Asteroseismische studies van twee dubbelsterstelsels met pulserende componenten

摘要

Stellar pulsations propagate through the star and carry with them information about the condition within the deep stellar interior. This information is crucial for fine-tuning models of stars and allows us to test if real stars obey the current theory of stellar structure and evolution. Two stars orbiting around a common centre of mass form a binary system. Under certain conditions, these systems allow us to derive masses and radii of their component stars without relying on stellar models. Pulsating stars residing in binary systems thus offer rigorous tests for theoretical models. In this work, we present the detailed studies of two binary systems containing pulsating components.The first star that we studied is the well-known delta Scuti pulsator 4CVn. We discovered that this star is the primary of a wide, eccentric binary system. Unfortunately, 4CVn completely outshines its companion and no constraints could be derived from the binarity. In the line-profile variations of the spectroscopic observations we detected 20 pulsation modes. However, the star’s fast rotation hampered mode identification and made it impossible to derive unique results for any seismic interpretation.The second example is a double-lined eccentric binary system that contains two gravity and pressure-mode hybrid pulsators. This rich system was discovered from four years of data assembled by NASA's Kepler satellite. From the ellipsoidal variation and reflection signal in the Kepler light curve and the radial velocity measurements, we derived masses and radii. In the periodogram of the light curve we detected six series of equally spaced gravity-mode periods and rotational splitting in the gravity and pressure modes for both stars. We used these stringent observational constraints for seismic modelling. An estimate of the convective-core overshooting and additional internal mixing was derived. However, as the models failed to predict the detailed pattern of the period spacings to the high precision of the data, we concluded that mixing in only the radial direction is insufficient to describe the detailed stellar structure with current state-of-the-art one-dimensional stellar models. Our work delivered the first seismic estimates of the level of chemical mixing inside intermediate-mass binary pulsators and paves the way for more such types of studies in the near future.