[vsnet-chat 83] Re: Times of minima (Novak)

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

Rudolf Novak wrote:

> thank you for description. When I speak about minimum I think
> mathematicaly derived time of light curve. I didn't thought about
> astrophysical meaning,

    It would be rather difficult to define minima even mathematically, unless
the observations are error-free and continuous in time, which conditions are
probably not what you have assumed.

    Let's think of an extreme case.  If data are error-free and are in a
discrete time series, there are a number of ways of interpolation yielding
analytical functions of time, from which minima or maxima are easily obtained.
(Even in this case, we have to assume the knowledge that the real light curve
is well expressed by an analytical function of a certain degree).  Other than
these extreme cases, mathematical definitions will be much more difficult.
(If a light curve has a fractal structure, it would be even meaningless to
define maxima or minima).  We then should adopt certain constraints (e.g.
smoothness of the light curve) or modelling in order to choose from a number
of possibilities which give the same residuals to observations a certain
funtion of time which best expresses the astrophysical meaning.

Regards,
Taichi Kato

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