Issue |
A&A
Volume 441, Number 2, October II 2005
|
|
---|---|---|
Page(s) | 631 - 640 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20053001 | |
Published online | 19 September 2005 |
On the detection of chemically peculiar stars using
a photometry
Institut für Astronomie der Universität Wien, Türkenschanzstr. 17, 1180 Wien, Austria e-mail: ernst.paunzen@univie.ac.at
Received:
7
March
2005
Accepted:
3
June
2005
We have summarized all measurements for galactic field stars (1474 objects)
from the literature published over more than two
decades. These measurements were, for the
first time, compiled and homogeneously analyzed. The
intermediate
band photometric system
samples the depth of the 5200 Å flux depression by comparing the flux at the center
with the adjacent regions with bandwidths of 110 Å to 230 Å. Because it was slightly modified
over the last three decades, we checked for
systematic trends for the different measurements but found no correlations whatsoever.
The
photometric system is most suitable to detecting magnetic chemically
peculiar (CP) stars with high
efficiency, but is also capable of detecting a small percentage of
non-magnetic CP objects. Furthermore, the groups of (metal-weak) λ Bootis,
as well as classical Be/shell stars, can be successfully investigated.
In addition, we also analyzed the behaviour of supergiants (luminosity class I and II).
On the basis of apparent normal type objects, the correlation of the 3σ
significance limit and
the percentage of positive detection for all groups was derived.
We compared the capability of the
photometric system with the
and Z indices of the Geneva 7-color system to detect peculiar objects.
Both photometric systems show the same efficiency for the detection of CP
and λ Bootis stars, while the
indices in the Geneva system are even more efficient at detecting
Be/shell objects.
On the basis of this statistical analysis it is possible to derive the incidence of CP
stars in galactic open cluster and extragalactic systems including the former unknown bias
of undetected objects. This is especially important in order to make a sound statistical
analysis of the correlation between the occurrence of these objects and astrophysical parameters
such as the age, metallicity, and strength of global, as well as local, magnetic fields.
Key words: stars: chemically peculiar / stars: early-type / techniques: photometric
© ESO, 2005
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