Tango of celestial dancers: A sample of detached eclipsing binary systems containingg-mode pulsating components

Abstract

Context. Eclipsing binary systems with components that pulsate in gravity modes (g modes) allow for simultaneous and independent constraints of the chemical mixing profiles of stars. The high precision of the dynamical masses and radii as well as the imposition of identical initial chemical compositions and equivalent ages provide strong constraints during the modelling of g-mode period-spacing patterns. Aims. We aim to assemble a sample of g-mode pulsators in detached eclipsing binaries with the purpose of finding good candidates for future evolutionary and asteroseismic modelling. In addition, we present a case study of the eclipsing binary KIC9850387, identified as our most promising candidate, and detail the results of the observational spectroscopic, photometric, and asteroseismic analysis of the system. Methods. We selected all of the detached eclipsing binaries in the Kepler eclipsing binary catalogue with Kepler Input Catalogue (KIC) temperatures between 6000 K and 10 000 K, and performed a visual inspection to determine the presence and density of g modes, and the presence of g-mode period-spacing patterns in their frequency spectra. We then characterised our sample based on their g-mode pulsational parameters and binary and atmospheric parameters. A spectroscopic follow-up of our most promising candidate was then performed, and the orbital elements of the system were extracted. We then performed spectral disentangling followed by atmospheric modelling and abundance analysis for the primary star. We utilised an iterative approach to simultaneously optimise the pulsational and eclipse models, and subsequently performed an analysis of the pressure- (p-) and g-mode pulsational frequencies. Results. We compiled a sample of 93 Kepler eclipsing binary stars with g-mode pulsating components and identified clear g-mode period-spacing patterns in the frequency spectra of seven of these systems. We also identified 11 systems that contained hybrid p- and g-mode pulsators. We found that the g-mode pulsational parameters and the binary and atmospheric parameters of our sample are weakly correlated at best, as expected for detached main-sequence binaries. We find that the eclipsing binary KIC9850387 is a double-lined spectroscopic binary in a near-circular orbit with a hybrid p- and g-mode pulsating primary with Mp = 1.66−0.01+0.01 M⊙ and Rp = 2.154−0.004+0.002 R⊙, and a solar-like secondary with Ms = 1.062−0.005+0.003 M⊙ and Rs = 1.081−0.002+0.003 R⊙. We find ℓ = 1 and ℓ = 2 period-spacing patterns in the frequency spectrum of KIC9850387 spanning more than ten radial orders each, which will allow for stringent constraints of stellar structure during future asteroseismic modelling.

Asteroseismology of Close Binary Stars: Tides and Mass Transfer

“…They also find some other "tidal pulsators, " and most of them have circular orbits with self-excited modes, probably perturbed by tides. Sekaran et al (2020) compiled 95 g-mode pulsators in eclipsing binaries. The sample may contain tidally perturbed modes or tidally excited modes.…”

Space-Based Photometry of Binary Stars: From Voyager to TESS

“…Guo et al [228] studied KIC 9592855, a post-mass-transfer system with γ Dor and δ Sct pulsations in the secondary component that require both its core and envelope to rotate synchronously with the orbital motion. Sekaran et al [229,230] determined the masses and radii of KIC 9850387 to high precision and measured a large number of p-mode and g-mode frequencies. They found that the asteroseismic results constrained the interior properties of the stars better than their physical properties, that the envelope of the primary star was rotating three times faster than its core, and that interior mixing processes were stronger in its interior than for single stars of its mass and age.…”

TESS Eclipsing Binary Stars. I. Short cadence observations of 4584 eclipsing binaries in Sectors 1-26

“…Furthermore, detailed studies have demonstrated tension between the asteroseismic and binary results for both main sequence and evolved stars, indicating that evolutionary models still have room for improvement (Gaulme et al 2016;Themeßl et al 2018;Benbakoura et al 2021;Sekaran et al 2021). The large data-set provided by TESS will enable synergistic asteroseismic and binary modelling across a much larger parameter range than was previously possible with the more limited samples, allowing investigation into the relationship between pulsational properties and orbital properties (Liakos & Niarchos 2017;Gaulme & Guzik 2019;Sekaran et al 2020).…”