NIGHTFALL by Wichmann (2002) is a freely available amateur code2 for modeling eclipsing binary stars. It supports a large range of binary star configurations, including over-contact (common envelope) systems, eccentric (noncircular) orbits, mutual irradiance of both stars (reflection effect), surface spots and asynchronous rotation (stars rotating slower or faster than the orbital period), and the possible existence of a third star in the system. It allows the user to produce animated views of eclipsing binary stars, calculate synthetic light curves and radial velocity curves, and eventually determine the best-fit model for a given set of observational data of an eclipsing binary star system.

Douglas Phillips (University of Calgary) has been working with a number of useful visualization packages. The standard plotting tool for the University of Calgary workstations is XMGR, for two-dimensional plots, and AVS for three-dimensional plots. Figures 8.5 and 8.6 show high- and low-angle views of the phase and wavelength dependence of the residuals of intermediate modeling of the binary AI Phoenicis discussed in Sect. 7.3.7 and illustrates the power of the three-dimensional visualization techniques.

Figures 8.5 and 8.6 represent two viewings of the residuals plotted against phase for a succession of passbands. They therefore represent the spectra of the residuals for each phase, and can be used, in certain instances, to gauge the physical mechanism for the residuals if they are nonrandom. This case represents an unconverged solution and is shown only to illustrate the technique only.

2 Nightfall can be downloaded from http://www.hs.uni-hamburg.de/DE/Ins/Per/Wichmann/ Nightfall.html. It runs only on Linux platforms.

References

Bradstreet, D. H.: 1993, Binary Maker 2.0 - An Interactive Graphical Tool for Preliminary Light Curve Analysis, in E. F. Milone (ed.), Light Curve Modeling of Eclipsing Binary Stars, pp. 151-166, Springer, New York Bradstreet, D. H. & Steelmans, D. P.: 2004, Binary Maker 3.0, Contact Software, Norristown PA, 19087

Castelli, F. & Kurucz, R. L.: 2004, New Grids of ATLAS9 Model Atmospheres, ArXiv Astrophysics e-prints

Prsa, A. & Zwitter, T.: 2005b, A Computational Guide to Physics of Eclipsing Binaries. I. Demonstrations and Perspectives, ApJ 628, 426-438 Terrell, D., Munari, U., Zwitter, T., & Nelson, R. H.: 2003, Observational Studies of Early-Type

Overcontact Binaries: TU Muscae, AJ 126, 2988-2996 Wichmann, R.: 2002, NIGHTFALL User's Guide, Technical report, Hamburger Sternwarte, Hamburg, Germany

Wilson, R. E.: 1979, Eccentric Orbit Generalization and Simultaneous Solution of Binary Star

Light and Velocity Curves, ApJ234, 1054-1066 Wilson, R. E. & Devinney, E. J.: 1971, Realization of Accurate Close-Binary Light Curves: Application to MR Cygni, ApJ 166, 605-619 Zwitter, T., Castelli, F., & Munari, U.: 2004, An Extensive Library of Synthetic Spectra Covering the Far Red, RAVE and GAIA Wavelength Ranges, A&A 417, 1055-1062

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