A Study of Stellar Pulsations in Eclipsing Binary Stars

Villanova University, Villanova PA

Investigators

Abstract

Among the ways by which astronomers measure fundamental properties of stars (such as mass, radius, temperature, and luminosity), two stand out: by using closely observing binary stars orbiting each other, and by studying oscillations in stars -- asteroseismology -- akin to how geologists study the Earth through seismology. This team at Villanova University seeks to bridge the two techniques by incorporating the physics of stellar pulsations into their eclipsing binary star computer code known as PHOEBE. The project will provide the opportunity to better understand pulsating stars by studying their properties within eclipsing binary systems, and also the other way around, to learn how pulsations influence binarity. The astronomy group at Villanova has a long tradition of involving undergraduates in their research programs. The project will involve two undergrads per year in this research. Two community workshops will provide training in the use of PHOEBE for early career scientists, with special consideration given to geographic diversity, gender balance, and representation from traditionally underrepresented groups. The research team will provide a PHOEBE interface to the virtual reality infrastructure CAVE (Cave Automatic Virtual Environment) at Villanova, and to off-the-shelf VR headsets. PHOEBE works on the premise that binary component surfaces can be approximated by a mesh of triangles where each triangle has an assigned set of local quantities (temperature, surface gravity, velocity, emergent intensity, etc). This mesh effectively describes physical circumstances across distorted surfaces and accounts for many effects we see manifested in binary star light curves: gravity brightening due to tidal interaction and rotation, surface brightness variation due to reflection, heating and limb darkening, prominences such as spots, and, through this project, stellar pulsations. Asteroseismologists are able to recover detailed information on stellar properties from the power spectra of the observed light curves, which are in turn used to deduce fundamental parameters of stars by way of the so-called scaling relations. Incorporating stellar pulsations into PHOEBE will provide fundamental stellar parameters of pulsating stars to 1% or better, thus validating asteroseismic scaling relations while providing asteroseismologists with accurate parameters for their models of stellar pulsation mechanisms. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.