Pulsations and planets: The asteroseismology‐extrasolar‐planet connection

Abstract

The disciplines of asteroseismology and extrasolar planet science overlap methodically in the branch of high-precision photometric time series observations. Light curves are, amongst others, useful to measure intrinsic stellar variability due to oscillations, as well as to discover and characterize those extrasolar planets that transit in front of their host stars, periodically causing shallow dips in the observed brightness. Both fields ultimately derive fundamental parameters of stellar and planetary objects, allowing to study for example the physics of various classes of pulsating stars, or the variety of planetary systems, in the overall context of stellar and planetary system formation and evolution. Both methods typically also require extensive spectroscopic follow-up to fully explore the dynamic characteristics of the processes under investigation. In particularly interesting cases, a combination of observed pulsations and signatures of a planet allows to characterize a system's components to a very high degree of completeness by combining complementary information. The planning of the relevant space missions has consequently converged with respect to science cases, where at the outset there was primarily a coincidence in instrumentation and techniques. Whether space-or ground-based, a specific type of stellar pulsations can themselves be used in an innovative way to search for extrasolar planets. Results from this additional method at the interface of stellar pulsation studies and exoplanet hunts in a beyond-mainstream area are presented.

Non-Detection of the Putative Substellar Companion to Hd 149382

“…There are several claims of substellar companions in orbit around hot subdwarf stars, summarized in Schuh (2010). With the exception of HD 149382 and SDSS J08205+0008 (discussed below), these claims are all based on the interpretation of residuals in an O − C diagram, in which observed ("O") moments of eclipse or pulsation maximum are compared with a calculated ("C") ephemeris.…”

Starspots on WASP-107 and pulsations of WASP-118

“…The observations provided by the K2 mission have led to the discovery of another pulsating transiting exoplanet host star, namely HAT-P-56 which is likely a γ Doradus pulsator (Huang et al 2015). While the exact asteroseismic analysis approach can vary depending on the class of variability, one can investigate any potential starplanet interactions and derive precise stellar mass, radius and the depth-dependant chemical composition, given the appropriate modelling capabilities (Schuh 2010).…”

WASP-33: the firstδScuti exoplanet host star

“…These allow us to provide the first evidence for photometric oscillations on the star WASP-33, and to analyse their amplitude and periodicity. The presence of a large planet close to a star may cause tidal effects that are responsible for multiperiodic non-radial pulsations, and in special cases radial pulsations, on its host star (Schuh 2010). However, there are only a few known exoplanets orbiting pulsating stars, such as Photometric data is only available in electronic forrm at CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/526/L10 V391 Pegasi (sdB type), whose planet was discovered using the timing method (Silvotti et al 2007).…”