H
emission line spectroscopy in NGC 330
On the hybrid model for global oscillations in Be star
circumstellar disks
W. Hummel1,6
W. Gässler1,7
B. Muschielok1,
H. Schink2,
H. Nicklas2,
G. Conti3,
E. Mattaini3,
S. Keller4,
K.-H. Mantel1,
I. Appenzeller5,
G. Rupprecht6,
W. Seifert5,
O. Stahl5, and
K. Tarantik1,8
1
Institut für Astronomie und Astrophysik und
Universitäts-Sternwarte München, Scheinerstr. 1,
D-81679 München, Germany
2
Universitäts-Sternwarte Göttingen, Geismarlandstr. 11,
D-37083 Göttingen, Germany
3
CNR - Istituto Fisica Cosmica, Via Bassini 15,
I-20133 Milano, Italy
4
Mount Stromlo Observatory, Private Bag, Weston Creek, Weston,
ACT 2611, Australia
5
Landessternwarte Heidelberg, Königstuhl 12,
D-69117 Heidelberg, Germany
6
European Southern Observatory, Karl-Schwarzschildstr. 2,
D-85748 Garching, Germany
7
National Astronomical Observatory of Japan, Subaru Telescope,
650 North A'ohoku Place, Hilo, Hawaii, HI 96720 USA
8
Max-Planck-Institut für extraterrestrische Physik, Postfach 1312,
D-85741 Garching, Germany
We perform an observational test on global
oscillations in Be star circumstellar disks in the metal deficient
environment of the SMC. According to the hybrid model of disk
oscillations early-type Be stars require an optically thin line force
to establish a density wave. The low metallicity in the SMC should
therefore diminish or prevent the formation of disk oscillations in
early-type Be stars. We present short wavelength range spectra around
H
of 48 Be stars in the young open cluster NGC 330 in the SMC.
We find that the fraction of early-type Be stars in NGC 330 which host
a global disk oscillation does not differ from the known fraction of
Galactic field Be stars. This observational result is in
contradiction to the theoretical prediction. We discuss several
interpretations and propose a further observational test.
Accepted by A&A
Preprints from
whummel@eso.org
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