HD 172189: another step in furnishing one of the best laboratories known for asteroseismic studies

Abstract

HD 172189 is a spectroscopic eclipsing binary system with a rapidly-rotating pulsating δ Scuti component. It is also a member of the open cluster IC 4756. These combined characteristics make it an excellent laboratory for asteroseismic studies. To date, HD 172189 has been analysed in detail photometrically but not spectroscopically. For this reason we have compiled a set of spectroscopic data to determine the absolute and atmospheric parameters of the components. We determined the radial velocities (RV) of both components using four different techniques. We disentangled the binary spectra using KOREL, and performed the first abundance analysis on both disentangled spectra. By combining the spectroscopic results and the photometric data, we obtained the component masses, 1.8 and 1.7 M , and radii, 4.0 and 2.4 R , for inclination i = 73.2 • , eccentricity e = 0.28, and orbital period Π = 5.70198 days. Effective temperatures of 7600 K and 8100 K were also determined. The measured v sin i are 78 and 74 km s −1 , respectively, giving rotational periods of 2.50 and 1.55 days for the components. The abundance analysis shows [Fe/H] = -0.28 for the primary (pulsating) star, consistent with observations of IC 4756. We also present an assessment of the different analysis techniques used to obtain the RVs and the global parameters.

The envelope of the power spectra of over a thousand δ Scuti stars

“…14and the values of mass, radius, rotation, inclination, and/or projected velocity (v sin i) provided by the different authors (see Table 2). Two of these δ Scuti stars, CID 1043 (star 1) and CID 8170 (star 6), are well-known spectroscopic binaries whose structural and orbital parameters were studied by Hareter et al (2014) and Creevey et al (2009), respectively. The δ Scuti star with chemical peculiarities studied by Escorza et al (2016), CID 5685 (star 4), is a good example of the observed difference in temperature when two different methods are used.…”

The CoRoT ground‐based asteroseismological programme

“…In the case of the eclipsing binary HD 172189, the spectra were very useful for identifying the δ Scuti component (see Fig. 4) and disentangling the stars (Creevey et al 2009).…”

Ground‐based follow‐up in relation to Kepler asteroseismic investigation

“…First, through the spectra it is possible to derive constraints on the component masses (e.g. Tango et al 2006;Vučkovic et al 2007;Creevey et al 2009;Desmet et al 2010), which is valuable information for seismic models and models on stellar structure and (binary) evolution. Second, in the case of doublelined spectroscopic binaries it is possible to disentangle the component spectra (Harmanec et al 2004) and to study the line-profile variability of the disentangled components in full detail .…”