Physics of Formation of FeII Lines Outside LTE

The same kind of physics is frequently common to very different fields of Astrophysics, so experts in each of these fields have often much to learn from each others. It was therefore logical that the International Astronomical Union should sponsor a colloquium about an ion which pro­ duces many spectral lines that can be used as a diagnostic for many sorts of objects, and which may sometimes have a major influence on physical processes occurring in astro­ physical sources. The lines of singly ionized iron (FeII) are present in absorption and emission in the spectra of objects such as the Sun, cool stars, circumstellar envelopes of hot stars, novae, diffuse nebulae including the supernova remnants, and active galactic nuclei. These lines are very often formed far from LTE, and their interpretation is not easy in view of the complex Grotrian diagram for FeII, and the gaps in the knowledge of various physical parameters. In addition, the density of very strong FeII lines becomes very large in the ultraviolet, and the lines can play a major role in the line blanketing. They need therefore to be taken into account in any energy balance argument.

Inhalt

General Introduction to the "FeII Problem".- FeII Reference Catalogue.- Session 1 - Basic Atomic Data.- The Laboratory Spectrum and Atomic Structure of FeII.- New Laboratory Recordings of FeII in the IUE Region.- Semiempirical Determination of FeII Oscillator Strengths.- Theoretical Determination of FeII Atomic Parameters.- Calculations of Transition Probabilities for Forbidden Lines in the 3d7 Configuration in FeII.- Accidental Degeneracy Between Doubly Excited States in FeII.- Experimental Determination of FeII gf-Values: Review of Available Data and Works in Progress.- A Photospheric Solar Iron Abundance from Weak FeII Lines.- Empirical gf-Determination from the Solar Spectrum.- Session 2 - Observation of FeII Lines in Different Astrophysical Objects.- FeII Emission Line Profiles in the Ultraviolet Spectrum of Cool, Luminous Stars.- Observation of FeII in Cool Variables.- Ultraviolet FeII Emission Lines in Novae.- FeII in Luminous Hot Stars.- FeII Lines in Herbig Ae Stars.- FeII Line Profile Variability in the Herbig Be Star Z CMa.- A Transient FeII Phenomenon in the Optical Spectrum of the Be/X Ray Binary System HDE 245770/A0535+26.- FeII Lines in the Palomar Bright Quasar Survey.- Observations of FeII in Active Galactic Nuclei.- FeII Lines in the UV Spectra of Type I Supernovae.- Infrared Lines of FeII from Supernova Remnants.- Session 3 - Theory of Line Formation. Models.- The NLTE Formation of Iron Lines in the Solar Photosphere.- Stark Broadening of the FeII Lines in the Solar and Stellar Spectra.- FeII Lines in the Presence of Photospheric Oscillations.- Ultraviolet FeII Emission from Cool Star Chromospheres.- On the Excitation of the FeII Multiplet UV 191 in Stellar Spectra.- Doubly Excited FeII Lines in the A Star 21 Pegasi.- The Formation of FeII Emission Lines.- Formation of FeII Lines in AGN.- FeII and Balmer Continuum Emission in AGNs.- A Computer Program for Solving Multi-Level non-LTE Radiative Transfer Problems in Moving or Static Atmospheres.- Semi-Empirical Methods of Analysis of FeII Emission and Absorption Lines Formed in Diffuse Media.- The UV Emission of the Symbiotic Star CH Cyg.- Analysis of the FeII Lines in the Ultraviolet Spectrum of the VV Cep Star KQ Puppis.- FeII Spectral Synthesis of the Ultraviolet Spectrum of Hot Stars with Cool Winds.- Session 4 - Future Plans and Conclusions.- Future Laboratory Work on FeII.- FeII Prospects in Solar Physics.- Prospectives of Ground Based Observations.- Space Telescope and the FeII Problem.- Can We Bridge the Gap between Observation and Theory?.- Concluding Remarks.- Astrophysical Objects Index.