WinFitter is an integrated Windows environment that provides a variety of tools that can be used in the analysis of the light curves of both eclipsing binary stars and transiting exoplanets, spot fitting of short period eclipsing binary stars, spectrographic velocity curves of binary stars, spectrographic line profiles, and astrometric orbital elements. It includes the following tools: Fitter Application In both an eclipsing binary star system and a transiting planetary system as the planet or star passes in front of the other star, there is a measureable reduction in the observed light output of the system. The Fitter application uses χ2-minimization computational algorithms developed by Budding and Najim (1980) and refined by Budding and Zeilik (1987, see also Budding and Demircan 2007). These algorithms make it possible to effectively evaluate the information content of the data, by reference to the curvature Hessian, as mentioned in the Introduction (see also Bevington, 1969; Budding & Demircan, 2007). The best (or optimal) fit is found by minimizing the value of χ2. The program includes an optimizing routine that makes it possible to follow and control the approach to the optimum, and then calculates the curvature Hessian and its inverse, the error matrix, in the vicinity of this optimum. Negative eigenvalues of the Hessian signal a breakdown of determinacy (also shown by negative elements on the central diagonal of the error matrix), and the corresponding eigenvectors indicate, by their relative orientations to the various parameter axes, which parameters are intrinsically well determined. The precision with which one can estimate optimal parameter values is clearly dependent on the inherent observational accuracy. In short, Fitter’s output makes the analyst keenly aware of an information limit in the data, so he or she can be on guard against going beyond this limit in the model’s parameterization.
SpotFitter Application The spot fitting algorithms model the maculation effects by one or more large, dark, circular regions on the photosphere. Circular regions yield the minimum possible area for a given maculation effect. In essence, a circular spot gives the smallest mean radius that an extended maculation region could have. This circular spot model has a very concise algebraic form, lending itself to quick calculations while thoroughly searching parameter space for optimal solutions. Moreover, it parameterizes the properties of the starspot is such a way as to represent the main average properties of a large active region. The derived parameter sets are then suitable measures of the maculation. As with the previous binary fitting process, it is possible to effectively evaluate the information content of the solution by reference to the curvature Hessian in the vicinity of the optimal solution. In summary, this modelling of the photometric maculation effects contains information about the net surface areas, longitudes, latitudes, and temperatures of localized active regions.
Cleaner Application This application is used to deal with residuals from the initial fitting to the “dirty” light curve. The underlying idea is separate out small systematic but unmodeled effects that might remain in the light curve. Our fitting function will now take the form (with a representation similar to the actual Fortran instruction) cul = a(1) + a(2)cos(ph) + a(3)sin(ph) + a(4)cos(2*ph) + a(5) sin(2*ph) + a(6)cos(3*ph) + a(7)sin(3*ph) ... a(18)cos(9*ph) + a(19)sin(9*ph) where a1, a2, a3, a4, … a(2n) are the amplitudes of the first n terms in this Fourier expansion and a3, a5, ... a(2n+1) are the corresponding phase shifts applied to these n harmonics.
FitterRV Application This application performs an optimized fitting of radial velocity curve data using the same χ2-minimization computational algorithms as the Fitter, SpotFitter, and Cleaner applications. The final main output from the FitterRV application can be expected to be: (1) The radial velocity semi-amplitude K, (2) Any correction to the zero point of the phase Δφo, if significant, (3)* The gamma velocity γ, all with error measures.
ProfileFitter Application The ProfileFitter application performs spectrometric line profile analysis, in which use is made of the Doppler effect to ‘scan’ the line. The program can be adapted to determine the locations and sizes of spot-like features on stars. It uses the same χ2-minimization computational algorithms as the Fitter, SpotFtter, Cleaner, and FitterRV applications.
FitAstrometry Application This application uses the same χ2-minimization computational algorithms as the Fitter, SpotFitter, Cleaner, FitterRV, and ProfileFitter applications. FitAstrometry finds – essentially by an informed trial-and-error procedure – that set of elements that produces the best fitting model to the data, in the sense of minimizing the sum of the squares of the differences between observed and calculated measurement points.
Bin Data Application This application bins light curve data files. It can handle file sizes up to 2,000,000 data points and up to 2000 data points per bin. The light curve data need not be sorted because the application first sorts the data in ascending order of phase before doing the binning.
BJD to Phase Application This application converts a data file of Barycentric Julian Date (BJD) and Flux or Magnitude to Phase (in phase units) and Flux or Magnitude.
Limb Darkening Coefficients Application This application calculates the limb darkening coefficients from Walter Van Hamme's limb darkening tables using bilinear interpolation.