Eclipse Timing Modeling of Three Post-Common Envelope Binaries: Hybrid Solutions

Abstract

We report 88 new observations of three post common envelope binaries at primary eclipse spanning between December 2018 to February 2021. We combine recent primary eclipse timing observations with previously published values to search for substellar circumbinary components consistent with timing variations from a linear ephemeris. We used a least-squares minimization fitting algorithm weighted by a Hill orbit stability function, followed by Bayesian inference, to determine best-fit orbital parameters and associated uncertainties. For HS2231+2441, we find that the timing data are consistent with a constant period and that there is no evidence to suggest orbiting components. For HS0705+6700, we find both two and three-component solutions that are stable for at least 10 Myr but have very different parameters. For HW Vir, we find multi-component solutions that fit the timing data but they are unstable on short timescale, and therefore highly improbable. Conversely, both the least-squares and Bayesian solutions provide a poor fit. In both systems, the best-fit stable solutions significantly deviate from the ensemble timing data.For both HS0705+6700 and HW Vir, substellar component solutions that fit all observed eclipse timing data are dynamically unstable, whereas best-fit solutions with stable orbits provide poor O-C fits. We speculate that the observed timing variations for these systems, and very possibly other sdB binaries, may result from a combination of substellar component perturbations and an Applegate-Lanza mechanism.

Magnetic field evolution of the K2 dwarf V471 Tau

“…Marsh 2018 ). In particular, some of the circumbinary objects inferred from the ETVs have been refuted afterwards using dynamical stability analysis (Horner et al 2011(Horner et al , 2012(Horner et al , 2014Wittenmyer et al 2012 ;Marsh 2018 ;Mai & Mutel 2021 ) or high-resolution direct imaging of the systems (e.g. V471 Tau; Hardy et al 2015 ).…”

Magnetic field evolution of the K2 dwarf V471 Tau

“…However, recent investigations showed that caution must be taken when interpreting ETVs as caused by circumbinary objects (e.g., Marsh 2018). In particular, some of the circumbinary objects inferred from the ETVs have been refuted afterwards using dynamical stability analysis (Horner et al 2011(Horner et al , 2012(Horner et al , 2014Wittenmyer et al 2012;Marsh 2018;Mai & Mutel 2021) or high-resolution direct imaging of the systems (e.g. V471 Tau, Hardy et al 2015).…”