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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents



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ID: 50767.0, MPI für Astronomie / Publikationen_mpia
On the Period-Luminosity-Colour-Metallicity
relation and the pulsational characteristics of
lambda Bootis type stars
Authors:Paunzen, E.; Handler, G.; Weiss, W. W.; Nesvacil, N.; Hempel, A.; Romero-Colmenero, E.; Vuthela, F. F.; Reegen, P.; Shobbrook, R. R.; Kilkenny, D.
Date of Publication (YYYY-MM-DD):2002
Title of Journal:Astronomy and Astrophysics
Volume:392
Start Page:515
End Page:528
Review Status:not specified
Audience:Experts Only
Abstract / Description:Generally, chemical peculiarity found for
stars on the upper main sequence excludes delta
Scuti type pulsation (e.g. Ap and Am stars), but
for the group of lambda Bootis stars it is just
the opposite. This makes them very interesting
for asteroseismological investigations. The group
of lambda Bootis type stars comprises late B- to
early F-type, Population I objects which are
basically metal weak, in particular the Fe group
elements, but with the clear exception of C, N, O
and S. The present work is a continuation of the
studies by Paunzen et al. (\cite{Pau97},
\cite{Pau98}), who presented first results on the
pulsational characteristics of the lambda Bootis
stars. Since then, we have observed 22 additional
objects; we found eight new pulsators and
confirmed another one. Furthermore, new
spectroscopic data (Paunzen \cite{Pau01})
allowed us to sort out misidentified candidates
and to add true members to the group. From 67
members of this group, only two are not
photometrically investigated yet which makes our
analysis highly representative. We have compared
our results on the pulsational behaviour of the
lambda Bootis stars with those of a sample of
delta Scuti type objects. We find that at least
70% of all lambda Bootis type stars inside the
classical instability strip pulsate, and they do
so with high overtone modes (Q < 0.020 d).
Only a few stars, if any, pulsate in the
fundamental mode. Our photometric results are in
excellent agreement with the spectroscopic work
on high-degree nonradial pulsations by Bohlender
et al. (\cite{Boh99}). Compared to the delta
Scuti stars, the cool and hot borders of the
instability strip of the lambda Bootis stars are
shifted by about 25 mmag, towards smaller
(b-y)_0. Using published abundances and the
metallicity sensitive indices of the Geneva
7-colour and Strömgren uvbybeta systems, we have
derived [Z] values which describe the surface
abundance of the heavier elements for the group
members. We find that the
Period-Luminosity-Colour relation for the group
of lambda Bootis stars is within the errors
identical with that of the normal delta Scuti
stars. No clear evidence for a statistically
significant metallicity term was detected. Based
on observations from the Austrian Automatic
Photoelectric Telescope (Fairborn Observatory),
SAAO and Siding Spring Observatory.
Free Keywords:stars; lambda Bootis; stars; chemically peculiar; stars; early type
Comment of the Author/Creator:Date: 2002, September 1, 2002
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
External Affiliations:Wien, Türkenschanzstr. 17, 1180 Wien, Austria;
Zentraler Informatikdienst der Universität Wien,
Universitätsstr. 7, 1010 Wien, Austria), AB(South
African Astronomical Observatory, PO Box 9,
Observatory 7935, South Africa), AC(Institut für
Astronomie der Universität Wien, Türkenschanzstr.
17, 1180 Wien, Austria), AD(Institut für
Astronomie der Universität Wien, Türkenschanzstr.
17, 1180 Wien, Austria), AE(Department of
Physics, University of Cape Town, Private Bag,
Rondebosch 7701, South Africa;
Max-Planck-Institut für Astronomie, Königsstuhl
17, 69117 Heidelberg, Germany), AF(South African
Astronomical Observatory, PO Box 9, Observatory
7935, South Africa), AG(South African
Astronomical Observatory, PO Box 9, Observatory
7935, South Africa; Department of Physics,
University of the North-West, Private Bag X2046,
Mmabatho 2735, South Africa), AH(Institut für
Astronomie der Universität Wien, Türkenschanzstr.
17, 1180 Wien, Austria), AI(Research School of
Astronomy and Astrophysics, Australian National
University, Canberra, ACT 0200, Australia),
AJ(South African Astronomical Observatory, PO Box
9, Observatory 7935, South Africa)
Identifiers:URL:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bi... [ID No:1]
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