[vsnet-chat 1628] Re: [AAVSO-DIS] Re: FASTT-2 variables

[Taichi Kato <tkato>]

Re: [vsnet-chat 1620] Re: [AAVSO-DIS] Re: FASTT-2 variables

Brian Skiff wrote:

> In brief, the more I use the Hipparcos database, the more I distrust it.
> It did not find HD 23642, an Algol binary in the Pleiades, for instance,
> and resulted also in a lot of spurious variables, such as Altair and the
> fainter star star mentioned in recent 'vsnet' posts, which also probably
> spurious.

   I have the practically same feeling.  In the astronomy course in
my university, I have examined, with students, all the Hipparcos Annex
photometry.  For about half of stars listed, we had to reject something.
There seem to be confusions in separating double stars, etc.  One might
be interested to know about 90% of first-magnitude stars are now flagged
for variability (accordingly, Sirius has been registered as a new suspected
variable (NSV) star).

   The temporary coverage is not usually suited for variability analysis
(we've had a lot of difficulties in analyzing).  Things look worse when
the Hipparcos was forced to work in two- or one-gyro mode, the last period
of its operation.  Spuriously looking data seem to cluster around this period,
but we couldn't find a reliable way to distingish them from normal
observations.  Much is clearly left to ground-based observers.

Regards,
Taichi Kato

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