Eugene H. Avrett
Harvard-Smithsonian Center for Astrophysics
60 Garden Street, Cambridge, MA 02138

Pandora is a general-purpose non-LTE computer program for calculating stellar atmosphere models and detailed line and continuum spectra. The program was written by Eugene Avrett and Rudolf Loeser during more than 40 years, into early 2007. Avrett (physicist) devised and specified Pandora's astrophysics and numerical methods, Loeser (programmer) designed and built the program and superintended its actual ongoing use.

Pandora supports ongoing research by Avrett and collaborators on various specific problems of radiative transfer. Recent applications include extensive modeling of the outer atmosphere of the Sun and other late-type stars, including effects of mass flows; the atmospheric response to external ionizing radiation; and the effects of ion diffusion. Pandora can also be used for simple illustrative studies of optically thick non-LTE spectral line formation for different multilevel atoms and atmospheric models, using plane-parallel and spherical geometries. The program output files include extensive documentation and explanations of the computational procedures so that the results are reasonably self-explanatory.

For an overall description of the program, see "Modeling with Pandora" (choose format: .dvi or .ps).

An excellent set of lecture notes on "Radiative Transfer in Stellar Atmospheres" by Robert J. Rutten can be found at . The "Astronomy course material on radiative transfer and spectral line formation in stellar atmospheres" is a graduate-level introduction to the subject and may serve as a foundation for understanding the Pandora calculation.

Computer-proficient researchers who understand basic stellar atmosphere theory and modeling, and who are willing to make the effort to become successful users, are welcome to obtain from CfA the final version of Pandora (see below).

If you want to become a new user of Pandora:

Learning to use Pandora successfully generally requires a significant commitment of time and effort. It is not a task to be embarked on lightly.

Pandora is a batch (non-interactive) program written in Fortran-77 and running under Unix. You can sample the flavor of the program by reading the main source file. Should you decide to try to get Pandora running and to learn to use it, begin with this Read-me file, which explains how to get started, and then use FTP to download the Pandora_kit , which is a compressed tar file (about 30 Mb) containing the source and data files you need, as well as another Read-me file, test runs, the manual, and a Unix script to generate an executable program file. This Pandora Kit was set up by Loeser over a period of years. As far as understanding and using it to get Pandora up and running you're on your own since Loeser has retired and is no longer available to help in any way. A good knowledge of Unix is necessary and you would benefit from familiarity with SUN Solaris and its f90 compiler.

Once a functioning version of Pandora has become available to you, Avrett may be able to help with questions about the physical and mathematical aspects of the program, and how to use it for empirical modeling. He can be reached by e-mail (

R. Loeser (Last reviewed: 2007 Apr 25)