[vsnet-chat 2154] Re: Missing CoD stars

[bas@lowell.Lowell.Edu (Brian Skiff)]

     The best way to get CoD (or any other) corrections into the 'system'
is to publish a paper containing such.  It's really hard to get such a
paper published in a refereed journal, since the referee says "there's no
science here".  There is another way, however.  If a particular star or
stars are already in SIMBAD (a much bigger number now that the complete
Tycho catalogue has been integrated into their database), then if you can
show where the error lies, send a note to them (question@simbad.u-strasbg.fr)
saying what you've found.  I've done this quite a lot (many thousands of
stars and other objects in the last few years), and as long as there's convincing
evidence (a paper trail in the literature is helpful, if such exists), then
the fix will get made within a few days.  Often, the "errors" are merely
objects that are given several times in SIMBAD with different names, and
by simply linking them, the problem is solved.  Examples are red variables
with IRAS sources, or an O or B subdwarf in the PG catalogue with a source
detected in the UV.
     Be aware also of the typical positional uncertainties in various
catalogues.  The comparison between the CPD and CoD is a good example:  the
CPD stars are usually within 5"-10" of their true location (often much better),
whereas the CoD positions can be an arcminute or so off (although usually
within a few tenths of an arcminute).  Many of the examples Mati cited are
probably real stars, but ones that have crummy CoD positions.  Comparison
with the sky usually allows one to sort out the problems.  Remember also that
the CPD was done on blue-light plates, whereas the CoD was done visually and
goes to much fainter yellow-light magnitudes, so favors red stars to a great
degree, even more than the BD/SBD.  Taking all this into consideration, my
experience working on identifying stars in southern spectral surveys is that
there are not very many true errors in the CoD in the sense of missing stars
and such.  Cases such as Mati found where he linked a large proper-motion
star with its position at the epoch of the CoD should certainly be reported
to SIMBAD if the name is not already linked there (you have to check that,
too, because somebody may have already noticed it!).

\Brian

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