AAS 199th meeting, Washington, DC, January 2002
Session 152. Variable Stars
Oral, Thursday, January 10, 2002, 2:00-3:30pm, Jefferson East

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[152.04] Tipping the pulsation axis: A pulsating star in a close binary.

M.D. Reed (Southwest Missouri State University and Iowa State University), Whole Earth Telescope Xcov 17 and 21 Team

We present a preliminary analysis of time series photometry on the pulsating subdwarf B star PG~1336-018 acquired as part of two Whole Earth Telescope runs. PG~1336-018 is a multi-mode pulsator with at least 15 periods centered around 175 seconds. It is also an HW~Vir-type eclipsing binary with a period of 2.4 hours.

During primary eclipse, the companion covers approximately half of the pulsating star; partially resolving the surface of this distant star. Since pulsation is a geometric effect, during eclipse, we expect the changing geometry to affect the pulsations. We examine how this may be used to identify pulsation modes.

We also examine the consequences of such a close binary on the pulsations. Much like the magnetic field determines the pulsation axis in roAp stars, the tidal force may determine the pulsation axis in close binaries.

The author(s) of this abstract have provided an email address for comments about the abstract: mdr131f@smsu.edu

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