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Astron. Astrophys. 356, 895-902 (2000)

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1. Introduction

The very wide double star CCDM 23239-5349 is an interesting study case of a pulsating star within a common origin pair or wide binary. The detailed investigation of the difference in variability and physical parameters between two components of a physical couple is particularly worthwhile when both stars are located in the same area of the colour-magnitude diagram, in this case both components are in the [FORMULA] Scuti instability strip. The aim of such a study is to search for clues to understand what factors determine the pulsation characteristics such as modes and amplitudes among [FORMULA] Scuti stars in general.

The Hipparcos satellite measurements confirm what was already hinted by the ground-based astrometric data in the Washington Double Star Catalogue (WDS 1996.0, Worley & Douglass 1997), namely that the wide angular separation of 26.5 " of the system is accompanied by a very small relative proper motion ([FORMULA] milli-arcsec/yr (mas/yr), [FORMULA] mas/yr with errors of the same order). The new parallaxes are furthermore compatible to better than [FORMULA]. This may indicate a common origin if not a true physical association (Sect. 4.1).

Regular short-period light variations on a time scale of [FORMULA] 5 hr have been detected for the brightest component of this visual double star (Lampens 1992). We describe the available observations and the reduction methods in Sect. 2. The results of the period analyses are presented in Sect. 3. Also included is the analysis of a selection of the Hipparcos Epoch Photometry data. We discuss the nature of the association and of the variability in Sect. 4. Finally we draw our conclusions in Sect. 5 and we explain why additional observations for both stars of the system would be highly desirable.

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© European Southern Observatory (ESO) 2000

Online publication: April 17, 2000
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