Intrinsic Variability of Eclipsing Binaries Components

In Chap. 1 we introduced extrinsic and intrinsic variables stars; in the latter group, we find pulsating stars. As more than 50% of all stars are members of binary or multiple systems, we should expect to find pulsating stars, or more generally, intrinsic variables in binary and multiple systems, and also in EBs. As pulsation indicates instability, we might be concerned with stellar evolution effects if such pulsating stars happen to be a binary member. However, at least for well-detached EBs we should expect that each star evolves independently. Pigulski (2006) presented a brief overview of the present knowledge of intrinsic variability in binary and multiple systems and discusses various examples of EBs in the literature. Adding intrinsic variability to a component of an EB, the stellar parameters of a binary component become further constrained.

Pigulski & Michalska (2007) reported detection of pulsating components in 11 EBs in the ~ 11,000 stars from the public ASAS-3 database. Among them are three classical Algols, MX Pav, IZ Tel, and VY Mic, with 5 Scuti-type primary components. In six other EBs, the short-period variability can also be interpreted in terms of 5 Scuti-type pulsations, where both components are probably main sequence stars. The pulsation mode in HD 99612 shows significant amplitude decrease during the observed interval. In addition, one component of the eclipsing and double-lined spectroscopic O-type binary ALS 1135 shows p Cep-type pulsation. Finally, Y Cir is a good candidate for a slowly pulsating B-star in an EB.

Given that the physical processes that cause pulsations lead to time-dependent temperatures and radii, it is not surprising that no light curve program yet exists that can determine both the normal EB parameters and the parameters describing the intrinsic variability. However, Wilson (2009) has already started the first numerical experiments on the subject. Overall, as discussed by Lampens (2006), the field has many open questions - among them whether binarity can influence pulsations or whether binarity can explain the exotic behavior of some pulsating stars.

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