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Astron. Astrophys. 331, 995-1001 (1998)

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Pulsating and nonpulsating stars in Hyades observed by Hipparcos satellite *

E. Antonello 1 and L.E. Pasinetti Fracassini 2

1 Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-22055 Merate, Italy (elio@merate.mi.astro.it)
2 Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria 16, I-20133 Milano, Italy (pasinetti@mi.infn.it)

Received 2 October 1997 / Accepted 18 November 1997


A study of the stars in the instability strip of Hyades cluster has been performed taking into account the new estimate of the stellar parallaxes. For taking advantage of the improved accuracy of the distances and hence absolute magnitudes it is necessary to separate the photometric effects of close companions, which appear quite common in Hyades. The [FORMULA] Scuti stars, differently from nonpulsating stars, appear to be located also above the main sequence, and this is due probably to their large rotational velocity. The comparison of the rotational effects on the star position in the color-magnitude diagram with theoretical model predictions tends to confirm the importance of differential rotation. A brief discussion of [FORMULA] Tau and some remarks on the X-ray emission of other two [FORMULA] Scuti stars are also reported.

Key words: binaries: general – stars: distances – stars: fundamental parameters – stars: rotation – open clusters and associations: individual: Mel 25

* Based on data from Hipparcos astrometry satellite

Send offprint requests to: E. Antonello

© European Southern Observatory (ESO) 1998

Online publication: March 3, 1998