The Wilson Devinney Program Extensions and Applications

Since the Wilson-Devinney program is the most widely used of all the light curve modeling tools, it is appropriate to describe its features, capabilities, and continuing development in some detail. The WD program itself has seen continual improvements, and the current version (briefly summarized in Chap. 6) with its powerful features provides the opportunity to extract a maximum of information from a variety of observational data. As a side-effect, publications on the WD model and on the WD program1 have stimulated the development of new programs, which in their kernel use the WD program. Several such programs with new innovative features or added functionality now coexist with the WD program. Some of these features were developed independently in several programs, including WD.

Starting in the 1980s, several extensions and enhancements to the original WD program have been implemented in the programs LCCTRL and LC83KS by Kallrath (1987), WD83K83 by Stagg & Milone (1993), WD83K93 by Milone et al. (1992b), WD93K93 by Stagg & Milone (1993)), and LC93KS by Kallrath (1993). The successor to these programs is WD9 5 (Kallrath et al. 1998) and versions up to WD2 0 07 (Milone & Kallrath, 2008). The naming is now unified to WDx2 0 07 with the WDx indicating extensions to the WD program. WD has now also become the physical model engine of PHOEBE, a simulation and analysis tool developed by Prsa & Zwitter (2005b) and described in Sect. 8.2 that offers an attractive graphical user interface.

The first section of this chapter describes the functionality of WDx2 0 07, the second focuses on the Kurucz atmospheres option in WDx2 0 07 and WD, the third gives a brief review of research performed with the WD program and its offspring versions (LC83KS, WD93K93, LC93KS, and WDx2 0 07), which include enhanced features by other authors. The third section also discusses analyses of astrophysically interesting systems such as X-ray binaries and EBs in globular and open clusters. Finally, in the fourth section, some future prospects for the WD program are considered.

1 The WD program itself continues to be developed by R. E. Wilson.

J. Kallrath, E.F. Milone, Eclipsing Binary Stars: Modeling and Analysis, Astronomy and Astrophysics Library, DOI 10.1007/978-1-4419-0699-1_7, © Springer Science+Business Media, LLC 2009

7.1 Current Capabilities of WDx2007

Ad vitam aut culpam (For life - or, until you mess up)

The stand-alone Fortran77 program WDx2 0 072 enables the user to make use of the Wilson-Devinney (WD) program3 to compute EB light and radial velocity curves and to analyze data, i.e., to fit light curves or merely to compute a synthetic light curve. WDx2 0 07 contains the WD program but provides several features around it, which enables the user to

• carry out computations using the original WD programs LC and DC;

• convenient preprocessing of the input data to LC and DC;

• use the Kurucz atmospheres and to model better the wavelength-dependent stellar flux (Milone et al. 1992b);

• on-fly computation of limb-darkening coefficients using an interpolation scheme based on the Van Hamme (1993) tables (during the iterations of the least-squares iteration the limb-darkening coefficients are automatically computed as a function of temperature, log g and wavelength);

• fit EB observables using the simplex method (Kallrath & Linnell 1987), differential corrections (Wilson & Devinney 1971), a Levenberg-Marquardt scheme (Kallrath et al. 1998), or simulated annealing as described in Milone & Kallrath (2008);

• do automatic iterations (Kallrath 1987);

• produce gnuPlot graphics files;

• obtain best-fit solutions for grids or tables over fixed parameters (Kallrath & Kamper 1992) which otherwise may be poorly determined; and

• develop and test new features, e.g., the analysis of large number of light curves using the matching approach described in Sect. 5.3.2.

WDx2 0 07 couples directly to the WD code which may cause some delays in keeping up with newly issued versions of the WD program. It runs under the operating system LINUX (especially, Ubuntu Linux), CygWin, as well as in Windows Command Shell under Win95, Win98, WinNT, Win2000, and WinXP. WDx2 0 07 has been developed upon the framework of the preceding programs LCCTRL (Kallrath 1987), WD93, WD9 5, WD9 8 (Kallrath et al. 1998), and WD2 0 02, the first that combined all previous developments and included all stellar atmosphere improvements by Milone et al. (1992b) and local limb-darkening coefficients. These additional atmosphere and limb-darkening features are now an integral part of the WD program.

2 This program, maintained and further developed by Josef Kallrath, and its documentation is available at http://www.astro.ufl.edu/~kallrath/

3 The Wilson-Devinney program is distributed by Robert E. Wilson (University of Florida) and available at ftp://ftp.astro.ufl.edu/pub/wilson/lcdc2007

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