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On the Potential of Tidal Excitation of Gravity Modes in Hot B
Subdwarfs
G. Fontaine1, P. Brassard1, S. Charpinet2,
E.M. Green3, and B. Willems4
1 Département de Physique, Université de Montréal,
Montréal, Québec, Canada H3C 3J7
2 Observatoire Midi-Pyrénées, 14 Avenue Edouard Belin, 31400 Toulouse, France 3 Steward Observatory, University of Arizona, Tucson, Arizona 85721, U.S.A. 4 Department of Physics and Astronomy, The Open University, Milton Keynes, MK7 6AA, U.K.
Given that about half of the known hot B subdwarf (sdB) stars
in the field belong to close binary systems, we examine the possibility
that dynamic tides can excite high-order gravity modes in these
objects. Contrary to solar-type stars, we find that the ratio of the
work done by the tidal force (through an oscillation mode) to the
kinetic energy of that mode increases with increasing radial order. This
implies that the probability of tidal coupling increases with increasing
periods and thus suggests that this mechanism may be of key importance
for exciting low-frequency gravity modes in sdB stars. Our result is of
particular interest in the light of the recent discovery of a new class
of sdB pulsators (see the presentation of E.M. Green at this conference)
featuring unexpected long-period (
Last changed: 2002/Jun/21
©1996-2002 CAUP |
1 h) luminosity variations
associated with high-order gravity modes in these stars.