Recent Progress of Spectral Line Shapes in Astrophysics

Dear Colleagues,

The shape of spectral lines in astronomical objects are almost unique tool for getting insight in physical processes in variety of astrophysical gases and plasmas. The shapes reflect not only the objects where the lines are formed but also the environment photons are passing through. The interpretation of line shapes is tricky – we need to know the underlying atomic/molecular physics and have reliable data describing those processes. We also have to consider the environment where photons are formed and the influence of interplanetary, interstellar and/or intergalactic media. On top of that we need reliable radiative transfer tools so that we can extract as many physical parameters as possible. To extract those parameters we need high resolution spectroscopic measurements of spectra of astronomical objects which are not easy to obtain. All of this gives us an opportunity to sample various scenarios of what happens in different types of astronomical objects which gives us an insight their nature.

This issue will not only present recent progress in the various fields needed for the interpretation of astronomical spectra, but also point towards what we can expect in the near (or not so near) future. We would like to be as open as possible and have results from the variety of fields. Some topics we would like to cover (of course, others are welcome) are:

• new developments in precise measurements of the spectral lines, both in astrophysical and laboratory plasmas
• stratification of elements in different environments
• how the line shapes reflect condition of objects from the origin through environment to the observer on Earth
• mechanisms of the line formation
• radiation transfer through different media including multi dimensional radiative transfer
• atomic and molecular processes in different plasmas and data describing them
• databases and datasets providing necessary atomic and molecular data for modeling and interpretation of astronomical spectra
• new approaches in using the machine learning and the artificial intelligence tools on large homogeneous spectral datasets of astronomical objects to extract hidden properties of underlying objects

Prof. Dr. Darko Jevremović
Guest Editor

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• spectral line formation
• radiative transfer
• diagnostics of astrophysical plasmas
• atomic/molecular/grain processes and data
• large AMG databases
• machine learning