[vsnet-chat 80] Re: Times of minima

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

Rudolf Novak wrote:

> There are certainly many ways how to determine time of
> minimum but what shall I do if minimum is not symetric? And of course is
> there some alghoritm to determine time of RR Lyr, delta Sct or delta Cep
> time of maxima? I know that this question is not very suitable for many of
> readers but there are not just CVs :-)

    I have a question to eclipsing binary observers.  How should we (or do
you) define the "minimum" or "mid-eclipse" for non-symmetric eclipses?
Mathematical minimum?  Or, some specially defined point which represents
a certain binary phase?  This problem also arises in CVs eclipses, in which
non-axisymmetric accretion disks inevitably exist.

    I tentatively and usually determine mid-eclipse points of classical
eclipsing binaries using the following scheme:

1) Give a trial time for minimum (T)
2) Transform observation set (t_i, m_i) to (x_i, y_i) = (abs(t_i)-T, m_i)
3) Determine summed residuals of (x_i, y_i) from a fitted line or a curve
4) Determine T which minimizes the summed residual

Regards,
Taichi Kato

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