[vsnet-chat 449] Re: SS Cyg: comparison between sequences

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

Brian Skiff wrote:

> They provide a rough transformation for little-reddened star of ordinary
> color that they claim adds about 0.015 uncertainty to the nominal e_VT.
> So to first order, V_err = sqrt(V_T_err^2 + 0.015^2).

    Wouldn't it refer to the error introduced by the transformation process
itself, not including the error in the colors used?  It seems to me difficult
to reconcile with a constant error irrespective of the error in the color,
which may, as stated, become quite large for red stars in the faint end.
Please forgive me if I understand incorrectly, since we have not yet obtained
the printed version of the catalogue.

> The net result is that for fainter red stars, the (B-V)T is
> much too blue, since in effect the noisier "red" colors were omitted from
> the mean (or thinking of it another way, the B mags. are systematically too
> bright for these cases).

    I have also read somewhere this "null detection" effect has been
considered and the value has been corrected in order to avoid this kind of
systematic error.

Regards,
Taichi Kato

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