Origin of eclipsing time variations in Post-Common-Envelope binaries: role of the centrifugal force
arXiv:2205.03163 · doi:10.1051/0004-6361/202243917
Abstract
Eclipsing time variations (ETVs) in post-common-envelope binaries (PCEBs) were proposed to be due to the time-varying component of the stellar gravitational quadrupole moment. This is suggested to be produced by changes in the stellar structure due to an internal redistribution of angular momentum and the effect of the centrifugal force. We examined this hypothesis and present 3D simulations of compressible magnetohydrodynamics (MHD) performed with the {\sc Pencil Code}. We modeled the stellar dynamo for a solar-mass star with angular velocities of 20 and 30 times solar. We included and varied the strength of the centrifugal force and compared the results with reference simulations without the centrifugal force and with a simulation in which its effect is enhanced. The centrifugal force causes perturbations in the evolution of the numerical model, so that the outcome in the details becomes different as a result of nonlinear evolution. While the average density profile is unaffected by the centrifugal force, a relative change in the density difference between high latitudes and the equator of is found. The power spectrum of the convective velocity is found to be more sensitive to the angular velocity than to the strength of the centrifugal force. The quadrupole moment of the stars includes a fluctuating and a time-independent component, which vary with the rotation rate. As very similar behavior is produced in absence of the centrifugal force, we conclude that it is not the main ingredient for producing the time-averaged and fluctuating quadrupole moment of the star. In a real physical system, we thus expect contributions from both components, that is, from the time-dependent gravitational force from the variation in the quadrupole term and from the spin-orbit coupling that is due to the persistent part of the quadrupole.
arXiv comment8 pages, 7 figures. Accepted in A&A
References in corpus (23)
- Tidal dissipation in rotating solar-type stars
- The Pencil Code, a modular MPI code for partial differential equations and particles: multipurpose and multiuser-maintained
- Two planets orbiting the recently formed post-common envelope binary NN Serpentis
- Effects of enhanced stratification on equatorward dynamo wave propagation
- Detection of a period decrease in NN Ser with ULTRACAM: evidence for strong magnetic braking or an unseen companion?
- Origin of apparent period variations in eclipsing post-common-envelope binaries
- The quest for companions to post-common envelope binaries. II. NSVS14256825 and HS0705+6700
- Eclipsing time variations in close binary systems: Planetary hypothesis vs. Applegate mechanism
- Transition from axi- to nonaxisymmetric dynamo modes in spherical convection models of solar-like stars
- Second generation planet formation in NN Serpentis?
- Planet formation from the ejecta of common envelopes
- Long-term eclipse timing of white dwarf binaries: an observational hint of a magnetic mechanism at work
- The First Science Results from SPHERE: Disproving the Predicted Brown Dwarf around V471 Tau
- Main-sequence progenitor configurations of the NN Ser candidate circumbinary planetary system are dynamically unstable
- The quest for companions to post-common envelope binaries IV: The 2:1 mean-motion resonance of the planets orbiting NN Serpentis
- The V471 Tauri System: A Multi-datatype Probe
- The physics of the Applegate mechanism: Eclipsing time variations from magnetic activity
- Sensitivity to luminosity, centrifugal force, and boundary conditions in spherical shell convection
- Effect of the radiative background flux in convection
- The Applegate mechanism in Post-Common-Envelope Binaries: Investigating the role of rotation
- Eclipse Timing Modeling of Three Post-Common Envelope Binaries: Hybrid Solutions
- Magnetic field evolution of the K2 dwarf V471 Tau
- Origin of eclipsing time variations: Contributions of different modes of the dynamo-generated magnetic field