and then moving to a broad overview of emission line stars including early and late type stars as well as pre-main sequence stars.

A full colour reference featuring detailed commented spectral profiles of more than one hundred astronomical objects.

Star-formation is one of the key processes that shape the current state and evolution of galaxies. This volume provides a comprehensive presentation of the different methods used to measure the intensity of recent or on-going star-forming activity in galaxies, discussing their advantages and complications in detail. It includes a thorough overview of the theoretical underpinnings of star-formation rate indicators, including topics such as stellar evolution and stellar spectra, the stellar initial mass function, and the physical conditions in the interstellar medium. The authors bring together in one place detailed and comparative discussions of traditional and new star-formation rate indicators, star-formation rate measurements in different spatial scales, and comparisons of star-formation rate indicators probing different stellar populations, along with the corresponding theoretical background. This is a useful reference for students and researchers working in the field of extragalactic astrophysics and studying star-formation in local and higher-redshift galaxies.