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Photometric Variability of Helium Stars in the Z-bump Instability Strip

Published online by Cambridge University Press:  12 April 2016

R. Aznar Cuadrado ,
P. Montañés Rodríguez ,
C. S. Jeffery  and
D. Pollacco
R. Aznar Cuadrado
Affiliation:
Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland
P. Montañés Rodríguez
Affiliation:
Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland
C. S. Jeffery
Affiliation:
Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland
D. Pollacco
Affiliation:
Isaac Newton Group, Santa Cruz de La Palma, Tenerife 38780, Canary Islands, Spain

Abstract

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Z-bump opacities are known to excite radial pulsations in helium stars with 102 ≲ L/M ≲ 104 and Teff ∼ 25 000K. Well-studied cases are V652 Her and BX Cir. The absence of variations in the metalpoor star HD 144941 demonstrates the importance of Z-bump opacities to drive these pulsations. Several other helium-rich stars lie close to the theoretical blue-edge of the Z-bump instability strip. One of these, LS IV+6°2, is a known radial velocity variable. We report on recent (1999 June) observations of two helium stars close to the Z-bump instability boundary. Both appear to be variable.

Type
Part 6. Variables Close to the Main Sequence
Information
International Astronomical Union Colloquium , Volume 176: The Impact of Large-Scale Surveys on Pulsating Star Research , 2000 , pp. 438 - 439
Copyright
Copyright © Astronomical Society of the Pacific 2000

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