The purpose of this consolidated catalogue of 45 stars is to
establish an as large as
possible group of 
Bootis stars with high membership probability.
Based on this catalogue, we
derive photometric and spectroscopic parameter values which shall
help to successfully
preselect candidates for a spectroscopic survey of field and cluster
candidates in
order to increase the number of known 
Bootis stars. An efficient
preselection of candidates
is absolutely necessary for telescope time consuming surveys.
In an iteration, the extended list of members shall provide us with a sample of
unquestionable 
Bootis stars which is large enough for a sound statistical
analysis of the group properties. This knowledge has to be well
established prior to
any attempt to develop theories concerning the 
Bootis phenomenon.
Narrow band photometry has often been used to distinguish chemically peculiar from normal stars. The Geneva (Figs.1 (click here) and 2 (click here)) and Strömgren (Figs.3 (click here), 4 (click here) and 5 (click here)) photometric systems provide estimates for temperature, surface gravity and chemical composition of stars. However, we have to stress again that these calibrations were derived for normal abundant stars. We conclude from the figures mentioned:
Bootis stars cannot be distinguished from normal dwarf stars.
Bootis stars: As is also obvious from
the figures,
other stars populate the same parameter space.
An unambiguous detection of 
Bootis stars with standard
photometry alone is
impossible, although to some extend a discrimination
with metallicity sensitive indices is useful. But such attempts
have led in the past to many spurious
entries in various catalogues and in a confusion of the subject.
Figure 5: 
versus b-y. The solid line is the standard relation after
Philip & Egret (1980). Symbols are the same as in Fig.1
Parallel to the photometric observations needed for the colour indices,
we investigated
also the photometric stability of our catalogue stars which is
reflected by the column
"VAR" in Table1 (click here). For nearly 50% of investigated catalogue
members we found definite indications for
a variability in time scales which are typical for pulsating
Scuti stars. This
high incidence of rather large amplitude multifrequency pulsation
makes asteroseismic
techniques an interesting tool for investigating the structure of these stars.
Several authors (Gray & Corbally 1993, and references therein) used the
rotational velocity as additional criterium for 
Bootis stars. These authors
suggest that only stars with 
> 50 kms
should be
included to this group. We therefore investigated the rotational velocity
distribution of normal A0V to F0V stars from
Gray & Garrison (1987, 1989a,b)
with 
values taken from the catalogue of Uesugi
& Fukuda (1982). In addition, we considered all stars
from the Michigan Spectral Catalogue (Houk & Cowley 1975; Houk 1978, 1982;
Houk & Smith-Moore 1988) within the relevant spectral classes.
The distribution
of 
-values for normal stars (Fig.6 (click here)) is in good
agreement with the literature (Abt & Morrell 1995).
The distribution for 
Bootis stars (Fig.6 (click here)) is similar to
that for normal stars, but no 
Bootis star is presently known
with 
< 50kms
.
To what extend this distribution is intrinsic or distorted by small number
statistics remains open.
We are not able to rule out measurement errors due to the
weakness of the spectral lines
and a bias due to the 
"classification criterion".
We suggest therefore to drop the 
membership criterion.
Figure 6: Rotational velocity distribution for stars from A0 to F0 from Gray
& Garrison (1987, 1989a,b) and the
Michigan Spectral Catalogue (Houk & Cowley 1975; Houk 1978, 1982;
Houk & Smith-Moore 1988), 
\
values from Uesugi & Fukuda (1982). Rotational velocity distribution
for all 
Bootis stars in this catalogue
Table 2: Geneva colours from the Geneva database, 
combined magnitudes for close
binary systems
Table 3: Strömgren colours
from Hauck & Mermilliod (1990) and Handler (1995), 
-photometry
from Maitzen & Pavlovski (1989a,b), 
combined magnitudes for close
binary systems
Acknowledgements
This research was done within the working group Asteroseismology-AMS with
funding from the Fonds zur Förderung der wissenschaftlichen
Forschung (project
S7303-AST) and the Hochschuljubiläumsstiftung der Stadt Wien (project
Bootis Sterne).
EP and UH acknowledge partial financial support by the
Austrian Zentrum für Auslandsstudien.
This work was supported in part by the Swiss Fonds National
de la Recherche Scientifique and use was made of the Simbad database,
operated at CDS, Strasbourg, France.
We want to thank B. Nicolet for providing us the programmes for the Geneva
database and an anonymous referee for helpful comments.
